UC-NRLF 


B    M 


.  D. 


*  SAN  FRANCISCO  * 

•MEUICA1'    *     LIBRARY 


MEDICAL 
UWfc 

.SCHOOL 
&1EY 

John  Marshall  Williamson 
Memorial 


AN 


ELEMENTARY  TREATISE 


ON 


BY 

JOSEPH  LEIDY,  M.D.,  LL.D, 

PROFESSOR   OF    HUMAN    AND   COMPARATIVE   ANATOMY   AND   ZOOLOGY    IN   THE   UNIVERSITY   OF 

PENNSYLVANIA,    PRESIDENT   OT   THE    ACADEMY   OF   NATURAL   SCIENCES,    AND 

OF   THE    FACULTY   OF   THE    WAGNER    FREE    INSTITUTE   OF 

SCIENCES,    PHILADELPHIA. 


SECOND  EDITION,   REWRITTEN. 

WITH  FOUR   HUNDRED   AND   NINETY-FIVE,    ILLUSTRATIONS. 


PHILADELPHIA: 
J.   B.   LIPPINCOTT    COMPANY. 

1889. 


Copyright,  1889,  by  J.  B.  LIPPINCOTT  COMPANY. 


PREFACE. 


TWENTY-EIGHT  years  have  passed  since  the  publication  of  a 
former  edition  of  the  present  work,  entitled  "  An  Elementary 
Treatise  on  Human  Anatomy,"  and  it  is  at  the  repeated  solici- 
tation of  medical  students,  who  have  been  pupils  of  the  author, 
that  another  edition  has  now  been  prepared.  With  the  excellent 
and  admirably  illustrated  text- books  on  the  same  subject  from 
the  English  press,  such  a  work  may  seem  to  be  inferior  and 
superfluous ;  but  the  experience  of  the  author  as  a  teacher  leads 
him  to  believe  that  our  students  generally  desire,  if  they  do  not 
require,  such  a  treatise  as  he  has  attempted  to  provide  them. 
With  the  view  of  facilitating  the  study  of  anatomy  and  its.  com- 
mitment to  memory,  in  the  employment  of  the  multitude  of 
necessary  technical  terms,  as  a  rule,  one  name  for  an  organ  or 
part  is  used,  and  that  one  selected  which  is  simplest  and  most 
expressive  of  its  character.  The  name,  also,  as  far  as  may  be 
permitted,  is  rendered  into  English.  Many  phrases  in  common 
use  as  names  have  been  curtailed  of  what  have  appeared  un- 
necessary portions,  and  sometimes  the  adjective  portion  of  the 
phrase  has  been  retained,  in  preference  to  the  substantive  por- 
tion, where,  for  various  reasons,  it  has  seemed  more  appropriate. 
Where  names  of  persons  are  applied  to  parts  they  are  generally 
avoided,  and  others  in  all  respects  better  adapted  to  the  pur- 
pose are  used.  Some  further  attempts  have  been  made  to  im- 
prove the  nomenclature,  and  it  is  hoped  that  the  experiment 
may  prove  successful  in  helping  the  student  in  acquiring  a 
knowledge  of  the  subject.  While  the  author  regards  with 
favor  the  proposed  improvement  in  anatomical  nomenclature 
of  able  authorities,  he  has  not  followed  them  completely,  in 

3 


4  PREFACE. 

apprehension  that,  with  the  prevalent  nomenclature,  a  radical 
change  would  confuse  rather  than  facilitate  the  study  of  anatomy. 
The  present  edition  of  the  book  has  been  entirely  rewritten, 
and,  though  the  author  has  taken  due  precaution  to  avoid  pal- 
pable errors  and  omissions,  he  nevertheless  asks  indulgence  for 
such  as  may  have  escaped  his  notice. 


CONTENTS. 


CHAPTEE    I.  PAGE 

INTRODUCTION 25 

Man  as  related  to  the  other  Vertebrate  Mammals 25 

Anatomy,  General,  Special,  Systematic,  Surgical,  etc 26 

Proximate  Physical  Elements  and  Tissues  of  the  Human  Body 27 

Ultimate  Physical  Elements  of  the  Human  Body 28,  29 

CHAPTEE    II. 

GENERAL  ANATOMY  OF  THE  SKELETON 32 

The  Bones  Classified 33 

Structural  and  Chemical  Elements  of  the  Bones 33 

The  Periosteum 41 

The  Marrow 42 

Vessels  and  Nerves  of  the  Bones 43 

Development  and  Growth  of  the  Bones 44 

Articulations  of  Joints  of  the  Skeleton • 50 

Of  the  Kelative  Position  of  the  Different  Structures  entering  into  the  Com- 
position of  Articulations 52 

CHAPTEE    III. 

SPECIAL  ANATOMY  OF  THE  SKELETON 54 

The  Vertebral  Column. — The  Vertebrae 54 

The  Sacrum 62 

The  Coccyx •  63 

The  Vertebral  Column  viewed  entire 64 

Development  and  Growth  of  the  Vertebral  Column 69 

Articulations  of  the  Vertebral  Column 71 

Movements  of  the  Vertebral  Column 79 

The  Kibs 80 

The  Sternum 82 

Articulations  of  the  Kibs 85 

The  Thorax 87 

The  Skull 89 

The  Occipital  Bone 90 

The  Sphenoid  Bone 93 

The  Parietal  Bones 101 

The  Frontal  Bone 102 

The  Ethmoid  Bone 106 

The  Temporal  Bones 109 

The  Maxillse 118 

5 


CONTENTS. 

PAGE 

The  Palate  Bones 122 

The  Turbinal  Bones 124 

The  Lachrymal  Bones 125 

The  Nasal  Bones 126 

The  Vomer '.'.127 

The  Malar  Bones 128 

The  Mandible 129 

The  Entire  Skull 133 

The  Sutures  of  the  Skull 134 

Supernumerary  or  Sutural  Bones 137 

The  Interior  of  the  Cranium 137 

The  Lateral  Kegion  of  the  Skull , 141 

The  Base  of  the  Skull 143 

The  Face 144 

The  Orbits -. 145 

The  Nasal  Cavities 146 

Development  and  Growth  of  the  Skull 149 

Variations  of  the  Skull 151 

Mechanical  Construction  of  the  Skull 153 

Articulation  of  the  Lower  Jaw 165 

The  Hyoid  Bone 156 

Bones  of  the  Tipper  Limbs 1 57 

The  Scapula 158 

The  Clavicle 162 

The  Humerus f  .  163 

The  Ulna 167 

The  Radius 169 

The  Hand 171 

The  Carpus 171 

The  Metacarpus 174 

The  Digits 177 

The  Articulations  of  the  Upper  Limbs 178 

The  Sterno-Clavicular  Articulation 178 

The  Scapulo-Clavicular  Articulation .  179 

The  Shoulder-Joint 179 

The  Elbow-Joint 181 

The  Radio-Ulnar  Articulation 182 

The  Articulations  of  the  Hand 183 

The  Wrist-Joint 184 

The  Intercarpal  and  Carpo-Metacarpal  Articulations 185 

The  Metacarpo-Phalangeal  and  Phalangeal  Articulations 186 

The  Bones  of  the  Lower  Limbs 187 

The  Hip  Bones 187 

The  Pelvis 192 

The  Articulations  of  the  Pelvis 195 

The  Femur 196 

The  Patella 200 

The  Hip-Joint 200 

The  Bones  of  the  Leg 202 

The  Tibia 202 

The  Fibula 204 

The  Knee-Joint 206 

Articulations  of  the  Tibia  and  Fibula 210 


CONTENTS.  7 

PAGE 

Bones  of  the  Foot 211 

The  Tarsus 211 

The  Metatarsus 215 

The  Foot 217 

Ossification  of  the  Bones  of  the  Foot 218 

The  Ankle-Joint 218 

Articulations 'of  the  Tarsus                                                                               .  219 


CHAPTEE    IY. 

THE  CONNECTIVE  TISSUES 223 

Fibro-Connective  Tissue 223 

Areolar  Tissue 225 

Elastic  Tissue 227 

Adipose  Tissue  . 228 

The  Cartilages 230 

Cartilage 230 

Fibro-Cartilage 234 

Elastic  Cartilage 235 

Fasciae 235 

CHAPTBK    V. 

THE  MUSCULAR  SYSTEM 237 

General  Remarks  on  the  Head 237 

The  .Unstriped  or  Involuntary  Muscles 238 

The  Striped  or  Voluntary  Muscles 239 

The  Cardiac  Muscular  Tissue 243 

Muscles  and  Fascia  of  the  Cranial  Vault 246 

The  Auricular  Muscles 248 

Muscles  of  the  Face 248 

Muscles  of  the  Eyelids  and  Eyebrows 248 

Muscles  of  the  Nose 250 

Muscles  of  the  Mouth,  Lips,  and  Cheeks 251 

Muscles  of  Mastication 254 

Muscles  and  Fasciae  of  the  Neck 256 

Supra-  and  Infra-Hyoid  Muscles 260 

Lateral  Cervical  Muscles 263 

Prevertebral  Muscles  of  the  Neck 264 

Postvertebral  Muscles  of  the  Neck 265 

Muscles  of  the  Thorax 266 

The  Diaphragm 267 

Muscles  and  Fasciae  of  the  Abdomen       270 

Fasciae  of  the  Pelvis 279 

Fasciae  and  Muscles  of  the  Back  of  the  Trunk 280 

Superficial  Muscles  of  the  Back .  281 

Deep  Muscles  of  the  Back 285 

Fasciae  and  Muscles  of  the  Upper  Limb 290 

Muscles  of  the  Breast  and  Shoulder 291 

Muscles  of  the  Back  and  Shoulder 293 

Muscles  of  the  Shoulder 293 

Muscles  of  the  Arm 296 

Fasciae  and  Muscles  of  the  Forearm  and  Hand 300 


8  CONTENTS. 

PAGE 

Fascia  of  the  Forearm 300 

Fasciae  of  the  Hand 301 

Muscles  of  the  Front  and  Inner  Part  of  the  Forearm 302 

Muscles  of  the  Outer  and  Back  Part  of  the  Forearm 307 

Muscles  of  the  Hand ...  312 

Muscles  of  the  Thumb 313 

Muscles  of  the  Little  Finger 314 

Fasciae  and  Muscles  of  the  Lower  Limb • 315 

Muscles  of  the  Front  and  Outer  Part  of  the  Thigh 318 

Muscles  on  the  Inner  Fore  Part  of  the  Thigh 321 

Muscles  of  the  Buttock 324? 

Muscles  of  the  Back  of  the  Thigh 328 

Fasciae  of  the  Leg  and  Foot 330 

Muscles  of  the  Inner  Fore  Part  of  the  Leg  and  Back  of  the  Foot  ....  333 

Muscles  on  the  Outer  Part  of  the  Leg 335 

Muscles  on  the  Back  of  the  Leg 336 

Muscles  of  the  Foot 341 

CHAPTEE    VI. 

GENERAL   COMPOSITION   OF    THE   SKIN,   THE   Mucous   MEMBRANES,   THE 
GLANDS,  THE  LUNGS,  THE  SEROUS  AND  SYNOVIAL  MEMBRANES,  AND 

THE  LINING  OF  THE  VASCULAR  SYSTEM 345 

General  Remarks 345 

Epithelial  Tissue 345 

Serous  Membranes 351 

Synovial  Membranes 353 

Serum. — Synovia 355 

Mucous  Membranes 355 

Mucus 358 

The  Glandular  System 358 

CHAPTEE    VII. 

THE  NECK,  THORAX,  AND  ABDOMEN 363 

The  Neck 363 

The  Thorax 363 

The  Abdomen 366 

The  Peritoneum 368 

CHAPTEE    VIII. 

THE  ALIMENTARY  APPARATUS 376 

The  Mouth 377 

The  Glands  of  the  Mouth 380 

The  Tonsils 381 

Muscles  of  the  Palate 381 

The  Tongue 383 

Muscles  of  the  Tongue 386 

The  Salivary  Glands 389 

The  Saliva 393 

The  Teeth 393 

The  Permanent  Teeth  .                             394 


CONTENTS.  9 

PAGE 

The  Temporary  Teeth 399 

Structure  of  the  Teeth 401 

The  Pharynx •    .  410 

Muscles  of  the  Pharynx 411 

The  (Esophagus 414 

The  Organs  of  Digestion 416 

The  Stomach 416 

The  Small  Intestine 424 

The  Large  Intestine 432 

The  Gastric  Juice 440 

The  Intestinal  Juices 440 

The  Pancreas 440 

The  Pancreatic  Juice 442 

The  Liver   . 442 

Structure  of  the  Liver 446 

The  Bile  .                                                                                                            .  452 


CHAPTEE    IX. 

THE  VASCULAR  SYSTEM 453 

The  Blood- Vessels 453 

The  Arteries 453 

The  Veins 458 

The  Capillaries 460 

The  Blood 463 

The  Heart 467 

Structure  of  the  Heart 474 

Vessels  and  Nerves  of  the  Heart 476 

Kelative  Position  of  Important  Parts  of  the  Heart  to  the  Anterior  Wall  of 

the  Chest 477 

The  Aorta 477 

The  Arch  of  the  Aorta 479 

Branches  of  the  Aorta 479 

The  Innominate  Artery 480 

The  Common  Carotid  Arteries 480 

The  Subclavian  Arteries 482 

The  Internal  Carotid  Artery 483 

The  Ophthalmic  Artery 485 

The  External  Carotid  Artery 487 

The  Subclavian  Artery 496 

The  Axillary  Artery 502 

The  Brachial  Artery 504 

The  Radial  Artery 507 

The  Ulnar  Artery 511 

The  Descending  Thoracic  Aorta 514 

The  Branches  of  the  Descending  Thoracic  Aorta 515 

The  Abdominal  Aorta 517 

The  Branches  of  the  Abdominal  Aorta 518 

The  Common  Iliac' Arteries 525 

The  Internal  Iliac  Artery 526 

The  External  Iliac  Artery 532 

The  Femoral  Artery 533 

The  Popliteal  Artery 537 


10  CONTENTS. 

PAGE 

The  Anterior  Tibial  Artery 539 

The  Dorsal  Pedal  Artery 541 

The  Posterior  Tibial  Artery 542 

The  Plantar  Arteries 544 

The  Veins  of  the  Heart 546 

The  Superior  Cava 548 

The  Innominate  Veins 548 

Veins  of  the  Head  and  Neck 550 

The  Internal  Jugular  Vein 550 

Veins  of  the  Cranium 556 

Sinuses  of  the  Dura 556 

The  Ophthalmic  Vein 559 

Veins  of  the  Brain 560 

The  Diploic  Veins 561 

The  Emissary  Veins 562 

Veins  of  the  Upper  Limbs 562 

The  Inferior  Cava 565 

The  Azygos  and  Hemiazygos  Veins 566 

Veins  of  the  Spine 568 

Branches  of  the  Inferior  Cava 569 

Veins  of  the  Pelvis  and  Lower  Limbs „ 570 

The  Portal  System  of  Veins 574 

The  Vascular  System  of  the  Foetus 576 

The  Lymphatic  System 579 

The  Lymph 584 

The  Chief  Trunks  of  the  Lymphatics 585 

The  Thoracic  Duct 585 

The  Eight  Lymphatic  Duct 586 

Lymphatics  of  the  Lower  Limbs 586 

Lymphatics  of  Ihe  Pelvis  and  Abdomen .  588 

Lymphatics  of  the  Thorax 591 

Lymphatics  of  the  Upper  Limbs 592 

Lymphatics  of  the  Head  and  Neck 594 


CHAPTEE    X. 

THE  KESPIRATORY  APPARATUS  AND  LARYNX 597 

The  Lungs 598 

The  Trachea 602 

Structure  of  the  Lungs 605 

The  Larynx ' 608 

Cartilages  of  the  Larynx 608 

Ligaments  and  Articulations  of  the  Larynx 612 

Muscles  of  the  Larynx 615 

The  Interior  of  the  Larynx 617 


CHAPTEE    XL 

THE  URINARY  ORGANS 621 

The  Kidneys 621 

The  Ureters 627 

The  Urinary  Bladder 629 


CONTENTS.  11 

CHAPTEE    XII. 

PAGE 

THE  MALE  KEPRODTTCTIVE  APPARATUS 634 

The  Penis 634 

The  Prostate 639 

The  Urethra 640 

The  Testicles 643 

The  Semen 653 

CHAPTEE    XIII. 

THE  FEMALE  KEPRODUCTIVE  APPARATUS 654 

General  Description  .    .* 654 

The  Vulva 654 

The  Clitoris 655 

The  Nymphse 657 

The  Urethra 658 

The  Vagina 659 

The  Uterus 661 

The  Oviducts 666 

The  Ovaries 667 

The  Mammae .  672 

The  Milk 675 

The  Perineum 675 

Muscles  and  Fasciae  of  the  Perineum 676 

CHAPTEE    XIV. 

GLAND-LIKE  ORGANS  WHOSE  FUNCTION  is  OBSCURE  OR  UNKNOWN  ....  680 

The  Spleen 680 

The  Thyroid  Body 683 

The  Thymus 685 

The  Suprarenal  Bodies 686 

The  Carotid  Gland 688 

The  Coccygeal  Gland 688 

CHAPTEE    XV. 

THE  NERVOUS  SYSTEM 689 

The  Nerves  and  Nerve-Substance  in  General 689 

The  Nerve-Fibres 691 

The  Nerve-Cells 695 

The  Nerves 697 

The  Ganglia 700 

The  Cerebro-Spinal  Axis 703 

The  Spinal  Cord 703 

Origin  of  the  Spinal  Nerves 711 

The  Brain 713 

The  Medulla  Oblongata 716 

The  Fourth  Ventricle 719 

The  Interior  of  the  Oblongata 722 

The  Pons 726 

The  Cerebellum  .                                                                                                     .  728 


12  CONTENTS. 

PAGE 

The  Cerebrum 734 

The  Cerebral  Crura,  etc 747 

The  Lateral  Ventricles 749 

The  Fifth  Ventricle 751 

The  Corpora  Striata 751 

The  Fornix 752 

The  Hippocampus 754 

The  Third  Ventricle 757 

The  Thalamus 757 

The  Commissures 759 

The  Optic  Tract 759 

The  Optic  Commissure 760 

The  Quadrigeminal  Body 761 

The  Pineal  Body 762 

The  Pituitary  Body 763 

The  Gray  Cortex.— The  White  Matter 763 

The  Fibres  of  the  Cerebrum 765 

The  Brain  of  the  Embryo    . 767 

The  Choroid  Telse  and  Plexuses 768 

The  Ependyma 769 

Membranes  of  the  Cerebro-Spinal  Axis 769 

Membranes  of  the  Brain 770 

The  Dura  Mater 770 

The  Pia  Mater 771 

The  Arachnoid 772 

Pacchionian  Bodies 772 

Membranes  of  the  Spinal  Cord. — The  Dura,  the  Pia 773 

The  Arachnoid 774 

Blood- Vessels  of  the  Spinal  Axis 775 

The  Nerves  of  the  Brain 778 

Origin  of  the  Cerebral  Nerves 778 

The  Olfactory,  or  First  Pair  of  Nerves 778 

The  Optic,  or  Second  Pair  of  Nerves 778 

The  Oculo-Motor,  or  Third  Pair  of  Nerves 778 

The  Trochlear,  or  Fourth  Pair  of  Nerves 779 

The  Trifacial,  or  Fifth  Pair  of  Nerves 779 

The  Abducent,  or  Sixth  Pair  of  Nerves 779 

The  Facial,  or  Seventh  Pair  of  Nerves 779 

The  Auditory,  or  Eighth  Pair  of  Nerves 780 

The  Glosso-Pharyngeal,  or  Ninth  Pair  of  Nerves 780 

The  Pneumogastric,  or  Tenth  Pair  of  Nerves 780 

The  Accessory,  or  Eleventh  Pair  of  Nerves 780 

The  Hypoglossal,  or  Twelfth  Pair  of  Nerves 780 

Distribution  of  the  Nerves  of  the  Brain 781 

Distribution  of  the  Third  Nerve 781 

Distribution  of  Fourth  and  Fifth  Nerves 782 

The  Semilunar  Ganglion 782 

The  Ophthalmic  Nerve 783 

The  Lachrymal  Nerve,  etc 783 

The  Ophthalmic  Ganglion 785 

The  Superior  Maxillary  Nerve 786 

The  Spheno-Palatine  Ganglion 788 

The  Inferior  Maxillary  Nerve 790 


CONTENTS.  13 

PAGE 

The  Otic  Ganglion 793 

The  Submaxillary  Ganglion 794 

The  Abducent  Nerve    ...        794 

The  Facial  Nerve 794 

The  Auditory  Nerve 798 

The  Glosso-Pharyngeal  Nerves , 798 

The  Vagus  Nerves 800 

The  Accessory  Nerve 805 

The  Hypoglossal  Nerve 805 

Distribution  of  the  Spinal  Nerves 806 

The  Posterior  Spinal  Nerves 807 

The  Anterior  Spinal  Nerves 808 

The  Cervical  Plexus 809 

The  Brachial  Plexus. — Nerves  of  the  Arms  and  Hands 812 

The  Anterior  Thoracic  Nerves 821 

The   Anterior    Lumbar,    Sacral,   and   Coccygeal    Nerves. — The   Lumbar 

Plexus 823 

The  Sacral  Plexus 828 

The  Coccygeal  Plexus 835 

The  Sympathetic  Nerves 835 

The  Cervical  Portion  of  the  Sympathetic. — The  First  Cervical  Ganglion   .  836 

The  Carotid  Plexus 838 

The  Second  and  Third  Cervical  Ganglia 839 

The  Cardiac  Plexus 840 

The  Thoracic  Portion  of  the  Sympathetic 841 

The  Solar  Plexus   ........ 843 

The  Sympathetic  Nerve,  Lumbar  and  Sacral  Portions 842,  844,  845 

The  Hypogastric  Plexus 845 

CHAPTEE    XVI. 

ORGANS  OF  SPECIAL  SENSE 847 

The  Nose 847 

The  Eyes  and  their  Appendages 854 

The  Eyebrow  and  Eyelids 854 

The  Conjunctiva .    .  857 

The  Lachrymal  Apparatus 859 

The  Muscles  of  the  Eyeball 860 

The  Eyeball 862 

The  Sclerotica 863 

The  Cornea 864 

The  Choroidea 866 

The  Iris 870 

The  Ketina 873 

The  Vitreum 881 

The  Lens 882 

The  Aqueous  Humor 884 

The  Ear.— The  External  Ear 884 

The  Middle  Ear 890 

The  Tympanum 890 

The  Tympanic  Membrane 894 

The  Eustachian  Tube •    ...  894 

The  Ear  Ossicles ,    .    .  895 


14  CONTENTS. 

PAGE 

Articulation  and  Connection  of  the  Ear  Ossicles 897 

Muscles  of  the  Tympanum 898 

The  Lining  Mucous  Membrane  of  the  Tympanum 899 

Vessels  and  Nerves  of  the  Tympanum 900 

The  Labyrinth 903 

The  Osseous  Labyrinth 904 

The  Membranous  Labyrinth 908 

The  Skin 915 

The  Nails 922 

The  Sebaceous  Glands 928 

The  Sweat-Glands                                                                                              .  929 


CHAPTEE    XYII. 

ANATOMY  or  THE  GROIN  IN  KELATION  TO  HERNIA 931 

Inguinal  Hernia 931 

Femoral  Hernia 933 

INDEX  .  .  935 


LIST  OF  ILLUSTRATIONS. 


[Those  marked  with  an  asterisk  are  original,  mostly  by  the  author  or  by  Dr.  Schmidt.    The 
names  opposite  the  others  indicate  the  authorities  from  which  they  have  been  obtained.] 

FIG. 

1  The  organic  cell.* 

2  Longitudinal  section  of  the  proximal  extremity  of  the  femur.* 

3  Horizontal  section  of  the  condyles  of  the  femur.* 

4  Vertical  section  of  the  calcaneum.* 

5  Transverse  section  of  the  shaft  of  a  phalanx.* 

6  Transverse  section  of  bone  from  the  shaft  of  the  femur.* 

7  Thin  plate  from  the  ethmoid  bone.* 

8  Portion  of  the  compact  substance  of  the  parietal  bone.* 

9  Femur  at  about  the  sixteenth  year  of  life.* 

10  The  vertebral  column.     Morton. 

11  Side  view  of  a  dorsal  vertebra.      Wilson. 

12  Upper  view  of  a  cervical  vertebra.     Ibid. 

13  Upper  view  of  the  atlas.     Ibid. 

14  Side  view  of  the  axis.     Ibid. 

15  Side  view  of  a  thoracic  vertebra.     Ibid. 

16  Side  view  of  a  lumbar  vertebra.     Ibid. 

17  Front  view  of  the  sacrum.     Ibid. 

18  Back  view  of  the  sacrum.     Ibid. 

19  Back  view  of  the  coccyx.     Morton. 

20  Development  of  the  vertebrae.     Sharpey  $•  Quain. 

21  Development  of  the  epiphyses  to  the  vertebrae.     Ibid. 

22  Upper  view  of  a  lumbar  vertebra.     Ibid. 

23  Vertical  section  of  two  lumbar  vertebra.     Ibid. 

24  Portion  of  the  occipital  bone,  with  the  atlas  and  axis.      Wilson. 

25  Three  thoracic  vertebrae,  with  costal  articulations.     Ibid. 

26  Portion  of  the  cranium  and  of  the  atlas  and  axis.     Ibid. 

27  Centra  of  three  thoracic  vertebrae.     Ibid. 

28  Three  arches  removed  from  thoracic  vertebrae.     Ibid. 

29  Portion  of  the  occipital  bone,  with  the  atlas  and  axis,  front  view.     Ibid. 

30  Portion  of  the  occipital  bone  and  of  the  three  upper  cervical  vertebrae.     Ibid. 

31  Part  of  the  skull,  the  atlas,  and  the  axis,  from  behind.     Ibid. 

32  Front  view  of  the  thorax.     Ibid. 

33  Front  view  of  the  thorax.     Ibid. 

34  Anterior  view  of  three  thoracic  vertebrae,  with  the  costal  articulations.     Ibid. 

35  Posterior  view  of  four  thoracic  vertebrae,  with  the  costal  articulations.     Ibid. 

36  External  view  of  the  occipital  bone.     Ibid. 

37  Internal  view  of  the  occipital  bone.     Ibid. 

38  Front  view  of  the  sphenoid  bone.     Ibid.  » 

39  Upper  view  of  the  sphenoid  bone.* 

15 


16  LIST   OF   ILLUSTRATIONS. 

FIG. 

40  Inferior  view  of  the  intermediate  portion  of  the  sphenoid  at  birth.* 

41  Outer  view  of  left  parietal  bone.     Wilson. 

42  Inner  view  of  left  parietal  bone.     Ibid. 

43  External  view  of  frontal  bone.     Ibid. 

44  Internal  view  of  frontal  bone.     Ibid. 

45  Upper  view  of  the  ethmoid  bone.* 

46  Left  side  view  of  the  ethmoid  bone.* 

47  Inner  view  of  the  right  ectethmoid.* 

48  External  view  of  the  temporal  bone,  right  side.* 

49  Internal  view  of  the  temporal  bone,  left  side.* 

50  Inferior  view  of  the  temporal  bone,  left  side.* 

51  Temporal  bone  near  the  time  of  birth.* 

52  Temporal  bone,  the  three  pieces  separated.* 

53  Temporal  bone  with  portion  of  the  petro-squamosal  suture  retained.* 

54  Maxilla,  left  side,  outer  view.* 

55  Maxilla,  left  side,  inner  view.* 

56  Posterior  view,  right  palate  bone.      Wilson. 

57  Exterior  view,  right  palate  bone.     Ibid. 

58  External  view,  right  turbinal  bone.     Homer. 

59  External  view,  right  lachrymal  bone.      Wilson. 

60  Anterior  view,  left  nasal  bone.     Ibid. 

61  The  vomer,  left  side.     Ibid. 

62  Outer  view,  right  malar  bone.     Ibid. 

63  The  mandible.     Ibid. 

64  The  skull.* 

65  Internal  view  of  the  base  of  the  cranium.* 

66  Eight  side  of  a  portion  ot  the  face  and  cranium.* 

67  External  view  ot  the  base  of  the  skull,  right  side.* 

68  Left  side  of  face,  outer  walls  of  orbit  and  antrum  removed.* 

69  Vertical  section  of  the  face.* 

70  Outer  wall  of  right  nasal  cavity.* 

71  The  cranium,  antero-posterior  section.* 

72  The  cranium,  horizontal  section.* 

73  The  cranium,  transverse  section  through  the  front.* 

74  The  cranium,  transverse  section  in  advance  of  the  middle.* 

75  The  cranium,  transverse  section  through  the  middle.* 

76  The  cranium,  transverse  section  posterior  to  the  middle.* 

77  Articulation  of  the  lower  jaw,  vertical  section.      Wilson. 

78  External  view  of  the  temporo-mandibular  articulation.     Ibid. 

79  The  hyoid  bone.     Ibid. 

80  The  scapula,  left  side,  posterior  view.     Ibid. 

81  The  scapula,  left  side,  anterior  view.     Ibid. 

82  The  right  clavicle.     Ibid. 

83  The  left  humerus.     Ibid. 

84  The  left  ulna  and  radius.     Ibid. 

85  Bones  of  the  carpus.     Ibid. 

86  The  left  hand.     Ibid. 

87  Sterno-clavicular,  costo-clavicular,  and  costo-sternal  articulations.     Ibid. 

88  Scapulo-clavicular  and  scapulo-humeral  articulations.     Ibid. 

89  Eight  elbow-joint,  antero-internally  viewed.     Ibid. 

90  Eight  elbow-joint,  externally  viewed.     Ibid. 

91  Ligaments  of  the  wrist  and  hand.     Ibid. 

92  Left  hip-bone,  inner  view.* 


LIST  OP   ILLUSTKATIONS.  17 

FIG. 

93  Left  hip-bone,  outer  view.      Wilson. 

94  Female  pelvis,  front  view.     Ibid. 

95  Ligaments  of  the  pelvis  and  hip-joint.     Ibid. 

96  Ligaments  of  the  pelvis  and  hip-joint.     Ibid. 

97  Right  femur.     Ibid. 

98  Eight  patella.     Ibid. 

99  Ligaments  of  the  hip.     Ibid. 

100  Left  tibia  and  fibula.     Ibid. 

101  Right  tibia  and  fibula,  posterior  view.     Ibid. 

102  Right  knee-joint,  front  view.     Ibid. 

103  Right  knee-joint  laid  open.     Ibid. 

104  Longitudinal  section  of  knee-joint.     Ibid. 

105  Right  foot,  dorsal  surface.     Ibid. 

106  Left  foot,  plantar  surface.     Ibid. 

107  External  view  of  ankle-joint.     Ibid. 

108  Internal  view  of  ankle-joint.     Ibid. 

109  Posterior  view  of  ankle-joint  and  of  inferior  tibio-fibular  articulations.     Ibid. 

110  Ligaments  of  the  sole  of  the  foot.     Ibid. 

111  Bundles  of  fibro-connective  tissue  from  a  ligament.* 

112  Fibro-connective  tissue  from  the  heart  and  from  the  dura.* 

113  Fibro-connective  tissue  pertaining  to  the  synovial  sheath -of  the  flexor  tendons 

of  the  wrist.* 

114  Areolar  tissue  from  the  axilla.* 

115  Arrangement  of  fibro-connective  tissue  in  the  external  coat  of  blood-vessels.* 

116  Elastic  tissue.* 

117  Elastic  tissue  from  pulmonary  artery  of  the  horse.     Kolliker. 

118  Elastic  tissue  from  carotid  artery  of  the  horse.     Ibid. 

119  Adipose  tissue,  with  connective  tissue.* 

120  Cartilage.* 

121  Articular  cartilage,  vertical  section.* 

122  Section  of  costal  cartilage.*  • 

123  Section  of  costal  cartilage.* 

124  Elastic  cartilage  from  the  auricle  of  the  ear.* 

125  Unstriated  muscle-fibres.* 

126  Section  of  the  ulno-carpal  flexor.* 

127  Structure  of  striped  muscle.* 

128  Transverse  section  of  the  brachial  biceps.     Frey. 

129  Transverse  section  of  a  fascicle  of  the  cremaster.* 

130  Muscle-fibrils  from  the  axolotl.     Kolliker. 

131  Muscle-fibre  from  a  salamander.* 

132  Striated  muscle-tissue  from  the  walls  of  the  heart.* 

133  Plexus  of  non-medullated  nerve-fibres.     Frey. 

134  A  motorial  end-plate.     Ibid. 

135  Muscles  of  the  head  and  neck.     Sappey. 

136  The  temporal  muscle.     Bonamy  $  Beau. 

137  Interior  part  of  the  left  side  of  the  face.     Jamain. 

138  Front  view  of  the  muscles  of  the  neck.     Wilson. 

139  Deep  muscles,  front  of  the  neck.     Sappey. 

140  Inferior  view  of  the  diaphragm.     Wilson. 

141  Muscles  of  the  front  of  the  thorax  and  abdomen.     Ibid. 

142  Left  side  of  abdomen.     Ibid. 

143  The  inguinal  canal.* 

144  Muscles  of  the  back.     Wilson. 

2 


18  LIST  OF   ILLUSTRATIONS. 

FIG. 

145  Deep  muscles  of  the  back.      Wilson. 

146  Muscles  of  the  front  of  the  trunk.     Ibid. 

147  Muscles  of  the  back  of  the  scapula.     Bonamy  $•  Beau. 

148  Muscles  of  the  front  of  the  scapula.     Ibid. 

149  The  deltoid  muscle.     Ibid. 

150  Muscles,  fore  part  of  the  arm.      Wilson. 

151  The  brachial  triceps.     Ibid. 

152  Superficial  muscles,  front  of  the  forearm.     Ibid. 

153  Deep  muscles,  front  of  the  forearm.     Ibid. 

154  Metacarpal  bone,  phalanges,  tendons,  and  ligaments.     Sharpey  $  Quain. 

155  Muscles,  back  of  the  forearm.     Wilson. 

156  Deep  muscles,  back  of  the  forearm.     Ibid. 

157  Muscles,  palmar  surface  of  the  hand.     Ibid. 

158  Femoral  fascia.* 

159  Muscles  of  the  thigh,  front  and  outer.      Wilson. 

160  Muscles  of  the  buttock.     Ibid. 

161  Muscles,  back  of  buttock  and  thigh.     Ibid. 

162  Muscles,  front  of  leg  and  dorsum  of  foot.     Ibid. 

163  Superficial  muscles,  back  of  leg.     Ibid. 

164  Deep  muscles,  back  of  leg.     Ibid. 

165  Muscles,  sole  of  foot.     Ibid. 

166  Deep  muscles,  sole  of  foot.     Ibid. 

167  Kelative  position  of  anatomical  elements  in  serous  and  mucous  membranes, 

glands,  lungs,  and  skin.* 

168  Pavement  epithelium.* 

169  Mucous  membrane  of  small  intestine,  vertical  section.* 

170  Columnar  epithelium.* 

171  Vertical  section  of  bronchial  mucous  membrane.* 

172  Columnar  epithelium.* 

173  Polyhedral  epithelium.* 

174  Section  of  submaxillary  gland.     Frey. 

175  Stratified  epithelium,  corneal  conjunctiva.* 

176  Epithelium  of  urinary  bladder.* 

177  Squamous  epithelium.* 

178  The  relations  of  the  pleura  illustrated.* 

179  Peritoneal  surface  of  the  diaphragm.* 

180  Simple  tubular  glands.* 

181  Simple  follicular  gland.* 

182  Compound  tubular  gland.* 

183  Compound  follicular  gland.* 

184  Simple  tubular  gland  convoluted.* 

185  Gland  of  complex  form.* 

186  Gland  of  complex  form.* 

187  Gland  of  complex  character.* 

188  A  racemose  gland.* 

189  Posterior  mediastinum  and  lungs.     Sappey. 

190  Abdominal  cavity  and  viscera.      Wilson. 

191  Vertical  section  of  abdomen ;  apparent  arrangement  of  the  course  of  the  peri- 

toneum.* 

192  Course  of  the  peritoneum  in  the  foetus.* 

193  The  abdominal  viscera.* 

194  Section  of  mouth,  nose,  pharynx,  and  larynx.     Sappey. 

195  A  follicular  lymphoid  gland.     Kolliker. 


LIST   OF   ILLUSTRATIONS.  19 

FIG. 

196  Muscles  of  the  palate.     Bonamy  $  Beau. 

197  Dorsum  of  the  tongue.     Sappey. 

198  Papillae  of  taste.* 

199  Side  view  of  muscles  of  tongue.     Bonamy  $•  Beau. 

200  Section  of  the  submaxillary  gland.     Frey. 

201  Permanent  teeth,  exterior  view.* 

202  Permanent  teeth,  lateral  view.* 

203  Molar  teeth,  triturating  surface.* 

204  Temporary  teeth.* 

205  Vertical  section  of  a  molar  tooth.* 

206  Vertical  section,  fang  of  a  canine  tooth.* 

207  Section  of  dentine.* 

208  Crown  of  a  canine  tooth.* 

209  Three  enamel  columns.* 

210  Section  of  enamel.* 

211  Development  of  the  teeth.     After  Goodsir,  Kolliker. 

212  Development  of  the  teeth  in  the  pig.     Frey. 

213  Vertical  section  of  the  germ  of  a  molar.     Ibid. 

214  Muscles  of  the  pharynx,  posterior  view.      Wilson. 

215  Muscles  of  the  pharynx,  side  view.     Ibid. 

216  The  abdominal  viscera.     Ibid. 

217  Mucous  membrane  of  the  stomach.     Sappey. 

218  Mammillae  of  mucous  membrane  of  the  stomach.     Ibid. 

219  Gastric  glands  in  mucous  membrane.* 

220  A  gastric  gland.* 

221  Cardiac  gastric  gland  of  the  dog.* 

222  Bottom  of  a  gastric  gland.* 

223  Columnar  epithelium.* 

224  Columnar  epithelium  from  an  intestinal  villus.     Frey. 

225  Portion  of  mucous  membrane  from  the  jejunum.* 

226  Portion  of  mucous  membrane  from  the  ileum.* 

227  Structure  of  mucous  membrane  from  the  ileum.* 

228  Portion  of  the  duodenum.     Sappey. 

229  Vertical  section  of  the  duodenum.* 

230  Portion  of  mucous  membrane,  upper  part  of  the  ileum.     Sappey. 

231  Portion  of  the  ileum,  from  without ;  agminated  glands.     Ibid. 

232  The  abdominal  viscera.     Ibid. 

233  The  caecum  and  ileo-colic  valve.     Morton. 

234  Mucous  membrane  of  the  colon.* 

235  Viscera,  upper  part  of  the  abdomen.     Sappey. 

236  The  liver,  inferior  surface.* 

237  Portions  of  the  liver  of  the  hog.     After  Kiernan,  Kolliker. 

238  Portions  of  the  liver  of  the  hog.     Ibid. 

239  Lobules  from  the  liver  of  the  rabbit.     Kolliker. 

240  Hepatic  cells.* 

241  Transverse  section  of  a  hepatic  lobule.* 

242  Commencement  of  bile-ducts  in  the  canaliculi.* 

243  Transverse  section  of  the  wall  of  an  artery.* 

244  A  small  branching  artery.     Frey. 

245  Elastic  tissue,  middle  coat  of  popliteal  artery.     Kolliker. 

246  TJnstriated  muscular  fibres,  from  the  middle  coat  of  an  artery.     Ibid. 

247  Endothelium  of  the  blood-vessels.* 

248  Transverse  section  of  the  wall  of  the  aorta.    Kolliker. 


20  LIST  OF  ILLUSTEATIONS. 

FIG. 

249  Valves  of  veins.     Morton. 

250  Structure  of  a  capillary  vessel.* 

251  Artery  passing  into  the  capillary  structure.     Kolliker. 

252  Red  blood-corpuscles.* 

253  "White  blood-corpuscles.     Frey. 

254  White  blood-corpuscles.     Ibid. 

255  Front  view  of  the  heart.* 

256  The  heart,  anterior  portion  of  ventricles  removed.* 

257  The  aorta.     Bourgery. 

258  Left  common  carotid  ;  external  and  internal  carotids.     Ibid. 

259  Arteries  of  the  interior  of  the  cranium.     Ibid. 

260  External  carotid  and  its  branches.     Ibid. 

261  Internal  maxillary  artery.     Ibid. 

262  Arteries  of  the  interior  of  the  cranium.     Ibid. 

263  The  axillary  artery.* 

264  Axillary  and  brachial  arteries.* 

265  Arteries  of  the  forearm.     Bourgery. 

266  Arteries  of  the  palmar  surface  of  the  hand.     Ibid. 

267  Arteries  of  the  palmar  surface  of  the  hand.     Ibid. 

268  The  aorta.     Ibid. 

269  The  cceliac  artery.      Wilson. 

270  Superior  mesenteric  artery.     Jamain. 

271  Inferior  mesenteric  artery.     Ibid. 

272  The  pelvis  and  its  viscera  and  arteries.     Ibid. 

273  The  perineum,  internal  pudic  artery.     Bourgery. 

274  Arteries  of  the  front  of  the  thigh.     Jamain. 

275  Arteries  of  the  back  of  the  thigh.     Ibid. 

276  Arteries  of  the  front  of  the  leg.     Ibid. 

277  Arteries  of  the  back  of  the  leg.     Ibid. 

278  Arteries  of  the  sole  of  the  foot.     Ibid. 

279  Veins  of  the  heart,  posterior  view.* 

280  Veins  of  the  thorax  and  abdomen.     Bourgery. 

281  Veins  of  the  head  and  neck.     Ibid. 

282  Sinuses  at  the  base  of  the  cranium.* 

283  Vertical  section  of  skull ;  veins  of  the  dura.* 

284  Superficial  veins  of  the  upper  limb.* 

285  Veins  of  the  thorax  and  abdomen.     Bourgery. 

286  Superficial  veins  of  the  back  of  the  leg.     Ibid. 

287  Superficial  veins  of  the  inner  part  of  lower  extremity.     Ibid. 

288  The  portal  system.* 

289  The  foetal  circulation.* 

290  Lymphatic  vessels  in  the  skin  of  the  ear.     Sappey. 

291  A  lymphatic  vessel  and  its  valves.* 

292  Endothelium  of  a  commencing  lymphatic.* 

293  Lymphatic  gland  and  vessels.* 

294  Lymphatic  gland,  small,  in  section.     Frey. 

295  Follicle  from  the  cortex  of  a  lymphatic  gland.     Ibid. 

296  Lymph-corpuscles.     Ibid. 

297  Lymph-corpuscles.     Ibid. 

298  The  great  lymphatic  trunks.     Bourgery. 

299  Lymphatics  of  the  head  and  neck.     Ibid. 

300  The  lungs,  anterior  view.     Sappey. 

301  The  lungs,  posterior  .view.     Ibid. 


LIST  OF  ILLU&TKATIONS.  21 

FIG. 

302  Portion  of  the  exterior  surface  of  an  inflated  lung.* 

303  Larynx,  trachea,  and  hronchi.     Richardson. 

304  Primary  lohules  of  the  lungs.* 

305  Primary  lobules  of  the  lungs.     Kolliker. 

306  Section  of  lung-tissue.* 

307  Capillary  nets  of  the  air-cells.     Kolliker. 

308  The  larynx,  front  view.     Sappey. 

309  The  larynx,  hack  view.     Ibid. 

310  The  larynx,  muscles  of.* 

311  The  vocal  memhrane.* 

312  Inner  view  of  the  larynx.     Sappey. 

313  The  kidney,  longitudinal  section.* 

314  Uriniferous  tuhules.* 

315  Structure  of  the  kidneys.* 

316  Epithelium  of  the  ureter.* 

317  Male  pelvis  and  its  contents.      Wilson. 

318  Part  of  the  hladder  and  penis.     Ibid. 

319  Vertical  section  of  bladder  and  penis.* 

320  Transverse  section  of  penis.      Weber. 

321  Part  of  the  bladder  and  penis,  the  urethra  laid  open  from  above.      Wilson. 

322  Transverse  section  of  the  testicle.     Kolliker. 

323  Testicle,  with  the  vaginal  tunic  laid  open.     Quain  $•  Sharpey. 

324  Testicle  deprived  of  its  tunics.     After  Arnold,  Kolliker. 

325  Portion  of  a  seminiferous  tubule.     Kolliker. 

326  Posterior  view  of  the  fundus  of  the  bladder.     Cruveilhier. 

327  Spermatozoa.     Kolliker. 

328  Section  of  female  pelvis.     Schmidt. 

329  Female  organs  of  generation.     Sappey. 

330  External  organs  of  generation.* 

331  Virgin  uterus  at  maturity.* 

332  Uterus  which  has  given  childbirth.* 

333  Muscle-fibre  cells  of  the  uterus.     Kolliker. 

334  Ovary,  parovarium,  and  oviduct,  left  side.* 

335  Transverse  section  of  an  ovary.     Kolliker. 

336  Section  of  an  ovary  of  the  rabbit.     Frey. 

337  Human  ovum.     Kolliker. 

338  Two  corpora  lutea.     Ibid. 

339  Milk-duct  and  lobules  of  the  mammary  gland.* 

340  Alveolus  of  the  mammary  gland.* 

341  Corpuscles  observed  in  milk.     Kolliker. 

342  View  of  the  perineum.     Bourgery. 

343  Diagram  of  the  termination  of  a  capillary  vessel  in  the  splenic  pulp.* 

344  Small  branch  of  the  splenic  artery,  with  lymphoid  nodules,  from   the   dog 

Kolliker. 

345  Portion  of  the  thyroid  body,  in  section.     Ibid. 

346  One  lobe  of  the  thymus  laid  open.     Ibid. 

347  Section  of  a  lobule  of  the  thymus  body.* 

348  Section  of  the  cortical  substance  of  a  suprarenal  body.     Kolliker. 

349  Cells  from  a  suprarenal  body.     Ibid. 

350  Structure  of  nerve-fibres.*  . 

351  A  medullated  nerve-fibre.* 

352  Mode  of  branching  of  a  medullated  nerve-fibre.* 

353  Portion  of  a  sympathetic  nerve.     Frey. 


22  LIST  OF   ILLUSTRATIONS. 

FIG. 

354  Nerve-cells  from  the  brain.     Frey. 

355  Transverse  section  of  the  small  sciatic  nerve  of  a  calf.     Kolliker. 

356  The  anastomosis  and  branching  of  nerves.* 

357  Diagram  of  a  spinal  ganglion  and  its  connections*    Frey. 

358  Diagram  of  a  ganglion  of  the  sympathetic  nerve.     Ibid. 

359  Nerve-cells  from  the  semilunar  ganglion  of  the  trigeminal  nerve.     Kolliker. 

360  Medullated  nerve-fibres  of  the  white  matter  of  the  cerebrum.* 

361  The  spinal  cord  with  the  oblongata.     Sappey. 

362  Transverse  sections  of  the  spinal  cord.* 

363  Transverse  section  of  the  lumbar  enlargement  of  the  spinal  cord.* 

364  Transverse  section  of  a  portion  of  the  spinal  cord  at  the  entrance  of  the  anterior 

root  of  a  nerve.* 

365  Diagram  of  sections  of  the  spinal  cord.* 

366  Diagram  of  origin  of  a  spinal  nerve.* 

367  Base  of  the  brain.     After  Hirschfeld,  Sappey. 

368  Fore  part  of  the  pons  and  oblongata.     Ibid. 

369  View  back  of  the  pons  and  oblongata.     Ibid. 

370  Posterior  part  of  oblongata  and  floor  of  fourth  ventricle.* 

371  Horizontal  section  of  the  oblongata  at  the  upper  part  of  the  decussation  of  the 

pyramids.* 

372  Horizontal  section  of  the  oblongata.* 

373  Fore  part  of  the  pons  and  oblongata.     Sappey. 

374  Section  across  the  pons.* 

375  Section  across  the  upper  part  of  the  pons.* 

376  Eight  hemisphere  of  the  cerebellum.* 

377  Vertical  section  of  the  cortex  of  the  cerebellum.* 

378  Section  of  the  brain  along  the  great  longitudinal  fissure.     After  Hirschfeld, 

Sappey. 

379  Left  hemisphere  of  the  cerebrum  of  a  white  man,  outer  view.* 

380  Left  hemisphere  of  the  cerebrum  of  a  negro  male,  outer  view.* 

381  Under  surface  of  the  frontal  lobe  of  the  left  cerebral  hemisphere.* 

382  Eight  hemisphere  of  the  cerebrum  of  a  white  man,  inner  view.* 

383  Eight  hemisphere  of  the  cerebrum  of  a  negro  male,  inner  view.* 

384  Sections  across  the  cerebral  crura  and  quadrigeminal  body.* 

385  Transverse  section  of  the  cerebrum  on  a  level  with  the  callosurn.* 

386  Transverse  section  of  the  cerebral  hemispheres,  the  callosum  removed,  and  the 

lateral  ventricles  exposed.* 

387  Section  of  the  left  cerebral  hemisphere.* 

388  Transverse  vertical  section  of  the  right  hemisphere  of  the  cerebrum.* 

389  Transverse  vertical  section  of  the  left  hemisphere  of  the  cerebrum.* 

390  Striata,  thalami,  quadrigeminal  body,  and  cerebellum.     Hirschfeld,  Sappey. 

391  Horizontal  section  through  the  right  hemisphere  of  the  cerebrum.* 

392  Vertical  section  through  the  deeper  portion  of  the  cerebral  cortex.* 

393  Ependyma  of  the  ventricles.     Kolliker. 

394  Horizontal  section  of  the  spinal  cord,  showing  the  general  mode  of  the  distri- 

bution of  the  arteries.* 

395  Section  across  a  cerebral  convolution,  showing  the  arterial  arrangement.* 

396  Horizontal  section  of  the  oblongata ;  distribution  of  the  arteries.* 

397  Oculo-motor  and  abducent  nerve.     After  Hirschfeld,  Sappey. 

398  Trifacial  nerve.     Ibid. 

399  The  ophthalmic  ganglion  ;  outer  part  of  the  right  orbit  removed.     Ibid. 

400  Superior  maxillary  nerve ;  the  external  wall  of  the  left  orbit  and  of  the  maxilla 

removed.     Ibid. 


LIST   OF   ILLUSTRATIONS.  23 

FIG. 

401  View  of  the  spheno-palatine  ganglion,  the  outer  wall  of  the  left  nasal  cavity, 

and  the  olfactory  nerve.     After  Hirschfeld,  Sappey. 

402  Distribution  of  the  inferior  maxillary  nerve.     Ibid. 

403  The  otic  ganglion  and  its  connections.* 

404  The  facial  nerve.     After  Hirschfeld,  Sappey. 

405  The  last  four  cerebral  nerves,  the  facial  nerve,  the  sympathetic,  and  the  upper 

two  cervical  nerves.     Ibid. 

406  The  vagus  nerve.     Ibid. 

407  The  cervical  and  brachial  plexuses.* 

408  The  brachial  plexus.     After  Hirschfeld,  Sappey. 

409  Cutaneous  nerves  of  the  upper  extremity.     Ibid. 

410  Cutaneous  nerves  of  the  upper  extremity.     Ibid. 

411  Musculo-cutaneous,  median,  ulnar,  and  musculo-spiral  nerves.     Ibid. 

412  Musculo-cutaneous,  median,  ulnar,  and  musculo-spiral  nerves.     Ibid. 

413  Lumbar,  sacral,  and  coccygeal  plexuses.* 

414  Cutaneous  nerves  of  the  front  of  the  thigh.     After  Hirschfeld,  Sappey. 

415  Lumbar  plexus  and  its  branches.     Ibid. 

416  Peroneal  nerve  and  its  branches.     Ibid. 

417  Popliteal  nerve.     Ibid. 

418  The  sympathethic,  vagus,  and  other  nerves.     Ibid. 

419  The  sympathetic,  lumbar,  and  sacral  portions.     Ibid. 

420  Outer  wall  of  left  nasal  cavity.     Sappey. 

421  Portion  of  the  nose.     Ibid. 

422  Cartilages  of  the  nose.     Ibid. 

423  Vertical  section  of  the  nasal  mucous  membrane.     Kolliker. 

424  Nerves  of  the  partition  of  the  nose.     Sappey. 

425  Nerves  of  the  outer  wall  of  the  nasal  cavity.     Ibid. 

426  Left  eyebrow  and  lachrymal  glandj  inner  surface.     Ibid. 

427  Nerve  end-bulbs,  from  the  conjunctiva.     Frey. 

428  The  left  eye,  with  a  portion  of  the  eyelids  removed ;  lachrymal  canals  and  sac. 

Sappey. 

429  Muscles  of  the  eye.     Morton. 

430  Vertical  section  of  the  eyeball.     Sappey. 

431  The  choroidea  and  iris.     Ibid. 

432  Veins  of  the  choroidea  and  iris.     Ibid. 

433  View,  from  behind,  of  the  anterior  half  of  the  eyeball.     Ibid 

434  The  same  view,  with  the  lens  and  retina  removed.     Ibid. 

435  Segment  of  the  choroidea  and  iris,  inner  surface.     Ibid. 

436  Section  through  the  ciliary  region  of  the  eye.     Frey. 

437  Pigment-cells  of  the  uvea.     Kolliker. 

438  Arteries  of  the  iris.     Sappey. 

439  Vessels  of  the  ciliary  body  and  iris.     Kolliker. 

440  Eyeball,  with  sclerotica,  cornea,  choroidea.  and  iris  removed.     Sappey. 

441  Ketina,  seen  on  its  posterior  inner  surface.     Ibid. 

442  Vertical  sections  of  the  retina.     Frey. 

443  Kod  and  cone  layer  of  the  retina.* 

444  Kod  and  cone  from  the  retina.* 

445  Diagram  of  the  arrangement  of  the  structural  elements  of  the  retina.     Frey. 

446  Vertical  section  through  one  side  of  the  yellow  spot  and  central  fovea.* 

447  The  crystalline  lens.     Sappey. 

448  Crystalline  lens,  breaking  up  into  segments.     Ibid. 

449  Segment  of  the  crystalline  lens.     Ibid. 

450  Crystalline  lens  of  the  adult,  showing  the  arrangement  of  the  fibres.    Kolliker. 


24  LIST  OF   ILLUSTEATIONS. 

FIG. 

451  Fibres  of  the  crystalline  lens.* 

452  Diagram  of  the  blood-vessels  of  the  eye.     Frey. 

453  The  pinna.     Sappey. 

454  General  view  of  the  ear,  laid  open  from  the  front.     Ibid. 

455  Section  through  the  skin  of  the  auditory  meatus.     Kolliker. 

456  Section  across  the  pyramid  of  the  left  temporal  bone.* 

457  Cavity  of  the  tympanum.     Sappey. 

458  Ear  ossicles.     Ibid. 

459  Cribriform  plate  of  the  left  internal  auditory  meatus.* 

460  Internal  ear  laid  open.     Sappey. 

461  Nerves  of  the  vestibule  and  semicircular  canals.     Ibid. 

462  Distribution  of  the  cochlear  nerve.     Ibid. 

463  The  right  labyrinth.* 

464  Interior  of  the  vestibule,  superior  and  posterior  semicircular  canals.* 

465  The  cochlea,  laid  open  ;  its  summit  turned  upward.     Sappey. 

466  The  cochlea,  laid  open  and  viewed  from  its  summit.     Ibid. 

467  The  membranous  labyrinth.* 

468  Diagram  of  a  cross-section  of  a  semicircular  canal.* 

469  Diagram  of  acoustic  epithelium.* 

470  Otolites.* 

471  Diagram  of  a  cross-section  of  the  acoustic  crest  of  an  ampulla.* 

472  Diagram  of  a  cross-section  of  one  of  the  turns  of  the  cochlea.* 

473  Diagram  of  a  vertical  section  of  the  skin  of  the  forefinger.* 

474  Two  tactile  papillae.     Frey. 

475  Pacinian  corpuscles.* 

476  Diagram  of  the  epidermis,  with  a  tactile  papilla.* 

477  Corrugated  or  furrowed  cells  from  the  epidermal  rete.     Frey. 

478  Scurf  from  the  leg.* 

479  Fragment  of  dandruff  from  the  head.* 

480  Cells  from  the  epidermal  rete.* 

481  Bed  of  the  nail.     Sappey. 

482  Under  surface  of  the  nail.     Ibid. 

483  Vertical  section  of  the  end  of  a  finger.     Ibid. 

484  Transverse  section  through  the  nail  and  its  bed.     Kolliker. 

485  Cells  of  the  nail.     Ibid. 

486  Hair-follicle.     Ibid. 

487  Section  of  the  skin  of  the  scalp,  with  a  hair-follicle.* 

488  Portion  of  a  hair  from  the  outer  part  of  the  thigh.* 

489  Portion  of  the  shaft  of  a  light  hair.     Kolliker. 

490  Diagram  of  the  structure  of  the  root  of  a  hair  and  its  follicle.* 

491  Diagram  of  the  structure  of  a  transverse  section  of  a  hair  with  its  follicle.* 

492  Sebaceous  glands  opening  into  the  mouth  of  a  hair-follicle.     Todd  $•  Bowman. 

493  A  large  sebaceous  gland  from  the  nose.     Kolliker. 

494  Sebaceous  matter,  from  one  of  the  sebaceous  glands  of  the  nose.* 

495  Structure  of  the  sebaceous  glands.     Kolliker. 


AN 

ELEMENTARY  TREATISE 


ON 


HUMAN   ANATOMY 


CHAPTER  I. 

INTRODUCTION. 

Anatomy  is  the  name  given  to  a  knowledge  of  the  structure  of  or- 
ganized bodies,  which  are  distinguished  as  plants  and  animals.  Human 
anatomy,  the  subject  of  the  present  work,  applies  to  the  description  of 
the  structure  of  the  human  body. 

Man  is  an  animal,  and  belongs  to  the  principal  division  of  the  ani- 
mal kingdom  named  the  vertebrates,1  primarily  distinguished  from 
other  principal  divisions  by  the  possession  of  an  internal  skeleton  with  a 
median  axis,  which  is  usually  divided  into  transverse  segments  called 
vertebrae.  These  and  other  parts  of  the  skeleton  mostly  consist  of 
bones,  with  cartilages  and  ligaments.  The  vertebral  axis  or  column, 
more  familiarly  known  as  the  spine,  is  enclosed  within  the  trunk  of 
the  body  and  tapers  away  in  the  tail.  To  its  opposite  extremity  is 
appended  the  skull,  usually  composed  of  bones.  The  spine  and  skull 
contain  the  spinal  cord  and  brain,  from  which  emanate  the  nerves,  in 
pairs,  distributed  to  the  muscles,  the  skin,  and  the  organs  of  special 
sense.  Within  the  trunk  of  the  body  are  contained,  for  the  most  part, 
the  alimentary,  respiratory,  and  genito-urinary  apparatus,  and  the 
chief  organs  of  the  circulation  of  the  blood. 

Among  vertebrates  man  belongs  to  the  class  of  mammals,  of  which 
the  primary  distinctive  character  is  the  possession  of  mammae,  or  milk- 
glands,  important  organs  in  the  female  sex,  but  rudimentary  in  the  male. 
Highest  of  mammals  is  the  order  of  the  primates,  to  which  belong 
.both  man  and  monkeys,  whose  primary  distinction  is  the  possession  of 
thumbs  ;  that  is  to  say,  the  first  digits  opposed  to  the  others,  in  one  or 
both  pair  of  limbs,  adapting  them  as  organs  of  prehension,  or  instru- 
ments for  taking  hold  of  things. 

1  Vertebrata. 

25 


26  INTRODUCTION. 

Man  is  distinguished  among  primates  as  a  separate  genus,  strikingly 
characterized  from  the  rest,  and  indeed  from  all  other  vertebrates,  by 
the  habitually  erect  position  of  the  body,  which  is  supported  alone  by 
the  pelvic  limbs,  used  in  progression,  while  the  pectoral  limbs,  entirely 
relieved  from  this  office,  are  devoted  to  prehension.  Thus,  under  the 
most  favorable  conditions,  man  is  endowed  with  instruments  which 
give  him  capabilities  far  exceeding  those  of  other  animals. 

While  the  anatomy  of  man,  in  the  kind,  number,  and  construction 
of  the  organs,  nearly  accords  with  that  of  the  higher  monkeys,  as  ex- 
emplified in  the  gorilla,  orang,  chimpanzee,  and  gibbon,  it  is  more  or 
less  varied,  as  it  is  also  among  these,  in  accordance  with  requirements 
related  to  differences  in  the  habits  and  conditions  of  each. 

Naturalists  generally  regard  all  the  observed  kinds  of  man,  or 
the  genus  homo,  as  of  one  species,  distinguishing  them  as  varieties. 
The  most  striking  of  these  are  the  white,  Mongolian,  and  negro ;  the 
others  being  less  obviously  marked.  All,  under  ordinary  circumstances, 
retain  their  distinctive  marks,  which  are  perpetuated  from  generation 
to  generation,  and  only  through  sexual  intermixture  do  they  produce 
hybrid  offspring  of  intermediate  character.  The  varieties,  or  races  as 
they  are  also  called,  are  mainly  distinguished  by  differences  in  the 
color  of  the  skin,  the  character  of  the  hair,  exact  conformation  of  the 
features  and  skull,  degree  of  development  of  the  brain,  and  in  the 
less  evident  variation  of  other  parts.  Independent  of  these  differ- 
ences, the  anatomy  of  the  races  of  men  is  so  nearly  alike  that  for  the 
ordinary  purposes  of  the  physician  and  surgeon  it  may  be  regarded 
as  identical. 

Descriptive  or  special  anatomy  applies  to  the  description  of  the 
distinct  parts  or  organs  of  the  human  body,  or  that  of  any  other  ani- 
mal, examined  as  relates  to  their  shape,  position,  connections,  structure, 
and  other  characters.  When  organs  of  the  same  kind  are  investigated 
in  consecutive  order,  as  the  bones,  the  muscles,  etc.,  the  study  is  called 
systematic  anatomy ;  and  when  they  are  examined  in  their  relative 
position  in  particular  regions,  it  is  topographical  or  regional  anat- 
omy, often  also  called  surgical  anatomy  from  its  importance  in  the 
operations  of  surgery.  An  account  of  the  origin  and  development  of 
the  animal  and  its  organs  constitutes  embryology.  To  the  knowledge 
of  the  materials  of  structure  or  the  tissues  is  applied  the  name  of  his- 
tology or  general  anatomy. 

Animals,  and  likewise  plants,  except  the  simplest  forms,  are  com- 
posed of  distinct  parts  or  organs,  which  are  instruments  adapted  to 
the  various  purposes  of  life.  The  organs  are  composed  of  different 
materials,  which  in  many  cases  resemble  artificial  woven  fabrics,  and 
are  hence  in  general  called  the  tissues. 

The  tissues  of  the  human  body  may  be  classified  according  to  their 
general  character  under  the  following  principal  groups,  though  it  must 
be  understood  that,  while  some  are  clearly  distinct,  they  mostly  com- 


INTRODUCTION.  27 

prise  widely  different  varieties,  and  in  some  cases  they  more  or  less 
gradate  into  one  another  : 

Corpuscular  tissue.      Of  the  blood  and  lymph ;  of  the  solid  lym- 
phatic structures ;  of  the  spleen  ;  and  of  the  red  marrow  of  the  bones. 

Epithelial  tissue.     Epithelium  of  mucous  membranes  and  glandular 
structures ;  the  epidermis  and  its  appendages ;  and  endothelium. 

Connective  tissue.     Fibro-connective  tissue ;  elastic  tissue ;  adipose 
tissue ;  and  the  neuroglia. 

Cartilaginous  tissue.     Cartilage  and  its  varieties. 

Osseous  tissue.     Bone.  » 

Muscular  tissue.     Muscle  or  flesh,  striated  and  unstriated. 

Nervous  tissue.     Nerve-cells  and  nerve-fibres. 

In  most  of  the  organs  a  single  tissue  predominates  and  is  charac- 
teristic of  the  organ,  as  thus  the  bones  are  mainly  composed  of  osseous 
tissue  and  the  muscles  of  muscular  tissue,  though  both  contain  propor- 
tions of  several  other  tissues.  In  organs  composed  of  two  or  more 
principal  tissues,  each  of  these  as  a  rule  maintains  its  continuity ;  thus, 
in  the  walls  of  the  blood-vessels  and  the  intestines,  the  like  tissues  are 
continuous  throughout.  The  different  tissues  are  composed  of  charac- 
teristic particles  or  units,  which  are  called  their  structural  elements. 
These  exhibit  much  variety  of  form  and  structure,  both  physically  and 
chemically,  but  all  are  derived,  through  more  or  less  transformation, 
from  a  common  structural  element,  which  from  the  universality  of  its 
existence  as  the  basis  of  structure  of  organized  bodies,  both  plant  and 
animal,  is  named  the  organic  cell.  The  primitive  or  typical  form 
of  this  element  is  a  sphere,  and  is  exempli- 
fied by  a  colorless  blood-corpuscle,  a  resting 
amoeba,  a  protococcus,  or  the  primitive  ovum, 
or  egg,  of  animals. 

In  the  corpuscular  and  epithelial  tissues, 
and  to  a  variable  degree  in  most  others,  the 
organic  cell  retains  so  much  of  its  original 
character  that  it  is  readily  recognized  as 
the  structural  element  of  the  tissue  at  all 
times.  In  the  production  of  some  of  the 

*  THE  ORGANIC  CELL.    1,  2,  a  par- 

tlSSUeS  the  Cell  undergoes  more  Or  less  trans-  asitic  amoeba  of  the  cockroach, 
formation  which  proportionately  obscures  its  magnified  ieo  diameters,  i,  in 

.    .      ,  , . . .          ,  the  quiescent  state :   2,  in  move- 

ongmal  condition,  but  mostly  the  cell  char-  ment  3>  4>  a  coioriess  biood-cor- 
acter  of  the  structural  element  may  readily  pnscie,  soo  diameters.  3,  quies- 

i        j    ,       ,    j         -r  „    ,,         ,.  ,,          cent;  4,  in  movement. 

be  detected,      in    some  of  the   tissues  the 

cells  become  greatly  elongated  and  assume  the  form  of  fibres,  rods, 
or  tubes,  and  become  otherwise  altered  in  both  physical  and  chemical 
composition,  as  exemplified  in  fibro-connective  and  muscular  tissue,  in 
capillary  vessels,  and  in  nerve-fibres. 

The  cellular  elements  of  solid  tissues  are  connected  together  by  an 
intervening,  homogeneous,  cementing  substance.     This  intercellular 


28  INTRODUCTION. 

substance  is  usually  in  so  small  a  quantity  as  to  be  inconspicuous, 
but  sometimes,  as  strikingly  observed  in  cartilage,  is  comparatively 
abundant,  when  the  cells  appear  embedded  in  a  matrix.  It  is  acted  on 
by  certain  reagents  differently  from  the  cells  ;  and  thus  the  application 
of  silver  nitrate  to  an  endothelium,  by  staining  the  cement,  distinctly 
outlines  the  cells. 

The  simplest  of  animals,  the  protozoa,  are  single-celled  organisms, — 
that  is  to  say,  consist  essentially  of  single  or  isolated  cells, — and  such, 
likewise,  is  the  case  with  the  circulating  corpuscles  of  the  blood  and 
lymph  of  higher  animals.  All  plants  and  animals,  with  the  exception 
of  the  simplest  kinds  or  unicellular  forms,  are  built  up  of  aggregations 
of  similar  cells  or  structural  elements  derived  from  the  transformation 
of  cells,  and  being  thus  composed  are  distinguished  as  organized 
bodies,  the  highest  forms  of  which  consist  of  almost  incalculable 
aggregations  of  organic  cells. 

The  organic  cell,  now  recognized  as  the  common  physical  element 
of  organization  or  of  the  structure  of  plants  and  animals,  is  in  general 
microscopic.  In  a  few  plants  it  is  sufficiently  large  to  be  distinguished 
by  the  unaided  eye,  as  exemplified  in  the  houseleek  (Sempervivum)  and 
eel-grass  (  Vallisneria) ;  and  rarely  it  reaches  a  large  size,  as  in  Cham,  in 
which  it  grows  to  an  inch  or  more  in  length.  Commonly  it  is  other- 
wise, as  in  the  lowest  plants  exemplified  by  the  fission-fungi,  Schizo- 
mycetes,  to  which  belong  the  bacteria.  The  forms  are  of  such  exceeding 
minuteness  as  to  be  recognizable  only  through  the  aid  of  the  highest 
powers  of  the  microscope.  In  man  and  other  animals  of  his  class  the 
cells  rarely  exceed  one  three-hundredth  of  an  inch,  and  more  com- 
monly they  approach  only  a  tenth  of  that  size. 

The  organic  cell  in  its  primitive  condition,  or  prior  to  any  change 
it  may  undergo  in  the  production  of  different  tissues,  is  composed  of  a 
peculiar  complex  chemical  substance  distinguished  as  protoplasm. 

In  the  production  of  the  tissues  the  cell  may  retain  its  original  form 
and  constitution,  or  it  may  undergo  transformation  to  a  variable  degree, 
both  physically  and  chemically.  The  cell  almost  constantly  contains  a 
conspicuous  spherical  or  oval  body  among  the  contents,  which  is  named 
the  nucleus,  and  this  also  is  composed  of  a  variety  of  protoplasm. 
Many,  if  not  most,  cells,  in  advancing  to  maturity,  in  the  production 
of  the  various  tissues,  acquire  a  membranous  investment  called  the 
cell-wall,  which  is  due  to  a  partial  solidification  or  coagulation  of  the 
superficial  protoplasm ;  and  through  this  wall,  in  the  solid  tissues,  the 
contiguous  cells  become  more  or  less  firmly  united  together.  The  cell- 
wall  was  formerly  regarded  as  an  essential  constituent  of  the  organic 
cell ;  but  it  has  been  ascertained  that  in  young  and  growing  cells,  and 
in  many  others,  at  least,  in  their  more  active  state,  no  such  envelope 
exists,  though  some  of  the  authorities  consider  it  to  be  present  in  a 
condition  of  extreme  tenuity.  As  examples,  it  appears  to  be  absent 
in  the  colorless  blood-  and  lymph-corpuscles,  the  secreting  cells  of  the 


INTRODUCTION.  29 

liver,  and  nerve-cells ;  on  the  other  hand,  it  is  very  evident  in  adipose 
cells,  and  in  the  mature  egg  it  is  called  the  vitelline  membrane. 

One  of  the  simplest  of  animal  organisms,  the  amoeba,  exemplifies 
an  isolated  organic  cell,  which  in  its  ordinary  condition  is  a  tiny  parti- 
cle of  fluent  and  contractile  protoplasm  with  an  internal  nucleus,  and 
with  no  membranous  covering.  In  this  state  the  microscopic  bit  of 
jelly  moves  about  from  place  to  place,  seizes  and  swallows  solid  food 
and  digests  it  and  rejects  the  waste  matter,  respires,  and  reproduces  itself. 
.  Under  certain  circumstances  the  amoeba  becomes  quiescent,  assumes  a 
spherical  form,  and  acquires  a  membranous  investment.  In  this  the 
encysted  or  resting  condition  the  amoeba  is  a  nucleated  cell  with  a  cell- 
wall.  Most  mature  vegetal  structures  exemplify  the  cell-structure,  in 
which  each  cell  is  enclosed  in  a  membranous  wall,  as  seen  in  the  section 
of  the  leaf  of  a  plant. 

Protoplasm,  the  material  of  composition  in  the  production,  de- 
velopment, and  growth  of  organized  bodies,  has  been  distinguished  as 
the  common  physical  basis  of  organization.  It  is  a  transparent  jelly, 
which  in  its  qualities,  both  physical  and  chemical,  resembles  albumen, 
as  exemplified  by  the  white  of  eggs.  It  is  more  or  less  viscid,  and  con- 
tains a  large  proportion  of  water;  which  liquid  it  also  readily  imbibes, 
but  appears  ordinarily  not  to  be  soluble  in  it.  It  is  homogeneous,  but 
commonly  exhibits  a  finely  granular  aspect,  though  the  granules  seem 
not  to  be  essential  to  its  constitution ;  and  wrhen  they  are  sufficiently 
large  to  show  the  action  of  reagents,  they  mostly  prove  to  have  a  dif- 
ferent chemical  composition.  The  granules  often  appear  as  fat-mole- 
ules  or  more  or  less  conspicuous  oil-globules,  and  these  at  times  may 
completely  replace  the  protoplasm,  as  in  the  production  of  the  cells  of 
adipose  tissue.  In  vegetal  cells  the  granules  often  appear  as  drops 
of  oil,  starch-grains,  and  other  substances,  and  sometimes  in  the  form 
of  crystals. 

Recent  observations  would  appear  to  indicate  that  the  protoplasm, 
notwithstanding  its  diffluent  character,  is  not  actually  homogeneous, 
but  consists  of  a  more  tenacious  fibrillar,  reticular,  or  spongy  basis,  with 
the  interstices  occupied  by  a  more  liquid  or  fluent  material;  and  it  has 
been  explained  that  the  ordinary  granular  aspect  of  protoplasm  is  due 
to  the  optical  section  of  the  fibrillar  material.  In  addition  to  this  gen- 
eral constitution,  the  protoplasm  often  encloses  true  granules  of  varia- 
ble size  and  constitution.  There  often,  also,  appear  in  it  clear  globules, 
or  spherical  spaces  filled  with  liquid,  and  named  vaeuoles. 

The  most  remarkable  physiological  character  of  living  protoplasm 
in  its  active  state  is  its  quality  of  motility,  exhibited  in  contraction  and 
extension,  as  strikingly  observed  in  the  movements  of  the  amoeba,  and 
only  in  a  less  obvious  manner  in  the  colorless  blood-corpuscles. 

The  nucleus  of  the  organic  cell,  a  most  constant  element  though  not 
always  persistent,  is  a  spherical  or  oval  body,  which  usually  occupies 
a  position  at  or  near  the  centre  of  the  protoplasmic  mass.  Generally 


30  INTRODUCTION. 

single,  sometimes  several  occupy  the  same  cell.  The  white  blood- 
corpuscles  often  contain  two  or  three  nuclei,  and  the  giant-cells  of 
the  bone-marrow  contain  many.  The  nucleus  is  ordinarily  defined  by 
a  thin  membranous  wall,  and  appears  also  to  have  a  similar  constitu- 
tion to  the  surrounding  protoplasm ;  consisting  of  a  reticular  structure 
with  a  more  fluent  material,  and  named  the  nucleoplasm. 

Within  the  nucleus  there  is  very  constantly  to  be  seen  a  clear  and 
highly  refractive  spherule,  the  nucleolus,  regarded  as  a  central  ac- 
cumulation of  the  reticular  nucleoplasm.  Not  unfrequently  several 
nucleoli  are  contained  within  the  nucleus. 

Though  the  nucleus  exhibits  a  constitution  similar  to  that  of  the 
surrounding  cell  protoplasm,  it  is  not  identical  in  chemical  composition ; 
for  dilute  acids,  which  commonly  dissolve  the  latter,  do  not  act  in  the 
same  manner  on  the  nucleus.  Further,  certain  reagents,  as  hsema- 
toxylon,  stain  it  more  intensely,  and  while  gold  chloride  colors  the 
cell  protoplasm,  it  does  not  affect  the  nucleus  in  this  way. 

From  the  phenomena  observed  in  cell  production  and  reproduction, 
the  nucleus  appears  to  be  the  starting-point  of  the  action  which  results 
in  the  division  and  multiplication  of  the  cell.  In  mature  structures  the 
cell  contents  exhibit  a  great  variety  in  physical  and  chemical  constitu- 
tion, and  the  nucleus  ordinarily  appears  of  uniform  character  and  inert; 
and  only  in  the  reproduction  of  the  cell  does  it  appear  as  an  active 
agent. 

In  the  production  and  development  of  the  tissues  through  cells, 
these  are  commonly  multiplied  or  reproduced  through  the  division  or 
segmentation  of  a  pre-existing  cell.  The  original  cell,  exemplified  by 
the  primitive  egg  of  animals,  divides  into  two,  and  these  then  divide 
each  into  two,  and  in  the  same  manner  the  multiplication  proceeds 
until  the  whole  are  produced  in  the  development  of  the  animal,  and 
subsequently  throughout  its  life  in  the  renewal  of  the  cell  elements  of 
its  structure. 

The  reproduction  of  the  cell  commences  with  a  series  of  remarkable 
changes  in  the  nucleus,  the  phenomena  of  which  have  been  named 
karyokinesis ;  and  the  progress  of  research  appears  to  indicate  that 
the  process  is  essentially  the  same  in  both  plants  and  animals.  In  this 
wonderful  process  the  nucleus,  as  it  were,  seems  to  awake  from  its 
resting  condition,  and  gradually  assumes  the  appearance  of  a  tangled 
skein  of  contorted  threads  embedded  in  a  clearer  matrix,  from  which 
the  nuclear  wall  has  melted  away,  but  which  still  remains  distinct 
from  the  surrounding  cell  protoplasm.  The  nuclear  skein  then  changes 
to  the  form  of  a  rosette,  and  this,  by  the  breaking  of  the  peripheral 
threads,  to  that  of  a  star.  This  afterwards  becomes  successively 
barrel-shaped,  and  then  more  elongated  and  spindle-shaped.  The 
spindle  next  divides  at  the  equator  into  two  portions,  which  sepa- 
rate and  recede  from  each  other  towards  the  poles  of  the  nucleus, 
where  they  gradually  acquire  the  form  of  the  resting  nucleus  from 


INTRODUCTION.  31 

which  they  started.  With  the  division  of  the  nuclear  skein  its  matrix 
is  constricted,  and  finally  the  nucleus  is  completely  divided.  At  the 
same  time  the  surrounding  cell  protoplasm  likewise  undergoes  con- 
striction and  division,  and  thus  ultimately  two  cells  are  produced,  each 
with  its  nucleus.  In  the  further  reproduction  of  cells  the  same  steps 
are  repeated,  and  the  process  may  start  in  the  new  pair  of  nuclei  before 
the  complete  separation  of  their  cells.  The  new  cells  produced  by 
segmentation  are  often  called  the  daughter-cells,  in  contradistinction 
to  that  from  which  they  are  derived,  which  is  named  the  mother- 
cell.  The  former  are  smaller  than  the  latter,  but  quickly  grow  to  the 
mature  size,  when  the  act  of  karyokinesis  may  be  repeated  and  new 
cells  formed,  and  finally  they  may  remain  without  further  change,  or 
they  may  undergo  more  or  less  transformation  in  the  production  of 
the  various  tissues. 

It  is  generally  admitted  as  the  result  of  all  observation  that  all  cells 
are  derived  from  pre-existing  cells,  and  hence  the  axiom,  "omnis  cellula 
e  cellulis,"  The  primitive  germ  of  plants  and  the  primitive  ovum  of 
animals  is  a  single  cell,  and  from  this  are  derived  all  the  cells  which, 
unchanged  or  variably  metamorphosed,  compose  the  structural  ele- 
ments of  the  tissues  and  organs  of  all  plants  and  animals. 

The  simplest  and  minutest  living  bodies  are  unicellular  organisms, 
as  exemplified  by  an  amoeba  among  animals,  and  these  exhibit  in  a 
wonderful  manner  all  the  phenomena  which  distinguish  life  in  the 
most  complex  organisms,  plants,  and  animals.  These  consist  of  an 
aggregation  of  similar  cell  elements  with  similar  qualities,  each  in  a 
measure  acting  independently  but  in  concert  with  one  another.  In 
the  course  of  development  from  the  cell  which  constitutes  the  primi- 
tive ovum,  in  the  production  of  the  various  tissues  and  organs  the 
cells  become  widely  differentiated  in  shape,  chemical  and  physical 
composition,  and  qualities.  Certain  cells  become  comparatively  inert 
and  subserve  mechanical  purposes,  as  in  the  structural  elements  of 
cartilages,  bones,  and  connective  tissues  ;  others  become  special  agents 
of  motor  power,  as  in  the  muscles ;  others  active  chemical  agents,  as  in 
the  glandular  organs ;  others  as  the  subtle  agents  of  nerve  power ;  and 
some  as  superlative  in  the  power  of  reproduction  for  the  maintenance 
of  the  species. 


OHAPTEE  II. 

GENERAL  ANATOMY  OP  THE  SKELETON. 

The  skeleton  is  the  hard  framework  of  the  body,  to  which  it  con- 
forms in  general  shape  and  construction  and  gives  stability.  It  affords 
a  basis  of  support  to  the  softer  structures,  forms  cases  for  the  protec- 
tion of  delicate  and  important  organs,  gives  attachment  to  muscles, 
and  provides  levers  of  movement.  The  parts  of  which  it  consists  are 
the  bones,  with  a  few  cartilages,  all  connected  together  by  ligaments. 
The  bones  are  closely  invested  with  a  fibrous  membrane,  the  perios- 
teum, except  on  their  articular  surfaces,  where  cartilage  or  fibro- 
cartilage  is  substituted.  They  are  everywhere  pervaded  by  blood- 
vessels, and  the  cavities  of  their  interior  structure  are  occupied  by  the 
marrow  or  medulla.  When  the  softer  adherent  parts  are  removed, 
the  dry  bones  are  in  the  most  convenient  condition  for  ordinary  study. 

The  number  of  bones  in  the  skeleton  depends  upon  what  we  may 
regard  as  such,  for  the  number  of  pieces  varies  at  different  periods  of 
life,  and  each  is  not  in  all  cases  viewed  as  a  distinct  bone  by  the  anato- 
mist. Some  pieces  are  single  and  distinct  bones  from  their  earliest 
appearance  to  the  end  of  life,  but  most  named  bones  are  derived  from 
a  variable  number  of  pieces,  which  are  produced  at  different  periods 
before  and  after  birth,  and  successively  unite  at  different  times  before 
they  are  complete.  Even  after  maturity  many  bones  regarded  as  dis- 
tinct become  ankylosed,  and  in  this  way,  in  advanced  age,  the  entire 
skull,  with  the  exception  of  the  mandible,  may  become  a  single  bone. 

The  bones  which  are  more  persistent  as  single  pieces,  and  which  are 
named  and  described  as  such,  are  as  follows : 

Bones. 
For  the  spine,  including  24  vertebrae,  the  sacrum  and  coccyx,  together  with 

12  pairs  of  ribs  and  the  sternum 51 

For  the  skull,  22,  together  with  the  hyoid  and  6  ear  ossicles 29 

For  the  upper  limbs,  in  each  34 68 

For  the  lower  limbs,  in  each  33 66 

214 

The  number  of  distinct  osseous  pieces  at  the  time  of  birth  is  278 ; 
at  the  age  of  twenty -five  years,  regarded  as  maturity,  224 ;  the  whole 
number  at  all  periods,  approximatively,  668 ;  and  in  advanced  old  age 
normally  reduced  to  194. 

The  bones  are  mostly  in  pairs,  as  those  of  the  limbs,  the  ribs,  and 
32 


GENERAL  ANATOMY  OF  THE  SKELETON.  33 

most  of  those  of  the  skull ;  the  others  are  single  and  symmetrical,  or 
consist  of  like  halves,  as  those  of  the  vertebral  column,  the  sternum, 
the  hyoid,  and  several  of  the  skull. 

The  bones  exhibit  a  great  variety  in  size,  shape,  and  proportions, 
though  most  are  referable  to  a  few  general  forms,  which  are  usually 
distinguished  as  long,  short,  and  broad,  while  others  are  of  a  mixed 
character,  and  mostly  irregular.  The  long  bones,  like  most  of  those 
of  the  limbs,  have  the  length  conspicuously  exceeding  the  other  meas- 
urements. They  commonly  possess  a  cylindroid  or  primitive  shaft  or 
body,  with  expanded  extremities,  of  which  that  nearest  the  spine,  or 
central  axis  of  the  skeleton,  is  the  proximal,  and  the  other  the  distal 
extremity.  The  short  bones,  exemplified  by  those  of  the  wrist  and 
ankle,  differ  little  in  their  diameters.  The  broad  bones,  as  those 
of  the  cranial  vault,  the  scapula,  and  the  hip,  are  conspicuously  broad. 
Irregular  bones,  partaking  of  the  characters  of  the  others,  are  ex- 
emplified by  the  sphenoid  bone  and  the  vertebra. 

Any  projection  of  a  bone  is  a  process  or  an  apophysis.  If  it 
has  an  articular  surface,  mostly  smooth,  it  is  an  articular  process ; 
and  this,  usually  from  its  relative  position  and  rounded  shape,  is  often 
called  a  head.  A  pair  of  similar  processes  on  the  same  plane  are 
termed  condyles.  An  obtuse  prominence  is  a  tubercle  or  a  tuber- 
osity.  A  long,  tapering  process  is  a  spine  or  a  spinous  process, 
though  the  same  term  is  sometimes  applied  to  a  tuberosity.  A  thick- 
ened border  of  a  bone  is  a  crest ;  a  slight  elevation  extended  along  a 
surface,  a  line ;  and  a  more  prominent  one,  a  ridge.  A  hole  is 
named  by  the  anatomist  a  foramen,  the  plural  of  which  is  foramina. 
The  prolongation  of  a  foramen  is  a  canal ;  and  a  more  conspicuous 
passage-way  is  a  meatus.  A  broad,  depressed  surface  is  a  fossa ; 
and  a  cavity  with  diminished  outlet  is  a  sinus,  though  this  name  is 
also  applied  to  some  of  the  larger  vascular  channels  in  the  interior 
spongy  structure  of  bones. 

Bones  in  the  fresh  condition,  freed  from  the  softer  attachments,  are 
dull  white,  or  in  the  infant  bluish  white,  and  in  the  aged  yellowish 
white,  with  more  or  less  of  a  reddish  hue  where  they  are  most  porous 
and  spongy,  as  at  the  extremities  of  the  long  bones ;  and  young  bones 
appear  proportionately  more  red,  from  their  greater  degree  of  vascu- 
larity  than  in  the  adult.  After  maceration,  in  the  ordinary  dried  state, 
bones  are  opaque,  dull  yellowish  white ;  exposure  to  light  renders  them 
more  or  less  chalky  white  ;  and  prolonged  absence  of  light  causes  them 
gradually  to  become  dull  yellow  to  brownish. 

Except  the  teeth,  bone's  are  the  hardest  parts  of  vertebrate  ani- 
mals, and  they  possess  considerable  tenacity  and  elasticity.  These 
qualities  in  some  degree  vary  with  age,  younger  bones  being  more  tough 
and  elastic,  while  older  ones  are  harder  and  more  brittle.  Fresh  bones, 
together  with  their  softer  constituents,  are  solid,  and  have  nearly  twice 
the  specific  gravity  of  water.  Ordinary  dry  bones  are  not  only  much 

3 


34  GENERAL  ANATOMY  OF  THE  SKELETON. 

lighter,  but  vary  in  this  respect  in  proportion  to  their  spongy  character 
and  the  air  they  contain.  Some  are  so  light  as  to  float  on  water,  while 
others  quickly  sink.  The  substance  of  bones  is  bone  or  osseous 
tissue,1  and  compact  portions  have  a  specific  gravity  of  about  1-9. 

Bones  deprived  of  their  soft  matters  in  common  are  composed  of 
about  one-third  by  weight  of  a  peculiar  tough  animal  substance,  the 
bone-cartilage2  or  ossein,3  and  two-thirds  of  a  chalk-like  substance, 
the  bone-earth  or  ossiterra.  According  to  Berzelius,  the  composi- 
tion of  adult  bone  is  as  follows : 

Bone-cartilage 33-30 

Calcium  phosphate 51-04 

Calcium  carbonate 11-30 

Calcium  fluoride 2  00 

Magnesium  phosphate 1-16 

Sodium  chloride  and  soda 1-20 

100-00 

The  exact  proportions  of  the  ossiterra  and  ossein  vary  under  dif- 
ferent circumstances,  as  those  of  age,  sex,  and  condition  of  vigor 
and  health ;  they  also  vary  in  different  bones  of  the  same  individual, 
and  even  in  the  compact  and  spongy  substance  of  the  same  bone.  It 
has  been  generally  stated  that  with  age  the  proportion  of  bone-earth 
increases,  while  the  bone-cartilage  diminishes;  but  it  would  appear 
from  the  recent  researches  of  Sappey  and  Nelaton  that  the  change 
is  not  very  great ;  the  increase  of  the  former  from  childhood  to  adult 
age  scarcely  amounting  to  three  per  centum,  while  there  is  nearly  the 
same  amount  of  decrease  in  old  age.  The  difference  in  the  proportions 
of  the  two  substances  is  very  much  greater  in  different  bones  of  the 
same  individual,  amounting  nearly  to  eighteen  per  centum.  Thus, 
according  to  a  table  of  analyses  given  by  the  authorities  just  named, 
the  following  differences  were  observed  : 

Bone-earth.  Bone-cartilage. 

Humerus 69-25  30-75 

Radius 68-68  31-32 

Femur 68-61  31-36 

Tibia 6842  31-58 

Clavicle 67-51  32-29 

Scapula 65-38  34-62 

Ribs 64-57  35-43 

Hip 59-97  40-03 

Vertebrae 54-25  45-75 

Sternum  .                                               .  51-43  48.57 


1  Tela  ossea. 

2  Cartilage  of  bone ;  organic  or  animal  matter,  substance,  or  part  of  bone, 

3  Osseine ;  osteine. 


GENERAL   ANATOMY   OF   THE   SKELETON.  35 

From  this  table  it  will  be  seen  that  the  long  bones  of  the  limbs  con- 
tain the  largest  quantity  of  bone-earth,  and  the  vertebrae  and  sternum 
the  least.  The  bones  of  the  shoulder  most  nearly  correspond  in  com- 
position with  the  analysis  of  bone  given  by  Berzelius ;  the  proportions 
of  the  bone-cartilage  and  bone-earth  being  about  one-third  of  the  former 
and  two-thirds  of  the  latter,  while  in  the  sternum  the  proportions  of 
the  two  substances  are  nearly  half  and  half. 

To  the  bone-cartilage  bones  mainly  owe  their  tenacity  and  elasticity ; 
to  the  bone-earth  they  owe  their  hardness,  rigidity,  and  stability. 

When  bones  are  burned  without  free  access  of  air  the  bone-carti- 
lage is  charred,  and  they  become  black  and  brittle,  and  in  this  condi- 
tion form  bone-black,  or  animal  charcoal,  as  employed  in  the  arts.  When 
burned  with  free  access  of  air,  the  bone-cartilage  is  consumed,  while 
the  bone-earth  remains  chalk-white  and  exceedingly  friable,  but  still 
retains  the  original  shape  and  size  of  the  bones.  Bone-earth  is  em- 
ployed in  the  arts,  and  it  is  the  chief  source  of  phosphorus. 

When  bones  are  subjected  to  the  action  of  diluted  muriatic  acid  the 
bone-earth  is  dissolved,  while  the  bone-cartilage  remains  intact,  tough, 
and  flexible,  and  still  retains  the  original  shape  and  size  of  the  bones. 
The  bone-cartilage  when  torn  exhibits  a  laminated  and  fibrous  structure. 
Though  insoluble  in  water  at  ordinary  temperatures,  by  boiling  it  is 
resolved  into  gelatin,  and  hence  bones  are  one  of  the  sources  of  glue. 
Bones  used  as  food  by  carnivorous  animals  in  like  manner  have  the 
bone-cartilage  dissolved  by  the  gastric  juice,  while  the  bone-earth,  for 
the  most  part,  reduced  to  powder,  is  voided  with  the  excrement. 

The  bones  are  constructed  of  an  exterior  la}-er  of  more  compact 
substance  of  variable  thickness,  with  an  interior  looser  structure  of 
the  same  material,  named  the  spongy  or  cancellated  substance. 
(Figs.  2,  3,  4.)  The  compact  substance  is  in  greater  proportion  where 
most  strength  and  protection  are  required,  as  in  the  shaft  of  long  bones, 
in  those  of  the  skull,  and  in  the  processes  and  arches  of  the  vertebra ; 
while  the  spongy  substance  predominates  wThere  extent  of  surface  is 
important  for  articulation  and  support,  as  in  the  extremities  of  long 
bones  and  the  bodies  or  centra  of  the  vertebrae. 

The  short  bones  are  composed  of  a  mass  of  spongy  substance,  with 
a  thin  and  mostly  uniform  exterior  layer  of  compact  substance.  The 
broad  bones  consist  of  two  chief  layers  of  compact  substance,  with 
an  intervening  layer  of  spongy  substanc.e.  In  those  of  the  cranial 
vault  the  latter  is  stronger  than  elsewhere,  and  is  named  the  diploe. 
In  thin  bones,  and  in  parts  of  others  in  the  like  condition,  it  is  absent, 
in  which  cases  the  distinction  of  two  layers  of  compact  substance  does 
not  exist.  In  the  vertebra?  the  more  massive  centrum  or  body  is  con- 
structed like  the  short  bones,  while  the  arches  and  processes  are  mainly 
composed  of  the  compact  substance.  In  the  long  bones  of  the  limbs  the 
shaft  encloses  a  large  central  cavity,  which  is  occupied  by  a  soft  marrow 
and  is  thence  called  the  medullary  cavity.  At  the  middle  of  the 


36  GENERAL  ANATOMY  OF  THE  SKELETON. 

shaft  the  wall  of  the  cavity  is  composed  of  compact  substance,  and  is 
very  thick,  but  gradually  thins 'away  towards  the  extremities  and  is 
in  great  measure  replaced  by  spongy  substance.  The  extremities  of 
these  bones  are  almost  wholly  composed  of  the  latter,  defined  by  a  thin 
layer  of  compact  substance.  Approaching  the  central  medullary  cavity, 
the  spongy  substance  becomes  more  cavernous  and  finely  reticular,  and 
in  this  condition  forms  a  delicate  trellis  for  the  support  of  the  marrow 
and  its  vessels. 

The  presence  of  the  spongy  substance  in  the  construction  of  the 
bones  is  accompanied  by  a  proportionate  increase  in  bulk,  without  cor- 
responding augmentation  of  weight  or  reduction  of  strength.  The 
extension  of  surface  is  adapted  to  the  requirements  of  attachment  for 
the  soft  parts  and  to  the  articulations,  in  which  the  bones  in  their 
expanded  condition  are  least  liable  to  displacement  or  dislocation.  An 
incidental  advantage  of  the  presence  of  the  spongy  substance  in  the 
extremities  of  the  long  bones  of  the  limbs  and  in  the  vertebral  centra 
lies  in  its  quality  to  reduce  the  force  of  shocks.  With  the  addition 
of  elastic  plates  of  cartilage  in  the  articulations,  the  skeleton  in  its 
construction  exhibits  an  admirable  provision  to  neutralize  or  greatly 
weaken  concussions  from  blows  or  falls,  which  otherwise  might  prove 
to  be  more  or  less  injurious  to  the  nerve-centres  and  other  delicate 
organs  it  encloses. 

The  exterior  surface  of  bones,  besides  exhibiting  variable  marks  of 
the  attachment  and  impression  of  the  contiguous  soft  parts,  in  general 
presents  a  more  or  less  smooth  or  a  finely-striated  and  porous  aspect. 
The  articular  surfaces  are  most  uniformly  smooth  and  devoid  of  visible 
porosity.  The  numerous  foramina  of  the  surface  are  continuous  with 
vascular  canals  which  pervade  the  osseous  structure,  and  are  in  gen- 
eral distinguishable  as  of  three  kinds, — 1,  those  which  are  minute,  or 
scarcely  visible  without  magnifying,  and  give  to  the  bones,  when  not 
thoroughly  clean,  a  finely-punctate  appearance,  for  the  transmission  of 
minute  blood-vessels ;  2,  larger  and  more  conspicuous  foramina,  espe- 
cially numerous  at  the  ends  of  the  long  bones  of  the  limbs,  and  on  the 
more  massive  portions  of  others,  for  the  passage  of  larger  vessels;  and, 
3,  usually  a  single  well-marked  foramen  near  the  middle  of  the  shaft 
cf  the  long  bones,  and  one  or  several  near  the  centre  of  the  broad 
ones,  for  the  principal  medullary  blood-vessels. 

The  compact  substance  qf  bones  is  laminar  and  fibrous.  When 
bones  are  exposed  to  the  weather,  the  compact  substance  not  unfre- 
quently  exhibits  a  disposition  to  break  up  into  its  constituent  laminae 
and  fibres ;  in  the  shaft  of  long  bones  separating  concentrically,  and  in 
the  broad  bones  from  the  more  extended  surfaces.  On  the  interior  of 
the  bones  the  compact  substance  resolves  itself  into  the  condition  of 
the  spongy  substance  by  the  apparent  separation  of  the  constituent 
laminae  and  fibres.  Thus,  in  a  long  bone,  as  the  compact  substance  of 
the  shaft  thins  away  towards  the  extremities  it  appears  to  do  so  by 


GENERAL  ANATOMY  OF  THE  SKELETON. 


FIG.  2. 


successively  giving  off  thin  plates  and  fibres,  which  contribute  to  form 
the  spongy  substance. 

The  spongy  substance  of  bones  is  composed  of  thin  plates  and  bars 
or  fibres,  intersecting  one  another,  and  including  intervals,  which  are 
occupied  with  marrow.  In  certain  positions  it  is  traversed  by  narrow, 
irregular  channels,  which  are  occupied  by  vessels,  mostly  veins,  com- 
municating with  the  exterior  by  some  of  the  more  conspicuous  fora- 
mina of  the  surface.  In  the  broad  bones  of  the  cranial  vault  these 
•channels  are  usually  well  marked,  and  are  called  the  diploic  sinuses. 
In  the  vertebral  centra  similar  channels  diverge  from  foramina  com- 
municating between  the  vertebral  canal  and  the  sides  of  the  bones. 

The  spongy  substance  is  arranged  on  a  more  or  less  definite  plan, 
which,  though  varying  in  different  bones,  is  always  alike  in  the  same 
bone.  The  general  arrangement  is  such 
as  to  contribute  to  the  strength  of  the 
bones  in  the  direction  they  habitually 
require  to  resist  the  greatest  pressure. 
Thus,  in  a  longitudinal  Section  of  the 
proximal  extremity  of  the  femur,  as  in 
Fig.  2,  it  may  be  observed  that  as  the 
thick,  compact  substance  of  the  shaft 
thins  away  it  appears  to  do  so  by  suc- 
cessively giving  off  thin,  arching  plates 
and  fibres,  which  intersect  one  another. 
Those  from  the  inner  side  of  the  shaft 
ascend  to  the  great  trochanter  and  the 
upper  part  of  the  neck  and  head  of  the 
bone,  while  the  opposite,  ones,  springing 
from  the  outer  side  of  the  shaft,  ascend 
to  the  inner  part  of  the  neck  and  head. 
The  arrangement  strengthens  and  sus- 
tains the  head  and  neck  of  the  bone  in 
their  connection  with  the  shaft,  and  en- 
ables them  better  to  bear  the  weight  of 
the  upper  part  of  the  body.  Similar  ar- 
rangements contributing  to  the  strength  of  the  bones  and  rendering 
them  able  to  resist  pressure  are  seen  in  a  transverse  section  of  the  con- 
dyles  of  the  femur,  as  represented  in  Fig.  3,  and  in  a  vertical  section 
of  the  calcaneum,  as  in  Fig.  4.  A  section  across  one  of  the  tabular 
bones  of  the  cranial  vault  resembles  in  construction  the  extended 
arches  which  support  the  roof  of  a  railway-station.  The  short  inter- 
vening columns  of  the  spongy  substance  between  the  compact  layers 
are  further  sustained  by  short  transverse  bars.  Everywhere,  indeed, 
in  the  construction  of  the  bones  we  find  an  arrangement  of  the  spongy 
substance  favorable  to  the  greatest  degree  of  resistance. 

The  hollow  columnar  condition  of  the  long  bones  o-f  the  limbs, 


LONGITUDINAL  SECTION  OF  THE  PROXI- 
MAL EXTREMITY  OF  THE  FEMUR,  exhib- 
iting the  arrangement  of  the  spongy 
substance.  1, 2,  positions  in  which  the 
compact  substance  appears  to  resolve 
itself  into  a  series  of  arching  fibres. 


38 


GENERAL  ANATOMY  OF  THE  SKELETON. 
FIG.  3.  FIG.  4. 


HORIZONTAL  SECTION  OF  THE  CONDYLES 
OF  THE  FEMUR,  exhibiting  the  arrange- 
ment of  the  spongy  substance. 


VERTICAL  SECTION,  ANTERO-POSTERI- 
ORLY,  OF  THE  CALCANEUM,  exhibiting 
the  arrangement  of  the  spongy  sub- 
stance. 1,  accumulation  of  compact 
substance  below  the  articulation  of  the 
astragalus,  from  which  start  off  numer- 
ous radiating  fibres ;  2,  nucleus  of  com- 
pact substance,  sending  off  numerous 
arching  h'bres. 

while  it  proportionately  increases  their  bulk  to  an  extent  which  is  most 
favorable  for  support  and  the  attachment  of  the  soft  parts,  at  the  same 
Fro.  5.  time  renders  them  lighter  and  very 

much  stronger,  for  it  is  abundantly 
proved  that  a  hollow  column  is  ca- 
pable of  sustaining  a  far  greater 
weight  than  a  solid  rod  of  the  same 
amount  of  material.  Advantage  is 
taken  of  the  principle  in  the  same 
manner  in  grasses,  in  which  we  ob- 
serve the  slender  hollow  stems  sup- 
porting heavy  heads  of  grain.  In 
birds  the  bones  are  proportionately 
more  hollow  than  in  the  other  classes 
of  vertebrates,  and  in  them  the  spaces 
are  occupied  by  air,  which  renders 
the  skeleton  specifically  lighter,  and, 
therefore,  more  readily  sustained  in 
flight. 

The  structure  of  bone  or  osseous 
tissue  may  be  studied  by  making 
thin  sections  prepared  for  the  mi- 
croscope. The  appeai'ance  of  a  trans- 
verse section  from  the  compact  sub- 
stance of  the  shaft  of  a  long  bone  is 
represented  in  Fig.  5. 

The  compact  substance  is  traversed 
TRANSVERSE  SECTION  OF  THE  SHAFT  OF  A  -1  . 

PHALANX,  moderately  magnified.  The  upper     by  fine  tubes,  which  are  named  trom 
part  of  the  figure  corresponds  with  the  ex-     their  chief  function   the  vascular 

terior  surface  of  the  bone;  the  lower  part,  ^  .  ,  .  .        m, 

with  the  interior  spongy  substance.  canals  (Hdversian  canals)  \     These 


Canaliculi  vasculares  ;  medullary  canals 


GENERAL  ANATOMY  OF  THE  SKELETON. 


39 


FIG.  6. 


mostly  pursue  a  longitudinal  course  in  the  long  bones,  but  are  joined  by 
many  shorter  transverse  or  more  or  less  oblique  canals,  altogether  form- 
ing a  plexus.  The  osseous  tissue  for  the  most  part  appears  in  concentric 
laminae1  surrounding  the  vascular  canals,  each  of  which,  together  with 
its  series  of  enveloping  laminae,  forms  a  cylindrical  rod.2  The  rods 
are  collected  in  a  close 
bundle,  with  the  inter- 
vals occupied  by  inter- 
rupted laminae,3  and. 
the  whole  together  are 
surrounded  by  osseous 
laminae,4  which  are  ar- 
ranged confoi'mably 
to  the  surface  of  the 
bone.  The  superficial 
or  subperiosteal  lami- 
nae are  traversed  di- 
rectly by  many  vascu- 
lar canals,5  which  are 
not  separately  sur- 
rounded by  concentric 
laminae  like  those  more 
deeply  situated.  The 
vascular  canals,  as  ob- 
served in  the  trans- 
verse section  of  the 
bone,  commonly  ap- 
pear as  circular  or 
oval  apertures  of  vari- 
able size.  Those  to- 
wards the  exterior  are 
the  smaller,  and  commonly  range  from  one  two-hundredth  of  an  inch 
to  about  one-fifth  that  diameter,  while  those  towards  the  interior 
become  larger,  and  irregularly  merge  into  the  more  conspicuous  med- 
ullary spaces6  contiguous  to  the  main  medullary  cavity.  On  the  ex- 
terior surface  of  the  bones  the  vascular  canals  open  by  funnel-like 
apertures,  and  in  like  manner  communicate  with  the  marrow-spaces 
within.  The  canals  are  occupied  by  blood-vessels,  invested  with  deli- 
cate connective  tissue,  continuous  with  those  of  the  periosteum  exter- 
nally and  of  the  marrow  internally.  The  canals,  except  the  larger 
ones,  have  generally  been  regarded  as  transmitting  single  vessels, 
which  together  form  the  capillary  plexus  of  the  osseous  tissue ;  but 


TRANSVERSE  SECTION  OF  BONE  FROM  THE  SHAFT  OF  THE  FEMUR, 
highly  magnified.  The  large  circular  orifices  are  transverse 
sections  of  the  vascular  canals,  surrounded  by  concentric  layers 
of  osseous  substance.  Between  the  latter  are  seen  the  lenticu- 
lar excavations  or  lacunae  intercommunicating  by  means  of 
canaliculi. 


1  L.  ossium ;  Haversian  lamellae ;  secondary  or  special  lamellae.   2  Haversian  system. 

3  Primary,   fundamental,    interstitial,    interlamellar,   ground,   or    intermediate 

lamellae.         *  Peripherie  lamellae.         5  Canals  of  Volkmann.         6  Haversian  spaces. 


40  GENERAL  ANATOMY  OF  THE  SKELETON. 

some  of  the  later  observers  describe  them  as  each  containing  an 
artery,  a  vein,  lymphatics,  and  nerves,  together  invested  with  connec- 
tive tissue.1 

Thin  bones  like  the  lachrymal,  and  the  equally  thin  parts  of  others, 
as  in  the  ethmoid,  contain  few  or  no  vascular  canals,  and  are  composed 
of  laminae  of  osseous  tissue  arranged   conformably  to  the  investing 
periosteum.      The  plates  and  fibres  also,  which  enter   into  the  con- 
struction of  the  spongy  substance,  are  for  the 
most  part  devoid  of  vascular  canals,  and  consist 
of  laminae  and  fibres  of  osseous  tissue,  arranged 
conformably  to  the  medullary  spaces  they  enclose. 
Situated  in  the  laminae  of  osseous  tissue,  and 
less  frequently  between  them,  there  are  numerous 
little  cavities  or  lacunae,2  from  which  radiate  a 
multitude  of  minute  tubes  or  canaliculi.     In  the 
transverse  section  of  the  compact  substance  of  a 
THIN  PLATE  FROM  THE    long  bone  they  appear  arranged  in  circular  rows 

ETHMOID     BONE,     Without  ,     .  ... 

preparation;  highly  mag-    concentric  with  the  vascular  canals,  and  conform- 

nifled.  TWO  planes  of  la-  ably  with  the  laminae  of  osseous  tissue.  In  the 
cunse  visible,  but  one  only  -,  .,  ,.  •.  ,.  ,,  i  . 

in  focus.  longitudinal  section  they  are  arranged  in  a  cor- 

responding manner.      The  lacunae  are  generally 

of  uniform  size,  and  are  oval,  lenticular  in  shape,  several  times  longer 
than  wide,  and  of  least  thickness.  They  range  from  0-018  to  0-05  mm. 
in  length,  0-006  to  0-0135  mm.  in  width,  and  0-0045  to  0-009  mm.  in 
thickness.  The  canaliculi  proceeding  from  the  lacunae  in  all  directions 
perforate  the  osseous  tissue,  branch  in  their  course,  and  freely  com- 
municate with  one  another,  and  with  the  contiguous  vascular  canals, 
the  medullary  spaces,  and  the  free  surfaces  of  the  bones. 

In  thin  sections  of  bone  viewed  beneath  the  microscope  by  trans- 
mitted light,  the  lacunae  and  their  canaliculi  appear  as  black  spots  with 
black  radiating  lines  on  a  translucent  ground,  while  by  reflected  light 
they  appear  chalk-white  on  a  less  white  ground.  In  fresh  bones  the 
lacunae  are  each  occupied  by  a  soft,  nucleated  mass  of  protoplasm  or 
cell,  the  bone-corpuscle  or  osteoblast,3  from  which  delicate  processes 
extend  into  the  canaliculi. 

The  laminae  of  osseous  tissue,  after  the  solution  of  the  bone-earth, 
viewed  with  the  microscope,  exhibit  a  reticular  structure,  due  to  inter- 
lacing fibres  of  generally  uniform  size.  The  fibres  consist  of  bundles 

1  Kolliker  describes  the  vessels  as  forming  a  net-work  of  wide  canals.    Sappey  says 
each  vascular  canal  encloses  a  capillary.     Klein  observes  that  each  Haversian  canal 
contains  a  blood-vessel,  one  or  two  lymphatics,  and,  according  to  its  size,  a  greater  or 
lesser  amount  of  connective  tissue.     Schafer  (Quain's  "  Anatomy,"  9th  ed.)  figures 
as  the  contents  of  a  Haversian  canal  an  artery,  a  vein,  lymphatics,   and  nerves 
enveloped  in  connective  tissue. 

2  L.  ossium ;  bone-corpuscles ;   corpuscula  ossea,  radiata,  or  chalicophora ;  cor- 
puscles of  Purkinje  ;  osteoplasts.  3  Bone-cell. 


GENERAL    ANATOMY  OF    THE   SKELETON.  41 

of  fibrillae,  which  resemble  those  of  fibre-connective  tissue.  The  in- 
tervals of  the  fibres  are  occupied  by  a  homogeneous  or  indistinctly 
granular  matrix.  Associated  with  the  osseous  structure  there  is  also 
more  or  less  elastic  tissue  mingled  with  fibro-connective  tissue. 

The  bone-earth  consists  of  exceedingly  minute  granules,  which  are 
deposited  in  the  fibrous  matrix  of  the  osseous  lamellae,  and  also  in  or 
among  the  constituent  fibrillae 
of  the  fibres. 

In  the  compact  substance 
of  the  bones,  especially  in  the 
long  bones  of  the  limbs  and  in 
the  broad  ones  of  the  cranium, 
the  osseous  laminae  give  off* 
at  right  angles  numerous  ta- 
pering, perforating  fibres,1 

which  penetrate  the  subjacent         PORTION  OF  THE  COMPACT  SUBSTANCE  OF  THE  PARI- 
laminae,  nailing  them  together.      ETAL  BONE,  softened  in  acid,  and  with  one  of  the 
From  the  free  communica-     ^med!  "^  *°  """'  **"  perf°rating flbres'  2: 
tion  of  the  vascular  canals  of 

the  osseous  substance  with  one  another  and  with  the  lacunae  through 
their  canaliculi,  nutritive  matter  is  readily  conveyed  throughout  every 
part  of  the  most  compact  structure  of  the  bones. 

PERIOSTEUM. 

The  periosteum  is  a  fibrous  membrane  which  invests  the  free  sur- 
faces of  the  bones  except  at  the  point  of  tendinous  and  ligamentous  at- 
tachment, and  on  the  articular  surfaces  where  cartilage  is  substituted.  It 
is  in  general  thicker  on  the  larger  bones,  especially  those  of  the  limbs, 
and  is  thickest  approaching  the  extremities  of  these.  It  is  thinner  on 
the  surface  of  the  cranial  vault  than  at  the  base  of  the  skull,  and  is 
thinnest  in  the  various  sinuses  of  the  same.  It  adheres  most  tightly  to 
uneven  and  the  more  porous  surfaces,  and  is  most  readily  detached 
from  compact  even  surfaces.  In  the  removal  of  the  cranial  vault  in 
post-mortem  examinations  of  the  brain,  the  vault  is  torn  from  its 
lining  periosteum,  which  remains  as  an  integral  part  of  the  dura.  At 
the  base  of  the  cranial  cavity  it  for  the  most  part  adheres  more  closely 
to  the  bones,  especially  along  the  lines  of  the  sutures  and  at  the  outlets 
of  the  foramina.  It  appears  as.  a  more  distinct,  dense,  tough  membrane 
in  young  growing  bones,  and  is  then  readily  detached  as  such  ;  but 
after  maturity  it  becomes  more  intimately  associated  with  the  osseous 
structure,  is  more  attenuated,  and  cannot  be  easily  separated  from  the 
bones  without  laceration  or  the  destruction  of  its  integrity.  It  is 
pearly  or  bluish  white,  and  when  thick  is  more  or  less  tendinous  and 

1  Fibres  of  Sharpey. 


42  GENERAL  ANATOMY  OF  THE  SKELETON. 

glistening  in  appearance.  When  thin  it  is  translucent,  and  permits 
the  color  of  the  bone  to  be  seen  through  it. 

The  periosteum  is  composed  of  an  intertexture  of  fibro-connective 
tissue  bundles,  which  on  the  long  bones  in  general  pursue  a  longitudinal 
direction,  especially  where  it  is  thickest,  and  in  other  bones  also  extend 
in  one  direction  more  than  another.  Where  tendons  and  ligaments 
are  attached  to  the  bones  there  is  an  interchange  of  bundles  with  the 
periosteum,  and  thus  the  structures  appear  more  or  less  blended.  The 
deeper  portion  of  the  periosteum 4  mainly  consists  of  denser  fibrous 
bundles,  which  resemble  in  appearance  the  fibres  of  elastic  tissue.  In 
young,  growing  bones  the  deeper  layer  of  the  periosteum  contains 
numerous  nucleated  cells,  which  occupy  the  intervals  of  the  fibrous 
bundles.  This  is  the  bone-producing  or  osteogenic  layer  of  the  peri- 
osteum, the  cells  of  which  are  the  osteoplasts.  By  its  continued 
production  and  conversion  into  bone  the  bones  grow  in  thickness. 
Mingled  with  the  predominant  fibrous  element  of  structure  of  the 
periosteum  there  is  a  considerable  amount  of  elastic  tissue. 

Numerous  blood-vessels  from  the  neighboring  trunks,  arteries  with 
their  accompanying  veins,  are  distributed  in  the  periosteum,  forming 
together  a  copious  plexus  investing  the  bones.  From  the  plexus  the 
smallest  branches  everywhere  enter  the  orifices  of  the  vascular  canals 
of  the  surface  of  the  bones.  Lymphatics  form  numerous  cleft-like 
spaces  among  the  fibrous  elements  of  structure  of  the  periosteum, 
communicating  with  those  of  the  vascular  canals  of  the  bones,  and 
joining  trunks,  which  pursue  the  course  of  the  larger  blood-vessels. 
Fine  nerves  also  are  distributed  through  the  periosteum,  mainly  follow- 
ing the  arteries  into  the  bones. 

The  periosteum,  besides  forming  a  nidus  of  growth  for  the  bones  and 
a  support  to  their  nutritive  vessels,  serves  as  an  intermediate  attach- 
ment of  the  softer  organs,  as  the  ligaments,  tendons,  muscles,  vessels, 
nerves,  membranes,  etc.  Eemoval  of  the  periosteum  results  in  necrosis 
or  death  of  the  subjacent  bone,  apparently  by  cutting  off  the  supply 
of  blood  through  the  destruction  of  the  vessels.  The  membrane  is 
said  to  possess  the  quality  of  producing  osseous  tissue,  so  that  if  it  be 
not  destroyed  the  surface  of  bone  may  be  regenerated. 

THE   MAKKOW. 

The  hollow  shaft  of  the  long  bones  of  the  limbs  and  the  interstices 
of  the  spongy  substance  of  bones  generally  are  filled  with  a  soft  ma- 
terial, the  marrow  or  medulla,  which  also  extends  into  the  larger 
vascular  canals  of  the  compact  substance.  The  marrow,  as  commonly 
observed,  appears  of  two  kinds, — that  occupying  the  medullary  cavity 
of  the  limb  bones  and  extending  into  the  spongy  substance  of  the  ex- 
tremities, which  is  a  soft,  yellow  fat ;  and  that  occupying  the  spongy 
substance  of  the  vertebrae,  ribs,  sternum,  and  the  bones  of  the  skull, 


GENERAL  ANATOMY  OF  THE  SKELETON.  43 

which  is  a  soft,  red  pulp.  At  birth  the  bones  contain  only  red  marrow, 
but  in  approaching  maturity  that  of  the  shaft  of  the  long  bones  of 
the  limbs  becomes  the  yellow  fat,  which  also  extends  into  the  spongy 
substance  of  the  extremities.  In  the  advance  of  age  the  yellow,  fat 
marrow  more  or  less  invades  all  the  bones. 

The  yellow  marrow  is  a  delicate  fat  or  adipose  tissue,  essentially 
the  same  as  that  elsewhere  in  the  body,  but  differing  in  the  small  pro- 
portion of  connective  tissue  associated  with  it,  and  consequently  in  its 
move  homogeneous  appearance  and  less  consistent  character.  It  con- 
sists of  groups  of  fat-cells  included  in  the  meshes  of  a  delicate,  connec- 
tive-tissue membrane,  associated  with  an  abundant  plexus  of  capillary 
blood-vessels.  The  investing  membrane  of  the  mass  of  marrow  in  the 
medullary  cavity  has  been  viewed  as  a  lining  to  the  latter  under  the 
name  of  the  endosteum. 

The  red  marrow  owes  its  distinctive  color  mainly  to  its  nutritive 
blood-vessels,  independently  of  which  it  consists  of  a  soft,  cellular  pro- 
toplasm. This  is  for  the  most  part  composed  of  rounded  marrow- 
cells,  which  resemble  the  colorless  blood-corpuscles,  but  are  generally 
larger,  more  translucent,  and  have  a  larger  nucleus.  Mingled  with 
them  are  smaller  nucleated  cells  of  a  reddish  hue,  which  are  regarded 
as  in  a  transition  stage  from  the  former  to  the  condition  of  red  blood- 
corpuscles,  of  which  the  red  marrow  is  supposed  to  be  one  of  the 
sources.  There  also  occur  in  the  red  marrow  a  third  kind  of  cells, 
remarkable  for  their  comparatively  large  size  and  many  nuclei.  They 
are  irregular,  flattened  spheroidal  masses  of  protoplasm  of  very  variable 
size,  and  contain  from  several  to  several  dozen  nuclei.  They  usually  lie 
directly  in  contact  with  the  osseous  tissue,  of  which  they  are  supposed 
to  be  active  absorbents,  whence  they  have  been  named  osteoclasts.1 

VESSELS  AND   NEKVES   OF   THE   BONES. 

The  bones  are  abundantly  supplied  with  blood-vessels,  which  are 
generally  small  branches  derived  from  the  neighboring  larger  ones. 
The  arteries,  with  their  companion  veins,  single  or  in  pairs,  for  the 
most  part  ramify  in  the  periosteum,  and  in  this  membrane  together 
form  a  fine  net-work  or  plexus  over  the  surface  of  the  bone.  From  the 
plexus  the  smallest  arteries  and  veins  penetrate  and  traverse  the  vas- 
cular channels  of  the  osseous  structure,  and  in  the  interior  freely  com- 
municate with  the  vessels  of  the  marrow.  Larger  arteries,  together 
with  their  companion  veins,  more  directly  enter  the  spongy  portions 
of  the  bones,  and  are  especially  distributed  to  the  marrow.  The  vessels 
which  extend  to  the  articulating  surfaces  do  not  penetrate  the  invest- 
ing cartilages.  The  long  bones  of  the  limbs  have  commonly  a  single 
principal  medullary  artery,  which  with  a  companion  vein  traverses  the 
walls  of  the  medullary  cavity  of  the  shaft  near  its  middle  through  a 

1  Myeloplaxes  ;  giant-cells. 


44  GENERAL  ANATOMY  OF  THE  SKELETON. 

long  oblique  canal.  Entering  the  medullary  cavity,  the  artery  divides 
into  an  ascending  and  a  descending  branch,  and  these  with  the  accom- 
panying veins  are  distributed  on  and  within  the  marrow.  The  vessels 
freely  anastomose  with  those  of  the  vascular  canals  of  the  compact 
wall  of  the  medullary  cavity  and  with  those  of  the  spongy  substance. 
In  the  broad  bones  of  the  cranium  the  chief  vessels  are  the  meningeal 

O 

arteries  and  accompanying  veins  in  pairs,  which  traverse  channels  on 
the  inner  surface  of  the  bones  next  the  periosteal  layer  of  the  dura. 
In  the  broad  bones,  as  the  scapula  and  the  hip-bone,  one  or  two  prin- 
cipal medullary  arteries  with  accompanying  veins  enter  corresponding 
foramina  on  the  broad  surfaces,  nearly  centrally,  and  are  especially 
destined  to  the  spongy  substance  within.  In  the  spongy  substance  of 
the  bones  many  of  the  veins  unite  in. trunks,  which  are  conspicuous  for 
their  size,  and  they  pursue  an  independent  course  in  corresponding 
channels  of  the  spongy  substance,  and  emerge  from  the  larger  foramina 
of  the  surface  of  the  bones.  In  the  bones  of  the  cranium  these  veins 
are  especially  conspicuous  and  tortuous,  and  are  named  the  diploic 
sinuses.  They  emerge  from  some  of  the  larger  foramina  of  the  sur- 
face, and  communicate  with  the  veins  of  the  scalp  and  with  the  sinuses 
and  veins  of  the  dura.  In  the  vertebral  centra  similar  veins  pursue  a 
course  fore  and  aft,  and  communicate  with  the  exterior  by  one  or  more 
of  the  larger  foramina  at  the  sides,  and  by  a  central  pair  behind,  with 
the  superficial  veins. 

Lymphatics  traverse  the  vascular  canals  of  bones  in  company  with 
the  blood-vessels,  and  are  continuous  with  those  of  the  periosteum  and 
with  those  of  the  marrow. 

Fine  nerves  accompany  the  blood-vessels  of  the  bones,  extending 
into  the  marrow,  but  they  have  not  been  detected  terminating  in  the 
osseous  tissue. 

In  the  ordinary  healthy  condition  the  bones,  including  their  perios- 
teum and  articular  cartilages  and  the  marrow,  are  insensible  to  im- 
pressions of  pain,  but  become  more  or  less  sensitive  in  pathological 
conditions. 

DEVELOPMENT  AND  GKOWTH  OF  THE  BONES. 

The  development  or  production  of  the  completely  formed  bones 
and  their  growth  proceed  together.  Most  of  the  bones  originate  in 
a  matrix  of  cartilage,  but  the  frontal  and  parietal  bones,  the  squamosa 
of  the  temporals,  and  the  upper  division  of  the  supra-occipital,  to- 
gether with  the  bones  of  the  face,  except  the  turbinal  bones,  proceed 
from  fibro-connective  tissue.  Both  the  latter  and  the  cartilage  are 
derived  from  the  soft  cellular  structure  of  the  middle  layer1  of  the 
germinal  membrane2  of  the  egg.  The  transformation  of  the  matrix 

1  Mesoderm.  2  Blastoderm. 


GENERAL  ANATOMY  OF  THE  SKELETON. 


45 


FIG.  9. 


into  bone  or  osseous  tissue  is  termed  ossification,  and  the  point  at 
which  this  commences  is  named  the  centre  of  ossification.1  The 
centres  vary  in  number  from  a  single  one  in  bones  of  the  simplest 
form  to  two,  three,  or  more  in  those  of  complex  form.  Thus,  as  ex- 
amples, the  patella  and  parietal  bones  have  a  single  centre,  the  frontal 
bone  and  the  phalanges  have  two  centres,  the  vertebrae  generally  seven 
centres,  the  sphenoid  bone  fourteen  centres,  and  the  sacrum  thirty- 
eight  centres.  Ossification  begins  in  the  skeleton  in  the  sixth  week  of 
foetal  life,  and  subsequently  it  occurs  in  the  different  bones,  both  before 
and  after  birth,  at  different  times,  to  nearly  adult  age.  The  centres 
which  first  appear  in  the  principal  part  or 
parts  of  a  bone  are  distinguished  as  primary, 
and  those  which  follow  in  accessory  parts  of 
many  bones  are  termed  secondary.  In  the 
long  bones  the  principal  part  or  shaft  which 
grows  from  the  primary  centre  is  named  the 
diaphysis,  and  the  accessory  parts  of  dif- 
ferent bones  which  grow  from  secondary 
centres  are  named  epiphyses.  The  latter 
are  connected  with  the  diaphysis,  or  princi- 
pal parts  of  a  bone,  by  cartilage,  and  each 
grows  separately  until  it  has  reached  its 
full  size  before  it  co-ossifies  or  ankyloses 
with  the  rest.  For  example,  in  the  develop- 
ment and  growth  of  the  femur,  or  thigh- 
bone, the  shaft  or  diaphysis  grows  from  the 
primary  centre  of  ossification,  which  makes 
its  first  appearance  in  the  fcetus  in  the  sixth 
week.  A  secondary  centre  appears  in  the 
epiphysis  of  the  lower  extremity  at  birth ; 
another  for  the  head  of  the  bone  during  the 
first  year ;  then  one  for  the  great  trochanter 
in  the  third  year ;  and  finally  one  for  the 
small  trochanter  about  the  ninth  year  or 
later.  Each  part  grows  from  its  own  centre 
until  it  reaches  mature  size,  after  which  it 
coalesces  with  the  contiguous  part;  and  it 
is  not  until  about  the  twenty-fifth  year  that 
all  are  completed  and  thoroughly  united  in 
one  bone. 

After  the  primary  centres  of  ossification  appear,  the  process  of  ossi- 
fication advances  with  rapidity,  so  that  at  birth  the  principal  parts  of 
most  bones  are  well  produced,  at  which  time  the  skeleton  exhibits  about 
two  hundred  and  seventy-eight  pieces,  as  follows : 


FEMUR,  from  an  individual 
about  sixteen  years  of  age,  ex- 
hibiting the  diaphysis  (1)  distinct 
from  the  epiphyses  (2,  3,  4,  5). 


1  Puncturn  ossificationis. 


46  GENERAL  ANATOMY  OF  THE  SKELETON. 

For  the  skull,  including  8  ear  ossicles  and  the  hyoid  bone 45 

For  the  vertebral  column,  ribs,  and  sternum 125 

For  the  upper  limbs 48 

For  the  lower  limbs 60 

The  diaphyses  of  the  long  bones,  and  the  half  arches  of  the  ver- 
tebrae, produced  in  solid  moulds  of  cartilage,  ossify  throughout  at  an 
early  period, — between  the  third  and  fourth  months  of  foetal  life.  They 
continue  to  grow  in  length  at  the  ends  by  the  incessant  production  of 
cartilage,  which  ossifies  as  fast  as  it  is  produced.  At  the  same  time  they 
grow  in  thickness,  but  this  increase  is  due  to  the  production  of  succes- 
sive layers  of  osseous  tissue  from  the  periosteum.  In  the  mean  while 
the  cartilages  of  the  epiphyses  grow  in  all  directions,  but  their  centres 
of  ossification  do  not  appear  until  birth,  and  subsequently  to  the  ninth 
year  or  later.  Once  started,  the  centres  grow  in  all  directions,  but  more 
quickly  towards  the  diaphysis  or  principal  part  of  the  bone,  so  that 
they  soon  come  to  be  separated  only  by  a  thin  layer  of  cartilage,  from 
which  both  diaphysis  and  epiphyses  continue  to  grow  until  they  have 
attained  their  full  size,  when  they  become  ankylosed  by  the  ossification 
of  the  intervening  plate.  The  time  of  ankylosis  differs  not  only  in  dif- 
ferent bones  but  in  different  parts  of  the  same  bone,  nor  does  it  accord 
with  the  order  of  appearance  of  the  ossific  centres  in  the  epiphyses. 
On  the  contrary,  the  order  of  ankylosis  is  often  reversed,  as  in  the  case 
of  most  of  the  larger  long  bones  of  the  limbs.  It  would  appear  in  these 
that  the  union  in  order  of  time  is  related  to  the  direction  in  which 
the  medullary  nutritious  arteries  enter  the  bones.  After  ankylosis  of 
the  epiphyses,  the  long  bones  cease  to  grow  in  length.  The  skeleton 
is  completed  by  the  ankylosis  of  all  parts  of  its  respective  bones  about 
the  twenty-fifth  year,  at  which  time  it  commonly  consists  of  two  hun- 
dred and  twenty-four  distinct  pieces  or  bones.1  Subsequently  the  bones 
continue  slightly  to  increase  in  thickness  or  bulk  to  thirty  or  forty 
years.  In  extreme  old  age,  especially  through  ankylosis  of  the  bones 
of  the  skull,  the  number  of  distinct  pieces  of  the  skeleton  is  reduced 
to  one  hundred  and  ninety-four.2 

During  the  time  the  diaphysis  of  a  bone  grows  in  thickness  from 
the  periosteum  the  original  cartilage  bone  undergoes  partial  absorption 
and  is  converted  into  spongy  substance,  and  this  then  disappears  in 
the  production  of  the  medullary  cavity.  Step  by  step,  as  the  shaft 
of  the  bone  grows,  its  interior  is  resolved  into  spongy  substance,  and 
this  disappears  in  degree  proportioned  to  the  enlargement  of  the 
medullary  cavity.  The  spongy  substance  of  epiphyses  and  of  the 
broad  and  other  bones  is  produced  in  the  same  manner  as  in  the 

1  In  this  enumeration  the  sphenoid  and  occipital  are  regarded  as  one,  the  ear 
ossicles  as  six,  the  styloids  as  two,  the  hyoid  as  five,  and  the  sternum  as  three  pieces. 

2  The  skull  and  styloids  together  as  one ;  mandible,  hyoid,  sternum,  and  coccyx 
each  as  one. 


GENERAL  ANATOMY  OF  THE  SKELETON.  47 

diaphysis  of  a  long  bone.  In  the  production  of  the  spongy  substance 
by  the  removal  of  osseous  tissue,  the  remaining  osteoplasts  of  the 
latter  are  probably  the  source  of  the  marrow-cells  of  the  red  marrow, 
and  these  by  transformation  may  become  the  adipose  cells  of  the 
yellow  marrow.  With  the  advance  of  age  the  medullary  cavity  of 
the  limb  bones  enlarges  with  the  proportionate  reduction  of  its  walls 
at  the  expense  of  both  the  spongy  and  the  compact  substance. 

The  broad  bones,  whether  produced  in  membrane,  as  those  of  the 
cranial  vault,  or  in  cartilage,  as  the  scapula  and  the  ilium,  grow  in 
breadth  by  the  continuous  production  and  ossification  of  their  respec- 
tive matrices  at  the  borders,  and  all  grow  in  thickness,  as  in  the  dia- 
physes  of  long  bones,  by  the  production  of  successive  layers  of  osseous 
tissue  from  the  periosteum.  The  centres  of  ossification  of  the  bones 
of  the  cranial  vault  make  their  appearance  during  the  third  month 
of  foetal  life.  They  commence  as  an  osseous  net,  from  which  rays 
extend  in  all  directions  towards  the  border  of  the  bone ;  additional 
intervening  rays  being  produced  as  the  former  grow  and  diverge.  At 
birth  the  bones  appear  as  thin  osseous  plates,  with  a  prominent  centre, 
from  which  rays  extend  to  the  border,  where  they  project  in  points. 
The  prominent  centre  accords  with  that  of  ossification,  and  the  rays 
indicate  the  direction  in  which  the  ossification  proceeds.  As  the  bones 
continue  .to  grow  in  breadth  by  addition  at  the  borders,  they  grow  in 
thickness  from  the  periosteum.  As  they  increase  in  thickness  the 
original  osseous  plate  is  converted  into  spongy  substance,  and  thus 
the  bones  come  to  be  composed  of  the  exterior  compact  layers  with 
the  intervening  diploe.  The  continued  growth  of  the  bones  and  the 
proportionate  production  of  spongy  substance  and  compact  layers  pro- 
ceed in  the  same  manner  as  in  the  growth  of  the  shaft  of  a  long  bone. 
The  short  bones,  like  those  of  the  carpus  and  tarsus  and  the  patella 
and  the  bodies  of  the  vertebrae,  grow  essentially  in  the  same  manner 
as  the  epiphyses  of  long  bones. 

That  the  chief  bones  of  the  limbs  grow  in  the  manner  indicated 
was  long  ago  proved  by  the  famous  experiments  of  Hale,  Duhamel,  and 
Hunter.  In  these  experiments  holes  were  bored  at  a  certain  distance 
apart  in  the  shaft  of  a  long  bone  of  a  young  animal,  and  metallic  shot 
were  introduced  into  the  holes.  Subsequently,  after  the  animal  had 
grown  and  was  killed,  it  was  found  that  although  the  bone  had  in- 
creased in  length  the  shot  remained  the  original  distance  apart.  In 
another  case,  in  which  shot  were  introduced  near  the  end  of  a  shaft 
and  in  the  contiguous  epiphysis,  these  were  afterwards  found  to  be 
removed  a  greater  distance  from  each  other.  Further,  in  an  experi- 
ment in  which  a  fine  wire  was  made  to  encircle  the  shaft  of  a  growing 
bone,  it  was  subsequently  found  within  the  medullary  cavity. 


48  GENERAL    ANATOMY   OF    THE   SKELETON. 

DEVELOPMENT   AND   GROWTH  OF   BONE   OR  OSSEOUS   TISSUE. 

The  bones,  except  most  of  those  of  the  skull,  originate  in  form  as 
corresponding  cartilages,  which  are  derived  from  the  common  cellular 
structure  of  the  mesoblast  of  the  egg.  At  first  the  cartilages  are  soft, 
but  gradually  acquire  the  consistence  as  well  as  the  structure  of  ordi- 
nary cartilage.  They  are  invested  with  a  vascular,  incipient  connective- 
tissue  membrane,  the  perichondrium,  which,  after  the  production  of 
a  subjacent  lamina  of  bone  or  osseous  tissue,  assumes  the  name  of  the 
periosteum. 

Ossification,  or  the  production  of  bone  or  osseous  tissue,  is  a  com- 
plicated process.  As  exemplified  in  the  long  bones  of  the  limbs,  it 
commences  at  the  middle  of  the  shaft  or  diaphysis  and  proceeds  towards 
the  extremities,  which,  with  few  exceptions,  remain  cartilaginous  until 
birth,  when  the  centres  of  ossification  of  the  epiphyses  begin  to  make 
their  appearance.  In  the  first  stage  of  ossification,  at  the  centre  of  the 
diaphysis,  the  cartilage-cells  become  enlarged  and  separated  to  a  greater 
extent  than  elsewhere  by  an  increase  of  the  intervening  matrix.  Mole- 
cules of  bone-earth,  consisting  of  calcareous  salts,  are  deposited  in  the 
matrix,  rendering  it  harder,  granular,  and  more  opaque ;  this  action 
being  distinguished  as  calcification.  At  the  same  time  the  neighbor- 
ing cartilage-cells  become  enlarged,  flattened,  and  arranged  in  longitu- 
dinal rows  or  columns,  which  generally  radiate  from  the  centre  of 
ossification  towards  the  ends  of  the  diaphysis.  Calcification  extends 
into  the  matrix  between  the  cell  columns,  which  thus  become  enclosed 
in  spaces,  termed  the  primary  areolae.  Simultaneously  a  lamina  of 
bone  is  produced  from  the  vascular  perichondrium,  which  chiefly  con- 
sists of  incipient  connective  tissue  and  protoplasmic  cells,  named  osteo- 
blasts.  These,  in  the  subsequent  production  of  the  osseous  lamina, 
become  enclosed  by  them,  and  thus  form  the  bone-corpuscles  con- 
tained in  lacunae.  From  the  function  of  the  deeper  portion  of  the 
perichondrium,  or  periosteum,  in  producing  osseous  tissue,  it  is  distin- 
guished as  the  osteogenic  layer  or  tissue.1 

In  the  next  stage  of  ossification,  through  absorption  of  the  osseous 
lamina  at  one  or  more  points,  the  vascular  osteogenic  tissue  is  extended 
by  development  to  the  centre  of  the  calcified  cartilage.  "With  this  ex- 
tension the  matrix  of  the  latter  is  partially  absorbed,  and  the  primary 
areolse  break  up,  two  or  more  together,  into  the  larger  medullary 
spaces,2  which  are  filled  with  embryonic  marrow,  consisting  of  branch- 
ing connective-tissue  cells  and  osteoblasts,  and  penetrated  axially  by  a 
capillary  vessel,  which  is  blind  or  looped  at  the  extremity. 

Calcification  advances  in  the  matrix  of  the  cartilage  towards  the 
ends  of  the  diaphysis,  and  the  cell  columns  continue  to  be  enclosed 
in  primary  areolse,  while  the  osteogenic  tissue  incessantly  follows,  and 

1  Osteoblastic  layer  or  tissue.  *  Secondary  areolse. 


GENERAL,  ANATOMY  OF  THE  SKELETON.  49 

the  latter  are  resolved  into  medullary  spaces.  As  ossification  proceeds, 
the  medullary  spaces  first  formed  still  enlarge  by  absorption ;  but  finally 
their  walls,  remaining  from  the  original  calcified  cartilage  matrix,  begin 
to  thicken  by  the  production  of  osseous  laminae  from  the  marrow.  As 
successive  laminae  are  formed,  the  medullary  spaces  are  contracted  into 
a  central  vascular  canal,1  with  its  contained  vessels  and  a  little  incipient 
connective  tissue,  with  a  few  osteoblasts.  Between  the  concentric 
laminae  many  of  the  latter  are  included  as  bone-corpuscles  contained 
in  lacunae. 

The  osteogenic  layer  of  the  perichondrium  and  periosteum,  con- 
cerned in  the  production  of  successive  laminae  of  osseous  tissue  at  the 
periphery  of  the  diaphysis  of  the  long  bones,  is  composed  of  narrow 
connective-tissue  bundles,  named  osteogenic  fibres,  and  nucleated, 
granular,  protoplasmic  cells,  the  osteoblasts,  together  embedded  in  a 
homogeneous  ground  substance  and  pervaded  with  blood-vessels.  Ossi- 
fication occurs  in  the  osteogenic  layer  by  the  production  of  a  net-work 
of  osseous  tissue,  in  which  molecules  of  bone-earth  are  deposited  in  and 
between  the  osteogenic  fibres,  and  enclose  the  osteoblasts  as  bone-cor- 
puscles. In  the  advancement  of  ossification  the  meshes  of  the  net- 
work, forming  medullary  spaces,  become  contracted  into  vascular 
canals,  in  the  same  manner  as  above  described  in  the  production  of 
bone  in  cartilage. 

The  early-formed  osseous  tissue  differs  from  that  of  maturity  in  its 
more  reticular  and  less  regularly  laminated  character,  and  for  a  long 
time  even  the  shafts  of  the  long  bones  are  rather  spongy  than  compact 
in  their  texture.  They  acquire  a  more  obvious  laminar  condition  during 
the  year  after  birth,  when  a  series  of  concentric  laminae  are  produced 
from  the  periosteum.  The  vessels  from  the  latter  penetrating  the  lam- 
inae are  at  first  not  enclosed  by  series  of  concentric  laminae,  but  these 
are  subsequently  produced  as  in  the  medullary  spaces. 

The  bones  of  the  skull,  excluding  the  occipital,  except  the  upper 
division  of  its  supraoccipital  division,  the  petrosal  division  of  the 
temporals,  the  sphenoid,  the  ethmoid,  and  the  turbinated  bones,  origi- 
nate in  fibro-connective  tissue,  and  grow  from  the  osteogenic  layer  of 
the  periosteum  in  the  same  manner  as  the  principal  parts  of  other 
bones  of  the  skeleton. 

In  the  ossification  of  epiphyses,  vessels  are  previously  developed  in 
the  cartilage  extending  from  those  of  the  ossified  principal  part  of  the 
bones.  The  vessels  are  associated  with  osteoblasts,  which  together 
occupy  canals  of  the  cartilage  produced  by  absorption.  The  subsequent 
steps  of  ossification  are  the  same  as  in  the  production  of  osseous  tissue 
in  the  cartilaginous  diaphysis  of  a  long  bone. 

In  the  absorption  of  bone,  occurring  at  every  step  in  the  develop- 
ment and  growth  of  the  bones,  in  the  production  of  the  spongy  snb- 

1  Haversian  canal. 
4 


50  GENERAL  ANATOMY  OF  THE  SKELETON. 

stance  and  the  medullary  cavity,  and  the  continued  increase  of  these 
through  life,  an  important  agent  appears  to  be  large  multinucleated 
cells,  which  from  their  function  have  been  named  osteoclasts.1  They 
are  commonly  observed  occupying  shallow  recesses  of  the  medullary 
cavity  and  spaces,  directly  in  contact  with  the  osseous  tissue.  They 
differ  greatly  in  size,  and  are  usually  irregularly  spheroidal  and  flat- 
tened, though  often  variable  in  outline.  They  consist  of  granular  pro- 
toplasm, and  contain  from  several  to  a  dozen  or  more  nuclei.  They 
frequently  present  a  thickened  border  next  the  surface  of  contact  with 
the  osseous  tissue,  and  this  border  is  represented  as  being  striated  like 
that  of  the  free  extremity  of  the  intestinal  epithelial  cells.  The  osteo- 
clasts are  probably  derived  from  osteoblasts,  with  which  they  are 
associated,  and  they  probably,  after  fulfilling  their  function,  revert  to 
the  same. 

AKTICULATIONS  OK  JOINTS  OF  THE  SKELETON. 

The  articulations  or  joints2  of  the  skeleton  exhibit  a  gradation 
of  union  from  those  which  are  immovable  to  such  as  possess  motion  in 
all  directions. 

The  most  immovable  articulations3  are  those  which  exist  be- 
tween the  bones  of  the  skull,  constituting  what  are  called  the  sutures.* 
Many  of  the  sutures  are  formed  through  indentations  of  the  contigu- 
ous margins  of  the  bones,  which  are  mutually  adapted  to  one  another, 
often  in  a  somewhat  dovetailed  manner.  From  their  toothed  appear- 
ance they  are  called  dentated  or  serrated  sutures.5  Examples  of 
them  are  seen  in  the  union  of  the  frontal,  parietal,  and  occipital  bones. 
In  other  sutures  the  contiguous  borders  of  bones  are  bevelled  off  and 
mutually  coadapted,  as  observed  in  the  union  of  the  sphenoid  and 
temporal  bones  with  the  parietal.  Such,  from  their  scale-like  arrange- 
ment, are  called  squamous  sutures.6  In  some  sutures,7  plane  borders 
of  contiguous  bones,  slightly  roughened,  are  coadapted,  as  in  the  union 
of  the  maxillary  bones.  Occasionally  the  border  of  one  bone  is  grooved 
to  receive  the  sharpened  edge  of  another,8  as  in  the  articulation  of 
the  vomer  with  the  sphenoid  bone. 

The  next  form  of  articulation  possesses  more  or  less  flexibility 
without  allowing  other  motion.  Such  a  joint  is  called  a  symphysis,9 
and  is  formed  by  the  union  of  broad  surfaces  of  contiguous  bones 
through  means  of  an  intervening  plate  of  fibro-cartilage.  Examples 
of  this  mode  of  junction  are  presented  in  the  union  of  the  bones  of  the 
pelvis,  the  centra  of  the  vertebra,  and  the  pieces  of  the  sternum. 

1  Myeloplaxes ;  giant-cells.  *  Arthroses. 

3  Synarthroses.  *  S.uturae. 

5  S.  dentatse  ;  s.  serratse.  6  S.  squamosae. 

7  Harmonia ;  harmony  ;  false  suture.  8  Schindylesis. 
9  Amphiarthrosis. 


GENERAL.  ANATOMY  OF  THE  SKELETON.  51 

In  the  movable  articulations l  the  bones  have  their  opposed  sur- 
faces invested  with  cartilage,  and  their  union  is  preserved  by  means  of 
ligaments,  which  enclose  the  joints.  Muscles  or  their  tendons,  which  in 
many  instances  more  or  less  surround  these  joints,  very  much  contrib- 
ute to  the  firmness  of  their  union,  and  thus  to  prevent  dislocation.  To 
facilitate  movement,  they  are  lined  with  sy  no  vial  membrane,  which 
secretes  a  lubricating  liquid,  named  the  synovia. 

Of  the  movable  articulations  there  are  several  varieties,  which 
exhibit  different  degrees  of  mobility. 

In  some  instances  the  movements  are  exceedingly  limited,  amount- 
ing only  to  a  slight  degree  of  gliding  of  the  opposed  surfaces  upon 
each  other,  as  instanced  in  most  of  the  joints  of  the  carpus  and  tarsus, 
and  those  of  the  articular  processes  of  the  vertebrae. 

In  other  cases  the  joints  are  restricted  to  a  hinge-like  motion,2  as 
observed  in  the  elbow-  and  knee-joints,  and  those  of  the  fingers  and 
toes.3  The  hinge-like  movement,  together  with  a  motion  towards  either 
side,  is  observed  in  the  wrist-  and  ankle-joints. 

Occasionally  joints  admit  only  of  a  rotary  motion,  as  in  the  two 
radio-ulnar  articulations  and  those  between  the  atlas  and  the  axis. 

The  most  movable  articulations  are,  the  ball-and-socket  joints,*  in 
which  the  head  of  one  bone  fits  into  a  more  or  less  deep  cup-shaped 
concavity  of  the  contiguous  bone.  Examples  of  such  joints  are  pre- 
sented in  the  shoulder  and  hip.  The  movements  of  these  joints  are 
those  of  flexion  and  extension,  abduction  and  adduction,  circumduction 
and  rotation. 

Of  the  different  movements  of  the  articulations,  flexion  is  that  in 
which  one  or  more  bones  of  a  joint  are  made  to  describe  an  angle  with 
others,  in  moving  either  backward  or  forward.  Thus,  the  bending  of 
the  bones  of  the  forearm  forward  is  the  flexion  of  the  forearm  upon 
the  arm ;  the  bending  of  the  leg  backward  is  its  flexion  upon  the 
thigh.  Extension  is  the  opposite  movement  to  flexion,  in  which  the 
bones  are  generally  brought  into  a  line  with  one  another.  Thus,  the 
bending  of  the  forearm  backward  after  it  has  been  flexed,  so  as  to 
bring  it  on  the  same  line  with  the  arm,  is  the  extension  of  the  fore- 
arm. 

Abduction  is  that  movement  in  which  a  bone  is  directed  outwardly 
from  another,  or  from  the  body ;  and  adduction  is  the  opposite  move- 
ment, in  which  a  bone  is  directed  inwardly.  Thus,  the  movement  by 
which  the  thumb  is  moved  outwardly  from  the  fingers  is  abduction, 
and  that  by  which  it  is  made  to  approach  them  is  adduction. 

Circumduction  is  the  motion  made  by  a  bone  when  its  head  acts  as 

a  pivot  and  the  distal  end  is  made  to  describe  a  circle.     This  character 

of  movement  is  best  exemplified  with  the  humerus  and  glenoid  cavity 

i 

1  Diarthroses  ;  diarthrodial  articulations.  2  Ginglymus  ;  ginglymoideus. 

3  Ginglymoid  joints.  *  Enarthroses. 


52  GENERAL  ANATOMY  OF  THE  SKELETON. 

of  the  scapula.     Rotation  is  the  motion  made  by  a  bone  when  it  rolls 
on  its  axis,  as  in  the  movements  of  the  radius  upon  the  ulna. 

OF   THE   KELATIVE  POSITION  OF  THE  DIFFEEENT  STRUCTURES 
ENTERING  INTO   THE  COMPOSITION   OF   ARTICULATIONS. 

The  bones  articulating  by  suture  are  continuously  associated  by 
intervening  fibro-cartilage,  which  is  apt  to  ossify  after  the  bones  have 
reached  maturity.  The  fibrous  periosteum  in  all  cases  passes  over  the 
sutures,  resembling  in  this  position  the  capsular  ligaments  of  movable 
joints.  In  symphyses  an  intervening  plate  of  fibro-cartilage  inti- 
mately connects  the  surfaces  of  the  contiguous  bones;  and  they  are 
surrounded  with  bands  of  fibrous  tissue,  corresponding  with  the  cap- 
sular ligaments  of  movable  articulations. 

In  movable  joints  the  opposed  surfaces  of  the  bones  are  invested 
with  a  layer  of  cartilage,  which  from  its  position  is  called  articular 
cartilage.1  When  the  cartilage  covers  a  depressed  or  concave  surface, 
it  usually  becomes  thicker  towards  the  borders,  so  as  to  deepen  the 
concavity ;  but  if  it  invests  a  head,  condyle,  or  other  articular  promi- 
nence, it  becomes  thinner  towards  the  margins. 

The  ligaments  surrounding  movable  joints  are  of  two  kinds, — the 
capsular2  and  the  band-like  ligaments.3  The  former  are  cylindrical 
sacs,  including  by  their  extremities  the  borders  of  the  articular  sur- 
faces of  bones,  where  they  become  continuous  with  the  periosteum  of 
the  latter,  and  frequently  with  the  contiguous  tendons  of  muscles. 
They  vary  in  thickness,  are  composed  of  an  intertexture  of  bundles 
of  fibrous  tissue,  and  are  highly  flexible  and  slightly  extensible.  In 
many  positions,  broad  tendons  of  muscles,  passing  over  joints,  assume 
their  place,  as  in  the  case  of  the  tendon  of  the  quadriceps  extensor 
muscle  of  the  thigh  and  the  extensor  tendons  on  the  backs  of  the 
phalangeal  articulations.  The  band-like  ligaments  are  accessory  to 
the  capsular  ligaments,  contributing  to  the  strength  of  joints  in  partic- 
ular positions.  They  are  strong  bundles  of  parallel  bundles  of  fibrous 
tissue,  quite  flexible,  but  entirely  inextensible.  They  constitute  the 
numerous  lateral  ligaments  of  the  joints. 

The  synovial  membranes  belong  to  the  class  of  serous  mem- 
branes. They  line  the  interior  of  capsular  ligaments,  and  in  the  adult 
are  reflected  upon  the  border  of  the  articular  cartilages  ;  but  in  infancy 
they  invest  the  entire  cavity  of  joints.  They  secrete  a  viscid,  albu- 
minoid liquid  resembling  the  white  of  eggs,  and  called  the  synovia, 
which  lubricates  the  surfaces  of  joints,  and,  by  lessening  friction, 
facilitates  motion. 

The  synovial  membranes,  like  the  serous,  are  composed  of  a  layer 
of  connective  tissue,  in  which  blood-vessels  are  distributed,  and  are 
invested  on  the  free  surface  with  an  endothelium.  Their  inner  surface 

1  Diarthrodial  cartilage.  2  Capsulse  articulares.  3  Funicular  ligaments. 


GENERAL  ANATOMY  OF  THE  SKELETON.  53 

is  smooth,  and  they  possess  no  glands.  At  the  borders  of  joints  they 
are  frequently  thrown  into  folds  and  processes,  containing  connective 
tissue,  fat,  and  an  occasional  isolated  cartilage-cell.  These  synovial 
fringes l  apparently  act  as  cushions  to  fill  up  interspaces ;  though,  from 
their  greater  vascularity  as  compared  with  other  portions  of  the  mem- 
brane, they  are  no  doubt  especially  active  in  the  production  of  synovia. 

Concave  articular  surfaces  are  frequently  rendered  deeper  by  the 
provision  of  a  band  of  fibro-cartilage  tipping  or  surrounding  their 
margin,  as  in  the  case  of  the  glenoid  cavity  of  the  shoulder  and  the 
acetabulum  of  the  hip-joint.  Occasionally  joints  are  partially  or  com- 
pletely divided  into  two. parts  by  the  introduction  of  an  interarticular 
fibro-cartilaginous  disk,  as  in  the  case  of  the  articulation  of  the  lower 
jaw  and  the  knee-joint. 

In  some  instances  bones  are  connected  by  ligaments  totally  different 
from  the  ordinary  ones ;  being  composed  of  an  elastic  material,  such 
as  the  elastic  ligaments  which  conjoin  the  vertebral  arches ;  and  such 
also  is  the  nature  of  the  nuchal  ligament  which  sustains  the  head  of 
quadrupeds.  ",, 

The  various  structures  which  have  been  mentioned  as  entering  into 
the  composition  of  the  articulations  consist  of  bones,  cartilages,  fibro- 
cartilages,  ligaments,  and  synovial  membranes.  The  constitution  of 
bones  or  of  the  osseous  tissue  has  been  described,  but  a  consideration 
of  the  tissues  composing  the  remaining  structures  is  deferred  at 
present,  on  account  of  their  entering  into  the  constitution  of  many 
other  organs.  The  structure  of  the  cartilages  and  fibro-cartilages  will 
be  found  under  their  appropriate  head;  the  structure  of  ligaments  in 
the  description  of  the  fibro-connective  and  elastic  tissues;  and  the 
structure  of  synovial  membranes  in  the  account  of ;  the  serous  mem- 
branes. 

1  Synovial  glands  of  Havers  ;  Haversian  glands  ;  glandulse  articulares  ;  synovial 
fimbrise. 


OHAPTEE  III. 


SPECIAL  ANATOMY  OP   THE    SKELETON. 
THE   VERTEBRAL   COLUMN. 


FIG.  10. 


The  vertebral  column,1  more  familiarly  known  as  the  spine, 
spinal  column,  or  backbone,  is  the  axis  of 
the  skeleton,  and  as  such  is  a  peculiar  charac- 
teristic of  the  highest  division  of  the  animal 
kingdom,  which  is  thence  named  the  verte- 
brata.  It  is  composed  of  a  series  of  articulated 
segments,  in  general  distinguished  as  verte- 
brae.2 In  the  human  skeleton  there  are  thirty- 
three  or  four  of  these  segments,  and  of  them 
twenty-four  remain  permanently  distinct  bones, 
and  are  those  which  are  especially  regarded 
as  the  vertebrae,  and  hence  called  the  true 
vertebrae.  The  succeeding  five  segments  ap- 
proaching maturity  ankylose  into  a  single  bone, 
whif  his  named  the  sacrum ;  and  the  remaining 
four  or  five  segments,  exhibiting  a  rudimentary 
condition  of  the  others,  in  the  advance  of  age 
commonly  ankylose  into  one  or  two  pieces, 
which  together  are  named  the  coccyx,  repre- 
senting the  tail  of  other  vertebrates. 


THE  VERTEBRAE. 

The  twenty-four  vertebra  form  a  continuous 
series  extending  from  the  skull  to  the  sacrum, 
and  they  successively  increase  in  size.  They 
are  nearly  alike,  and  consist  of  similar  parts 
variously  modified  in  diiferent  positions  to  serve 
special  purposes.  Each  in  general  is  composed 
of  an  anterior  massive  part,  named  the  cen- 
trum or  body,  and  a  posterior  part,  the  arch ; 
and  between  the  two  is  a  large  aperture,  tfee*- 
spinal  foramen,  which,  with  the  others,  con- 
tributes to  form  the  spinal  canal.  From  the 
arch  are  given  off  seven  processes,  of  which 
four  are  articular,  and  the  others  consist  of  a 
pair  of  transverse  processes  and  a  spinous 
process. 


THE  VERTEBRAL  COLUMN,  lat- 
eral view ;  exhibiting  the  cur- 
vatures. 1  to  24,  true  vertebrae ; 
25,  26,  false  vertebrae;  1  to  7, 
cervical  vertebrae ;  8  to  19,  dor- 
sal vertebrae ;  20  to  24,  lumbar 
vertebrae;  25,  sacrum;  26, 
coccyx. 


1  Columna  vertebralis,  or  spinalis  ;  spina  dorsi ;  rachis.     2  Spondyli ;  backbones. 
54 


SPECIAL    ANATOMY    OF   THE   SKELETON.  55 

The  centrum  or  body,1  at  the  fore  part  of  the  vertebra,  is  a  thick 
disk,  placed  horizontally,  with  its  front  and  sides  somewhat  narrowed 
towards  the  middle,  and  its  back  somewhat  JIIG 

concave  transversely,  where  it  contributes 
to  form  the  spinal  foramen.  Above  and 
below  it  presents  broad  articular  surfaces, 
mostly  nearly  flat,  but  with  a  slightly  ele- 
vated rim  and  a  somewhat  projecting  margin 
at  the  sides  and  in  front.  The  surface  of 
the  centrum  in  front  and  laterally  is  more  or 
less  conspicuously  porous,  and  that  behind 
exhibits  a  central  pair  of  larger  foramina  for 

the  passage  of  veins  from  the  interior.    The       gIDE  VIEW  OF  A  DORSAL 
arch2  of  the  vertebra  joins  the  back  of  the     BRA.    i,  centrum;  2,  articular 
centrum  by  strong,  rounded  pedicles,  be-    JSSSilJfiiSS: 

hind  which  it  is  formed  by  a  pair  of  deeper      cess ;  7,  transverse  process;  8,  pre- 

shelving  laminse,  which  converge  to  the  and  9-  Particular  processes. 
spinous  process,  and  in  the  series  overlap  one  another  and  present  an 
imbricated  appearance.  The  upper  borders  of  the  laminse  behind  and 
the  lower  borders  in  front  are  roughened  for  the  attachment  of  elastic 
ligaments,  which  occupy  the  intervals  of  the  vertebral  arches.  A  deep, 
rounded  notch  beneath  the  pedicles  and  commonly  a  shallow  one  above 
are  the  intervertebral  notches.3  These  form  between  the  adjacent 
vertebras  large  round  or  oval  holes,  the  intervertebral  foramina, 
through  which  the  spinal  nerves  emerge.  The  spinal  foramen,  en- 
closed by  the  centrum  and  arch,  varies  in  size  and  shape  in  different 
positions,  being  larger  and  triangular  in  the  upper  and  lower  vertebrae 
of  the  series,  and  smaller  and  circular  in  those  intermediate. 

Of  the  seven  processes  of  the  vertebral  arch  in  general,  the  most 
conspicuous  is  the  spinous  process,4  from  which  the  vertebral  column 
has  received  its  common  name  of  the  spine.  It  projects  backward  in 
the  median  line  at  the  conjunction  of  the  laminaa  of  the  arch,  and 
varies  in  size  and  shape  in  the  different  vertebrae. 

Four  articular  processes5  spring  from  the  union  of  the  pedicles 
and  laminaa  of  the  arch, — a  pair  of  prearticular  processes6  above 
and  a  pair  of  postarticular  processes7  below.  They  are  provided 
with  smooth,  articular  facets,  which  are  invested  with  cartilage ;  those 
of  the  prearticular  processes  looking  obliquely  backward  and  upward, 
those  of  the  postarticular  processes  in  the  opposite  direction.  The 

1  Corpus.  2Arcus;  neural  arch.  3  Incisura  vertebrales. 

*  Processus  spinosus  ;  neural  spine. 

5  P.  articulares  ;  oblique  processes  ;  zygapophyses. 

6  Superior  or  anterior  articular  processes  ;  prezygapophyses ;  preaxial  zygapo- 
physes. 

7  Inferior  or  posterior  articular  processes  ;   postzygapophyses  ;   postaxial  zygapo- 
physes. 


56  SPECIAL,   ANATOMY   OF   THE   SKELETON. 

pre-  and  postarticular  processes  of  adjacent  vertebrae  movably  articu- 
late with  one  another.  The  transverse  processes,1  of  variable  size 
and  shape,  project  outward  from  the  arch,  one  on  each  side,  from 
between  the  pre-  and  postarticular  processes. 

From  the  regions  they  occupy  the  vertebrae  are  named  cervical, 
thoracic,  and  lumbar. 

CEKVICAL  VERTEBKJE. 

Of  these  there  are  seven,  and  they  form  together  the  bony  axis 
of  the  neck,  connecting  the  skull  with  the  thorax.  They  are  the 

smallest  and  most  delicately  constructed  of 
the  vertebras.  The  first  two  depart  most 
from  the  ordinary  condition  of  these  bones ; 
being  specially  adapted  to  the  articulation 
and  movements  of  the  skull.  The  others 
are  more  like  one  another  and  the  rest  of 
the  series. 

The  centrum  of  the  cervical  vertebras 
generally  is  transversely  half  oval,  with  the 
UPPER  VIEW  OF  A  CERVICAL     flat  or  slightly  concave  part  next  the  spinal 
VERTEBRA,  from  the  middle  of     foramen.     It  is  but  feebly  narrowed  towards 

the  series.     1.  centrum;    2,  la-  . 

mina;  3, pedicle;  4, spinous pro-  the  middle,  and  the  margins  of  the  articular 
cess;  5,  transverse  and  costal  surfaces  scarcely  project.  The  upper  surface 

processes;    6,    foramen   for   the      ,         ,          ..  /...i,         11        i 

vertebral  artery ;  ?,  prearticuiar  "7  elevation  ot  its  lateral  borders  is  rendered 
process;  8,  postarticular  process;  transversely  concave,  and  the  lower  surface 
cenleruamed  lateral  b°rder  °f  the  V  extension  downward  mainly  of  its  front 

border,  but  in  a  less  degree  also  by  the  back 

border,  is  rendered  fore  and  aft  concave.  By  this  arrangement  of  the 
articular  faces  the  centra  interlock,  and  are  thus  less  liable  to  dislocation  j 
an  important  provision  where  the  vertebral  column  is  narrowest. 

The  arch  of  the  cervical  vertebrae  is  about  as  broad  as  in  the  largest 
vertebrae,  but  is  much  shallower  than  elsewhere.  Its  pedicles  extend 
outward  and  backward,  and  the  laminae  are  comparatively  long  and 
narrow.  The  spinal  foramen  is  larger  than  in  the  thoracic,  but 
smaller  than  in  the  lumbar  vertebrae.  It  is  triangular  with  rounded 
angles,  with  the  base-line  transversely  forward,  and  with  the  width 
greater  from  side  to -side  than  fore  and  aft.  The  spinous  process 
varies ;  usually  small  and  forked  at  the  end  in  the  intermediate  ver- 
tebrae, it  is  large  and  strong  in  the  second  and  last,  and  is  obsolete  in 
the  first  one. 

The  pre-  and  postarticular  processes  generally  form  the  ends 
of  short,  vertical,  cylindroid  columns,  which  are  situated  at  the  con- 
junction of  the  pedicles  and  laminae.  The  articular  facets  are  flat, 
circular,  and  oblique ;  those  above  looking  upward  and  backward,  and 
those  below  in  the  opposite  direction.  The  transverse  processes 

1  Diapophyses. 


SPECIAL   ANATOMY    OF   THE    SKELETON.  57 

are  small  and  weak,  and  generally  spring  from  the  articular  columns, 
from  which  they  are  directed  outward  and  forward,  and  end  in  a  little 
tubercle. 

Additional  elements  of  the  cervical  vertebrae  are  the  costal  pro- 
cesses, which  proceed  outward  from  the  sides  of  the  centrum  in 
advance  of  the  transverse  processes.  Near  the  end  they  join  the 
latter  by  an  isthmus,  and  thus  enclose  between  them  the  vertebral 
foramen,  a  circular  aperture,  which,  except  in  the  last  cervical  ver- 
tebra, accommodates  the  vertebral  artery  in  its  ascent  through  the 
neck.  A  groove  between  the  processes  directed  outward  from  the 
upper  intervertebral  notch  accommodates  the  cervical  nerves.  The 
costal  process  is  commonly  described  as  part  of  the  transverse  process, 
but  it  is  rather  to  be  viewed  as  homologous  with  the  ribs.  In  the  last 
cervical  vertebra  it  originates  as  a  separate  piece,  and  occasionally  it 
remains  permanently  distinct  and  variably  developed  as  a  movable 
cervical  rib. 

The  first  cervical  vertebra  immediately  articulates  with  and 
sustains  the  skull,  and  is  named  the  atlas.  It  differs  remarkably 
from  all  other  vertebrae  in  having  no  centrum,  the  position  of  which 
is  occupied  by  the  odontoid  process  ascending  from  the  centrum  of 
the  second  vertebra.  It  appears  as  a 
large  ring,  and  is  of  greater  breadth  FIG.  13. 

than  any  other  of  the  cervical  verte- 
bra3.  Its  most  massive  portions  form 
short  columns,1  one  on  each  side  ending 
in  the  pre-  and  postarticular  processes. 
The  articular  columns  are  joined  in 
front  by  a  transverse  bridge,  the  an- 
terior arch,2  which  is  rendered  promi-  UPPER  VIBW  OF  THE  ATLAS.  1(  anterior 
nent  in  front  by  a  conical  median  emi-  arch ;  2,  articular  facet  for  the  odontoid 

.          ,.'           .  ,     ,    -.     ,  .     i       ..,  process ;  3,  posterior  arch ;  4,  groove  for 

nence,8  and  IS  provided  behind  With  a  the  vertebral  artery;  5,  transverse  process; 

Circular  articular    facet,   invested    with  6,  vertebral  foramen ;  7,  prearticular  pro- 

,.-,             „                                                     ,1  cess;  8,  tubercle  for  the  transverse liga- 

cartilage,   for   movement    against    the  ment 

odontoid  process.     From  the  back  of 

the  columns  springs  the  posterior  arch,4  which  is  double  the  extent  of 
the  former,  and  surrounds  the  spinal  foramen  back  of  the  odontoid  pro- 
cess. It  is  thickened  towards  the  middle,  and  is  variably  produced  be- 
hind in  a  tubercle  or  rudimental  spinous  process.  From  the  outer  side 
of  the  articular  columns  arise  the  conjoined  transverse  and  costal  pro- 
cesses, with  their  enclosed  vertebral  foramen.  On  the  inner  part  of  the 
columns  is  a  tubercle  for  the  attachment  of  the  transverse  ligament, 
which  confines  the  odontoid  process  in  place.  The  prearticular  pro- 
cesses5 form  deeply-concave  facets  for  the  occipital  condyles.  The 

1  Massae  laterales.  "  Arcus  anterior.  3  Tuberculum  anterius. 

4  Arcus  posterior.  5  Fossae  articulares. 


58  SPECIAL,   ANATOMY   OF    THE    SKELETON. 

facets  are  variably  constricted,  elliptical  in  outline,  and  have  their  long 
diameter  convergent  forward  and  their  transverse  diameter  inclining 
inward  and  downward.  The  postarticular  processes  have  large 
circular  facets,  which  look  obliquely  downward  and  inward,  are  nearly 
straight  fore  and  aft.  and  slightly  concave  transversely. 

The  articular  columns  of  the  atlas,  together  with  the  prearticular 
processes  of  the  axis,  hold  a  more  advanced  position  than  the  corre- 
sponding columns  of  the  succeeding  vertebrae.  From  the  greater 
breadth  of  the  atlas  the  vertebral  foramen  holds  a  more  external  posi- 
tion than  in  the  other  cervical  vertebra?.  From  the  foramen  a  variably 
deep  groove  winds  backward  and  inward,  behind  the  prearticular  pro- 
cess, for  the  passage  of  the  vertebral  artery  and  first  spinal  nerve.  The 
groove  is  sometimes  bridged  over  on  one  or  both  sides  of  the  atlas, 
and  is  thus  converted  into  a  foramen.  A  less  marked  groove  crossing 
the  atlas  behind  the  postarticular  processes  forms  part  of  the  inter- 
vertebral  foramen  for  the  second  spinal  nerve. 

The  second  cervical  vertebra,  named  the  axis,1  is  remarkable  for 
its   nipple-shaped  eminence,  the  odontoid  process,2  which  ascends 
from  the  centrum  within  the  ring  of  the  atlas,  and  serves  as  a  pivot 
around  which  the  latter  moves  in  the  rotation  or  turning  of  the  head. 
The  centrum  is  longer  than  in  the  succeeding  vertebra?,  and  its  lower 
part  is  constructed   as   in   them.     In  front  it 
FlG-  14-  presents  a  median  ridge  expanding  below,  and  on 

each  side  of  this  it  is  depressed.     The  odontoid 
process  is  slightly  thickened  towards  the  end, 
which  is  distinguished  as  the  head,  and  below 
this  it  is  slightly  narrowed  as  the  neck.     The 
former  in  front  presents  an  articular  facet,  which 
is  invested  with  cartilage,  and  is  adapted  to  that 
SIDE  VIEW  OF  THE  AXIS,  i,     on  the  anterior  arch  of  the  atlas;  and  the  neck 
centrum;  2,  odontoid  pro-     behind  exhibits  another  facet,  which  is  slightly 

cess ;    3,    articular  facet ;  4,  -,   n      ±1         -i  ^  ^  i  • 

arch ;  5,  spinous  process ;  6,  grooved  for  the  play  of  the  transverse  ligament. 
transverse  process,  with  the  The  sides  and  back  of  the  head  are  impressed 

vertebral  foramen ;  7, 8,  pre-      1,1  i  *>  ±1,      i    ±        IJ-I-JT 

and  postarticular  proves.      by  the  attachment  of  the  lateral  odontoid  liga- 
ments, and  the  summit  is  variably  roughened 

or  smooth  for  the  attachment  of  the  middle  ligament.  The  arch  is 
thicker  and  stronger  than  in  the  succeeding  cervical  vertebra?,  and  the 
spinal  foramen  is  of  more  uniform  diameters.  The  spinous  process 
is  large  and  robust,  nearly  square  or  slightly  tapering,  sloping  and 
depressed  at  the  sides,  ridged  above,  channelled  beneath,  and  notched 
at  the  end.  The  prearticular  processes  project  outward  from  the  sides 
of  the  centrum,  and  are  joined  behind  by  the  pedicles  of  the  arch. 
Their  variably  circular  facets  incline  more  or  less  outward  and  down- 
ward, in  which  direction  they  are  nearly  straight,  but  fore  and  aft 

1  Epistropheus.  2  Processus  odontoideus,  or  dentatus  ;  dens. 


SPECIAL    ANATOMY   OF   THE   SKELETON.  59 

are  slightly  convex.  The  postarticular  processes  conform  to  those 
of  the  succeeding  vertebrae.  The  costal  processes  proceed  outwardly 
from  the  fore  part  of  the  prearticular  processes,  and  are  joined  behind 
by  the  transverse  process,  which  springs  from  the  usual  position.  The 
vertebral  foramen  ascends  beneath  the  prearticular  process,  and  opens 
outwardly  from  it. 

The  succeeding  four  cervical  vertebrae  especially  accord  with  the 
general  description  of  these  as  above  given.  In  the  seventh  cervical 
vertebra l  the  spinous  process  departs  from  the  more  common  char- 
acter, and  assumes  the  condition  of  that  of  the  first  thoracic  vertebra, 
being  long,  strong,  directed  obliquely  downward,  tapering,  and  ending 
in  a  thick  tubercle.  From  its  rather  abrupt  transition  of  form  and 
prominence  the  position  of  the  vertebra  to  which  it  belongs  is  readily 
distinguished  in  the  living  body.  The  vertebral  foramen  is  smaller  than 
in  the  preceding  vertebrae,  and  does  not  transmit  the  vertebral  artery. 

The  thoracic  vertebrae,2  twelve  in  number,  support  the  ribs  and 
enter  into  the  construction  of  the  thorax.  The  centrum  in  horizontal 
outline  is  transversely  reniform,  but  in  the  third  to  the  sixth  of  the 
series  varies  from  this  shape,  in  the  greater  fore  and  aft  extent,  and 
in  appearing  more  cordiform  or  trilateral. 
The  articular  margins  are  more  prominent 
than  in  the  preceding  vertebrae,  and  become 
more  so  in  the  lower  part  of  the  series; 
and  the  intervening  portion  of  the  centrum 
also  becomes  more  conspicuously  narrowed 
towards  the  middle,  especially  at  the  sides. 
The  principal  distinctive  character  of  the 
thoracic  vertebrae  is  the  costal  articular 
facets,3  which  are  mostly  half-oval,  smooth 
impressions,  situated  laterally  at  the  junc- 
tion of  the  centrum  and  arch.  One  is  placed  SIDE  VIEW  OF  A  THORACIC  VERTE- 
at  the  upper,  the  other  at  the  lower  corner  ? RA"  '•  ceQntruE? :  2- articular  facf 

for  ribs ;  3,  arch ;  4,  5,  interverte- 

of  the  centrum,  so  that  between  adjacent  brai  notches ;  6,  spinous  process;  v, 

vertebrae  a  contiguous  pair  of  facets  form  transverse  process;  8(Pre-  9,  post- 

.  .      i      .  „    ••       ,  articular  processes. 

a  pit  for  the  articulation  of  the  head  of  a 

rib.  The  first  vertebra  possesses  a  complete  circular  facet  for  the 
articulation  of  the  corresponding  rib,  besides  the  usual  half-oval  facet 
for  part  of  the  second  rib.  The  last  two  vertebrae  possess  each  a 
single  complete  facet  for  the  corresponding  ribs,  placed  nearly  midway 
on  the  conjunction  of  the  arch  and  centrum.  The  arch  is  deeper  and 
stronger  than  in  the  cervical  vertebrae,  but  its  laminae,  succeeding 


1  V.  prominens. 

2  Dorsal  vertebrae ;  v.  dorsales ;  v.  dorsi.  The  term  dorsal  applied  to  these  ver- 
tebrae is  objectionable,  as  they  are  not  more  dorsal  than  those  in  other  parts  of  the 
trunk.  *  Fossae  costales. 


60  SPECIAL   ANATOMY   OF   THE   SKELETON. 

those  of  the  first  vertebra,  become  considerably  shorter  or  of  less 
transverse  extent.  The  spinal  foramen  is  smaller  than  in  the  cervi- 
cal or  lumbar  vertebrae,  and,  though  of  much  less  transverse  width,  is 
wider  fore  and  aft  than  in  the  former.  It  is  mostly  circular  and  of 
uniform  diameters,  but  in  the  first  to  the  fourth  vertebra  passes  from 
transversely  triangular  oval  to  transversely  oval  and  circular. 

The  spinous  process  is  long,  pyramidal,  tapering,  directed  ob- 
liquely downward,  and  mostly  ends  in  a  narrow  tubercle  with  a  de- 
scending point.  It  is  longest,  most  tapering,  and  most  inclined  along 
the  middle  of  the  series.  The  first  one  inclines  much  less  than  that 
immediately  succeeding  it,  and  ends  in  a  thick  tubercle  like  that  of 
the  last  cervical  vertebra.  The  lowest  three  or  four  are  shorter,  less 
inclined,  and  end  in  larger  tubercles,  successively  increasing,  and  with 
the  last  one  disposed  to  divide  into  two.  The  articular  processes 
are  nearly  vertical  disks ;  the  upper  ones  projecting  above  the  junction 
of  the  laminae  and  pedicles,  and  separated  by  a  deep  wide  notch ;  the 
lower  ones  directed  downward  from  the  laminae  below  the  root  of  the 
transverse  processes.  The  articular  facets  are  circular  and  flat,  the 
upper  ones  looking  backward  with  a  slight  upward  inclination,  and 
the  lower  ones  looking  in  an  opposite  direction.  The  transverse  pro- 
cesses are  long  and  robust,  directed  outward  and  backward.  They 
end  in  a  compressed  tuberosity,  in  front  of  which  is  an  oval  or  circular, 
concave,  articular  facet,1  which  is  invested  with  cartilage  for  articu- 
lation with  the  tubercle -of  the  ribs,  ,  The  transverse  processes  of  the 
eleventh  vertebra  'are  much  reduced,  and  do  not  articulate  with  the 
corresponding  ribs;  and  those  of  the  twelfth  are  almost  obsolete, 
and  are  associated  with  two  additional  processes  to  be  subsequently 
described. 

The  lumbar  vertebrae,2  the  largest  and  most  robust  of  the  series,  are 
five  in  number,  and  form  together  the  bony  axis  of  the  loins,  extending 

from  the  thorax  to  the  pelvis.      The  cen- 
FIG.  16.  trum  has  the  same  shape,  especially  of 

that  of  the  lower  thoracic  vertebrae,  but  is 
slightly  more  prominent  at  the  articular 
margins,  and  more  conspicuously  narrowed 
in  the  intermediate  position.  The  arch  is 
proportionately  of  less  depth  than  in  most 
of  the  preceding  vertebrae,  so  that  wide 
intervals  are  left  between  the  laminae  of 

SIDE  VIEW  OF  A  LUMBAR  VERTEBRA.  .       . 

i,  centrum ;  2,  side  of  the  arch ;  3, 4,     the  contiguous  vertebrae,  not  existing  else- 
intervertebrai  notches;  5,  spinous     where,  except  between  the  upper  cervicals. 

process ;  6,  transverse  process ;  7,  pre-       _,  ,  , 

s,  postarticuiar  processes.  The  spinal  foramen  is  larger  than  m 

other  vertebrae,  being  about  as  wide  trans- 
versely as  that  of  the  cervicals,  but  wider  fore  and  aft.    As  in  the  latter, 

1  Fossa  transversalis.  2  V.  lumborum. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  61 

it  is  also  triangular,  but  of  more  equal  proportions  and  rounded  in  front 
instead  of  being  straight.  .The  spinous  process  is  a  broad  vertical 
plate,  thin  at  its  upper  border  but  thickening  below,  directed  back- 
ward, with  slight  inclination  downward,  and  ending  in  an  elliptical 
tubercle.  In  the  first  and  last  vertebrae  it  is  a  little  shorter  and  of  less 
depth  than  in  the  others,  and  the  tubercle  of  the  first  one  is  thicker 
and  triangular,  and  is  mostly  notched  below.  The  articular  processes 
together,  between  contiguous  vertebrae,  form  conspicuous  eminences  in 
the  interval  of  the  spinous  and  transverse  processes.  The  prearticular 
processes  ascend  from  between  the  pedicles  and  laminae,  and  are  sepa- 
rated by  a  wide,  deep  notch  above  the  latter.  Their  articular  facets 
are  vertically  nearly  straight,  transversely  concave,  and  look  towards 
each  other.  The  postarticular  processes  descend  from  the  junction 
of  the  laminae  and  spinous  process,  and  are  separated  by  a  deep  notch 
below  the  latter.  They  are  received  between  the  prearticular  processes 
of  the  adjacent  vertebrae,  and  have  narrower  and  transversely  convex 
facets,  which  look  outward  to  those  of  the  former.  The  transverse 
processes  are  long,  narrow,  flattened,  and  commonly  tapering,  but 
sometimes  expanded  at  the  ends,  and  are  directed  outward  with  a  slight 
bend  backward.  In  the  series  they  successively  increase  in  length  to 
the  third  or  fourth,  and  then  again  diminish. 

On  the  back  part  of  the  prearticular  processes  of  the  first  and 
second  lumbar  vertebrae  there  projects  an  elliptical  tubercle,  named  the 
metapophysis.1  Less  well  produced  it  exists  in  a  similar  position  in 
the  last  thoracic  vertebra,  and  further  in  a  successively  more  rudimen- 
tary condition  in  the  other  lumbars.  In  some  animals,  as  the  rabbit, 
the  metapophyses  are  long,  conspicuous  processes,  and  in  the  armadillos 
serve  to  support  the  osseous  buckler  which  covers  the  body.  In  the 
same  vertebrae  a  less  prominent  process,  the  anapophysis,*  occupies 
the  angle  between  the  former  and  the  transverse  process,  which  like- 
wise is  better  represented  in  some  other  animals,  as,  for  example,  in  the 
cat  and  the  dog. 

Structure  of  the  vertebrae.  The  vertebral  centra  are  composed  of 
spongy  substance  with  a  thin  covering  of  compact  substance ;  and  the 
principal  plates  and  fibres  of  the  former  are  for  the  most  part  arranged 
vertically,  and  are  intersected  by  others.  The  vertebral  arches  and 
their  processes  contain  a  less  proportion  of  spongy  substance.  The 
centra  are  traversed  by  large  channels,  for  veins,  especially  conspicuous 
in  the  thoracic  and  lumbar  vertebrae.  The  channels  ordinarily  com- 
mence in  pairs  at  the  corresponding  foramina  of  the  posterior  surface 
of  the  centra,  whence  they  advance  a  short  distance  and  then  diverge 
to  open  at  the  sides  of  the  centra. 

1  Mammillary  process  ;  processus  mammillaris  ;  posterior  superior  tubercle. 

2  Accessory  process ;  p.  accessorius ;  inferior  posterior  tubercle. 


62 


SPECIAL   ANATOMY   OF   THE  SKELETON. 


SACKUM. 

The  sacrum1  is  a  large,  curved,  pyramidal  bone,  situated  at  the 
lower  part  of  the  vertebral  column,  and  wedged  between  the  hip- 
bones, with  which  it  forms  the  pelvis.  In  childhood  it  consists  of  five 
distinct  pieces,  the  sacral  vertebrae,  but  these  approaching  maturity 
become  completely  ankylosed  into  a  single  bone,  which  affords  a  firm 
basis  of  articulation  to  the  hip-bones.  The  existence  of  a  sacrum, 
which  in  different  animals  consists  of  a  variable  number  of  anky- 
losed vertebrae,  is  correlated  with  the  presence  of  pelvic  limbs,  and 


FIG.  17. 


FRONT  VIEW  OF  THE  SACRUM.  1,  transverse 
ridges,  indicating  the  original  separation  of 
the  bone  into  five  segments ;  2,  sacral  foramina ; 
3,  promontory ;  4,  articular  surface  for  the  hip- 
bone ;  5,  sacral  border  of  the  sacro-sciatic 
notch ;  6,  base  of  the  sacrum,  with  its  articular 
surface  for  the  last  lumbar  vertebra;  7,  wing 
of  the  sacrum ;  8,  prearticular  process :  9,  apex 
of  the  sacrum,  with  its  articular  surface  for  the 
coccyx;  10,  cornu  of  the  last  vertebral  arch; 
11,  notch  for  the  last  sacral  nerve. 


FlG.   18. 


BACK  VIEW  OF  THE  SACRUM.  1,  rudimenta\ 
spinous  processes ;  2,  2,  sacral  canal :  3,  3,  rudi- 
mental  articular  processes ;  4,  cornu ;  5,  sacral 
foramina ;  6, 6,  rudimental  transverse  processes ; 
7,  articular[surface  for  the  hip-bone ;  8,  sacral 
border  of  the^acro-sciatic  notches;  9,  articular 
surface  for  the  last  lumbar  vertebra;  10,  pre- 
articular processes  for  the  latter  bone ;  11,  apex 
of  the  sacrum ;  12,  rough  surface  on  the  wing 
of  the  sacrum,  for  the  sacro-iliac  ligaments. 


when  these  are  absent,  or  are  disconnected  with  the  vertebral  column, 
isolated  vertebrae  form  an  uninterrupted  series  from  the  skull,  or  cer- 
vical region,  to  the  end  of  the  tail,  as  exemplified  in  cetaceans,  snakes, 
and  fishes. 

The  sacrum  is  a  very  variable  bone  in  its  proportions,  degree  of 
curvature,  and  in  other  respects.  The  vertebral  segments  of  which  it 
is  composed  successively  decrease  in  size  and  in  degree  of  development. 
Its  upper  part,  or  base,  is  widest  and  thickest,  and  articulates  with 
the  last  lumbar  vertebra.  It  tapers  below  to  the  apex,  which  articu- 
lates with  the  coccyx.  Its  sides  form  strong  processes,  named  the 
wings,  which  articulate  with  the  hip-bones. 


1  Os  sacrum  ;  os  latum. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  63 

The  sacrum  differs  but  little  in  length  and  breadth,  though  com- 
monly the  latter  dimension  is  the  greater.  It  is  directed  obliquely 
backward  from  the  vertebral  column  above,  so  that  its  base  is  placed 
considerably  in  advance  of  the  position  of  its  apex.  The  median  pro- 
jecting portion  of  its  base  is  the  promontory  of  the  sacrum,  forming 
with  the  contiguous  portion  of  the  centrum  of  the  last  lumbar  vertebra 
the  conspicuous  sacro-vertebral  angle,  which  overhangs  the  cavity 
of  the  pelvis. 

The  anterior  broadest  surface  of  the  sacrum  is  variably  concave 
and  smooth,  and  forms  the  posterior  part  of  the  cavity  of  the  pelvis. 
Its  median  portion  is  formed  by  the  vertebral  centra,  and  exhibits  a 
series  of  four  transverse  ridges,  which  indicate  the  original  lines  of 
separation.  On  each  side  are  the  four  large  anterior  sacral  foram- 
ina, which  communicate  inwardly  with  the  sacral  canal,  and  are 
directed  outwardly  in  large  grooves  on  the  sacral  wing. 

The  posterior  surface  of  the  sacrum,  of  less  width  than  the  ante- 
rior, is  convex  and  very  uneven.  Its  median  portion  is  composed  of 
the  arches  of  the  sacral  vertebrae  co-ossified  in  a  usually  continuous 
plate,  at  the  upper  and  lower  parts  of  which  are  large  notches  com- 
municating with  the  sacral  canal.  The  upper  sacral  notch l  is  wide, 
and  is  closed  in  the  recent  condition  by  the  last  pair  of  elastic  liga- 
ments. The  lower  sacral  notch2  is  narrower,  is  usually  produced  by 
imperfection  of  the  arch  of  the  last  sacral  vertebra,  and  in  the  recent 
state  is  closed  by  a  fibrous  membrane.  Frequently  this  notch  is  ex- 
tended upward  by  a  similar  imperfection  in  one  or  more  of  the  arches 
of  the  sacral  vertebra  above. 

Between  the  sacral  notches  extend  a  series  of  median  tubercles  as 
spinous  processes,  which  are  very  variably  produced  in  different 
specimens.  The  upper  three  or  four  are  often  more  or  less  united  in  a 
broken  ridge,  and  often  those  of  the  lower  one  or  two  sacral  vertebra 
appear  as  a  pair  of  tubercles  for  each,  very  variably  produced, — some- 
times to  a  greater  degree  than  the  upper  ones,  and  sometimes  scarcely 
at  all.  The  open  arch  of  the  last  sacral  vertebra  leaves  the  pedicles  as 
a  pair  of  downward-projecting  hook-like  processes,3  the  cornua,  be- 
neath which  the  notch  forms  part  of  the  intervertebral  foramen  for 
the  exit  of  the  last  sacral  nerve. 

On  each  side  of  the  sacrum  are  the  posterior  sacral  foramina, 
smaller  than  the  anterior,  situated  directly  opposite,  and,  like  them, 
communicating  inwardly  with  the  sacral  canal.  Internally  the  foram- 
ina are  skirted  by  feeble  processes,  rudimentary  of  the  articular  pro- 
cesses of  the  preceding  vertebrae.  Above  the  foramina,  at  the  sides 
of  the  upper  sacral  notch,  is  a  pair  of  well-produced  articular  processes, 
which  articulate  with  those  of  the  last  lumbar  vertebra.  External 
to  the  position  of  the  posterior  sacral  foramina  is  an  irregular  tuber- 

1  Hiatus  sacralis.  2  Incisura  sacro-coccygea.  3  Cornua  sacralia. 


64  SPECIAL   ANATOMY   OF   THE   SKELETON. 

cular  ridge,  which  seems  to  correspond  with  the  extremities  of  the 
transverse  processses  of  the  vertebrae. 

The  base  of  the  sacrum,  directed  upward  and  forward,  presents  a 
median,  transversely  elliptical,  flat  surface  for  articulation  with  the 
centrum  of  the  last  lumbar  vertebra.  Laterally  the  base  expands  out- 
wardly on  the  sacral  wing  in  a  quadrate  smooth  surface,  which  con- 
tributes to  the  upper  division  of  the  pelvis.  Behind  the  base  are  the 
pre-articular  processes  of  the  sacrum,  separated  by  the  sacral  notch. 

The  apex  of  the  sacrum  ends  in  a  transverse  elliptical  articular  facet 
for  the  coccyx. 

The  wings1  of  the  sacrum  appear  as  strong,  lateral,  pyramidal 
processes,  with  the  base  directed  upward  and  forward,  and  thence 
tapering  downward.  The  most  prominent  part  of  the  base  behind 
forms  a  tuberous  prominence  which  represents  the  transverse  process 
of  the  first  sacral  vertebra.  At  the  fore  part  of  the  wing  outwardly 
is  the  iliac  articular  surface,2  a  vertical,  uneven  plane  of  irregular 
reniform  outline.  It  usually  extends  upon  the  upper  two  sacral  ver- 
tebras, but  sometimes  reaches  a  little  way  on  the  third  vertebra.  Be- 
hind and  below  the  articular  surface  is  a  more  uneven  surface,  which 
gives  attachment  to  the  strong  posterior  sacro-iliac  and  sacro-sciatic 
ligaments. 

The  sacral  canal3  is  the  continuation  of  the  vertebral  canal 
through  the  sacrum,  in  which  it  follows  the  curvature  of  the  bone. 
It  is  triangular,  widest  transversely,  and  narrows  in  its  descent.  It 
communicates  laterally  by  apertures  which  open  into  the  anterior  and 
posterior  sacral  foramina  for  the  transmission  of  the  corresponding 
nerves.  • 

The  sacrum  accords  in  structure  with  the  vertebrae  above. 

In  the  female  the  sacrum  is  commonly  shorter  and  broader  in  pro- 
portion to  its  length,  and  usually  is  less  curved,  than  in  the  male. 

Occasionally  the  sacrum  is  composed  of  six  vertebral  segments, 
including  five  pairs  of  'sacral  foramina.  Commonly  the  additional 
segment  is  the  first  coccygeal  vertebra,  which  in  its  coalescence  with 
the  sacrum  more  or  less  conforms  in  its  development  to  the  usual  con- 
dition of  the  last  sacral  vertebra.  Less  frequently  the  increase  is  due 
to  the  ankylosis  of  the  last  lumbar  vertebra,  which  also  is  variably 
modified  to  conform  to  the  ordinary  condition  of  the  first  sacral  ver- 
tebra. In  such  cases  the  modification  may  be  confined  to  one  side, 
while  the  other  retains  more  or  less  of  its  usual  condition.  Sometimes 
the  co-ossification  of  the  lumbar  vertebra  with  the  sacrum  is  lateral 
only,  while  the  centra  remain  unankylosed.  Rarely  the  number  of 
sacral  vertebrse  is  reduced  to  four,  in  which  condition  there  is  an 
equivalent  accession  either  to  the  lumbar  or  the  coccygeal  series. 

1  Lateral  portions  ;  partes  laterales  ;  alae. 

2  Auricular  surface ;  facies  auricularis.  8  Canalis  sacralis. 


SPECIAL    ANATOMY    OF   THE   SKELETON.  65 

The  posterior  portion  of  the  sacrum  is  very  variable  in  the  degree 
of  production  of  the  arches  and  processes  of  the  sacral  vertebrae. 
Frequently  intervals  occur  between  the  laminae  of  the  segments,  es- 
pecially between  those  of  the  first  and  second  sacral  vertebrae.  This 
condition  is  often  accompanied  by  deficient  union  between  the  laminae 
of  each  arch  and  imperfect  development  of  the  spinous  process.  The 
notch  at  the  lower  end  of  the  sacral  canal  is  variably  extended,  some- 
times even  the  entire  length  of  the  sacrum. 

COCCYX. 

The  coccyx1  succeeds  the  sacrum,  and  continues  its  triangle  and 
curvature  downward  and  forward.     It  is  composed  of  four  or  five  seg- 
ments  or  coccygeal   vertebrae,   which   are 
homologous  with  the  caudal  or  tail  vertebrae  of  FIG.  19. 

o 

other  animals,  and  differ  from  the  preceding 
vertebrae  of  the  series  in  being  reduced  to  the 
most  rudimentary  condition. 

The  first  coccygeal  vertebra  is  best  devel- 
oped, and  nearly  conforms  to  the  last  one  of 
the  sacrum.  It  consists  of  a  centrum,  of  flat- 
tened cylindrical  shape,  with  lateral,  wing-like, 
blunt-pointed  processes.  Between  these  and  POSTERIOR  VIEW  OF  THE 
the  contiguous  margin  of  the  sacrum  on  each  COCCYX,  i,  first  segment;  2, 2, 

.,.  A   i_         -L  •    u    •       j.  u  •        the  cornua ;  3,  transverse  pro- 

side  is  a  notch,  which  m  the  recent  state  is     Ces8;  4f  5,  6,  lower  threeeoc- 
converted  by  the   sacro-sciatic   ligament  into     cygeai  vertebrae, 
a  foramen  for  the  passage  of  the  fifth  sacral 

nerve.  From  behind  the  centrum  ascend  a  pair  of  processes,  the  cornua,2 
which  represent  the  pedicles  of  a  vertebral  arch.  These  join  correspond- 
ing descending  processes  of  the  sacrum,  and  with  them  enclose  the 
intervertebral  foramina  for  the  fifth  sacral  nerves.  The  remaining  coc- 
cygeal vertebrae  are  rudimentary  centra,  successively  decreasing  in  size. 
The  second  coccygeal  vertebra  commonly  possesses  a  short,  blunt,  lateral 
process,  between  which  and  the  first  vertebra  is  a  notch.  This  is  con- 
verted by  the  sacro-sciatic  ligament  into  an  intervertebral  foramen  for 
the  passage  of  the  last  spinal  nerve.  The  fifth  coccygeal  vertebra, 
when  distinguishable,  is  a  little  nodule  of  bone,  which  in  early  youth 
becomes  united  with  the  fourth  vertebra.  The  union  of  the  coccygeal 
vertebrae  is  very  variable.  Commonly  after  adult  age  the  lower  two  or 
three  are  ankylosed,  while  the  first  remains  separate,  or  this  may  be 
united  with  the  second,  and  the  others  be  united  in  another  piece. 
Sometimes  the  first  vertebra  is  united  with  the  sacrum,  and  the  other 
vertebrae  are  joined  in  two  or  in  a  single  piece.  Late  in  life  all  the 
coccygeal  vertebrae  may  be  ankylosed  together,  and  sometimes  with 
the  sacrum. 

1  Os  coccygis ;  ossa  coccygis  ;  cauda,  rump-bone  ;  crupper-bone.      2  C.  coccygea. 

6 


66  SPECIAL,    ANATOMY   OF    THE   SKELETON. 

THE   VEETEBKAL   COLUMN  VIEWED   ENTIEE. 

The  vertebral  column,  or  spine,  is  an  upright,  flexuose  pillar,  in  which 
the  vertebrae  form  the  shaft,  and  the  sacrum,  with  the  coccyx,  forms 
the  base.  From  the  atlas  as  the  capital,  the  shaft  gradually  enlarges 
to  its  base,  which  is  a  curved  wedge  firmly  inserted  between  the  hip- 
bones. It  is  the  central  pillar  of  support  to  the  skeleton ;  upon  it  rests 
the  skull;  its  sides  sustain  the  ribs  with  the  sternum,  to  which  are 
suspended  the  upper  limbs ;  and  through  the  sacrum  it  transmits  the 
weight  of  the  body  to  the  lower  limbs. 

The  average  length  of  the  spine  is  estimated  to  be  about  twenty- 
eight  inches  in  the  male  and  a  couple  of  inches  less  in  the  female. 
From  this  size  it  commonly  deviates  but  little,  the  difference  of  stature 
among  persons  depending  mainly  on  variation  in  the  length  of  the 
lower  limbs.  At  birth  it  is  proportionately  longer  in  consequence  of 
the  relatively  short  growth  of  the  limbs.  Its  gradual  growth  continues 
until  about  twenty -five  years. 

In  a  side  view  the  spine  presents  a  succession  of  curves  alternating 
in  direction,  and  due  to  difference  in  thickness  between  the  front  and 
back  part  of  the  centra  of  the  vertebrae  and  the  intervertebral  disks ; 
most  conspicuously  observed  in  the  lumbar  region,  especially  in  the 
last  lumbar  vertebra  and  the  adjacent  intervertebral  disks.  The  curves, 
named  from  their  position,  are  the  cervical,  thoracic,  lumbar,  and 
sacro-coccygeal,  of  which  the  first  and  third  are  convex  in  front  and 
concave  behind,  and  the  others  are  the  reverse.  The  upper  three  curves 
gently  merge  in  one  another,  but  the  last  one  is  more  abrupt,  its  point 
of  departure  being  the  sacro- vertebral  angle,  which  is  formed  by  the 
centrum  of  the  last  lumbar  vertebra  and  the  promontory  of  the  sacrum. 
The  upper  curves  are  in  a  measure  proportioned  in  degree  with  one 
another,  and  ordinarily  increase  or  decrease  together.  They  are  in- 
fluenced by  habit,  and  thus  become  more  pronounced  in  persons  whose 
occupation  retains  them  habitually  in  a  bent  position,  as  in  the  miner, 
and  are  less  conspicuously  marked  in  those  habitually  erect,  as  in  the 
soldier.  At  birth  they  are  slight,  augment  as  the  child  learns  to  stand 
and  walk,  and  gradually  increase  to  maturity.  Subsequently,  uninflu- 
enced by  special  occupations,  they  continue  with  little  or  no  obvious 
change  until  late  in  life,  when  with  the  advance  of  years  they  slowly 
increase,  and  thus  contribute  to  the  diminution  of  stature  of  old  age. 

The  curves  of  the  spine  contribute  to  its  elasticity,  and  thus  render 
it  less  liable  to  injuries  than  if  it  were  straight ;  the  direction  of  the 
curves  also  in  the  thorax  and  pelvis  contributes  to  the  capacity  of  their 
cavities.  More  or  less  lateral  curvature  with  the  convexity  directed 
towards  the  right,  frequently  observed  in  the  thoracic  region,  is  attrib- 
uted to  more  habitual  use  of  the  right  upper  limb. 

In  the  front  view  of  the  spine  the  vertebrae  are  observed  to  have 
their  greatest  width  at  the  transverse  processes.  The  atlas  is  about 


SPECIAL   ANATOMY    OF   THE    SKELETON.  67 

equal  in  width  with  the  first  thoracic  vertebra,  and  these  are  the  widest 
of  the  series  except  the  lumbar  vertebrae.  The  axis  undergoes  an  abrupt 
decrease  in  width,  and  with  the  succeeding  two  cervical  vertebrae  is 
the  narrowest  of  the  series  except  the  lowest  two  thoracic  vertebrae. 
The  lower  cervical  vertebrae  successively  increase,  and  the  first  thoracic 
vertebra  undergoes  a  more  abrupt  enlargement  to  the  width  of  the 
atlas.  The  other  thoracic  vertebrae  gradually  diminish  in  width  to  the 
last,  which  is  the  narrowest  of  all  the  vertebrae.  The  first  lumbar  ver- 
tebra abruptly  increases  to  nearly  the  width  of  the  atlas,  and  the 
others  successively  increase  to  the  third,  the  widest  of  the  vertebrae, 
and  then  again  slightly  diminish  to  the  last  one.  The  sacrum  at  its 
base,  with  an  abrupt  increase,  is  nearly  half  the  width  more  than  the 
widest  portion  of  the  spine  above,  and  it  thence,  with  the  coccyx,  rapidly 
tapers  to  the  end  of  the  column.  The  centra  of  the  vertebrae  from 
that  of  the  axis  gradually  become  broader  to  that  of  the  first  or  second 
thoracic  vertebra,  then  diminish  to  that  of  the  fourth,  and  thence  again 
increase  in  breadth  to  the  promontory  of  the  sacrum.  In  the  side 
view  the  centra  of  the  cervical  vertebrae  are  of  nearly  uniform  width 
to  the  last,  while  those  of  the  thoracic  vertebrae  successively  increase, 
and  those  of  the  lumbar  vertebrae  remain  nearly  uniform.  The  artic- 
ular processes,  from  the  lower  pair  of  the  axis  to  those  of  the  sacrum, 
form  a  continuous  ridge,  extending  on  each  side  of  the  spine  along  the 
line  of  junction  of  the  pedicles  and  laminae  of  the  arches.  Immedi- 
ately in  advance  of  the  ridge  are  situated  the  intervertebral  foramina, 
and  behind  the  ridge  is  the  vertebral  groove.  In  front  of  the  cervi- 
cal portion  of  the  ridge  are  the  transverse  and  costal  processes,  with 
the  included  vertebral  foramen,  through  which  ascends  the  vertebral 
artery.  From  the  ridge  of  the  thoracic  vertebrae  project  the  transverse 
processes,  together  forming  a  curve  conforming  to  that  of  the  ver- 
tebrae. From  the  last  thoracic  vertebra  to  the  sacrum  the  adjoining- 
articular  processes  and  metapophyses  produce  a  row  of  conspicuous 
eminences,  situated  behind  the  bases  of  the  transverse  processes.  The 
articular  processes  of  the  atlas,  together  with  the  upper  pair  of  the 
axis,  form  on  each  side  a  short  column,  which  is  situated  in  advance  of 
the  position  of  the  articular  ridge  below,  and  is  immediately  devoted 
to  the  support  of  the  skull. 

The  intervertebral  foramina  appear  at  the  sides  of  the  spine,  from 
the  axis  to  the  sacrum,  as  a  row  of  large  round  or  oval  apertures, 
formed  by  the  apposition  of  adjacent  intervertebral  notches,  of  which 
the  upper  are  the  larger  in  the  cervical  region,  while  the  lower  are  the 
larger  in  the  thoracic  and  lumbar  regions.  Above  and  below  they  are 
formed  by  the  contiguous  pedicles,  in  front  by  the  centra  and  interver- 
tebral disks,  and  behind  by  the  conjoined  articular  processes  and  their 
capsular  ligaments. 

The  vertebral  grooves,  for  the  lodgement  of  the  extensor  muscles 
of  the  back  of  the  trunk,  extend  along  the  spine  on  each  side  of  the 


68  SPECIAL    ANATOMY    OF   THE    SKELETON. 

spinous  processes  outwardly  to  the  articular  processes.  In  the  cervical 
region  they  are  shallow ;  in  the  thoracic  region  they  are  deep,  and 
extend  farther  outwardly  to  the  ends  of  the  transverse  processes ;  in 
the  lumbar  region  they  are  narrower  and  shallower,  and  are  defined 
outwardly  by  the  articular  eminences ;  and  on  the  sacrum  they  become 
more  shallow  and  tapering,  and  are  defined  by  the  articular  rudi- 
ments skirting  the  sacral  foramina.  An  additional  groove  external 
to  the  principal  ones,  in  the  lumbo-sacral  region,  is  formed  between 
the  articular  eminences  and  the  ends  of  the  transverse  processes. 

The  bottoms  of  the  vertebral  grooves  are  formed  by  the  laminae  of 
the  vertebral  arches,  which  are  closely  fitted  and  imbricated  in  the 
lower  part  of  the  cervical  and  in  the  thoracic  region,  except  between 
the  last  two  vertebrae  of  the  latter.  The  laminae  of  these  and  of  the 
lumbar  vertebra,  together  with  their  postarticular  processes,  form  a 
series  of  quadrate  plates  which  are  directed  downward,  and  are  received 
into  square  grooves  formed  by  the  contiguous  prearticular  processes. 
Considerable  intervals  occur  between  the  laminae,  which  in  the  recent 
state  are  closed  by  elastic  ligaments.  This  arrangement,  while  it 
permits  a  considerable  degree  of  flexion  and  extension  of  the  spine  in 
the  lumbar  region,  closely  restricts  any  lateral  motion.  The  intervals 
between  the  laminae  of  the  intermediate  cervical  vertebrae  increase  or 
decrease  with  the  flexion  and  extension  of  the  neck,  and  in  the  recent 
condition  are  occupied,  like  all  similar  intervals,  with  elastic  ligaments. 
Large  intervals  also  exist  between  the  arches  of  the  axis  and  the  atlas, 
and  between  the  latter  and  the  occipital  bone,  and  these  in  .the  recent 
state  are  occupied  by  loose  membranous  ligaments,  which  are  pierced 
laterally  by  the  first  and  second  pair  of  intervertebral  foramina. 

The  spinous  processes  form  a  continuous  crest  from  the  axis  to  the 
sacrum.  The  crest  approaches  the  surface  of  the  body,  so  that  the 
ends  of  the  processes  may  be  felt  along  a  median  groove  of  the  back 
of  the  trunk  and  the  prominence  of  the  sacrum ;  but  in  the  neck  the 
processes  mostly  are  deeply  situated  between  the  lateral  muscles. 
Absent  in  the  atlas,  the  spinous  process  is  large  in  the  axis ;  then 
abruptly  reduced  in  the  three  or  four  succeeding  vertebrae,  it  again 
becomes  large  and  prominent  in  the  last  one.  Together  the  cervical 
spinous  processes  form  a  deep  curve  with  the  concavity  behind  ;  those 
of  the  axis  and  last  vertebra  forming  the  ends  of  the  curve.  The 
slope  backward  of  the  laminae  and  articular  processes  of  the  cervical 
vertebrae,  the  shortness  of  the  intermediate  spinous  processes,  and  the 
channelled  condition  beneath  of  that  of  the  axis,  all  favor  the  extension 
of  the  head.  The  spinous  process  of  the  first  thoracic  vertebra  is 
nearly  like  that  of  the  last  cervical  vertebra  in  form  and  direction. 
Those  following  are  more  tapering,  abruptly  incline  more  downward, 
successively  increase  in  this  disposition,  and  become  closely  applied  to 
one  another  in  an  imbricated  manner.  Below  the  middle  of  the  series 
they  become  successively  less  inclined  and  more  separated  towards 


SPECIAL   ANATOMY    OF    THE   SKELETON.  69 

the  ends,  and  in  the  last  two  are  directed  nearly  horizontally  back- 
ward. In  the  lumbar  region  the  deep  laminar  spinous  processes  are 
directed  horizontally  backward,  and  are  separated  by  well-marked 
intervals.  On  the  sacrum  the  crest  of  the  spinous  processes  gradually 
subsides. 

The  spinal  canal,  formed  by  the  succession  of  the  spinal  foramina, 
extends  from  the  occipital  foramen,  where  it  communicates  with  the 
cavity  of  the  cranium,  to  the  second  coccygeal  vertebra.  Its  lower 
extremity  is  closed  by  the  posterior  sacro-coccygeal  ligament,  which 
occupies  the  notch  behind  the  lowest  sacral  vertebrae  and  the  corre- 
sponding interval  of  the  adjacent  coccygeal  vertebra.  The  canal  in 
front  is  formed  by  the  vertebral  centra  and  intervertebral  disks  con- 
nected throughout  by  the  common  posterior  vertebral  ligament,  and 
behind  by  the  vertebral  arches  and  intervening  elastic  ligaments.  At 
the  sides  it  communicates  with  the  exterior  by  thirty-one  pairs  of  inter- 
vertebral  foramina  for  the  transmission  of  the  spinal  nerves  and  blood- 
vessels. It  is  most  capacious  in  the  lumbar  region,  nearly  as  large  in 
the  neck,  less  in  the  thoracic  region,  and  least  in  the  sacrum,  where 
it  tapers  to  the  lower  end.  In  the  neck  it  is  trilaterally  prismatic, 
becomes  cylindrical  in  the  thoracic  region,  and  is  again  trilaterally 
prismatic  in  the  lumbar  region  and  sacrum,  tapering  away  in  the  latter. 
In  the  neck  it  is  much  wider  transversely  than  fore  and  aft,  and  is  flat 
in  front ;  in  the  lumbar  region  it  is  of  greater  fore  and  aft  extent,  and 
rounded  in  front ;  and  in  the  sacrum  it  is  more  of  the  relative  propor- 
tions and  shape  of  that  in  the  neck. 

The  first  and  second  pair  of  intervertebral  foramina  open  behind 
the  articular  processes  between  the  occipital  bone  and  atlas  and  between 
the  latter  and  the  axi&.  Those  succeeding  to  the  sacrum  open  in  advance 
of  the  articular  processes.  Those  of  the  sacrum  open  in  a  correspond- 
ing position  into  the  recesses  of  the  sacral  foramina,  except  the  last 
pair,  which  open  between  the  cornua  of  the  sacrum  and  coccyx.  The 
last  pair,  at  the  end  of  the  spinal  canal,  open  outwardly  between  the 
first  and  second  coccygeal  vertebra  and  the  sacro-sciatic  ligament. 

DEVELOPMENT  AND  GKOWTH  OF   THE   VERTEBKAL   COLUMN. 

In  the  embryo,  ossification  of  the  vertebrae  commences  in  corre- 
sponding cartilaginous  segments,  which  are  developed  around  the 
notochordal  axis  of  the  embryo.  In  different  positions  of  the  column 
it  occurs  from  the  eighth  week  to  three  and  a  half  months,  proceeding 
generally  from  three  principal  centres  for  each  vertebra, — one  for  the 
main  portion  of  the  centrum,  and  one  for  each  half  of  the  arch,  in- 
cluding a  small  contiguous  portion  of  the  centrum.  At  birth  all  the 
vertebrae  except  the  atlas  and  the  axis  consist  of  three  osseous  pieces, 
which  accord  with  the  original  centres.  As  growth  proceeds,  the  laminae 
of  the  arches  for  the  most  part  coalesce  before  the  end  of  the  first  year. 
Those  of  the  upper  cervical  vertebrae  unite  from  the  second  to  the  third 


70 


SPECIAL,   ANATOMY   OF   THE   SKELETON. 


or  fourth  year.  The  processes  are  exogenous  growths  from  the  arch, 
which  for  some  time  remains  connected  with  the  main  part  of  the 
centrum  by  the  neuro-central  suture,  which  is  obliterated  from  the 
fourth  to  the  sixth  year.  The  vertebrae  gradually  assume  and  nearly 
reach  their  complete  shape  and  proportions  about  puberty,  subsequently 
to  which  they  acquire  a  number  of  epiphyses.  A  pair  of  these  appear 
on  the  articular  surfaces  of  the  centrum  in  the  form  of  a  marginal  zone, 


FIG.  21. 


FIG.  20. 


DEVELOPMENT  OF  THE  VERTEBRA,  a,  verte- 
bra of  a  foetus,  in  a  cartilaginous  condition, 
with  three  centres  of  ossification ;  1,  2,  lateral 
pieces  ;  3,  the  centrum ;  b,  vertebra  of  an  infant. 
The  lateral  pieces,  1,  2,  are  co-ossified  in  the 
spinous  process,  and  join  the  body,  3,  at  the 
sutures,  4.  The  ends  of  the  transverse  and 
spinous  processes  yet  in  a  cartilaginous  state. 


6  6 

DEVELOPMENT  OF  THE  EPIPHYSES  TO  THE  VER- 
TEBRAE, a,  thoracic  vertebra,  with  the  epiphyses 
4, 5,  to  the  transverse  processes ;  6,  to  the  spiuous 
process ;  and  7,  to  the  centrum  ;  b,  arch  with  its 
processes ;  and  c,  centrum  of  a  lumbar  vertebra ; 
4, 5,  epiphyses  of  the  transverse  processes ;  6,  of 
the  spinous  process ;  7,  8,  of  the  centrum ;  9, 10, 
epiphyses  of  the  metapophyses. 


attached  to  the  latter  by  cartilage,  from  which  the  centrum  continues 
to  grow.  Small  epiphyses  also  appear  at  the  ends  of  the  spinous  and 
transverse  processes  of  the  thoracic  and  lumbar  vertebrae,  and  likewise 
to  the  metapophyses  of  the  latter.  The  different  epiphyses  make  their 
appearance  up  to  eighteen  years,  and  unite  with  the  chief  part  of  the 
vertebra  from  that  time  up  to  twenty-five  years. 

The  atlas  at  birth  consists  of  two  lateral  portions,  corresponding 
with  the  half-arches  of  the  succeeding  vertebrae,  united  by  the  anterior 
arch  in  the  condition  of  cartilage,  in  which  one  or  two  ossific  centres 
appear  in  the  course  of  the  second  year.  Ankylosis  of  the  lateral 
portions  behind  occurs  about  the  fourth  year,  and  with  the  anterior 
arch  from  the  sixth  to  the  eighth  year. 

The  axis  at  birth  commonly  consists  of  four  osseous  pieces, — one 
for  the  lower  part  of  the  centrum,  one  for  the  upper  part,  with  the 
odontoid  process,  and  two  for  the  half-arches.  The  odontoid  process 
originates  in  a  pair  of  ossific  centres,  which  coalesce,  and  later  an  ad- 
ditional centre  appears  in  the  summit  and  speedily  unites  with  the  rest. 
The  pieces  all  coalesce  by  the  fifth  or  sixth  year.  As  in  the  other 
vertebrae,  an  epiphysis  is  added  to  the  lower  articular  surface  of  the 
centrum. 

In  the  seventh  cervical  vertebra  the  costal  processes  are  produced 
from  separate  centres,  and  they  ankylose  with  the  chief  part  of  the 


SPECIAL    ANATOMY    OF   THE   SKELETON.  71 

vertebra  from  the  fourth  to  the  sixth  year.  Earely  one  or  both  remain 
separate  and  become  larger  than  usual,  thus  forming  cervical  ribs. 
An  epiphysis  also  appears  on  the  end  of  the  spinous  process,  as  in  the 
succeeding  vertebrae. 

In  the  sacrum  each  vertebral  segment  commences  with  three  pri- 
mary centres  of  ossification,  as  in  the  vertebra?  above.  Later  an 
additional  pair  of  centres  appear  in  the  lateral  portions  of  the  upper 
three  or  four  segments.  At  birth  the  sacrum  commonly  consists  of  five 
osseous  pieces  for  each  of  the  upper  three  segments,  and  three  for  each 
of  the  other  two  segments.  The  pieces  of  each  segment  coalesce  to 
form  the  sacral  vertebra?  from  the  second  to  the  sixth  year.  As  in  the 
vertebra?  above,  epiphyseal  zones  make  their  appearance  on  the  ar- 
ticular surfaces  of  each  centrum  subsequent  to  puberty.  The  sacral 
vertebra?  commence  to  ankylose  through  their  lateral  portions  about 
the  tenth  year,  then  unite  through  their  arches,  and  finally  through 
their  centra  approaching  adult  age.  Near  the  latter  period  a  thin 
epiphyseal  plate  appears  in  the  position  of  the  articular  surface  for 
the  hip-bone,  and  another  on  the  margin  of  the  sacrum  below.  Small 
epiphyses  also  appear  on  the  tips  of  the  two  or  three  upper  spinous 
processes.  The  complete  fusion  of  all  the  pieces  of  the  sacrum  may 
extend  to  twenty-five  years  or  later. 

The  coccyx  does  not  commence  to  ossify  until  after  birth ;  a  single 
centre  appearing  successively  in  each  segment  at  variable  periods  up  to 
near  puberty,  after  which  epiphyseal  zones  appear  on  the  articular  sur- 
faces, as  on  the  centra  of  the  vertebra?  above.  The  coccygeal  vertebra? 
usually  coalesce  successively  from  below  upward,  the  last  two  uniting 
shortly  after  puberty.  Commonly  the  lower  three  or  four  become  anky- 
losed  before  middle  age,  while  the  union  of  these  with  the  first  coccygeal 
vertebra,  and  of  this  with  the  sacrum,  occurs  at  variable  periods  late  in 
life. 

ARTICULATIONS   OF   THE   VERTEBKAL   COLUMN. 

The  articulations  of  the  vertebral  column  are  formed  between  the 
centra,  the  lamina?,  the  articular  processes,  and  the  spinous  processes, 
and  others  between  the  vertebral  column  and  the  skull. 

The  intervertebral  ligaments1  or  disks  are  fibro-cartilaginous, 
and  occupy  the  intervals  of  the  vertebral  centra,  including  those  of  the 
sacrum  and  coccyx.  They  bind  the  vertebra?  closely  and  tenaciously 
together,  and  give  to  the  spine  a  remarkable  degree  of  flexibility  and 
elasticity,  combined  with  great  strength.  The  first  is  placed  between 
the  axis  and  third  cervical  vertebra,  and  they  continue  in  uninterrupted 
series  to  the  interval  between  the  last  lumbar  vertebra  and  the  sacrum, 
and  then  occupy  the  intervals  of  the  latter  and  the  coccyx  and  the 
pieces  of  this. 

1  Intervertebral  fibro-cartilages,  or  substance ;  1.  intervertebralia  ;  fibro-cartila- 
gines  intervertebrales. 


72 


SPECIAL,   ANATOMY    OP   THE   SKELETON. 


The  disks  conform  in  shape  to  the  articular  surfaces  of  the  verte- 
bral centra.  They  are  largest  and  thickest  in  the  loin,  where  they  are 
nearly  one-third  the  depth  of  the  centra  they  unite.  They  are  thin- 
nest between  the  centra  of  the  third  and  seventh  thoracic  vertebrae, 
above  which  they  gradually  increase.  They  are  thicker  in  front  or 
behind  in  accordance  with  the  convexity  of  the  spinal  curves,  which 


FIG.  22. 


FIG.  23. 


UPPER  VIEW  OF  A  LUMBAR  VERTEBRA, 

with  a  horizontal  section  of  an  inter- 
vertebral  ligament.  1,  concentric  layers 
of  fibrous  tissue ;  2,  pulpy  fibro-carti- 


VERTICAL  SECTION  OF  TWO  LUMBAR  VERTEBRAE,  with 
the  intervening  intervertebral  ligament.  The  inter- 
vening articular  processes,  enveloped  by  a  capsular 
ligament,  are  also  represented.  1, 1,  concentric  layers 
of  fibrous  tissue,  curving  outwardly ;  2,  2,  concentric 
layers  curving  inwardly;  3,  pulpy  nbro-cartilage  in 
the  middle. 


they  in  a  measure  contribute  to  produce.  They  are  also  thicker  cen- 
trally in  conformity  with  the  depression  of  the  articular  surfaces  of 
the  centra  they  unite. 

The  disks  are  of  complex  structure,  and  are  immediately  connected 
with  the  articular  surfaces  of  the  centra  through  thin  plates  of  carti- 
lage. They  are  composed  of  numerous  concentric  bands,  enclosing  a 
central  mass  of  pulpy  fibre-cartilage.  The  bands  are  closely  applied 
together,  and  in  a  horizontal  section  of  the  disks  appear  as  a  broad, 
dense  zone  of  concentric  parallel  rings ;  in  a  vertical  section  as  a  series 
of  parallel  upright  layers,  with  the  more  superficial  ones  slightly  bent 
outwardly  and  the  deeper  ones  inwardly.  In  a  fore  and  aft  section 
of  fresh  vertebrae,  the  central  pulp  projects  from  the  cut  surface,  appar- 
ently as  if  squeezed  out  through  contraction  of  the  exterior  bands,  or 
as  if  relieved  from  pressure  to  which  it  had  been  subjected  before  the 
section  was  made.  In  a  horizontal  section  of  the  disks  the  central 
pulp  commonly  rises  in  parts  and  sinks  elsewhere,  and  exhibits  a  more 
or  less  irregular  aspect.  The  concentric  bands  consist  of  bundles  of 
fibres  arranged  obliquely  and  parallel  with  one  another  between  the 
vertebrae,  alternating  or  crossing  in  their  direction  in  the  successive 
layers.  The  superficial  bands  are  composed  of  bundles  of  ordinary 
fibro-connective  tissue,  but  the  deeper  and  much  greater  part  of  the 
bands  is  composed  of  similar  bundles  of  more  elastic  character.  The 


SPECIAL    ANATOMY    OF   THE    SKELETON. 


73 


concentric  bands  and  their  constituent  bundles  of  fibres  are  associated 
with  an  intertexture  of  connective  tissue  and  elastic  fibres,  in  which 
are  embedded  cartilage-corpuscles,  especially  among  the  deeper  bands. 
These  corpuscles  occur  singly  or  in  groups,  and  often  in  rows  of  vari- 
able length.  The  intervertebral  pulp  is  soft,  but  is  very  tenacious.  It 
chiefly  consists  of  an  intertexture  of  fibro-elastic  bundles  with  em- 
bedded cartilage-corpuscles  like  those  situated  among  the  surrounding 
bands.  After  adult  age  it  commonly  exhibits  a  lacerated,  ragged,  and 
more  or  less  fissured  appearance,  and  when  placed  in  water  swells  and 
assumes  an  irregular  villous  aspect. 

The  anterior  vertebral  ligament1  is  a  strong,  thin,  fibrous  band, 
situated  in  front  of  the  vertebral  column,  and  extending  from  the  oc- 
cipital bone  the  entire  length  of  the  latter.  Starting  in  a  narrow  por- 
tion or  cord2  from  beneath  the  basilar  process  and  connected  in  front 


FIG.  24. 


FIQ.  25. 


PORTION  OF  THE  OCCIPITAL  BONE,  WITH  THE 
ATLAS  AND  AXIS,  front  view.  1,  origin  of  the 
anterior  vertebral  ligament  from  the  basilar 
process;  2,  anterior  atlanto-occipital  ligament 
on  each  side  of  the  former;  3,  widening  of  the 
anterior  vertebral  ligament  from  the  axis;  4, 
anterior  atlanto-axial  ligament;  5, 6,  7,  capsular 
ligaments  of  the  articular  processes. 


THREE  THORACIC  VERTEBRA,  with  the  articu- 
lations of  the  ribs,  viewed  in  front.  1,  portion 
of  the  anterior  vertebral  ligament ;  2,  radiating 
costo-central  ligament ;  3,  anterior  costo-trans- 
verse  ligament ;  4,  articulation  of  the  head  of  the 
rib,  laid  open,  and  exhibiting  the  interarticular 
ligament  separating  two  synovial  cavities. 


with  the  eminence  of  the  atlas  and  the  median  ridge  of  the  axis,  it 
thence  expands  and  is  attached  to  the  front  of  all  the  centra  of  the  ver- 
tebrae and  intervertebral  ligaments  to  the  end  of  the  coccyx.  On  the 
lumbar  vertebrae  it  spreads  over  half  their  width  ;  on  the  thoracic  ver- 
tebras it  is  proportionately  narrower  and  thicker ;  and  it  spreads  more 
laterally  on  the  cervical  vertebrae.  On  the  sacrum  it  merges  into  the 
periosteum  and  again  becomes  more  distinct,  extending  from  the  former 
to  the  end  of  the  coccyx  as  the  anterior  sacro-coccygeal  ligament.3 
In  its  course  it  adheres  most  closely  to  the  intervertebral  disks  and  the 
contiguous  margins  of  the  centra,  and  least  so  at  the  intermediate 
narrowed  portions  of  the  latter,  where  the  interval  is  occupied  by 

1  Ligamentum  commune  vertebrale   anticum ;   1.    longitudinale   ant. ;    anterior 
common  ligament. 

2  L.  occipitale  anterius  medium  ;  1.  atlanto-occipitale  superfic. 

3  L.  sacro-coccygeum  anticum. 


74 


SPECIAL    ANATOMY   OF    THE   SKELETON. 


looser  connective  tissue.  Its  lateral  borders  merge  into  the  periosteum 
of  the  vertebrae.  On  the  lumbar  vertebrae  it  is  intimately  associated 
with  the  tendinous  origin  of  the  diaphragm,  with  which  it  may  be  said 
to  interchange  bundles  of  fibres.  The  ligament  is  composed  of  parallel 
bundles  extending  variable  lengths,  the  more  superficial  to  the  extent 
of  three  or  four  or  more  vertebrae,  the  deepest  to  the  extent  of  a  con- 
tiguous pair.  The  surface  presents  a  glistening  white  appearance, 
divided  by  many  short  fissures,  which  give  passage  to  vessels  and  are 
occupied  with  looser  connective  tissue. 

The  posterior  vertebral  ligament1  is  a  strong  fibrous  band,  situ- 
ated at  the  fore  part  of  the  spinal  canal,  and  extending  from  the 
occipital  bone  the  entire  length  of  the  latter.  Commencing  in  an 
expansion2  from  the  inner  surface  of  the  basilar  process,  where  it  is 


FIG.  26. 


FIG.  27. 


PORTION  OF  THE  CRANIUM  AND  OF  THE  ATLAS 
AND  AXIS,  viewed  from  behind ;  the  posterior 
portions  of  the  occipital  and  two  last  bones  re- 
moved. 1,  declivity  of  the  sphenoid  bone ;  2, 
occipital  bone ;  3,  atlas ;  4,  axis ;  5,  origin  of  the 
posterior  vertebral  ligament  from  the  basilar 
process ;  6, 7,  capsular  ligaments  of  the  articular 
processes. 


CENTRA  OF  THREE  THORACIC  VERTEBRA,  con- 
nected by  the  iutervertebral  ligaments.'viewed 
from  behind ;  the  vertebral  arches  having  been 
removed.  1,  intervertebral  ligaments;  2,  pedi- 
cles of  the  vertebral  arches ;  3,  portion  of  the 
posterior  vertebral  ligament,  exhibiting  its 
lateral  festooned  borders,  4. 


closely  connected  superficially  with  the  dura,  it  descends  through  the 
occipital  foramen  and  behind  the  odontoid  process  to  be  attached  to 
the  centrum  of  the  axis,  and  thence  to  all  the  succeeding  vertebral 
centra  and  intervertebral  disks.  It  is  widest  at  the  latter,  to  which 
and  to  the  contiguous  margins  of  the  centra  it  most  closely  adheres ; 
and  it  successively  narrows  in  the  intervals  towards  the  middle  of 
the  centra,  an  arrangement  which  gives  it  laterally  festooned  borders. 
These  are  continuous  with  the  periosteum  of  the  sides  of  the  spinal 
canal  and  of  the  intervertebral  foramen,  and  are  adherent  to  the  an- 

1  L.  commune  vertebrale  posticum ;    1.   longitudinale  post. ;    posterior  common 
ligament. 

2  L.  latum  epistrophei ;  apparatus  ligamentosus  colli ;   membrana  ligamentosa  ; 
occipito-axoid  or  posterior  occipito-axial  ligament. 


SPECIAL   ANATOMY    OF   THE   SKELETON.  75 

terior  longitudinal  spinal  veins,  which  are  united  by  transverse  veins 
crossing  the  centra  beneath  the  ligament.  Superficially,  the  latter  is 
connected  with  the  dura  of  the  spinal  cord  by  loose  connective  tissue. 
The  ligament  is  composed  of  longitudinal  bundles  of  fibrous  tissue  con- 
taining a  large  proportion  of  elastic  tissue,  which  gives  it  a  yellowish 
appearance  and  a  high  degree  of  elasticity  compared  with  the  anterior 
vertebral  ligament. 

The  elastic  or  yellow  ligaments l  are  situated  at  the  back  of  the 
spinal  canal,  where  they  appear  in  pairs  between  the  laminae  of  contigu- 
ous vertebrae,  the  intervals  of  which  they  fill 
so  as  to  render  the  back  of  the  canal  even  FlG-  28- 

throughout.  They  are  attached  to  the  lower 
fore  part  of  the  laminae  above,  and  to  the 
upper  border  and  adjacent  back  part  of  the 
laminae  below,  extending  from  the  median 
line  outwardly  to  the  capsular  ligaments  of 
the  articular  processes.  They  are  widest  in 
the  cervical  region,  and  become  narrower 
below  ;  and  they  are  nearly  as  deep  in  front 
as  the  intervening  surfaces  of  the  lamina. 
Behind  they  are  scarcely  exposed,  except 
in  those  positions  in  which  the  laminae  do  THREE  AECHES  REMOVED  FEOM 

r  f  AS     MANY     THORACIC     VERTEBRAE, 

not   entirely  close  the   intervening   spaces,     viewed  in  front,  and  exhibiting, 

as  in  the  lower  part  of  the  thoracic  and  in     *•  the  elastic  ligaments;  and  2, 
.  the    capsular    ligaments  of  the 

the  lumbar  region  to  the  sacrum.     The  liga-     articular  processes. 

ments  are  composed  of  longitudinal  bundles 

of  elastic  tissue.  The  first  pair  occupies  the  interval  between  the 
laminae  of  the  axis  and  of  the  third  cervical  vertebra ;  the  last  pair, 
the  interval  between  those  of  the  last  lumbar  vertebra  and  the  sacrum. 

The  articular  ligaments 2  are  fibrous  capsules  enclosing  the  articu- 
lations, which  are  formed  by  the  articular  processes  of  contiguous  ver- 
tebrae. The  opposed  surfaces  of  the  processes  are  invested  with  car- 
tilage, and  the  capsular  ligaments  are  attached  around  the  adjacent 
borders.  Those  of  the  neck  are  comparatively  loose,  while  those  of 
the  thorax  and  loin  are  close. 

The  nuchal  ligament 3  forms  a  median,  triangular,  membranous 
partition  between  the  muscles  at  the  back  of  the  neck.  Below  it  is 
continuous  with  the  supraspinous  ligament,  and  extends  between  the 
ends  of  the  spinous  processes  of  the  cervical  vertebrae  and  the  occipital 
crest  and  protuberance.  It  is  a  loose  intertexture  of  bundles  of  fibro- 
connective  tissue  with  elastic  tissue.  The  bundles,  for  the  most  part, 
start  from  the  end  of  the  prominent  spinous  process  of  the  last  cervical 
vertebra,  and  thence  proceed  in  a  radiant  manner  to  the  ends  of  the 

1  L.  flava;  1.  subflava;  1.  intercruralia ;  1.  arcuum. 

'2  L.  capsularia  processum  articularium  ;  1.  c.  p.  obliquorum.  3  L.  nuchae. 


76  SPECIAL   ANATOMY    OF   THE   SKELETON. 

spinous  processes  above  and  to  the  occipital  crest  and  protuberance. 
The  bundles  to  the  latter  are  longitudinal  and  form  the  thickened 
border  of  the  ligament.  In  quadrupeds  the  nuchal  ligament  is  com- 
posed of  elastic  tissue,  and  is  adapted  to  sustain  the  skull,  which  in 
such  animals  is  suspended  from  the  spine.  In  those  with  a  large  head, 
sometimes  loaded  with  heavy  appendages,  as  in  the  stag  with  its  ant- 
lers and  the  elephant  with  its  huge  tusks,  it  forms  a  powerful  and  most 
efficient  instrument  in  supporting  the  weight  and  in  removing  all  strain 
from*  the  muscles. 

The  supraspinous  ligament l  is  a  narrow  and  not  very  distinct 
cord,  composed  of  longitudinal  bundles  of  fibres  connecting  the  summits 
of  the  spinous  processes,  and  extending  continuously  from  the  last 
cervical  vertebra  to  the  sacrum.  In  the  intervals  of  the  spinous 
processes  it  is  continuous  with  the  interspinous  ligaments,2  which 
are  thin  membranes  extended  between  the  contiguous  margins  of  the 
spinous  processes.  In  the  loin  these  ligaments  are  deep  and  strong ; 
in  the  thorax  short  and  thin ;  and  in  the  neck  feebly  produced  and 
continuous  with  the  nuchal  ligament.  The  intertransverse  liga- 
ments 3  are  thin  membranous  bands  extended  between  the  transverse 
processes  of  the  lumbar  vertebra?,  and  are  less  well  produced  between 
those  of  the  thoracic  vertebra. 

Adapted  to  the  movements  of  the  head,  the  articulations  of  the 
skull  with  the  atlas  and  the  latter  with  the  axis  are  modified  from 
those  of  the  spine  in  general. 

The  anterior  atlanto-occipital  ligament4  is  a  loose  fibrous  mem- 
brane, extended  between  the  anterior  border  of  the  occipital  foramen 
and  the  anterior  arch  of  the  atlas.  In  front  it  is  connected  with  the  an- 
terior vertebral  ligament,  and  at  the  sides  with  the  articular  ligaments. 

The  anterior  atlanto-axial  ligament,5  similar  to  the  former, 
connects  the  anterior  arch  of  the  atlas  with  the  front  of  the  centrum 
of  the  axis.  In  the  same  manner  it  is  connected  with  the  anterior 
vertebral  ligament  and  the  contiguous  articular  ligaments. 

The  posterior  atlanto-occipital  ligament6  is  a  broad,  loose 
membrane  connecting  the  margin  of  the  occipital  foramen  back  of  the 
condyles  with  the  posterior  arch  of  the  atlas.  In  front  it  is  closely 
adherent  to  the  dura,  and  just  behind  the  prearticular  processes  of 
the  latter  contributes  to  form  the  foramen  for  the  transmission  of 

1  L.  supraspinale ;  1.  longitudinale  posterius  ;  1.  apicum. 

2  L.  interspinale ;  membranse  interspinales.  3  L.  intertransversalia. 

4  L.   atlanto-occipitale    anticum ;    1.   obturatorium   atlanto-occipitale   anticum  ; 
anterior  occipito-atlantal  or  occipito-atloid  ligament  or  ligaments. 

5  L.  atlanto-axiale  anticum  ;    1.  obt.  atlanto-epistrophicum  anticum  ;  ant.  atlo- 
axoid  ligament  or  ligaments. 

6  L.  atlanto-occipitale  posticum  ;  1.  obt.  atl.  oc.  post.  ;  posterior  occipito-atlantal 
or  occipito-atloid  ligament. 


SPECIAL    ANATOMY    OF    THE   SKELETON. 


77 


the  vertebral  artery  into  the  cranial  cavity,  and  for  the  passage  of  the 
first  spinal  nerve. 

The  posterior  atlanto-axial  ligament,1  a  similar  membrane  to 
the  former,  connects  the  contiguous  arches  of  the  atlas  and  axis, 
between  the  articular  processes,  behind  which  it  contributes  to  form 
the  intervertebral  foramina  for  the  second  pair  of  spinal  nerves. 

The  atlanto-occipital  articulations,  formed  between  the  occipi- 
tal condyles  and  the  prearticular  processes  of  the  atlas,  are  enclosed 
by  loose  capsular  ligaments  in  accordance  with  the  movements  of 
flexion  and  extension  of  the  head.  They  are  reinforced  and  much 


PIG.  29. 


FIG.  30. 


PORTION  OF  THE  OCCIPITAL  BONE,  WITH  THE 
ATLAS  AND  AXIS,  front  view.  1,  origin  of  the 
anterior  vertebral  ligament;  2,  anterior  at- 
lanto-occipital ligament  on  each  side  of  the 
former;  3,  widening  portion  of  the  anterior 
vertebral  ligament;  4,  anterior  atlanto-axial 
ligament;  5, 6, 7,  capsular  ligaments  of  the  ar- 
ticular processes. 


PORTION  OF  THE  OCCIPITAL  BONE  AND  THE 

UPPER    THREE    CERVICAL   VERTEBR/E.     1,    atlas; 

2,  axis ;  3,  posterior  atlanto-occipital  ligament ; 
4,  capsular  ligaments  of  the  occipital  condyles 
and  articular  processes  of  the  atlas;  5,  posterior 
atlanto-axial  ligament;  6,  capsular  ligaments  of 
the  articular  processes  between  the  atlas  and 
axis ;  7,  first  pair  of  elastic  ligaments ;  8,  capsu- 
lar ligaments  of  the  articular  processes  between 
the  second  and  third  cervical  vertebrae. 


strengthened  by  lateral  portions  of  the  posterior  vertebral  ligament, 
extending  from  the  sides  behind  the  centrum  of  the  axis  to  the  inner 
fore  part  of  the  occipital  condyles.  In  the  flexion  and  extension  of  the 
head  the  ligaments  are  put  on  the  stretch  in  an  opposite  direction  to 
that  of  the  movement. 

The  atlanto-axial  articulations,  formed  between  the  contiguous 
articular  processes  of  the  atlas  and  axis,  are,  like  the  former,  enclosed 
by  loose  capsular  ligaments  in  accordance  with  the  rotary  movements 
of  the  head.  They  are  reinforced  by  a  strong  internal  lateral  liga- 
ment,2 which  is  attached  below  to  the  upper  part  behind  of  the  side 
of  the  centrum  of  the  axis,  and  above  to  the  articular  column  of  the 
atlas  behind  the  tubercle  of  attachment  of  the  transverse  ligament. 
When  the  head  is  turned  to  one  side  the  ligaments  of  both  articula- 
tions are  put  on  the  stretch  in  opposite  directions.  In  the  ordinary 
position,  with  the  face  directed  forward,  the  opposed  facets  of  the 


1  L.  atlanto-axiale  posticum  ;  1   obt.  atlanto-epistrophicum  post.  ;  posterior  atlo- 
3ixoid  ligament.  u  Accessory  atlanto-axial  ligament. 


78 


SPECIAL    ANATOMY   OF    THE   SKELETON. 


FIG.  31. 


at!  an  to-axial  articulations  are  in  contact  only  along  the  middle  trans- 
versely, and  diverge  in  front  and  behind.  In  rotation  the  facets  above 
and  below  become  about  half  displaced,  and  the  atlas  with  the  head 
descends  slightly  from  the  highest  level,  which  it  occupies  when  the 
face  is  directed  straight  forward.  Thus  it  appears  that  a  man  is  actu- 
ally taller  when  looking  directly  in  front  than  when  his  head  is  turned 
to  either  side. 

In  the  articulation  of  the  skull  with  the  atlas  and  with  the  axis  the 
odontoid  process  is  embraced  by  the  transverse  ligament,  and  is  con- 
nected with  the  skull  by  the  odontoid  ligaments,  which  are  included 

between  the  position  of  the  anterior 
atlan to-occipital  and  posterior  verte- 
bral ligaments. 

The  transverse  ligament l  is  a 
strong  fibrous  band  attached  by  ex- 
panded ends  to  the  tubercles  at  the 
inner  fore  part  of  the  articular  col- 
umns of  the  atlas,  and  passes  behind 
the  odontoid  process,  where  it  is  of 
considerably  greater  depth.  From  the 
middle  of  its  upper  border  a  band2 
ascends  to  be  attached  to  the  inner 
surface  of  the  basilar  process  at  the 
margin  of  the  occipital  foramen,  and 
from  the  lower  border  a  shorter  band 3 
descends  to  be  attached  to  the  cen- 
trum of  the  axis  in  conjunction  with 

the  posterior  vertebral  ligament.  The  accessory  bands  give  to  the 
ligament  the  form  of  a  cross,  whence,  also,  its  name  of  the  cruciform 
ligament. 

The  odonto-atlantal  articulation,  formed  between  the  front  of 
the  odontoid  process  and  the  anterior  arch  of  the  atlas,  is  a  synovial 
joint  enclosed  by  a  strong  capsular  ligament,  attached  around  the 
opposed  articular  facets,  which  are  covered  with  cartilage. 

The  odonto-transverse  articulation  is  a  synovial  joint  enclosed 
by  a  thin  capsular  ligament,  situated  between  the  odontoid  process  and 
the  transverse  ligament.  Occasionally  another  synovial  joint  occupies 
a  position  between  the  transverse  ligament  and  the  posterior  vertebral 
ligament. 

The  lateral  odontoid  ligaments4  are  two  strong,  thick  cords, 
which  spring  together  from  the  back  and  sides  of  the  summit  of  the 


PART  OP  THE  SKULL,  THE  ATLAS,  AND 
AXIS,  viewed  from  behind ;  the  posterior 
portions  removed.  1,  upper  extremity  of 
the  posterior  vertebral  ligament ;  2,  trans- 
verse ligament,  with  its  two  appendices, 
3  and  4 ;  5,  lateral  odontoid  ligaments ; 
6,  7,  capsular  ligaments  of  the  articular 
processes. 


1  L.  transversale  atlantis ;  1.  cruciatum ;  1.  c.  epistrophei. 

2  Appendix  superior.       .  8  A.  inferior. 

4  Alar  odontoid  ligaments  ;  check  or  moderator  ligaments  ;  1.  alaria  dentis  ;  1.  a. 
magna ;  1.  lateralia. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  79 

odontoid  process,  and  diverge  outward  and  slightly  upward  to  be 
attached  to  the  inner  borders  of  the  occipital  condyles.  These  check 
or  limit  the  lateral  movements  of  the  head. 

The  middle  odontoid  ligament *  is  a  loose  fibrous  bundle  ascend- 
ing from  the  fore  part  of  the  summit  of  the  odontoid  process  to  the 
anterior  margin  of  the  occipital  foramen  between  the  position  of  the 
lateral  odontoid  ligaments. 

The  posterior  sacro-coccygeal  ligament  is  a  strong  fibrous  mem- 
brane closing  the  lower  end  of  the  spinal  canal.  It  extends  between  the 
sides  of  the  notch  produced  by  imperfect  development  of  the  arches 
of  the  lower  one  or  two  sacral  vertebrae,  and  thence  between  the  cornua 
of  the  sacrum  and  coccyx  to  the  second  segment  of  the  latter. 

MOVEMENTS  OF   THE   VERTEBKAL   COLUMN. 

The  jointed  or  segmented  condition  of  the  spine  or  vertebral  column, 
and  the  mode  of  union  of  its  segments  or  vertebrae,  admirably  adapt  it 
for  its  purposes.  While  the  vertebrae  are  firmly  and  tenaciously  bound 
together,  the  entire  spine  exhibits  a  remarkable  degree  of  flexibility, 
which  is  only  restricted  within  limits  necessary  to  preserve  the  integrity 
of  the  important  organ  it  encloses,  the  spinal  cord.  With  the  exception 
of  the  atlas,  adapted  to  the  special  movements  of  the  head,  any  pair  of 
vertebras  alone  exhibits  comparatively  but  little  motion,  but  this  in- 
creases in  proportion  with  the  number  of  vertebras  included  in  the  act, 
so  that  the  whole  spine  is  capable  of  movement  in  any  direction,  but 
mainly  forward  and  backward,  and  more  or  less  restricted  in  degree. 
The  cervical  and  lumbar  regions  exhibit  most  flexibility,  the  thoracic 
region  least,  except  the  sacrum,  which  is  immovably  fixed.  A  feeble 
rotary  or  twisting  movement  is  obvious  in  the  spine,  but  is  greatly 
restricted  by  the  imbrication  of  the  arches  and  interlocking  of  the 
articular  processes  of  the  vertebrae,  and  from  the  condition  of  attach- 
ment of  the  intervertebral  disks  and  other  ligaments.  In  flexion  of 
the  spine  the  elastic  ligaments  are  stretched,  and  the  laminss  of  the 
arches  become  more  separated.  In  extension  the  laminae  become  more 
imbricated,  and  thus  tend  to  restrict  the  movement. 

The  movements  of  the  head  on  the  spine  are  those  of  flexion  and 
extension,  or  bending  forward  and  backward,  and  those  of  rotation,  or 
turning  from  side  to  side.  The  former  is  due  to  the  occipital  condyles 
rocking  in  a  cup  formed  by  the  prearticular  processes  of  the  atlas. 
The  movement  is  facilitated  by  the  comparative  looseness  of  the  liga- 
ments between  the  atlas  and  occipital  bone,  and  is  restricted  when  the 
ligaments  are  stretched.  Further  flexion  and  extension  of  the  head 
are  due  to  bending  of  all  the  cervical  vertebrae.  Lateral  bending  of  the 
head,  as  when  it  is  directed  towards  the  shoulder,  is  also  produced  by 

1  L.  rectum  medium ;  1.  medium  dentis  anticum  ;  1.  suspensorium  dentis ;  1. 
apicis  dentis. 


80 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


the  flexion  of  all  the  cervical  vertebrae  together.  In  turning  the  head 
the  motion  is  due  to  rotation  of  the  atlas  upon  the  axis,  which  re- 
mains fixed,  the  odontoid  process  and  the  prearticular  processes  being 
equally  the  fixed  surfaces  on  which  the  movement  of  the  atlas  occurs. 
The  motion  is  also  facilitated  'by  the  looseness  of  the  ligaments  con- 
necting the  atlas  and  axis,  and  is  restricted  by  these  and  the  odontoid 
ligaments  when  put  on  the  stretch. 

THE   KIBS. 

The  ribs 1  are  a  series  of  twelve  arching  bones  on  each  side  of  the 
thorax,  articulating  with  the  thoracic  vertebrae,  and  extended  through 
prolongations,  the  costal  cartilages.  The  upper  seven  ribs  by  means 
of  the  latter  join  the  sternum,  whence  they  are  distinguished  as  the 
sternal  ribs,2  while  the  others  are  the  asternal  ribs.3  Of  the  latter, 
each  of  the  upper  three  by  means  of  its  cartilage  joins  the  cartilage 
above,  while  the  remaining  two  have  their  cartilages  free,  and  are 
thence  more  movable,  and  are  called  the  floating  ribs.* 

The  ribs  successively  increase  in  length  from  the  first  to  the  seventh 
or  eighth,  and  then  successively  decrease  to  the  last,  which  is  a  rudiment 

of  the  others.  The  intermediate 
ribs  are  generally  the  broader  and 
most  nearly  alike.  The  vertebral 
extremity  or  head5  of  the  rib  com- 
monly presents  a  pair  of  articular 
facets,  which  slant  up  and  down 
from  an  intermediate  ridge  for  the 
attachment  of  an  interarticular  lig- 
ament, while  the  facets  articulate 
with  those  of  the  centra  of  a  con- 
tiguous pair  of  vertebras.  From 
the  head  extends  the  slightly-nar- 
rowed neck,6  defined  outwardly 
behind  by  an  eminence,  the  tuber- 
cle.7 The  neck  is  smooth  in  front 
and  roughened  behind  for  ligamen- 
tous  attachment.  The  tubercle  is 
roughened  outwardly  for  the  pos- 
terior costo  -  transverse  ligament, 
and  inwardly  presents  a  small, 
smooth  facet,  which  articulates  with 
the  end  of  the  transverse  process  of 
the  lower  of  the  two  vertebra?  with 
The  shaft  or  body8  of  the  rib,  beyond 


FRONT  VIEW  OF  THE  THORAX.  1,  2,  3,  the 
three  pieces  of  the  sternum  ;  4,  5,  the  thoracic 
vertebrae ;  6,  the  first  rib ;  7,  its  head ;  8,  neck ; 
9,  tubercle;  10,  the  seventh  rib ;  11,  costal  car- 
tilages ;  12,  the  floating  ribs ;  13,  groove  for 
the  intercostal  blood-vessels. 


which  the  head  is  connected. 


1  Costse ;  pleurapophyses.     2  True  ribs  ;  costse  verse.     3  False  ribs  ;  costae  spurise. 
4  C.  fluctuantcs.         6  Capitulum.         6  Collum.         *  Tuberculum.  Corpus. 


SPECIAL    ANATOMY   OF   THE   SKELETON.  81 

the  neck,  is  cylindrical,  compressed  from  within  outwardly,  nearly  flat 
on  the  exterior  surface,  and  convex  on  the  inner  surface,  thickest 
and  of  least  depth  behind,  and  becoming  deeper  and  thinner  in  front. 
The  upper  border  is  thick  and  rounded,  but  becomes  narrower  in  ad- 
vance. The  lower  border  is  thin  and  for  the  most  part  sharp,  and  its 
posterior  two-thirds  are  more  downwardly  extended,  and  in  this  posi- 
tion bound  a  groove1  along  the  inner  surface  for  the  accommodation  of 
the  intercostal  vessels  and  nerve.  The  anterior  extremity  of  the  rib, 
commonly  after  slightly  narrowing,  again  widens  a  little  and  thickens  at 
the  end,  where  it  presents  an  elliptical  pit  for  junction  with  the  costal 
cartilage.  At  the  back  part  of  the  shaft  behind  is  an  oblique  ridge, 
named  the  angle,  at  which  the  rib,  from  its  outward  direction,  is 
somewhat  abruptly  bent  forward  and  also  downward  in  its  further 
course.  The  rib  also  has  a  slight  twist  in  its  axis,  so  that  the  pos- 
terior surface  behind  the  angle  looks  downward,  and  that  in  advance 
of  the  latter  is  directed  in  front  a  little  upward.  The  angle  is  absent 
in  the  first  and  last  ribs,  commences  near  the  tubercle  in  the  second  rib, 
and  successively  increases  in  distance  from  the  latter  to  the  eleventh 
rib. 

The  first  rib,  most  unlike  the  others,  is  nearly  flat,  with  the  broad 
surfaces  directed  up  and  down,  and  with  its  narrow  borders  directed 
inward  and  outward.  The  head  is  small  and  rounded,  and  has  but  a 
single  faeet,  which  articulates  with  the  centrum  of  the  first  thoracic 
vertebra.  The  neck  is  slender,  and  is  marked  above  by  a  feeble  groove 
for  the  last  cervical  nerve.  The  tubercle  occupies  the  outer  border,  and 
is  thick  and  prominent.  The  shaft  curves  from  the  tubercle  outward, 
forward,  and  inward  to  a  thickened  end,  but  has  no  downward  bend  in 
its  course.  In  strongly-marked  specimens  the  upper  surface  of  the 
shaft,  in  advance  of  the  middle,  is  crossed  obliquely  by  two  shallow 
impressions,  which  accommodate  the  subclavian  blood-vessels  in  their 
course  over  the  rib.  A  slight  ridge  separates  the  impressions,  and  is 
variably  more  prominent  inwardly,  where  it  gives  attachment  to  the 
anterior  scalenus  muscle. 

The  second  rib  conforms  more  to  the  common  character,  but  its  broad 
surfaces  are  directed  obliquely  upward  and  downward,  and  its  borders 
are  directed  outward  and  inward.  The  angle  is  slight,  and  the  shaft 
is  not  twisted,  and  near  the  middle  is  usually  roughened  for  the  attach- 
ment of  the  great  serratus  muscle.  The  eleventh  and  twelfth  ribs, 
less  well  developed  than  the  others,  have  a  single  articular  facet  to 
the  head,  to  articulate  with  the  centrum  of  the  corresponding  thoracic 
vertebrae,  and  they  possess  no  tubercle. 

Occasionally  a  rudimental  thirteenth  rib  exists,  on  one  or  both  sides, 
articulating  with  the  first  lumbar  vertebra,  in  the  usual  position  of 
the  transverse  processes.  More  rarely  it  is  found  in  the  neck,  when 

1  Sulcus  costalis. 
6 


82  SPECIAL   ANATOMY    OF   THE   SKELETON. 

it  substitutes  the  usual  costal  process.  In  neither  case  does  its  presence 
accord  with  an  additional  vertebra  to  the  series. 

The  ribs  are  composed  of  a  thin,  compact  layer  enclosing  a  uniform 
spongy  substance. 

In  the  development  of  the  ribs  a  primary  centre  of  ossification 
appears  in  the  shaft  about  the  seventh  week  of  foetal  life.  Centres  for 
epiphyses  to  the  head  and  tubercle  appear  after  puberty,  and  ankylose 
with  the  rest  of  the  bone  from  the  twentieth  to  the  twenty-fifth  year. 

The  costal  cartilages1  are  prolongations  of  the  ribs,  and  are  di- 
rectly continuous  without  forming  an  articulation  with  them.  They 
successively  increase  in  length  from  the  first  to  the  seventh,  and  thence 
decrease  to  the  last  one.  Their  direction  is  generally  convergent  to  the 
sternum,  the  first  descending  a  little,  while  the  second  and  third  are 
nearly  horizontal,  and  the.  others  successively  become  more  ascending 
to  the  last  two,  which  continue  in  the  direction  of  the  corresponding 
ribs.  The  first  costal  cartilage  is  continuous  with  the  sternum,  but 
those  which  follow,  to  the  seventh  inclusive,  are  narrowed  at  the  ends 
and  form  a  blunt,  angular  point,  which  movably  articulates  with  the 
sternum.  The  ends  of  the  succeeding  three  cartilages  are  tapering 
and  turn  upward,  each  to  be  attached  by  ligamentous  bands  to  the 
cartilage  above.  The  remaining  two  cartilages  are  tapering  and  free. 
In  the  intervals  of  the  cartilages,  from  the  fifth  or  sixth  to  the  eighth 
or  ninth,  a  wide  process  projects  from  each  and  articulates  with  the 
other. 

In  youth  the  costal  cartilages  are  white,  flexible,  and  elastic  ;  after 
middle  age  they  appear  yellowish,  harder,  and  more  rigid.  As  life 
advances  they  are  prone  to  partial  ossification,  though  this  rarely,  if 
ever,  occurs  completely,  even  in  the  most  advanced  age.  The  ossifica- 
tion is  mostly  superficial,  and  especially  affects  the  first  cartilage.  The 
disposition  to  ossification  is  less  in  the  female,  and  occurs  later. 

THE   STEKNUM. 

The  sternum  or  breast-bone2  is  situated  in  front  of  the  thorax, 
retained  in  its  position  through  its  connection  with  the  upper  seven 
pairs  of  costal  cartilages.  It  is  a  moderately  thick  and  comparatively 
light  plate,  slightly  curved  in  the  length,  and  slanting,  with  its  ante- 
rior surface  looking  obliquely  forward  and  upward.  Before  complete 
coalescence  of  all  its  parts,  which  occurs  late  in  life,  it  consists  of  three 
pieces,  named  the  presternum,  the  mesosternum,  and  the  xiphisternum 
or  ensiform  process. 

The  presternum3  is  broadest  and  thickest  above,  where  it  is  ex- 
tended laterally  to  unite  with  the  first  pair  of  costal  cartilages  and  to 
articulate  with  the  clavicles;  and  is  narrowed  below  to  articulate 

1  Cartilagines  costarum  ;  hsemapophyses. 

2  Os  xiphoides  ;  scutum  pectoris  ;  haemal  spine.  3  Manubrium. 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


83 


FIG.  33. 


with  the  mesosternum  and  the  second  pair  of  costal  cartilages. 
The  anterior  surface  presents  a  slight  median  prominence  expand- 
ing outwardly  above,  and  is  slightly 
concave  at  the  sides  ;  the  posterior 
surface  is  slightly  concave  and 
even.  The  upper  border  forms  a 
median  transverse  concavity,  the 
interclavicular  notch,1  which  is 
rounded  fore  and  aft.  On  each  side 
of  this  is  the  clavicular  notch2 
for  articulation  with  the  clavi- 
cle. It  is  an  elliptical  concavity, 
inclining  outwardly,  and  is  nearly 
flat  or  slightly  convex  fore  and 
aft.  From  its  outer  extremity 
a  triangular,  rough  depression  ex- 
tends downward  for  union  with 
the  first  costal  cartilage.  The 
margin  below  is  acute,  and  con- 
verges to  the  inferior  angle,  which 
is  truncated  to  form  part  of  the 
notch  for  articulation  with  the  sec- 
ond costal  cartilage.  The  inferior 
extremity — somewhat  thickened, 
and  usually  slightly  prominent  in 

front — ends  in  a  horizontal,  roughened  surface  for  articulation  with 
the  mesosternum. 

The  mesosternum 3  is  the  intermediate,  longest  piece  of  the  ster- 
num, and  is  a  flat  plate  of  nearly  uniform  thickness.  The  anterior 
surface  not  unfrequently  exhibits  three  slight  transverse  lines,  indi- 
cating the  early  separation  of  the  piece  into  four  segments,  which  are 
commonly  feebly  depressed  towards  the  centre.  The  posterior  surface 
is  evenly  flat.  In  the  outline  of  shape  the  mesosternum  is  very  vari- 
able, and  is  commonly  somewhat  rectangular  or  elliptical,  and  fre- 
quently more  or  less  widened  at  the  lower  third,  so  as  to  appear 
clavate.  The  upper  extremity,  often  a  little  thickened,  is  adapted  to 
articulate  with  the  presternum,  and  on  each  side  has  the  corresponding 
angle  truncated  to  form  part  of  the  notch  for  articulating  with  the 
second  costal  cartilage.  The  lower  extremity  is  usually  more  or  less 
narrowed  and  rounded,  and  ends  in  a  transverse  pit,  which  articulates 
with  the  ensiform  process.  The  lateral  borders  are  thick  and  scalloped, 
presenting  a  series  of  vertically  concave  articular  notches,  separated 
by  mostly  longer  concave  notches.  The  former,  together  with  the 


FRONT  VIEW  OF  THE  THOKAX.  1, 2, 3,  the  three 
pieces  of  the  sternum  ;  4,  5,  the  thoracic  verte- 
brae ;  6,  the  first  rib ;  7,  its  head ;  8,  neck ;  9, 
tubercle;  10,  the  seventh  rib;  11, costal  carti- 
lages ;  12,  the  floating  ribs ;  13,  groove  for  the 
intercostal  blood-vessels. 


1  Incisura  semilunaris  ;  i.  jugularis. 
8  Body  ;  corpus  sterni ;  gladiolus. 


2  I.  clavicularis. 


84  SPECIAL    ANATOMY   OF   THE   SKELETON. 

contiguous  articular  surfaces  of  the  presternum  and  ensiform  process, 
articulate  with  the  costal  cartilages  from  the  second  to  the  seventh 
inclusive,  and  the  intervening  notches  correspond  with  the  fore 
part  of  the  intercostal  spaces.  The  articular  notches  for  the  sixth 
and  seventh  costal  cartilages  and  the  ensiform  process  are  in  close 
contiguity. 

The  ensiform  process,  or  xiphisternum,1  the  smallest  piece  of 
the  sternum,  projects  downward  from  the  mesosternum  between  the 
seventh  costal  cartilages,  occupying  a  somewhat  deeper  level  than  the 
front  surface  of  these.  It  is  of  very  variable  form,  and  is  more  com- 
monly observed  as  a  thin,  flat,  tongue-shaped  plate,  ending  in  a  cartilagi- 
nous prolongation.  Differing  greatly  in  the  proportion  of  length  and 
breadth,  it  may  be  narrow  and  pointed,  or  ensiform,  discoid  and  entire, 
forked  or  perforated,  straight  or  curved.  Its  upper,  thicker  border 
articulates  with  the  end  of  the  mesosternum,  and  on  each  side  of  this 
forms  part  of  the  articular  notch  for  the  seventh  costal  cartilage. 

Occasionally  a  perforation  appears  in  the  lower  part  of  the  meso- 
sternum, due  to  a  want  of  coalescence  of  the  lateral  centres  of  ossifi- 
cation, usually  of  the  fourth  segment. 

In  the  female,  ordinarily  the  presternum  is  proportionately  wider, 
and  the  mesosternum  longer  and  narrower,  than  in  the  male. 

The  sternum  is  composed  of  light,  spongy  substance,  with  a  thin 
layer  of  compact  substance.  Its  nutritious  foramina,  larger  on  the 
inner  surface,  are  for  the  most  part  inconspicuous.  It  is  invested  with 
a  much  thicker  periosteum  than  usual  in  other  bones. 

The  course  of  development  and  growth  of  the  sternum  is  very 
variable.  Ossification  commences  in  the  presternum  about  the  sixth 
month  of  foetal  life,  commonly  from  a  single  centre,  frequently  from  a 
pair,  and  occasionally  from  three  or  more  centres.  Ordinarily  when 
a  pair  occurs  the  centres  are  near  together,  one  larger  and  placed  on  a 
little  higher  level  than  the  other.  In  the  mesosternum  there  may  be 
a  series  of  three  or  four  centres,  or  there  may  be  double  the  number, 
in  pairs,  opposite  the  intercostal  spaces,  side  by  side,  or  arranged  in 
the  same  manner  as  the  presternal  pair.  The  upper  ones  appear  about 
the  seventh  month  of  foetal  life,  and  the  others  follow  in  succession  up 
to  the  ninth  or  tenth  year.  The  lateral  centres  quickly  coalesce,  but 
the  resulting  four  segments  remain  a  long  time  separated.  They  suc- 
cessively ankylose  from  below  upward,  and  the  upper  piece  frequently 
does  not  unite  with  the  rest  until  the  twenty-fifth  year  or  later.  The 
ensiform  process  commences  ossification  from  three  to  six  or  more 
years  after  birth,  usually  from  a  single  centre  at  the  base,  but  occa- 
sionally from  a  pair.  At  twenty  years  it  is  still  in  great  part  carti- 
laginous, nor  does  it  completely  ossify  before  the  thirtieth  or  fortieth 

1  Metasternum ;  hyposternum ;  processus  xiphoides  or  ensiformis ;  ensiform  or 
xiphoid  appendix ;  cartilage  ensiformis. 


SPECIAL   ANATOMY    OF    THE   SKELETON. 


85 


year.  It  commonly  ankyloses  with  the  mesosternum  after  fifty,  but 
sometimes  much  earlier.  The  mesosternum  unites  with  the  presternum 
at  a  still  later  period,  though  occasionally  the  union  occurs  even  long 
previously,  and  sometimes  it  remains  permanently  separated. 

Earely  a  pair  of  osseous  nodules,  named  the  episternal  bones,1  are 
found  attached  to  the  sternum,  one  on  each  side  of  the  interclavicular 
notch. 

ARTICULATIONS  OF   THE   RIBS   WITH   THE  VERTEBRAE   AND 

STERNUM. 

COSTO-VERTEBKAL   ARTICULATIONS. 

Costo-central  articulations.  These  are  formed  between  the 
heads  of  the  ribs  and  the.  centra  of  the  thoracic  vertebrae.  Each  ar- 
ticulation, except  the  first  and  the  last  two,  is  formed  by  the  head  of 
the  rib  in  conjunction  with  the  centra  of  two  adjacent  vertebras.  The 
articulation  is  enclosed  by  a  capsular  ligament,  and  is  divided  into  two 
synovial  cavities  by  an  interarticular  ligament,  which  is  a  hori- 
zontal band  of  short  fibres  passing  between  the  ridge  on  the  head  of 

FIG.  35. 


FIG.  34. 


ANTERIOR  VIEW  OF  THREE  THORACIC  VERTE- 
BRAE AND  THEIR  ARTICULATION  WITH  THE  RIBS. 

1,  portion  of  the  anterior  vertebral  ligament; 

2,  anterior  costo-central  ligament;  3,  anterior 
costo-transverse  ligament;  4,  articulation  of  the 
head  of  the  rib  laid  open,  exhibitingthe  cavity 
divided  into  two  by  an  interarticular  ligament. 


POSTERIOR  VIEW  OF  FOUR  THORACIC  VERTE- 
BRAE AND  THEIR  ARTICULATION  WITH  THE  RIBS. 

1,  supraspinous  ligament;  2,  elastic  ligament, 
seen  just  below  the  edge  of  the  vertebral  lam- 
inae; 3,  anterior  costo-transverse  ligaments;  4, 
posterior  costo-transverse  ligaments. 


the  rib  and  the  contiguous  intervertebral  disk.  The  articulation  in 
front  is  strengthened  by  the  anterior  costo-central  ligament,2 
which  consists  of  three  bands  radiating  from  the  front  of  the  head 
of  the  rib  to  the  sides  of  the  adjoining  pair  of  vertebrae  and  inter- 
vening disk. 

As  the  first  and  last  two  ribs  articulate  each  with  a  single  vertebral 

1  Ossa  suprasternalia  ;  episternal  granules. 

2  Anterior  costo-vertebral  ligament ;  stellate  or  radiate  ligament ;  ligamenta  costo- 
vertebralia  radiata  ;  1.  capituii  costarum. 


86  SPECIAL    ANATOMY   OF   THE   SKELETON. 

centrum^  the  joint  has  a  single  synovial  cavity,  and  its  anterior  costo- 
central  ligament  consists  of  but  two  bands,  of  which  one  joins  the 
vertebral  centrum  with  which  the  rib  articulates,  and  the  other  joins 
the  centrum  above. 

Costo-transverse  articulations.  A  joint  with  a  synovial  cavity 
is  formed  between  the  articular  facet  of  the  tubercle  of  the  ribs  and 
that  of  the  transverse  processes  of  the  thoracic  vertebrae,  and  is  en- 
closed by  a  capsular  ligament.  The  articulation  is  greatly  strength- 
ened by  three  additional  ligaments,  as  follows : 

The  posterior  costo-transverse  ligament l  is  a  well-marked  band 
which  extends  from  the  end  of  the  transverse  process  to  the  rib  just  out- 
side of  its  tubercle.  The  middle  costo-transverse  ligament 2  con- 
sists of  short  bundles  of  fibres  which  unite  the  posterior  surface  of 
the  neck  of  the  rib  to  the  front  of  the  contiguous  transverse  process. 
The  anterior  costo-transverse  ligament3  is  a  membranous  band 
extended  from  the  upper  border  of  the  neck  of  the  rib  obliquely  out- 
ward to  the  lower  margin  of  the  transverse  process  above.  Its  inner 
edge  is  thickened  and  free,  and  outwardly  it  is  continuous  with  the 
intercostal  fascia. 

No  synovial  articulation  exists  between  the  last  two  ribs  and  the 
transverse  processes  of  the  corresponding  vertebrae.  In  these,  also, 
the  posterior  and  middle  costo-transverse  ligaments  together  form  a 
longer  and  looser  band,  allowing  greater  freedom  of  motion  in  the  ribs. 

COSTO-STERNAL    ARTICULATIONS. 

The  periosteum  of  the  ribs  extended  upon  the  costal  cartilages 
forms  their  perichondrium.  The  first  costal  cartilage  is  a  continuous 
structure  with  the  sternum.  The  succeeding  costal  cartilages  to  the 
seventh,  inclusive,  form  a  series  of  joints  with  the  margin  of  the 
sternum,  which  nearly  resemble  the  costo-central  articulations.  The 
second  costo-sternal  articulation,  enclosed  by  its  capsular  ligament,  has 
two  synovial  cavities  separated  by  an  interarticular  ligament.  The  suc- 
ceeding articulation  commonly  has  a  similar  arrangement,  while  the 
others  have  a  single  cavity  or  none,  in  which  latter  case  the  end  of  the 
costal  cartilage  is  connected  with  the  sternum  by  a  stout  interarticular 
ligament.  Each  costo-sternal  articulation  is  especially  strengthened 
by  the  anterior  costo-sternal  ligament,4  which  consists  of  fibrous 
bundles  radiating  from  the  end  of  the  costal  cartilage  upon  the  front 

1  L.  costo-transversarium  posticum ;    1.  transversarium  externum  costarium  ;  1. 
cervicis  costae  externum. 

2  Interosseous  costo-transverse  ligament ;  1.  costo-transversarium  intermedium  ;  1. 
colli  costae. 

3  Superior  or  long  costo-transverse  lig.  ;  1.  costo-transversarium  anticum  or  in- 
ferium  ;  1.  trans,  internum  costarum. 

*  L.  costo-sternale  radiatum  ;  1.  sterno-costale  anticum. 


SPECIAL    ANATOMY    OF   THE   SKELETON.  87 

of  the  sternum,  where  the  fibres  interlace  with  those  of  the  ligaments 
above  and  below  and  on  the  opposite  side,  and  with  the  tendinous  fibres 
of  origin  of  the  pectoral  muscles.  The  posterior  costo-sternal  lig- 
ament l  is  the  corresponding  portion  of  the  capsular  ligament,  consist- 
ing of  fibrous  bundles,  which  reinforce  the  extension  over  the  joint  of 
the  contiguous  periosteum. 

The  costo-xiphoid  ligament 2  is  a  variable  and  mostly  thin  fibrous 
band,  which  extends  obliquely  in  front  between  the  ends  of  the  sixth 
and  seventh  costal  cartilages  to  the  side  of  the  ensiform  process. 

Intercostal  articulations.  The  intervening  processes  of  the  costal 
cartilages,  from  the  fifth  or  sixth  to  the  eighth  or  ninth,  form  joints 
with  nearly  flat,  articular  surfaces  enclosed  by  thin  capsular  ligaments. 
The  ends  of  the  asternal  costal  cartilages,  except  the  last  two,  are  each 
joined  to  the  cartilage  above  by  short  intervening  bundles  of  fibres,  the 
intercostal  ligaments. 

STERNAL   ARTICULATIONS. 

Prior  to  ankylosis  the  presternum  joins  the  mesosternum  by  an  in- 
tervening plate  of  cartilage,  which  sometimes  exhibits  a  central  fissure. 
The  articulation  is  enclosed  by  longitudinal  fibrous  bundles,  short  in 
front,  but  greatly  reinforced  behind  by  others  extending  the  whole 
length  of  the  sternum.  The  ensiform  process  is  joined  to  the  meso- 
sternum in  like  manner  with  the  preceding  articulation. 

The  numerous  ligaments  connected  with  the  sternum,  together  with 
the  tendinous  attachments  and  the  periosteum,  form  a  fibrous  sheath 
to  the  bone  unequalled  elsewhere  in  the  skeleton. 

THE   THOKAX. 

The  thorax,  or  chest,  is  a  conical  bony  cage,  composed  of  the 
thoracic  vertebrae,  the  ribs  with  their  cartilages,  and  the  sternum.  It 
is  compressed  fore  and  aft,  so  as  to  be  widest  from  side  to  side,  a 
condition  the  reverse  of  what  we  observe  in  many  animals,  and  one 
which  makes  it  easy  for  us  to  lie  at  rest  on  the  back,  while  it  is  in- 
convenient for  them.  The  thorax  rapidly  increases  in  dimension  from 
the  first  rib  to  the  third  or  fourth,  then  more  gradually  to  the  eighth 
or  ninth,  after  which  it  slightly  decreases.  Its  circumference  where 
greatest,  covered  with  the  soft  parts,  averages  about  thirty-two  inches, 
and  in  well-developed  subjects  reaches  three  feet,  but  in  feeble  ones 
only  twenty-nine  inches.  It  is  deepest  behind,  where  it  measures  about 
a  foot,  and  decreases  in  advancing  to  the  sternum,  where  it  is  about  half 
the  depth.  The  transverse  diameter,  greatest  at  the  eighth  or  ninth 
rib,  is  within  an  inch  of  the  posterior  depth,  and  the  fore  and  aft  diam- 
eter, greatest  at  the  end  of  the  ensiform  process,  is  nearly  a  fourth  less 
than  the  former  (Sappey). 

1  L.  sterno-costale  posticum.  *  L.  costo-xiphoidea. 


88  SPECIAL   ANATOMY   OF   THE   SKELETON. 

The  back  of  the  thorax  is  vertical,  moderately  convex  from  above 
downward,  and  flattened  from  side  to  side.  It  is  divided  by  a  promi- 
nent median  ridge  formed  of  the  spinous  processes  of  the  thoracic  ver- 
tebrae, and  is  laterally  defined  by  the  angles  of  the  ribs,  which  suc- 
cessively extend  more  outwardly  from  above  downward.  The  interval 
on  each  side  of  the  median  ridge  forms  a  depressed  space,  which  is  oc- 
cupied by  the  extensor  muscles  of  the  back.  The  space  is  divided  by 
the  series  of  transverse  processes,  the  ends  of  which  project  to  about 
the  level  of  the  angles  of  the  ribs. 

The  sides  of  the  thorax  are  most  prominently  convex,  both  from 
above  downward  and  from  before  backward.  The  lower  border  reaches 
about  on  a  level  with  the  third  lumbar  vertebra. 

The  front  of  the  thorax  is  flattened,  and  slopes  downward  and 
forward.  It  is  formed  by  the  sternum,  the  costal  cartilages,  and  the 
anterior  extremities  of  the  upper  eight  or  nine  ribs.  As  the  ribs  incline 
forward  and  downward,  their  anterior  ends  are  placed  on  a  consider- 
ably lower  level  than  the  heads.  The  anterior  end  of  the  sixth  rib  is 
about  on  a  level  with  the  head  of  the  last  rib.  The  upper  border  of 
the  sternum  is  on  a  level  with  that  of  the  third  thoracic  vertebra,  and 
its  end  with  the  last  thoracic  vertebra. 

The  cavity  of  the  thorax *  in  front  and  laterally  conforms  to  the 
outside,  but  behind  it  is  modified  by  the  projection  forward  of  the 
bodies  of  the  thoracic  vertebrae,  which  form  a  partial  partition  between 
the  two  sides  of  the  cavity.  The  projection  reduces  the  median  space 
occupied  by  the  heart,  and  at  the  same  time,  together  with  the  back- 
ward extension  of  the  ribs  to  their  angles,  it  produces  the  capacious 
dorsal  recesses,  at  the  sides  of  the  spine,  which  are  occupied  by  the 
posterior  portions  of  the  lungs.  The  projection  of  the  spine  diminishes 
to  nearly  one-half  the  median  fore  and  aft  extent  of  the  cavity  com- 
pared with  what  the  thorax  is  externally ;  while,  on  the  other  hand,  the 
transverse  diameters  within  and  without  differ  only  in  the  thickness  of 
the  side  walls  of  the  thorax.  With  the  antero-posterior  compression  of 
the  thorax  and  the  advancement  of  the  vertebral  column  this  assumes 
a  nearly  central  position,  which  is  most  favorable  in  maintaining  the 
equilibrium  of  the  body  in  the  erect  condition. 

The  horizontal  plane  of  the  cavity  of  the  thorax  is  transversely 
reniform.  The  superior  aperture  is  on  an  inclined  plane,  directed  for- 
ward, and  is  twice  the  width  or  more  from  side  to  side  that  it  is  fore 
and  aft.  It  is  formed  by  the  first  thoracic  vertebra,  the  first  pair  of 
ribs  with  their  cartilages,  and  the  presternum.  Through  it  pass  the 
trachea  and  oesophagus  and  the  great  blood-vessels  of  the  neck  and 
upper  limbs,  and  it  is  partially  occupied  by  the  apices  of  the  pleurae, 
into  which  the  lungs  extend.  The  inferior  aperture  has  its  plane 
interrupted  by  three  deep,  angular  notches.  Of  these  the  front  or  ab- 

1  Cavum  thoracis. 


SPECIAL    ANATOMY   OF    THE   SKELETON.  89 

dominal  notch  is  the  widest  and  deepest,  and  is  formed  on  each  side 
by  the  costal  cartilages  from  the  seventh  to  the  last,  and  has  project- 
ing into  it  the  ensiform  process.  The  posterior  or  lumbar  notches 
are  formed  on  each  side  by  the  last  thoracic  vertebra  and  the  last  rib. 
The  intercostal  spaces  are  formed  by  the  intervals  of  the  ribs  with 
their  cartilages,  closed  in  front  by  the  sternum,  and  below  this  by  the 
union  of  the  former,  except  in  the  last  two,  which  are  open.  Behind, 
they  are  closed  by  the  adjacent  vertebra?,  from  between  which  the 
intervertebral  foramina  open  into  the  spaces.  The  upper  intercostal 
spaces  are  widest  and  the  middle  ones  narrowest,  especially  laterally, 
and  mostly  they  are  widest  in  front. 

In  the  female  the  thorax  is  proportionately  longer,  narrower,  trans- 
versely more  circular,  and  vertically  more  oval,  than  in  the  male. 
Tight  lacing  reduces  the  breadth  of  the  thorax,  especially  towards  the 
base,  and  it  diminishes  the  intercostal  spaces, — in  extreme  cases  the 
contiguous  margins  of  the  ribs  being  more  or  less  brought  into  contact 
and  the  inferior  lateral  margin  of  the  thorax  nearer  the  crest  of  the 
ilium. 

Movements  of  the  thorax.  The  chief  movement  of  the  thorax, 
as  in  breathing,  consists  in  partial  rotation  of  the  ribs  on  their  axis, 
up  and  down,  where  they  articulate  with  the  vertebrae,  facilitated  by 
somewhat  similar  motion  in  the  costo-sternal  articulations.  In  the 
movement  the  ribs  are  alternately  raised  and  depressed  from  their  fore 
part.  When  lifted,  the  ribs  approach  a  more  horizontal  position,  and 
the  capacity  of  the  chest  is  proportionately  increased,  and  in  the  de- 
pression the  reverse  condition  follows.  The  sternum  is  lifted  with  the 
ribs,  and  at  the  same  time  projected  below,  thus  contributing  to  the 
enlargement  of  the  thoracic  cavity.  In  old  age  the  costo-vertebral  ar- 
ticulations become  less  movable,  the  costal  cartilages  rigid,  and  the  costo- 
sternal  articulations  obliterated,  in  which  condition  the  thorax  is  less 
dilatable,  and  respiration  is  mainly  carried  on  through  the  diaphragm. 

THE  SKULL. 

The  skull  includes  all  the  bones  of  the  head,  and  articulates  with 
the  vertebral  column  by  means  of  the  occipital  bone.  It  consists  of 
two  chief  parts, — the  cranium,  which  contains  the  brain ;  and  the  face, 
which  with  the  former  contains  the  orbits  or  eye-sockets  and  the  nasal 
cavities,  and  below  is  formed  by  the  jaws,  which  include  the  cavity  of 
the  mouth.  The  cranium  is  composed  of  eight  bones,  of  which  four 
are  single  and  symmetrical, — the  occipital,  sphenoid,  ethmoid,  and 
frontal, — and  the  others  are  in  pairs, — the  parietal  and  temporal  bones. 
The  face  is  composed  of  fourteen  bones,  of  which  two  only  are  single, — 
the  vomer  and  the  mandible, — and  the  others  are  in  pairs, — the  max- 
illary, palate,  malar,  nasal,  turbinal,  and  lachrymal  bones.  The  hyoid, 
a  single,  symmetrical  bone,  situated  in  the  neck,  is  included  in  the 
account  of  the  skull. 


90 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


THE   OCCIPITAL   BONE. 

The  occipital  bone l  occupies  the  back  part  of  the  cranium,  between 
the  parietals  above  and  the  temporals  below,  and  it  extends  forward  in 
the  middle  of  the  base  of  the  cranium  to  the  sphenoid  bone,  with  which 
it  is  commonly  ankylosed  at  adult  age.  It  is  irregularly  quadrate  in 
outline,  convex  externally  and  concave  internally ;  and  it  consists  of 
an  anterior  inferior,  narrow,  and  comparatively  thickened  and  spongy 
portion,  the  basilar  process,  and  a  posterior,  broad,  shell-like  portion, 
the  occipital  plate.  Between  the  two  portions  is  the  occipital  fora- 
men, through  which  the  cavity  of  the  cranium  communicates  with  the 
spinal  canal;  and  at  the  sides  of  the  foramen  are  the  condyles,  which 
form  movable  articulations  with  the  prearticular  processes  of  the  atlas 
or  first  vertebra. 


FIG.  37. 


FIG.  36. 


EXTERNAL  VIEW  OF  THE  OCCIPITAL  BONE.  1, 
superior  curved  line  ;  2,  external  occipital  pro- 
tuberance ;  3,  occipital  crest ;  4,  inferior  curved 
line ;  5,  occipital  foramen  ;  6,  condyle ;  7,  fossa 
behind  the  condyle,  into  which  a  venous  fora- 
men frequently  opens ;  8,  position  of  condylar 
foramen;  9,  jugular  process;  10,  notch  contrib- 
uting to  form  the  jugular  foramen ;  11,  basilar 
process. 


INTERNAL  VIEW  OF  THE  OCCIPITAL  BONE.  1, 
fossa  for  the  cerebrum ;  2,  fossa  for  the  cerebel- 
lum; 3,  groove  for  the  longitudinal  sinus;  4, 
ridge  for  the  attachment  of  the  cerebellar  falx; 
5,  groove  for  the  lateral  sinus  ;  6,  internal  oc- 
cipital protuberance;  7,  occipital  foramen;  8, 
basilar  process;  9,  10,  groove  for  the  lateral 
sinus,  descending  on  the  jugular  process  to  the 
jugular  notch ;  11,  border  for  the  parietal  bone ; 
12,  border  for  the  temporal  bone;  13,  position 
at  which  the  ninth,  tenth,  and  eleventh  cere- 
bral nerves  pass  through  the  jugular  foramen ; 
14,  condylar  foramen. 


The  basilar  process2  projects  in  advance  of  the  occipital  foramen 
obliquely  forward  and  upward  to  near  the  centre  of  the  base  of  the 
skull,  where  it  joins  the  body  of  the  sphenoid  bone.  It  is  irregularly 
quadrate  in  outline,  but  narrows  and  becomes  thicker  forward.  Its 
posterior  lower  border  is  thinnest,  and  is  notched  to  form  the  anterior 


1  Os  occipitis. 


2  Pars  basilaris  ;  basioccipital  bone  ;   basis  ;  corpus. 


SPECIAL,   ANATOMY   OF   THE   SKELETON.  91 

margin  of  the  occipital  foramen.  Its  anterior  extremity  ends  in  a 
quadrate  rough  surface,  which,  previous  to  ankylosis.  is  connected  with 
the  sphenoid  bone  by  cartilage.  The  lateral  borders  of  the  process  join 
the  pyramid  of  the  temporal  bone.  The  lower  surface  is  transversely 
convex,  and  is  sometimes  and  variably  produced  in  a  feeble  median 
ridge,1  which  gives  attachment  to  the  pharynx.  On  each  side,  the  sur- 
face is  marked  by  the  attachment  of  the  prerecti  muscles.  The  upper 
surface  forms  a  smooth  concave  gutter,  the  basilar  groove,2  which 
slopes  downward  to  the  occipital  foramen,  and  accommodates  the 
medulla  oblongata.  At  the  lateral  margins  it  is  marked  by  a  shallow 
furrow  for  the  infrapetrosal  sinus. 

The  occipital  plate 3  encloses  the  back  part  of  the  cranial  cavity 
in  the  interval  of  the  parietal  bones  and  the  mastoid  portion  of  the 
temporals.  The  upper  borders4  from  the  lateral  angles  converge  to 
the  superior  angle,  and  are  remarkably  jagged  for  sutural  union  with 
the  parietal  bones ;  the  lower  borders,5  converging  downward  and 
forward,  are  less  rugged  than  the  former,  and  articulate  with  the 
mastoid  portion  of  the  temporal  bones.  The  external  surface  is 
convex,  and  forms  the  prominent  back  part  of  the  skull.  Near  its 
centre  it  presents  a  variably  produced  and  roughened  eminence,  the 
occipital  protuberance,6  from  which  descends  to  the  occipital  fora- 
men a  slight  ridge,  the  occipital  crest,7  both  giving  attachment  to 
the  nuchal  ligament.  From  the  protuberance  another  ridge,  the 
superior  curved  line,8  arches  outwardly  on  each  side  to  the  lateral 
angle,  dividing  the  surface  into  two  portions,  of  which  the  upper  is 
more  prominent  and  evenly  convex,  and  is  covered  by  the  scalp. 
The  lower  portion  is  further  divided  by  the  inferior  curved  line,9 
which  runs  nearly  parallel  with  the  former.  The  curved  lines  and 
surfaces  below  them  give  attachment  to  muscles  of  the  neck,  the  im- 
pressions of  which  are  commonly  most  marked  in  vigorous  muscular 
subjects. 

The  internal  surface  of  the  occipital  plate  is  divided  into  four 
shallow  concave  recesses,  of  which  the  lower  and  larger  are  the  cere- 
bellar  fossae,  for  the  reception  of  the  hemispheres  of  the  cerebellum ; 
and  the  upper  are  the  cerebral  fossae,  for  the  accommodation  of  the 
hemispheres  of  the  cerebrum.  The  fossa?  are  defined  by  a  median  fore 
and  aft  and  a  horizontal  ridge,  which  together  form  the  occipital 
cross,  and  produce  at  their  conjunction  the  internal  occipital  protu- 
berance.10 To  the  upper  arm  of  the  cross  is  attached  the  cerebral 
falx,  and  it  is  impressed,  usually  to  one  side,  with  a  groove,11  which 


1  Crista  basilaris  ;  pharyngeal  tubercle.  2  Sulcus  basilaris. 

3  Supraoccipital ;  occipital  portion  ;  squama.  *  Margo  lambdoideus. 

s  Margo  mastoideus.  6  External  oc.  post.  7  Crista  occipitalis  externa. 

8  Linea  semicircularis  superior.  •  L.  s.  inferior. 

10  Eminentia  cruciata.  u  Sulcus  sagittalis. 


92  SPECIAL,   ANATOMY   OF   THE   SKELETON. 

accommodates  the  posterior  extremity  of  the  great  longitudinal  sinus. 
To  the  horizontal  arms  of  the  cross,  which  are  nearly  on  a  level  with 
the  external  superior  curved  lines,  is  attached  the  tentorium ;  and  they 
are  impressed  with  a  groove  for  the  lateral  sinus,  usually  larger  on  one 
side  than  on  the  other,  and  varying  in  size  in  accordance  with  the  sinus. 
The  lower  arm  of  the  cross  is  an  acute  ridge,  the  internal  occipital 
crest,  which  gives  attachment  to  the  cerebellar  falx. 

The  occipital  foramen,1  situated  at  the  lowest  level  of  the  bone, 
is  a  large  oval  hole,  with  its  rather  greater  diameter  fore  and  aft, 
and  with  its  margin  somewhat  thickened  for  ligamentous  attachment 
with  the  atlas.  Through  it  the  medulla  oblongata  is  continuous  with 
the  spinal  cord,  and  it  also  transmits  the  vertebral  arteries  and  spinal 
accessory  nerves. 

The  condyles2  are  placed  beneath,  at  the  sides  of  the  anterior  half 
of  the  occipital  foramen,  and  are  a  pair  of  articular  processes,  which 
are  invested  with  cartilage  and  adapted  to  the  prearticular  processes 
of  the  atlas.  They  are  irregular  elliptical  eminences,  convergent  for- 
ward, separated  in  front  by  a  wide  notch  in  advance  of  the  occipital 
foramen,  and  behind  by  the  greater  width  of  the  latter.  The}'  are 
sometimes  more  or  less  constricted  near  the  middle, — a  condition  re- 
maining in  the  line  of,  and  indicating  the  original  separation  of  the 
basilar  portion  from,  the  rest  of  the  bone.  The  articulating  surface  is 
convex  fore  and  aft,  but  forms  an  inclined  plane  looking  downward 
and  outward.  On  the  deeper,  inner  side  of  the  condyles,  bordering  the 
occipital  foramen,  there  is  usually  a  variable,  roughened  ridge,  which 
gives  attachment  to  the  lateral  odontoid  ligaments. 

Piercing  the  base  of  the  condyles  above  the  middle  is  a  short  canal, 
the  condylar  foramen,3  which  is  directed  from  within  the  cranial 
cavity  forward  and  outward  for  the  passage  of  the  hypoglossal  nerve. 
Back  of  the  condyles  is  a  variable  fossa,4  into  which  there  commonly 
opens  on  one  or  both  sides  of  the  bone  a  foramen8  for  the  passage  of  a 
vein  between  the  lateral  sinus  and  the  veins  of  the  scalp.  To  the  outer 
side  of  the  position  of  the  condyles  is  the  jugular  notch,6  which 
forms  the  back  part  of  the  jugular  foramen,  situated  between  the  oc- 
cipital and  temporal  bones.  Projecting  outwardly  from  the  notch  is  the 
jugular  process,7  ending  in  a  usually  quadrate,  roughened  facet,  which 
is  covered  with  cartilage  and  joins  the  pyramid  of  the  temporal  bone. 
Beneath  the  process  is  a  transverse  ridge,8  which  gives  attachment  to 
the  lateral  rectus  muscle;  and  above,  it  is  grooved9  for  the  accommo- 
dation of  the  lateral  sinus  as  it  terminates  at  the  jugular  foramen. 

At  birth  the  occipital  bone  consists  of  four  pieces,  which  are  united 


1  P.  occipitalis ;  f.  magnum.  2  Processus  condyloideus. 

3  Anterior  condyloid  foramen.  4  Fossa  condyloidea. 

5  Posterior  condyloid  foramen.  6  Incisura  jugularis. 

7  P.  jugularis ;  paroccipital  process.  8  Jugular  eminence.      9  Sulcus  transversus. 


SPECIAL   ANATOMY    OF   THE   SKELETON.  93 

by  cartilage.  The  pieces  are  named  the  basioccipital,  in  front ;  the 
exoccipitals,  at  the  sides  of  the  occipital  foramen ;  and  the  supra- 
occipital,  behind. 

The  basioccipital  comprises  the  basilar  process,  together  with  the 
fore  part  of  the  condyles  and  condylar  foramina,  both  of  which  are 
divided  by  the  suture.  The  exoccipitals '  comprise  the  parts  behind 
the  former  to  the  outer  side  of  the  occipital  foramen,  and  include  the 
back  part  of  the  condyles  and  condylar  foramina.  The  supraoccipital 
comprises  the  occipital  plate,  bounding  the  occipital  foramen  behind. 
A  transverse  fissure  extending  a  short  distance  inward  from  the  lateral 
angles  indicates  an  earlier  separation  of  the  supraoccipital  into  two 
pieces,  of  which  the  upper  one  originates  in  fibrous  membrane,  while 
the  lower  one,  together  with  the  other  pieces  of  the  occipital  bone, 
originates  in  cartilage.  The  upper  piece  of  the  supraoccipital  occa- 
sionally remains  separate  even  at  maturity,  when  it  is  united  with  the 
lower  by  suture.  In  some  animals,  as  the  rabbit,  it  remains  perma- 
nently distinct,  as  the  interparietal  bone.  The  upper  angle  of  the 
supraoccipital  is  also  divided  by  a  fissure,  and  this,  with  the  transverse 
fissures,  indicates  the  origin  of  the  supraoccipital  from  four  ossific 
centres.  The  occipital  bone  commences  to  ossify  about  the  seventh 
week  of  fcetal  life.  The  supraoccipital  ankyloses  with  the  exoccipitals 
variably  from  the  third  to  the  sixth  year,  and  then  with  the  basioccip- 
ital during  the  latter  part  of  the  same  time. 

THE   SPHENOID   BONE. 

The  sphenoid  bone2  extends  across  the  base  of  the  skull  in  ad- 
vance of  its  middle,  and  is  situated  between  the  occipital  and  temporals 
behind,  the  ethmoid  and  frontal  in  front,  and  the  parietals  above.  It 
articulates  with  all  the  other  bones  of  the  cranium,  and  with  five  of 
those  of  the  face ;  and  it  contributes  to  form  the  cranial  cavity,  the 
orbits,  the  nasal  cavities,  and  the  temporal,  zygomatic,  and  spheno- 
maxillary  fossse.  It  consists  of  a  central,  more  massive  portion,  the 
body,  and  four  pairs  of  conspicuous  processes :  the  small  and  great 
wings  and  the  ento-  and  ectopterygoid  processes. 

The  body  is  irregularly  cuboidal,  and  is  usually  before  adult  age 
firmly  ankylosed  with  the  basilar  process  of  the  occipital  bone,  from 
which,  in  prepared  specimens  for  study,  it  is  commonly  found  sepa- 
rated by  the  saw.  Before  ankylosis  it  presents  a  posterior,  vertical, 
quadrate  or  oval,  rugged  surface,  which  is  connected  with  the  basilar 
process  by  cartilage. 

The  upper  surface  of  the  body  is  within  the  cranial  cavity,  and 
extends  from  the  basilar  process  to  the  cribriform  plate  of  the  ethmoid 
bone.  Behind  its  middle  is  a  deep  hollow,  the  sella,3  which  lodges 

1  Lateral  occipitals  ;  condylar  portions.  2  Os  sphenoideum. 

3  S.  turcica  ;  pituitary  fossa  ;  ephippium  ;  fossa  hypophyseos. 


94 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


FIG.  38. 


the  pituitary  body.  The  back  of  the  sella  is  formed  by  an  oblique, 
overhanging,  quadrate  plate,  the  clivus,1  the  posterior  surface  of 
which  extends  the  slope  of  the  basilar  groove.  The  upper  thick- 
ened border  of  the  clivus  is 
transversely  concave,  and  at 
each  end  is  produced  in  a  vari- 
able tubercle,  the  postclinoid 
process,2  which  is  commonly 
extended  behind  in  a  short 
spine,  and  gives  attachment  to 
the  tentorium.  Below  the  sides 
of  the  clivus  is  a  process  di- 
rected outwardly  to  articulate 
with  the  end  of  the  temporal 
pyramid,  and  grooved  above 
to  accommodate  the  abducent 
nerve.  In  advance  of  the  sella 
is  a  variable,  obtuse  eminence, 
the  olivary  process,3  which  is 
usually  more  or  less  defined  in 
front  by  the  equally  variable 
optic  groove,  which  leads  out- 
wardly to  the  optic  foramina. 

The  side  of  the  body  slants  downward  and  outward  from  the  sella 
into  the  mesocranial  fossa,  and  is  crossed  fore  and  aft  by  the  carotid 
groove,4  which  accommodates  the  internal  carotid  artery.  The  groove 
pursues  a  sigmoid  course,  is  scarcely  marked  along  the  middle,  is  deep- 
est behind,  where  it  ascends  on  the  lingule,  and  terminates  in  front  in 
a  notch  between  the  olivary  and  preclinoid  processes.  The  lingule 5  is  a 
short  scroll-like  process,  which  projects  from  the  posterior  part  of  the 
body  on  each  side,  and  skirts  internally  the  lacerate  foramen. 

A  usually  slight  and  variable  eminence,  sometimes  present  on  the 
side  of  the  sella,  is  the  mesoclinoid  process.6  In  advance  of  the 
olivary  process  and  optic  groove  a  broad  and  nearly  flat  or  slightly- 
depressed  surface  is  continuous  outward  on  the  small  wings.  It  com- 
monly exhibits  a  slight  median  elevation,  and  is  variably  extended 
in  a  projection,  the  ethmoidal  process,7  which  articulates  with  the 
ethmoidal  cribriform  plate. 

The  front  of  the  sphenoidal  body  is  directed  towards  the  nasal  cavi- 
ties, and  is  divided  by  a  vertical,  median,  carinate  ridge,  the  sphenoidal 
crest,8  which  joins  the  ethmoidal  nasal  plate  in  the  formation  of  the 


FRONT  VIEW  OF  THE  SPHENOID  BONE.  1,  ethmoi- 
dal process;  2,  sphenoidal  crest  and  rostrum  for 
joining  the  nasal  plate  of  the  ethmoid  bone  and 
the  vomer ;  3,  entrance  of  the  sphenoidal  sinuses ; 
4,  small  wing ;  5,  optic  foramen  piercing  its  base ; 
6,  sphenoidal  foramen ;  7,  rotund  foramen ;  8,  or- 
bital surface  of  the  great  wing ;  9,  temporal  surface 
of  the  same  ;  10,  ridge  separating  the  temporal  and 
zygomatic  surfaces ;  11,  vaginal  process ;  12,  ptery- 
goid  canal ;  13,  entopterygoid  process ;  14,  hamu- 
lar  process ;  15,  ectopterygoid  process ;  16,  angular 
process ;  17,  oval  foramen ;  18,  spinous  foramen. 


1  C.  Blumenbachii ;  dorsum  sellse  or  ephippii.  2  Posterior  c.  p. 

3  Tuberculum  sellae.      *  Sulcus  caroticus  ;  impressio  carotica ;  cavernous  groove. 

5  Lingula  sphenoidalis.  6  Middle  c.  p. 

7  Spina  ethmoidalis.  8  Crista  sphenoidalis. 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


95 


FIG.  39. 


partition  of  the  nose.  The  surface  on  each  side  of  the  crest  is  a  variable, 
shallow,  quadrate  recess,  which  forms  the  back  part  of  the  roof  of  the 
corresponding  nasal  cavity.  About  the  middle  of  the  recess  is  a  vari- 
able, large,  irregular  hole,  which  communicates  with  the  sphenoidal 
sinus.  To  the  outer  side  of  the  recess  the  surface  articulates  with 
the  ectethmoid  and  the  orbital  process  of  the  palate  bone.  The  appo- 
sition of  the  former  partially  reduces  the  size  of  the  opening  of  the 
sphenoidal  sinuses.  These  are  two  variably  large  and  mostly 
unequal  cavities  within  the 
fore  part  of  the  sphenoidal 
body.  They  are  separated 
by  a  partition,  the  sphe- 
noidal septum,  of  which 
the  sphenoidal  crest  is  an 
extension.  The  partition 
is  more  or  less  unsymmet- 
rical,  and  produces  the 
same  condition  in  the  si- 
nuses. The  septum  not 
only  deviates  to  one  or  the 
other  side,  but  often  varies 
from  the  vertical  fore  and 
aft  direction.  Occasionally 
there  are  one  or  two  ad- 
ditional, incomplete  parti- 
tions. The  sinuses  occupy 
the  fore  part  of  the  body  to 
the  complete  exclusion  of 

the  spongy  substance,  which  occupies  the  back  part.  They  increase  in 
size  with  the  advance  of  age  at  the  expense  of  the  spongy  substance, 
but  never  to  such  an  extent  as  entirely  to  obliterate  the  latter. 

The  inferior  surface  of  the  sphenoidal  body  looks  downward  into 
the  nasal  cavities,  and  extends  from  these  into  the  guttural  region, 
where  it  is  continuous  with  the  under  surface  of  the  basilar  process. 
Its  fore  part  is  produced  into  a  median  keel-like  ridge,  the  rostrum,1 
which  is  wide  and  low  behind  and  becomes  deeper  and  narrow  in  front, 
and  is  received  in  the  upper  grooved  border  of  the  vomer.  The  rostrum 
is  continuous  with  the  sphenoidal  crest,  but  is  usually  defined  from  it 
by  a  notch,  which  remains  from  an  original  separation  of  the  body  into 
two  parts.  The  triangular  space  at  the  sides  of  the  rostrum,  defined 
outwardly  from  the  root  of  the  great  wing  by  a  groove,  exhibits  a 
low  convex  prominence,  which  forms  the  bottom  of  the  corresponding 
sphenoidal  sinus.  The  eminence  widens  forward,  and  its  surface  turns 
up  in  front  to  the  entrance  of  the  sinus.  In  infancy  it  appears  as  a 


UPPER  VIEW  OF  THE  SPHENOID  BONE.  1,  sella ;  2,  olivary 
process;  3,  clivus;  4,  preclinoid  process;  5,  postclinoid 
process ;  6,  posterior  border  of  the  body ;  7,  cerebral  sur- 
face of  the  great  wing;  8,  articular  surface  for  the  frontal 
bone ;  9,  articular  border  for  the  temporal  bone ;  10,  spi- 
nous  process ;  11,  small  wing ;  12,  border  articulating 
with  the  orbital  plate  of  the  frontal  bone ;  13,  border 
joining  the  ethmoid  bone ;  14,  optic  foramen ;  15,  sphe- 
noidal foramen ;  16,  rotund  foramen  ;  17,  oval  foramen ; 
18,  spinous  foramen ;  19,  groove  on  the  lingule  for  the 
internal  carotid  artery. 


1  K.  sphenoidale  ;  processus  azygos. 


96  SPECIAL    ANATOMY   OP   THE   SKELETON. 

distinct  bone,  the  spheno-turbinal,1  which  is  a  hollow  cone,  and 
subsequently  ankyloses  with  the  rest  of  the  sphenoid  to  form  the 
sphenoidal  sinuses.  Sometimes,  shortly  before  adult  age,  it  may  be 
found  as  a  separate  piece  articulating  with  the  body  of  the  sphenoid 
bone. 

The  small  wings2  are  a  pair  of  nearly  horizontal,  sabre-like  plates, 
which  extend  outwardly  from  the  fore  part  of  the  body,  and  are  sepa- 
rated from  the  great  wings  by  the  sphenoidal  fissure.  In  the  articu- 
lated skull  they  project  into  the  cavity  of  the  cranium,  where  they  are 
received  in  the  sylvian  fissure  of  the  brain.  They  are  connected  with 
the  body  by  two  roots,  which  include  between  them  the  optic  foramen. 
The  posterior  narrower  root  springs  from  below  the  olivary  process. 
The  anterior  root  unites  with  that  of  the  opposite  side  in  a  continuous 
plate,  which  forms  the  upper  part  of  the  body  in  advance  of  the  oli- 
vary process.  The  wing  tapers  outward  to  a  point  which  nearly  comes 
into  contact  with  the  upper  border  of  the  great  wing,  but  is  separated 
from  it  by  the  outer  or  open  extremity  of  the  sphenoidal  fissure.  The 
upper  surface  forms  the  posterior  limit  of  the  precranial  fossa,  and  the 
under  surface  overhangs  the  posterior  extremity  of  the  orbit,  the 
sphenoidal  foramen,  and  the  anterior  inner  part  of  the  mesocranial 
fossa.  The  anterior  thin  margin  is  serrated  for  articulation  with  the 
orbital  plate  of  the  frontal  bone.  The  posterior  margin  is  transversely 
concave,  and  forms  the  dividing  line  between  the  pre-  and  mesocranial 
fossa3.  It  is  thicker  and  rounded  inwardly,  and  thins  away  to  a  sharp 
edge  outwardly.  Its  inner  end  is  prolonged  backward  in  a  variable 
compressed  knob,  the  preclinoid  process,3  which  is  separated  from 
the  olivary  process  by  a  rounded  notch  terminating  the  carotid  groove. 
The  preclinoid  process  is  sometimes  united  with  the  mesoclinoid  pro- 
cess, when  the  notch  is  converted  into  a  foramen;  and  occasionally, 
also,  it  is  united  with  the  postclinoid  process. 

The  great  wings4  spring  from  the  sides  of  the  body,  and  are 
thence  extended  outward,  forward,  and  upward,  but  also  give  off  a 
large  angular  process  directed  horizontally  backward.  They  present 
three  principal  surfaces.  Of  these  the  internal  or  cerebral  surface 5 
contributes  to  form  the  mesocranial  fossa.  It  is  crescentic  in  outline, 
concave,  and  marked  by  cerebral  impressions.  The  external  surface 
is  crossed  below  its  middle  by  a  ridge 6  dividing  it  into  two  portions,  of 
which  the  upper  is  the  temporal  surface,7  looking  outward  and  form- 
ing part  of  the  temporal  fossa ;  and  the  lower  is  the  zygomatic  sur- 
face,8 looking  downward  and  forming  part  of  the  zygomatic  fossa. 
The  anterior  surface  in  great  part  is  formed  by  a  vertical,  quadrate 


1  Ossiculum  Bertini ;  cornu  sphenoidale  ;  pyramid  of  Wistar. 

2  Alae  parvse,  minores,  or  orbitales  ;  orbitosphenoids  ;  apophyses  of  Ingrassias. 

3  Anterior  c.  p.         4  Alae  magnse ;  alisphenoids.          5  Superficies  c'erebralis. 
6  Crista  alae  magnae.  7  Superficies  temporalis.  8  S.  zygomatica. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  97 

piano,  the  orbital  surface,1  which  looks  forward  and  inward,  and 
forms  the  back  part  of  the  outer  wall  of  the  orbit.  Its  anterior  mar- 
gin is  serrated,  and  joins  the  malar  bone ;  its  posterior  margin  is  the 
outer  and  lower  border  of  the  sphenoidal  foramen ;  its  upper  margin 
joins  the  orbital  plate  of  the  frontal  bone  ;  and  its  lower  margin  is  the 
upper  border  of  the  spheno-maxillary  foramen.  Below  the  orbital 
surface  inwardly  a  variable  smaller  surface 2  forms  part  of  the  spheno- 
maxillary  fossa.  The  angular  process  3  of  the  great  wing  is  received 
in  the  notch  between  the  squama  and  pyramid  of  the  temporal  bone. 
From  its  apex  a  variable  pointed  process,  the  sphenoidal  spine,4  is 
directed  downward,  and  abuts  against  the  entoglenoid  tubercle  of  the 
temporal  bone. 

The  posterior  border  of  the  great  wing,  extending  from  its  summit 
to  the  end  of  the  angular  process,  is  semicircular,  bevelled  outward 
above  and  inward  below,  and  is  serrated  for  articulation  with  the 
squama  of  the  temporal  bone.  A  crescentic,  roughened  area  at  the 
upper  part  of  the  wing,  included  between  its  three  chief  surfaces, 
articulates  with  the  frontal  bone ;  and  the  summit  is  bevelled  inwardly 
to  articulate  with  the  contiguous  angle  of  the  parietal  bone. 

The  pterygoid  processes,5  two  on  each  side,  the  ento-  and  ecto- 
pterygoid  processes,  descend  nearly  vertically,  with  a  slight  inclina- 
tion forward,  from  beneath  the  great  wing  where  it  joins  the  body. 
They  consist  of  a  pair  of  plates  conjoined  above  in  front  and  separated 
below  by  a  deep  angular  cleft,  the  pterygoid  notch.6  The  ento- 
pterygoid  process7  is  long  and  narrow,  and  terminates  below  in  the 
hamular  process,8  a  narrow  bar  bent  backward  and  outward  into  a 
hook,  through  which  passes  the  tendon  of  the  palatal  tensor  muscle. 
The  inner  surface  of  the  entopterygoid  process  forms  the  lateral  boun- 
dary of  the  postnasal  orifice.  The  ectopterygoid  process9  is  a 
shorter  and  wider  plate  than  the  former,  from  the  conjunction  of 
which  it  diverges  backward  and  outward.  Its  posterior  border  is 
thin  and  irregular,  and  is  often  variably  produced  into  one  or  two 
angular  points.  The  outer  surface  forms  the  inner  wall  of  the  zygo- 
matic  fossa,  and  gives  attachment  to  the  external  pterygoid  muscle. 
Through  the  divergence  of  the  ecto-  from  the  entopterygoid  process 
behind  is  formed  an  angular  niche,  the  pterygoid  fossa.10  This  in  the 
articulated  skull  is  completed  by  the  closure  of  the  pterygoid  notch 
through  the  pyramidal  process  of  the  palate-bone.  The  fossa  is 
mainly  occupied  by  the  internal  pterygoid  muscle.  To  its  inner  side 
the  root  of  the  entopterygoid  process  presents  an  elliptical  concave 


1  S.  orbitalis.  2  S.  spheno-maxillaris.  3  Processus  angularis. 

4  Spina  sphenoidalis  or  angularis.  5  Processus  pterygoidei. 

6  Incisura  pterygoidea.  7  Internal  pt.  process  or  plate. 

8  Hamulus  pterygoideus  ;  processus  uncinatus. 

9  External  pterygoid  process  or  plate.  10  Fossa  pterygoidea. 

7 


98  SPECIAL   ANATOMY   OF   THE   SKELETON. 

depression,1  from  which  arises  the  palatal  tensor  muscle.  Sometimes  a 
groove  descends  from  the  depression  to  the  hamular  process,  indi- 
cating the  course  of  the  muscle.  In  front  of  the  conjunction  of  the 
pterygoid  processes,  extending  to  the  great  wing  and  body,  is  the 
spheno-maxillary  surface,  which  is  triangular,  and  forms  the  pos- 
terior wall  of  the  spheno-maxillary  fossa.  The  borders  of  the  pro- 
cesses, at  the  sides  of  the  pterygoid  notch,  are  roughened  to  articu- 
late with  the  pyramidal  process  of  the  palate-bone.  Prom  the  inner 
side  of  the  root  of  the  entopterygoid  process  projects  the  vaginal 
process,2  a  narrow  ledge,  extending  inwardly  beneath  the  sphenoidal 
body  to  articulate  with  the  vomer. 

Many  important  foramina  for  the  passage  of  nerves  and  blood-vessels 
perforate  the  sphenoid  bone  on  each  side.  The  optic  foramen3  is  a 
short,  cylindrical  canal,  which  is  directed  from  the  cranial  cavity,  at 
the  side  of  the  body,  forward  and  outward  through  the  base  of  the 
small  wing  to  the  orbit.  It  transmits  the  optic  nerve  and  ophthalmic 
artery. 

The  sphenoidal  foramen,4  the  largest  of  the  apertures  in  the 
separated  bone,  appears  as  the  club-shaped  sphenoidal  fissure  be- 
tween the  small  and  great  wings.  It  is  variably  elliptical  near  the 
body,  and  tapers  to  its  outer  extremity,  where  it  is  closed  by  the 
articulation  of  the  frontal  bone  with  both  wings.  It  communicates 
between  the  mesocrauial  fossa  and  the  orbit,  and  gives  passage  to  the 
oculo-motor,  trochlear,  ophthalmic,  and  abducent  nerves,  and  the  oph- 
thalmic vein. 

The  rotund  foramen5  is  a  short,  cylindrical  canal,  which  pierces 
the  great  wing  a  little  way  behind  the  inner  extremity  of  the  sphe- 
noidal foramen.  It  is  directed  forward  from  the  mesocranial  fossa, 
and  opens  below  the  latter  on  the  spheno-maxillary  surface.  It  gives 
passage  to  the  supramaxillary  nerve. 

The  oval  foramen,6  next  in  size  to  the  sphenoidal,  is  an  elliptical 
nole  in  the  inner  side  of  the  angular  process,  about  half  an  inch  be- 
hind and  a  little  outward  from  the  rotund  foramen.  It  opens  down- 
ward from  the  mesocranial  fossa,  behind  and  outward  from  the  ptery- 
goid processes.  It  transmits  the  roots  of  the  inframaxillary  nerve. 

The  spinous  foramen,7  smaller  than  any  of  the  preceding,  per- 
forates vertically  the  apex  of  the  angular  process,  and  transmits  the 
great  meningeal  vessels. 

The  pterygoid  canal8  is  a  narrow  passage  fore  and  aft  through 
the  root  of  the  pterygoid  processes.  It  commences  on  the  spheno- 


1  Fossa  scaphoidea  or  navicularis.  2  Processus  vaginalis.  3  F.  opticum. 

4  F.  sphenoidale  ;  f.  lacerum  anterius  ;  f.  orbitale  superior. 

5  F.  rotundum  ;  canalis  rotundus,  or  maxillaris  superior. 

8  F.  ovale.  7  F.  spinosum. 

8  Vidian  foramen  ;  canalis  pterygoideus  ;  c.  Vidianus  ;  c.  recurrens. 


SPECIAL   ANATOMY    OF   THE   SKELETON. 


99 


maxillary  surface,  inward  and  behind  the  exit  of  the  rotund  foramen, 
and  opens  posteriorly  beneath  the  lingule,  contiguous  to  the  lacerate 
foramen.  It  transmits  the  pterygoid  nerve  and  vessels. 

The  pterygo-palatine  canal,1  smaller  than  the  former,  is  formed 
by  a  groove  beneath  the  vaginal  process,  closed  below  by  apposition 
of  the  sphenoidal  process  of  the  palate-bone.  It  runs  fore  and  aft 
from  the  spheno-maxillary  fossa  to  the  roof  of  th,e  postnasal  orifice, 
and  transmits  the  pterygo-paiatine  vessels  and  the  pharyngeal  nerve 
of  the  spheno-palatine  ganglion. 

Occasionally  a  fine  canal,2  for  the  small  superficial  petrosal  nerve, 
pierces  the  angular  process  near  the  spinous  foramen ;  but  commonly 
the  nerve  traverses  the  spheno-petrosal  suture. 

At  birth  the  sphenoid  bone  consists  of  three  pieces,  which  are 
united  by  cartilage,  one  consisting  of  the  body  with  the  small  wings, 
and  the  others  each  consisting  of  the  great 
wing  and  the  pterygoid  processes  of  the  same 
side.  The  bone  is  developed  from  seven  pairs 
of  ossific  centres,  which,  with  the  exception 
of  one  pair,  make  their  appearance  in  the 
third  and  fourth  months  of  foetal  life.  The 
centres  are  as  follows :  a  pair  which  subse- 
quently coalesce  in  a  single  piece,  forming 
the  posterior  part  of  the  body,  and  named 
the  basisphenoid ;  a  second  pair  for  the 
lingules  ;  a  third  pair  which  unite  to  form 
the  fore  part  of  the  body,  named  the  pre- 
sphenoid  ;  a  fourth  pair  for  the  great  wings 
with  the  ectopterygoid  processes,  named  the 
alisphenoids ;  a  fifth  for  the  small  wings, 
termed  the  orbitosphenoids ;  a  sixth  for 
the  entopterygoid  processes,  distinguished  as 
the  pterygoids ;  and  a  seventh  pair,  which 
originate  after  birth,  named  the  spheno-turbinals,  and  subsequently 
becoming  the  sphenoidal  sinuses. 

The  first  ossific  centres  appear  in  the  alisphenoids  near  the  rotund 
foramen,  and  thence  grow  outward  in  the  great  wing  and  downward 
in  the  ectopterygoid  process.  The  entopterygoid  processes  originate 
from  independent  centres,  and  subsequently  coalesce  with  the  former 
near  the  middle  of  foetal  life.  In  some  animals  they  remain  separated 
as  the  pterygoid  bones.  The  orbitosphenoids  commence  to  ossify  after 
the  alisphenoids,  the  centres  making  their  appearance  as  Y-like  islets 
embracing  the  optic  foramen  outwardly,  whence  they  grow  in  the  same 
direction.  Next  in  order  four  centres  appear  in  a  transverse  row,  of 
which  the  intermediate  pair  quickly  unite  as  the  basisphenoid,  and 


INFERIOR  VIEW  OF  THE  INTER- 
MEDIATE PORTION  OF  THE  SPHE- 
NOID BONE  AT  BIRTH,  CONSISTING 
OF  THE  BODY  AND  SMALL  WINGS. 

1,  the  presphenoid ;  2,  the  basi- 
sphenoid; 3,  pit  between  the 
former  occupied  with  carti- 
lage; 4,  orbitosphenoid  with 
optic  foramen ;  5,  the  lingule 
with  the  articulation  of  the 
great  wing. 


1  Canalis  or  sulcus  pterygo-palatinu!!. 


2  Canil/s  inriorainatu*. 


100  SPECIAL,    ANATOMY   OF   THE   SKELETON. 

the  others,  as  the  lingules,  soon  coalesce  with  it.  Then  follow  two 
centres  for  the  presphenoid,  appearing  as  islets  at  the  inner  side  of 
the  optic  foramina.  Growing  around  these,  they  join  the  orbito- 
sphenoids,  and  subsequently  coalesce  with  each  other.  In  the  seventh 
month  the  basisphenoid  and  presphenoid  ankylose ;  but  in  monkeys 
they  remain  separated  until  long  after  birth,  and  in  many  lower  mam- 
mals even  to  a  still  later  period. 

Of  the  three  pieces  of  the  sphenoid  at  birth,  that  consisting  of  the 
body  and  small  wings  is  composed  of  the  basisphenoid,  lingules,  pre- 
sphenoid, and  orbitosphenoids,  all  ankylosed.  The  lateral  pieces,  con- 
sisting each  of  the  great  wing  and  pterygoi4  processes  connected  with 
it,  are  composed  of  the  corresponding  alisphenoid  and  pterygoid  united 
together.  The  body  is  solid,  but  exhibits  a  variable  number  of  con- 
spicuous nutritious  foramina.  The  basisphenoidal  portion  is  cylindroid, 
and  includes  the  sella ;  but  the  clivus  is  yet  cartilaginous,  and  remains 
in  this  condition  for  some  time  after  birth.  The  lingules  are  proportion- 
ately large,  and  are  more  conspicuous  than  later.  They  are  directed  back- 
ward in  a  hook-like  process,  which  sustains  the  internal  carotid  artery 
as  it  enters  the  cranium.  Laterally,  they  are  connected  by  cartilage 
with  the  root  of  the  alisphenoids.  The  presphenoidal  portion  of  the 
body  is  oval,  and  is  obliquely  ankylosed  with  the  upper  fore  part 
of  the  basisphenoidal  portion  and  laterally  with  the  small  wings,  of 
which  the  anterior  roots  are  separated  by  a  deep  notch.  The  body 
beneath  presents  an  obtuse  prominence,  in  which  is  a  trilateral  pit 
tapering  upward  and  backward  into  the  sella.  The  pit  is  occupied  by 
cartilage  remaining  from  that  originally  connecting  the  basi-  and  pre- 
sphenoids,  and  finally  disappearing  after  birth.  The  prominence  con- 
tinues to  grow,  and  gradually  becomes  a  conspicuous  elliptical  process 
of  spongy  structure.  Shortly  after  birth  the  great  wings  ankylose  with 
the  lingules,  and  later  form  an  additional  union  with  the  fore  part  of 
the  body. 

In  infancy  the  spheno-turbinals *  appear  as  hollow  cones,  which 
occupy  the  angular  intervals  beneath  the  small  wings  and  at  the  sides 
of  the  inferior  median  process  of  the  body.  In  front  they  articulate 
with  the  ethmoid  bone,  and  later  become  ankylosed  with  it,  in  which 
condition,  when  the  ethmoid  bone  is  separated  from  the  others,  the 
spheno-turbinals  project  from  it  behind  as  a  pair  of  conical  processes. 
The  spheno-turbinals  subsequently  coalesce  with  the  adjacent  surfaces 
of  the  sphenoidal  body,  and  by  further  growth  and  partial  absorption 
of  the  contiguous  parts  they  become  the  walls  of  the  sphenoidal  sinuses. 
The  median  process  of  the  body  becomes  the  partition  separating  the 
latter,  while  it  also  forms  the  rostrum  beneath  and  the  sphenoidal  crest 
in  front. 


J  Cornua  spiier.c/idsli.a  ;  ossiouli  Eertiai ;  cornets  of  Bertin  ;  sphenoidal  spongy 
bcnjfes  ;  ip^rknjids  of  IW^is^ar.  W    «  it  c  '    • 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


101 


PAKIETAL   BONES. 

The  parietal  bone l  joins  its  fellow  in  the  median  line,  and  with  it 
forms  the  top  and  sides  of  the  cranium.  It  is  a  square  plate  of  nearly 
uniform  thickness,  presenting  for  examination  two  broad  surfaces  with 
four  borders  and  angles. 

The  external  surface,  looking  outward  and  upward,  is  convex, 
comparatively  even,  but  more  elevated  centrally  in  the  parietal  emi- 
nence,2 which  is  especially  conspicuous  in  infancy.  Near  the  middle 


FIG.  41. 


OUTER  VIEW  OF  THE  LEFT  PAKIETAL  BONE.  1, 
upper  border;  2,  bevelled  lower  border,  which 
articulates  with  the  squama  of  the  temporal 
bone;  3,  anterior  border,  joining  the  frontal 
bone ;  4,  occipital  border ;  5,  temporal  ridge ;  6, 
venous  foramen ;  7,  prolonged  anterior  inferior 
angle  joining  the  summit  of  the  great  wing  of 
the  sphenoid  bone ;  8,  posterior  inferior  angle 
articulating  with  the  mastoid  kportion  of  the 
temporal  bone. 


INNER  VIEW  OF  THE  LEFT  PARIETAL  BONE. 
1-4,  borders  corresponding  with  same  numbers 
in  former  figure ;  5,  groove  for  the  longitudinal 
sinus,  and,  communicating  with  it,  a  venous 
foramen,  6;  7,  8,  anterior  and  posterior  inferior 
angles ;  the  groove  on  the  latter  accommodates 
the  lateral  sinus.  The  arborescent  lines  on  the 
inner  concave  surface  of  the  bone  indicate 
grooves  for  the  great  meningeal  vessels. 


it  is  crossed  fore  and  aft  by  a  variably  distinct  arching  line,  the  tem- 
poral ridge,  which  marks  the  upper  boundary  of  the  temporal  fossa 
and  gives  attachment  to  the  temporal  fascia.  The  surface3  below 
forms  part  of  the  temporal  fossa,  and  that  above  is  covered  by  the 
epicranial  aponeurosis. 

The  internal  surface  is  concave  and  marked  with  shallow  im- 
pressions, conforming  to  the  convolutions  of  the  brain.  It  also  ex- 
hibits arborescent  channels,  which  accommodate  the  great  meningeal 
vessels ;  one  principal  branch  ascending  from  the  lower  anterior  angle, 
and  another  from  near  the  middle  of  the  lower  border.  The  com- 
mencement of  the  former  branch  is  sometimes  for  a  short  distance 
converted  into  a  complete  canal.  Along  the  upper  border  of  the  bone 


1  Os  parietale. 


2  Tuber  parietale. 


3  Planum  temporale. 


102  SPECIAL   ANATOMY   OF   THE   SKELETON. 

is  a  shallow  groove  for  the  longitudinal  sinus,  the  groove  being  more 
obvious  in  the  conjoined  bones. 

The  superior  border  of  the  parietal  is  thick,  straight,  and  strongly 
dentated  for  articulation  with  the  opposite  bone.  The  anterior  border, 
also  nearly  straight  and  strongly  dentated,  is  slightly  bevelled,  out- 
wardly above  and  inwardly  below,  to  accord  with  the  contiguous 
border  of  the  frontal  bone.  The  posterior  border,  less  regular  in  its 
course,  is  deeply  dentated  to  articulate  with  the  occipital  bone.  The 
inferior  border,  for  the  most  part  thinner  than  the  others,  consists 
of  three  portions.  The  intermediate  poi'tion  is  arched  and  deeply 
bevelled  outwardly  to  a  sharp  edge,  which  is  overlapped  by  the  tem- 
poral squama.  The  front  portion  is  formed  by  the  somewhat  prolonged 
antero-inferior  angle,  which  is  also  bevelled  outwardly  and  overlapped 
by  the  summit  of  the  sphenoidal  great  wing.  The  back  portion,  formed 
by  the  postero-inferior  angle,  is  thick  and  dentated  for  articulation 
with  the  mastoid  portion  of  the  temporal  bone,  and  its  inner  surface 
is  grooved  for  the  lateral  sinus.  Near  the  postero -superior  angle 
there  is  frequently  a  small  aperture,  the  parietal  foramen,1  which 
communicates  with  the  diploe,  and  often,  also,  with  the  interior  of 
the  cranium,  for  the  transmission  of  a  vein. 

The  parietal  in  its  production  is  one  of  the  purely  membrane  bones, 
and  is  developed  from  a  single  centre,  which  appears  about  the  seventh 
week  of  foetal  life  in  the  position  of  the  parietal  eminence.  At  birth 
the  bone  appears  as  a  simple  plate,  most  prominent  and  thickest  at  the 
centre,  whence  the  osseous  fibres  radiate  to  the  borders,  where  many 
of  them  project  in  spicules. 

THE   FKONTAL   BONE. 

The  frontal  bone 2  occupies  the  fore  part  of  the  cranium,  and  con- 
sists of  a  frontal  plate,  which  forms  the  basis  of  the  forehead,  and  a 
pair  of  orbital  plates,  which  extend  horizontally  backward  from  the 
lower  part  of  the  former  over  the  orbits. 

The  frontal  plate 3  externally  is,  for  the  most  part,  evenly  convex 
and  smooth,  and  is  covered  with  the  skin  of  the  forehead.  On  each  side 
it  exhibits  a  slightly  greater  prominence,  the  frontal  eminence,4  vari- 
able in  different  individuals,  and  most  conspicuous  in  infancy,  when  it 
is  commonly  a  striking  feature.  The  bone,  also,  occasionally  exhibits  a 
slight  median  elevation,  which  corresponds  with  its  early  separation  into 
two,  and  traces  of  the  original  suture  sometimes  remain  at  the  lower 
part.  Below,  the  surface  terminates  on  each  side  in  a  curved  ridge, 
the  supraorbital  arch,5  which  becomes  more  narrow  and  prominent 
outwardly,  and  forms  the  upper  border  of  the  orbital  entrance.  The 

1  Foramen  parietale.  2  Qs  frontis  ;  o.  sincipitis. 

3  Frontal  portion  ;  pars  frontalis,  perpendicularis,  or  ascendens. 

4  Tuber  frontale.  5  Orbital  arch  ;  margo  supraorbitalis. 


SPECIAL    ANATOMY    OF   THE   SKELETON. 


103 


FIG.  43. 


arch  terminates  in  the  internal  and  external  angular  processes, 
of  which  the  former  is  little  produced,  is  thin,  extends  backward,  and 
articulates  with  the  lachrymal  bone;  while  the  latter  is  thick  and 
prominent,  and  is  serrated  at  the  end  to  articulate  with  the  malar 
bone.  The  interval  of  the  internal  angular  processes  is  a  serrated, 
crescentic  surface,  the  nasal  notch,  which  articulates  with  the  nasal 
and  maxillary  bones.  From  its  middle  behind  there  projects  downward 
and  forward  a  narrow  process  of  variable  length,  the  nasal  spine,2 
which  articulates  with  the  ethmoid  nasal  plate  behind  and  with  the 
nasal  bones  in  front.  From  each  side  of  the  spine  is  reflected  out- 
wardly a  scroll-like  plate,  the  nasal  ala,3  which  contributes  to  form 
the  anterior  slope  of  the  roof  of  the 
nasal  cavity  and  contiguous  portion 
of  the  frontal  sinus ;  it  articulates  in 
froni  with  the  nasal  bones,  and  out- 
ward and  behind  with  the  maxillary 
and  ethmoid  bones.  From  the  ex- 
ternal angular  process  the  tem- 
poral ridge  curves  upward  and 
backward,  defining  the  fore  part 
of  the  temporal  fossa  from  the  sur- 
face of  the  forehead,  and  giving 
attachment  to  the  temporal  fascia. 
Above  the  supraorbital  arch  is  an 
obtuse  curved  eminence,  the  super- 
ciliary ridge,4  for  the  eyebrow, 
variably  prominent,  and  gradually 
subsiding  outwardly.  Its  promi- 
nence is  due  to  the  projection  of  a 
cavity,  the  frontal  sinus,  within  the 
bone.  The  ridges  of  the  two  sides 

conjoin  just  above  the  nasal  notch  in  a  flat  or  slightly-depressed  median 
eminence,  named  the  glabella,5  corresponding  with  the  smooth  surface 
between  the  eyebrows.  Near  the  middle  of  the  supraorbital  arch, 
mostly  inwardly,  is  an  aperture  or  a  notch  converted  into  one  by  a 
ligament,  the  supraorbital  foramen,6  for  the  passage  of  correspond- 
ing vessels  and  nerve.  Opening  into  the  foramen,  or  near  it,  there  is 
commonly  to  be  observed  a  smaller  one  for  the  passage  of  a  vein  from 
the  diploe. 

The  internal  surface  of  the  frontal   plate  is  deeply  concave,  and 
everywhere  marked  with  impressions  and  ridges,  conforming  to  the 


EXTERNAL  VIEW  OP  THE  FRONTAL  BONE. 
1,  position  of  the  frontal  eminence ;  2,  super- 
ciliary ridge;  3,  supraorbital  arch;  4,  5, 
external  and  internal  angular  processes ;  6, 
supraorbital  notch  or  foramen ;  7,  glabella ; 
8,  temporal  ridge ;  9,  nasal  spine. 


1  Margo  nasalis.  '2  Processus  nasalis  ;  spina  nasalis. 

3  Ala  spinse  nasalis.  4  Arcus  superciliaris. 

5  Nasal  eminence  or  boss  ;  inferior  or  middle  frontal  eminence  or  boss. 

6  Incisura  or  foramen  supraorbitale  ;  supraorbital  notch. 


104 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


FIG.  44. 


convoluted  surface  of  the  cerebrum.     In  the  median  line  is  a  groove,1 

wide  and  feebly  mai'ked  above,  and 
becoming  narrower  and  more  dis- 
tinct below,  where  it  is  defined  by 
elevated  margins  which  unite  in 
the  frontal  crest,2  a  variably 
prominent,  narrow  ridge,  descend- 
ing and  ending  at  the  ethmoidal 
notch.  The  groove  lodges  the  fore 
part  of  the  longitudinal  sinus,  and 
its  margins  and  frontal  crest  give 
attachment  to  the  cerebral  falx. 
Below  the  frontal  crest  is  a  little 
groove,  which,  by  apposition  with 
the  ethmoid  bone,  is  converted  into 
a  blind  pit3  or  a  short  canal,  giving 
passage  to  a  vein  from  the  nose  to- 
the  longitudinal  sinus.  The  pos- 
terior border  of  the  frontal  plate 
is  thick  and  strongly  serrated,  is 
slightly  bevelled  inwardly  above, 
and  to  a  greater  degree  outwardly 
at  the  sides,  for  articulation  with 
the  parietal  bones.  Below,  the 
border  widens  to  a  triangular 
rough  surface,  which  articulates 
with  the  great  wing  of  the  sphe- 
noid bone. 

The  orbital  plates4  extend,  in 
a  vaulted  manner,  horizontally  from 
the  supraorbital  arches  to  the  small 

wings  of  the  sphenoid  bone,  with  which  they  form  the  roofs  of  the 
orbits.  They  are  much  thinner  than  the  frontal  plate,  and  are  sepa- 
rated by  a  rectangular  interval,  the  ethmoidal  notch,5  which  is 
occupied  by  the  cribriform  plate  of  the  ethmoid  bone.  The  upper 
surface  is  convex,  and  deeply  marked  by  impressions  of  cerebral  con- 
volutions, while  the  inferior  surface  is  concave  and  even,  and  forms  the 
upper  boundary  of  the  orbital  cavity.  A  deeper  recess,6  within  the  ex- 
ternal angular  process,  lodges  the  lachrymal  gland  ;  and  a  small,  shallow 
pit 7  situated  above  the  internal  angular  process  accommodates  the  pulley 
of  the  trochlearis  muscle.  The  outer  border  of  the  orbital  plate  ar- 
ticulates with  the  great  wing  of  the  sphenoid  bone,  and  the  posterior 


INTERNAL  VIEW  OF  THE  FRONTAL  BONE.  1, 
groove  for  the  longitudinal  sinus,  narrowing 
below  on  the  frontal  crest;  2,  in  the  eth- 
moidal notch ;  3,  superior  dentated  border, 
articulating  with  the  parietal  bones;  4,  pos- 
terior border  of  the  orbital  plate  5,  which 
joins  the  small  wing  of  the  sphenoid  bone ; 
6,  irregular  inner  border  of  the  same  plate 
which  covers  the  upper  part  of  the  eth- 
moidal sinuses;  7,  points  to  the  position  of 
the  ethmoidal  foramina;  8,  nasal  spine;  9, 
thick  rough  border  articulating  with  the  great 
wing  of  the  sphenoid  bone ;  10,  refers  to  the 
black  spot,  which  indicates  the  position  of  a 
fossa  for  the  pulley  of  the  trochlearis  muscle ; 
to  its  outer  side  is  the  supraorbital  notch; 
11,  internal  angular  process,  and  entrance 
to  the  frontal  sinus;  12,  external  angular 
process. 


1  Sulcus  sagittalis. 
3  Foramen  ccecum. 
8  Incisura  ethmoidalis. 


2  Crista  frontalis. 

4  Plana  orbitalia  ;  partes  orbitales. 
6  Fossa  lachrymalis.  7  Fossa  trochlearis. 


SPECIAL,   ANATOMY   OF   THE   SKELETON.  105 

I 

border  with  the  small  wing,  completing  the  sphenoidal  foramen  out- 
wardly. The  inner  border  below  exhibits  a  number  of  shallow  recesses, 
which,  by  articulation  with  the  ectethmoid,  complete  the  contiguous 
ethmoidal  sinuses.  Crossing  this  border  transversely  are  two  grooves, 
which,  by  apposition  of  the  ethmoid  bone,  form  the  pre-  and  post- 
ethmoidal  foramina.  At  the  fore  part  of  the  same  border  is  the 
outlet  of  the  frontal  sinus,  a  large  cavity  which  occupies  the  interior 
of  the  bone,  extending  outwardly  above  the  supraorbital  arch  within 
the  position  of  the  superciliary  ridge.  The  frontal  sinuses  are  of 
variable  size,  and  increase  with  the  advance  of  age.  They  extend 
upward  and  outward  in  the  frontal  plate,  and  backward  in  the  orbital 
plates,  and  are  separated  by  a  mostly  unsymmetrical  partition.  They 
often  differ  in  size  on  the  two  sides,  and  are  occasionally  subdivided 
by  one  or  two  partial  partitions.  The  outlet  of  each  sinus,  named  the 
infundibulum,  descends  within  the  internal  angular  process,  and,  in 
the  articulated  frontal  with  the  ethmoid  bone,  opens  into  the  middle 
nasal  meatus. 

The  frontal  plate  of  the  frontal  bone  consists  of  a  nearly  uniform 
layer  of  spongy  substance,  enclosed  by  the  compact  layers,  of  which 
the  external  is  the  thicker,  while  the  orbital  plates  and  the  walls  of 
the  frontal  sinuses  consist  mainly  of  compact  substance. 

The  frontal  bone  is  produced  in  nbro-connective  tissue,  and  is  de- 
veloped from  two  centres,  which  make  their  appearance  about  the 
seventh  week  of  foetal  life,  one  on  each  side  above  the  supraorbital 
arch,  whence  ossification  extends  upward  in  the  frontal  plate  and  back- 
ward in  the  orbital  plate.  At  birth  the  bone  consists  of  two  pieces, 
corresponding  with  the  halves  of  the  frontal  at  maturity,  connected 
in  the  median  line,  but  separated  by  a  wide  membranous  interval  at 
the  upper  adjacent  angles.  The  frontal  eminences  are  conspicuous, 
but  the  superciliary  ridges  and  frontal  sinuses  do  not  yet  appear. 
Ankylosis  of  the  two  pieces  occurs  during  the  first  year,  commencing 
at  the  glabella  and  proceeding  upward,  but  the  union  is  not  com- 
pleted until  about  the  end  of  the  second  year  or  later.  Sometimes 
the  pieces  remain  permanently  distinct,  united  by  suture,  represent- 
ing the  normal  condition  in  some  animals  in  which  there  are  two 
frontals. 

The  frontal  sinuses  begin  to  make  their  appearance  about  the  second 
or  third  year,  and  are  produced  by  the  gradual  absorption  of  spongy 
substance,  commencing  in  the  internal  angular  processes  and  proceeding 
upward.  Later  they  enlarge  by  expansion  forward,  giving  rise  to  the 
superciliary  ridges.  They  continue  to  increase  even  after  maturity, 
extending  upward  and  outward  along  the  supraorbital  arch  and  back- 
ward within  the  orbital  plates.  Rarely  they  remain  small  or  altogether 
undeveloped.  They  reach  a  greater  degree  of  development  in  the  male 
than  in  the  female. 


106 


SPECIAL    ANATOMY   OF    THE    SKELETON. 


FIG.  45. 


THE    ETHMOID   BONE. 

The  ethmoid  bone  l  is  situated  at  the  fore  part  of  the  cranium,  in 
advance  of  the  sphenoid  and  beneath  the  frontal  bone.  It  occupies  the 
face  between  the  orbits,  and  chiefly  enters  into  the  construction  of  the 

upper  part  of  the  nasal  cavities,  and  only  a 
small  portion  contributes  to  the  cranial  cav- 
ity. It  is  a  light,  cuboidal  bone,  and  consists 
of  a  median  vertical  plate,  named  the  mes- 
ethmoid,  which  is  connected  by  a  narrow 
horizontal  portion,  the  cribriform  plate, 
with  a  pair  of  lateral  cellular  masses,  named 
the  ectethmoids. 

The  mesethmoid,2  for  the  most  part, 
enters  into  the  partition  of  the  nose  as  the 
nasal  plate,  while  the  smaller  portion  projects 
into  the  cranial  cavity  as  the  ethmoidal  crest. 
The  nasal  plate 3  occupies  a  median  po- 
sition in  the  upper  part  of  the  nasal  parti- 
tion, of  which  it  forms  about  one-third.  It 
is  broad,  thin,  and  smooth  except  at  the 
upper  part,  where  it  is  marked  by  descend- 
ing and  divergent  grooves,  which  proceed 
from  the  inner  series  of  foramina  of  the 
cribriform  plate  for  the  olfactory  nerves. 
The  fore  part  is  extended  in  a  triangle,  of 
which  the  upper  border  articulates  with  the 

frontal  nasal  spine,  sometimes  reaching  the  nasal  bones,  and  the  lower, 
somewhat  thickened  border,  joins  the  septal  cartilage.  The  posterior 
border  is  thin,  and  articulates  with  the  sphenoidal  crest,  while  the 
lower  border  articulates  with  the  vomer. 

The  ethmoidal  crest 4  projects  from  the  middle  of  the  cribriform 
plate  into  the  cranium,  and  gives  attachment  to  the  anterior  extremity 
of  the  cerebral  falx.  It  is  most  prominent  in  front,  where  it  forms  a 
knob  of  variable  shape  and  size,  and  thence  slants  away  behind  in  a 
narrow  ridge.  -From  its  fore  part  project  two  little  wing-like  or 
alar  processes,5  which  rest  against  the  frontal  bone  and  partially 
include  a  narrow  pit,  the  ccecal  foramen.6 

The  cribriform  plate7  extends  from  the  base  of  the  ethmoidal 
crest  on  each  side  to  join  the  ectethmoids,  occupying  the  ethmoidal 
notch  of  the  frontal  bone,  and  articulating  with  the  inner  borders  of  its 
orbital  plates.  Its  lower  surface  is  directed  into  the  nasal  cavities,  and 


UPPER  VIEW  OF    THE  ETHMOID 

BONE.  1,  orbital  plate  of  the  ect- 
ethmoid;  2,  posterior  imperfo- 
rate  extremity  of  the  cribriform 
plate;  3,  ethmoidal  crest;  on 
each  side  the  olfactory  fossa  with 
foramina  of  the  cribriform  plate, 
and  in  advance  the  alar  pro- 
cesses: 4,  anterior  extremity  of 
the  nasal  plate;  5,  ethmoidal 
sinuses. 


1  Os  ethmoides. 

3  Lamina  perpendicularis. 

5  Processus  alares. 


2  Median  ethmoid  ;  prefrontal. 
*  Crista  ethmoidalis  ;  crista  galli. 
6  F.  ccecum.  7  Lamina  cribrosa. 


SPECIAL,   ANATOMY   OF    THE   SKELETON.  107 

forms  the  middle  portion  of  their  roof  on  each  side  of  the  nasal  plate. 
Its  upper  surface  is  directed  into  the  cranial  cavity,  and  is  depressed  on 
each  side  of  the  crest  to  form  the  olfactory  fossa,  which  accommodates 
the  olfactory  bulb.  Within  the  fossa  the  plate  is  pierced  with  numer- 
ous foramina,  which  communicate  with  the  nasal  cavity  on  each  side 
and  transmit  the  olfactory  nerves.  A  larger  aperture  at  the  fore  part 
of  the  fossa  gives  passage  to  the  nasal  branch  of  the  ophthalmic  nerve. 
The  posterior  extremity  of  the  plate,  less  depressed  and  mostly  imper- 
forate,  articulates  with  the  ethmoidal  process  of  the  sphenoid  bone. 

The  ectethmoids,1  or  lateral  masses  of  the  ethmoid  bone,  are 
separated  from  the  nasal  plate  by  a  narrow  fore  and  aft  passage  at  the 
upper  part  of  the  nasal  cavities.  They  are  of  rectangular  shape,  and 
enclose  a  number  of  irregular  vacuities,  the  ethmoidal  sinuses,2 
which  are  separated  into  an  anterior  and  a  posterior  group.  In  the 
recent  condition  they  are  lined  with  mucous  membrane,  and  communi- 
cate with  the  nasal  cavities,  of  which  they  are  accessory  chambers.  In 
the  separated  bone  they  are  more  or  less  exposed  along  the  borders, 
especially  in  front  and  outwardly  above.  Articulated,  they  are  closed 
in  front  by  the  apposition  of  the  lachrymal  and  maxillary  bones,  above 
by  the  orbital  plates  of  the  frontal  bone,  behind  by  the  sphenoid  and 
palate  bones,  and  below  by  the  maxillae.  Outwardly  the  ectethmoid 
is  defined  by  the  smooth,  rectangular  orbital  plate,3  which  forms  the 
greater  part  of  the  inner  wall  of  the  orbit ;  articulating  in  front  with 
the.lachrymal  bone,  behind  with  the  sphenoid  and  palate  bone,  above 
with  the  frontal,  and  below  with  the  maxilla.  Inwardly  the  ecteth- 
moid presents  a  convex,  uneven,  and  rough  surface  *  directed  in  the 
nasal  cavity  towards  the  nasal  plate.  For  more  than  half  its  length 
behind  it  is  divided  by  a  deep  passage,  the  superior  nasal  meatus, 
which  slants  downward  and  backward,  and  is  overhung  by  a  thin 
curving  plate,  the  supraturbinal,5  of  the  nose.  Into  the  meatus  the 
posterior  ethmoidal  sinuses  open  by  several  apertures.  Not  unfre- 
quently  above  the  former  there  is  a  shorter  channel  extending  to  the 
back  part  of  the  bone. 

The  lower  part  of  the  ectethmoid  forms  a  conspicuous  scroll,  the 
mesoturbinal,6  of  the  nose,  extending  fore  and  aft,  and  overhanging 
the  middle  nasal  meatus.  The  anterior  extremity  is  rounded  and 
free;  the  posterior  is  tapering  and  attached  at  the  end  to  the  palate 
bone.  The  surface  directed  inwardly  is  convex  and  rough ;  that  out- 
wardly is  concave,  and  forms  the  upper  part  of  the  middle  meatus ;  and 

1  Lateral  ethmoids ;  ethmo-turbinals  ;  labyrinthi ;  prefrontals. 

2  Cellulae  ethmoidales.  3  Os  planum  ;  ectethmoid  ;  lamina  papyracea. 

4  Lamina  concharum. 

5  Superior  turbinated  bone ;  sup.  spongy  bone ;    os  turbinatum  or  spongiosum 
sup.  ;  ectoturbinal ;  concha  superior ;  c.  Morgagniana. 

6  Middle  turbinated  bone ;  middle  spongy  bone ;  os  turbinatum  or  spongiosum 
medium  ;  endoturbinal ;  concha  media. 


108 


SPECIAL    ANATOMY   OF    THE   SKELETON. 


the  lower  free  border  is  everted,  variably  thickened,  spongy,  and  rough. 
The  upper  part  of  the  internal  surface  of  the  ectethmoid  is  perforated 
by  numerous  fine  canals,  which  descend  from  the  outer  series  of  foram- 
ina of  the  cribriform  plate.  The  canals  transmit  the  olfactory  nerves 
to  the  inner  surfaces  of  the  upper  and  middle  turbinals,  and  are  com- 
monly more  or  less  incomplete  or  open  inwardly  in  their  course.  The 
fore  part  of  the  ectethmoid  extends  in  advance  of  the  middle  turbinal, 

FIG.  46. 


FIG.  47. 


73  43 

LEFT  SIDE  VIEW  OF  THE  ETHMOID  BONE.    1,  orbi-  INNER  VIEW  OF  THE  EIGHT  ECTETHMOID.     1, 

tal  plate ;  2,  anterior  ethmoidal  sinuses  ;    3,  the  cribriform  plate ;   2,   the    supraturbinal ;    3, 

mcsoturbinal ;  4,  uncinate  process;  5,  ethmoidal  mesoturbinal;    4,    supranasal   meatus;    5,  a 

crest ;  6,  alar  process ;  7,  nasal  plate ;  8, 9,  position  shorter  meatus  occasionally  present ;   6,  part 

of  the  pre-  and  postethmoidal  foramina.  of  the  ccecal  pit. 

and  encloses  the  anterior  ethmoidal  sinuses.  Above,  it  joins  the  frontal 
nasal  spine,  and  thence  outwardly  articulates  with  the  nasal  process 
of  the  maxilla  and  with  the  lachrymal  bone.  From  the  lower  part  of 
the  ectethmoid,  in  the  outer  part  of  the  middle  meatus,  a  narrow  plate, 
the  uncinate  process,1  descends  to  join  the  ethmoidal  process  of  the 
turbinal  bone,  the  two  serving  to  reduce  the  aperture  of  the  maxillary 
antrum. 

In  the  articulated  bone  the  frontal  sinus  communicates  by  a  pas- 
sage, the  infundibulum,  with  the  anterior  ethmoidal  sinuses,  and  with 
these  opens  by  two  or  three  apertures  into  the  middle  nasal  meatus. 

The  nasal  plate  of  the  ethmoid  bone  is  frequently  unsymmetrical, 
being  more  or  less  bent  to  either  side.  The  turbinals,  also,  are  fre- 
quently unsymmetrically  developed  on  the  two  sides,  and  mostly  in  a 
degree  proportioned  to  one  another. 

According  to  Sappey,  the  ethmoid  bone  is  developed  from  four 
centres  of  ossification,  one  for  each  ectethmoid  and  two  for  the  mes- 
ethmoid.  The  ectethmoid  commences  ossification  about  the  middle 
of  foetal  life,  starting  centrally,  and  proceeding  in  the  production  of 
the  sinuses,  orbital  plate,  and  turbinals.  Ossification  commences  in 
the  mesethmoid,  after  birth,  from  a  pair  of  centres  which  appear  in 

1  P.  uncinatus  or  hamatus  ;  naso-turbinal. 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


109 


FIG.  48. 


the  fore  part  of  the  crest.  The  centres  speedily  unite,  and  ossification 
thence  extends  in  the  crest  and  cribriform  plate,  and  subsequently  into 
the  nasal  plate.  The  ectethmoids  unite  with  the  mesethmoid  through 
the  cribriform  plate  towards  the  end  of  the  first  year  after  birth. 
Unlike  the  frontal  and  sphenoidal  sinuses,  the  ethmoidal  sinuses  are 
directly  produced,  and  not  formed  through  the  subsequent  absorption 
of  spongy  substance  as  in  the  former. 

THE  TEMPORAL  BONES. 

The  temporal  bone1  contains  within  its  interior  the  chief  portion  of 
the  organ  of  hearing  ;  and  with  it  the  lower  jaw  articulates.  It  occupies 
the  lower  part  of  the  side  of  the  cranium,  and  extends  inwardly  to  near 
its  centre.  It  is  enclosed  by  the  sphenoid  bone  in  front,  the  occipital  be- 
hind, and  the  parietal  above.  For  convenience  of  study  and  reference  it 
is  divided  into  the  squamous, 
mastoid,  and  petrous  por- 
tions, though  these  do  not 
accord  with  the  original  sep- 
aration of  the  bone  into 
pieces,  as  will  be  subse- 
quently described. 

The  squamous  por- 
tion J  is  the  outer  fore  part 
of  the  bone,  and  is  defined 
behind  from  the  mastoid 
portion  by  a  ridge  curving 
from  in  front  of  the  ear 
backward  and  upward.  It 
mainly  consists  of  an  irreg- 
ular  oval  or  nearly  circular 
upright  scale-like  plate,  the 

Squama     which,   alono-   the 

.  ° 

greater  part  of  its  free  bor- 

der,  18  deeply  bevelled  away 

.,  .  .          , 

inwardly    to    a    thin,    sharp 

edge,  and  overlaps  the  con- 

tiguous bevelled  borders  of  the  parietal  and  sphenoid  bones.  The  outer 
surface,  a  nearly  vertical  plane,  forms  part  of  the  temporal  fossa.  The 
inner  surface  within  the  bevelled  border  is  concave,  and  strongly  im- 
pressed by  the  contiguous  cerebral  convolutions.  Running  nearly  paral- 
lel with  the  anterior  and  upper  border  is  a  groove  for  the  great  menin- 
geal  vessels.  From  the  lower  part  of  the  squama  outwardly  projects  the 
zygomatic  process,3  a  horizontal  bar,  which  springs  by  a  broad  barse 


ExTEKNAL  VIEW  OF  THE  TEMPORAL  BONE  OF  THE  RIGHT 

SIDE.  1,  squama  ;  2,  mastoid  portion  ;  3,  apex  of  the 
Petrous  Portion  ;  4,  zygomatic  process  ;  5,  glenoid  fossa  ; 
6,  preglenoid  tubercle  ;  7,  glenoid  fissure  ;  8,  mastoid 
process;  9,  back  part  of  digastric  fossa;  10,  mastoid 
foramen  ;  ll,  tympanic  plate  forming  the  vaginal  and 
auditory  processes  ;  12,  auditory  meatus  ;  13,  styloid  pro- 
cess  ;  14,  slight  impression  of  the  deep  temporal  artery. 


1  Os  temporis,  temporum,  or  temporale. 
3  Processus  zygomaticus  ;  p.  jugalis. 


110  SPECIAL    ANATOMY   OF    THE   SKELETON. 

from  above  the  articulation  of  the  mandible,  thence  curves  outward 
and  forward,  and  ends  in  a  slightly  expanded  and  serrated  extremity, 
which  articulates  with  the  malar  bone.  From  the  upper  border 
of  the  zygomatic  process  a  ridge  curves  backward  and  upward  over 
the  ear-passage,  defining  the  squama  from  the  mastoid  portion  of  the 
bone. 

Beneath  the  squama,  and  extending  outwardly  under  the  base  of 
the  zygomatic  process,  is  the  articulation  for  the  lower  jaw,  consisting 
of  the  glenoid  fossa  and  articular  eminence.  The  glenoid  fossa1  is  a 
transverse,  elliptical  concavity,  which  is  defined  behind  by  the  glenoid 
fissure.2  The  articular  eminence3  in  front  of  the  former  is  a  trans- 
verse ridge,  variably  thick  and  convex  fore  and  aft,  and  slightly  con- 
cave to  straight  from  side  to  side.  Its  outer,  somewhat  more  promi- 
nent extremity  is  the  preglenoid  tubercle.  The  outer  back  part 
of  the  glenoid  fossa  is  extended  on  a  variable,  flattened  conical  process, 
the  postglenoid  tubercle  ;  and  the  inner  extremity  of  the  fossa  is 
also  prolonged  on  a  process,  the  entoglenoid  tubercle,  which  abuts 
against  the  sphenoidal  spinous  process.  In  advance  of  the  articular 
eminence  a  small  surface,  looking  downward,  forms  part  of  the  zygo- 
matic fossa. 

The  mastoid  portion4  of  the  temporal  bone  is  situated  behind  the 
squama,  from  which  it  is  separated  at  the  upper  border  by  a  notch, 
which  receives  the  adjacent  angle  of  the  parietal  bone.  It  is  prolonged 
downward  in  a  conspicuous  nipple-shaped  prominence,  the  mastoid 
process,5  from  which  the  portion  of  the  bone  is  named.  The  process 
is  laterally  compressed,  and  is  roughened  behind  and  at  the  point  for 
muscular  attachment.  Inward  to  the  process  is  a  deep  fore  and  aft 
groove,  the  digastric  fossa,6  which  gives  origin  to  the  digastric  muscle. 
Between  the  fossa  and  the  inner  border  of  the  bone  is  a  narrow  furrow,7 
which  is  traversed  by  the  occipital  artery. 

Internally,  the  mastoid  portion  extends  from  behind  the  position  of 
the  petrous  portion,  where  it  is  concave,  and  for  the  most  part  occupied 
by  a  variably  deep  groove,  which  accommodates  the  lateral  sinus.  The 
free  border  is  thick  and  rough,  and  articulates  with  the  parietal  bone 
above  and  the  occipital  bone  behind  and  below.  Near  or  at  the  pos- 
terior border,  the  bone  is  pierced  by  a  short  canal,  the  mastoid  fora- 
men,8 which  communicates  from  the  exterior  with  the  groove  for  the 
lateral  sinus,  and  transmits  a  vein. 

The  petrous  portion9  of  the  temporal  bone,  internal  to  the  others, 
appears  as  a  prostrate,  three-sided  pyramid,  with  its  base  directed 


1  Fossa  or  cavitas  glenoidalis  ;  fossa  articularis  ;  f.  mandibularis. 

2  Glaserian  fissure.  3  Tuberculum  articulare. 
*  Pars  mastoidea  ;  p.  mammillaris.  3  Processus  mastoideus. 

6  F.  digastrica ;  incisura  mastoidea.  7  Sulcus  arteriae  occipitalis. 

8  F.  mastoideum.  9  Pars  petrosa. 


SPECIAL,    ANATOMY    OF    THE   SKELETON. 


Ill 


outward,  and  its  apex  obliquely  forward  and  inward,  received  in  the 
angular  notch  between  the 

sphenoid      and      occipital  ^IG- 49- 

bones.  It  contains  within 
it  the  greater  part  of  the 
organ  of  hearing,  including 
the  tympanum  and  laby- 
rinth. Of  the  three  sur- 
faces of  the  pyramid,  two 
look  into  the  cranium, 
while  the  third  looks 
downward  in  the  base  of 
the  skull. 

The  anterior  surface 
of  the  pyramid  is  an  irregu- 
lar slope,  directed  into  the 
mesocranial  fossa.  Above 
its  middle  outwardly  is  an 
eminence,1  which,  together 
with  the  adjacent  inner  de- 
pression, indicates  the  po- 
sition, within  the  bone,  of 
the  labyrinth.  In  advance 
of  the  eminence  the  sur- 
face is  formed  by  a  plate, 
named  the  tympanic  teg- 
men,2  which  is  the  roof  of 
the  tympanum.  It  is  usu- 
ally more  or  less  defined 
from  the  squama  by  a  fis- 
sure remaining  as  part  of  the  petro-squamosal  suture ;  and  is  further 
defined  at  its  inner  extremity  by  a  narrow  groove,  which  proceeds  from 
the  notch  between  the  apex  of  the  pyramid  and  squama  outward  to  an 
opening,  or  hiatus,3  of  the  facial  canal,  for  the  transmission  of  the 
greater  petrosal  nerve.  On  the  inner  end  of  the  tegmen  is  another 
little  groove,  which  ends  in  a  fine  canal,  communicating  with  the 
tympanum,  for  the  passage  of  the  small  petrosal  nerve.  From  be- 
neath the  inner  extremity  of  the  tegmen  a  bar  or  ridge  dips  into 
the  glenoid  fissure,  between  the  glenoid  fossa  and  tympanic  plate. 

The  posterior  surface  of  the  pyramid  is  smaller  than  the  former, 
and  slopes  more  steeply  into  the  postcranial  fossa ;  and  is  outwardly  de- 
fined by  the  groove  of  the  lateral  sinus.  A  little  inward  from  the  centre 
is  the  internal  auditory  meatus,4  a  short,  wide  canal,  about  a  third 


INTERNAL  VIEW  OP  THE  TEMPORAL  BONE  OP  THE  LEFT 
SIDE.  1,  squamous  portion;  2,  posterior  border  of  the 
mastoid  portion  articulating  with  the  occipital  bone;  3, 
petrous  portion ;  4,  bevelled  edge,  which  overlaps  the 
lower  edge  of  the  parietal  bone;  5,  notch  between  the 
squama  and  the  mastoid  portion,  articulating  with  the 
posterior  inferior  angle  of  the  parietal  bone ;  6,  end  of  the 
zygomatic  process;  7,  groove  for  the  great  meningeal 
vessels;  8,  mastoid  process;  9,  digastric  fossa ;  10, mastoid 
foramen  opening  into  the  groove  11,  for  the  lateral  sinus; 
12,  internal  auditory  meatus ;  13,  styloid  process ;  14,  promi- 
nence produced  by  the  supra-semicircular  canal  of  the 
labyrinth ;  15,  tegmen  ;  16,  position  of  hiatus  of  the  facial 
canal ;  17,  cleft  which  communicates  with  the  aqueduct 
of  the  vestibule ;  18,  termination  of  the  carotid  canal ;  19, 
eustachian  tube ;  20,  groove  of  the  suprapetrosal  sinus. 


1  Eminentia  arcuata. 

3  H.  Fallopii ;  h.  canalis  facialis. 


2  Tegmen  tympani ;  tegmentum. 

*  Meatus  auditorius  internus  ;  porus  acusticus. 


112 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


FIG.  50. 


of  an  inch  deep,  proceeding  outwardly,  and  closed  at  bottom  by  the 
cribriform  lamina,1  which  is  a  perforated  plate  separating  it  from 
the  labyrinth.  The  meatus  gives  passage  to  the  facial  and  auditory 
nerves  and  accompanying  vessels.  From  the  bottom  of  the  meatus,  at 
the  upper  inner  part  of  the  cribriform  lamina,  commences  the  facial 
canal2  for  the  further  course  of  the  facial  nerve.  The  canal  is  di- 
rected a  little  way  forward,  and  communicates 
through  the  hiatus  with  the  anterior  surface 
of  the  pyramid,  thence  turns  abruptly  outward, 
and  proceeds  backward  in  the  inner  wall  of 
the  tympanum  to  its  back  wall,  in  which  it  de- 
scends to  the  stylo-mastoid  foramen,  the  outlet 
of  the  canal.  Outwardly  from  the  meatus  is  a 
variable  arching  eminence,  and  below  it  a  cleft, 
from  which  a  fine  canal,  the  vestibular  aque- 
duct,3 communicates  with  the  labyrinth. 

The  upper  border  of  the  pyramid  is  the 
longest,  and  is  for  the  most  part  acute.  It  gives 
attachment  to  the  tentorium,  and  is  commonly 
marked  in  its  course  by  a  groove  for  the  supra- 
petrosal  sinus,  while  its  inner  extremity  is  de- 
pressed for  the  passage  of  the  trifacial  nerve. 
The  posterior  border  is  irregular  and  notched, 
and  articulates  with  the  occipital  bone.  The 
anterior  is  shortest,  and,  together  with  the 
adjacent  border  of  the  squama,  forms  a  notch 
which  receives  the  sphenoidal  angular  process. 
The  inferior  surface  of  the  pyramid  is  very 
uneven,  and  presents  many  points  of  interest. 
At  its  outer  fore  part  is  the  tympanic  plate,4 
which  forms  the  floor  of  the  auditory  meatus, 
the  tympanum,  and  the  Eustachian  tube.  The 
plate  presents  a  broad  concave  surface  towards 
the  articulation  of  the  lower  jaw,  and  is  defined 
above  from  the  glenoid  fossa  by  the  glenoid 
fissure.5  Below  it  extends  in  an  acute,  jagged, 
and  somewhat  flexuose  ridge,  named  the  vagi- 
nal process,6  from  its  partially  ensheathing 
the  styloid  process.  The  outer,  thicker  portion 
of  the  plate  is  upwardly  involute,  and  forms 

the  bottom  and  sides  of  the  auditory  meatus ;  and  at  the  entrance  of 
this  it  is  produced  in  an  everted,  rough,  crescentoid  lip,  which  is  named 


INFERIOR  VIEW  OF  THE  LEFT 

TEMPORAL  BONE.     1,  SQUamOUS 

portion  ;  2,  mastoid  portion ; 
3.  petrous  portion  ;  4,  border 
articulating  with  the  great 
wing  of  the  sphenoid  bone; 
5,  zygomatic  process ;  6,  gle- 
noid fossa;  7,  articular  emi- 
nence; 8,  glenoid  fissure;  9, 
auditory  meatus;  10,  mastoid 
process;  11,  digastric  fossa; 
12,  styloid  process;  13,  stylo- 
mastoid  foramen;  14,  jugular 
fossa ;  15,  pit  which  communi- 
cates with  the  aqueduct  of  the 
cochlea;  16,  position  between 
which  and  the  occipital  bone 
the  ninth,  tenth,  and  eleventh 
cerebral  nerves  escape  from 
the  cavity  of  the  cranium  ;  17, 
articular  process ;  18,  vaginal 
process ;  19,  20,  entrance  and 
exit  of  the  carotid  canal ;  21, 
eustachian  tube;  22,  mastoid 
foramen. 


1  L.  cribrosa.  2  Canalis  facialis  ;  c.  Fallopii. 

3  Aquseductus  vestibuli.  *  Os  tympanica. 

5  Fissure  of  Glaser ;  fissura  petro-tympanica  et  petro-squamosa.       6  P.  vaginalis. 


SPECIAL    ANATOMY   OF   THE   SKELETON.  113 

the  auditory  process,1  and  gives  attachment  to  the  auricle.  The 
inner,  narrowed  extremity  of  the  plate  closes  the  bottom  of  the  tym- 
panum and  eustachian  tube. 

About  the  middle  of  the  glenoid  fissure  a  pair  of  short  passages,  the 
glenoid  canals,  communicate  with  the  tympanum,  the  outer  one  being 
occupied  by  a  process  of  the  malleus  with  its  ligament,  and  the  inner 
one2  transmits  the  tympanic  branch  of  the  facial  nerve. 

From  behind  the  vaginal  process  projects  the  styloid  process,3  a 
variably  long,  tapering  spine,  directed  downward,  forward,  and  inward. 
Before  adult  age  it  is  connected  with  the  temporal  bone  by  cartilage, 
joined  to  a  short  pedestal,4  which  occupies  a  pit  embraced  by  the 
vaginal  process.  It  is  sometimes  an  inch  or  more  in  length,  and  is 
connected  at  the  point  with  the  stylo-hyoid  ligament. 

Between  the  base  of  the  styloid  process  and  the  mastoid  process  is 
the  stylo-mastoid  foramen,5  the  outlet  of  the  facial  canal.  Behind 
the  inner  extremity  of  the  vaginal  process  is  the  entrance  of  the  carotid 
canal,6  which  ascends  vertically  and  bends  abruptly  inward,  and  pro- 
ceeds to  the  apex  of  the  pyramid,  whence  it  opens  upward  into  the 
cranial  cavity.  The  inner  fore  part  of  the  canal  is  frequently  more  or 
less  imperfect,  and  in  the  recent  condition  is  completed  by  fibrous  mem- 
brane. The  canal  transmits  the  internal  carotid  artery  and  carotid 
plexus  of  the  sympathetic  nerve. 

Externally  and  behind  the  carotid  canal  is  the  jugular  fossa,7  which 
is  variable  in  size  on  the  two  sides  of  the  skull  in  accordance  with  the 
difference  in  the  size  of  the  jugular  vein  it  accommodates.  Sometimes 
it  appears  as  a  shallow  groove  descending  from  a  notch  at  the  back 
border  of  the  pyramid,  and  from  this  it  varies  to  a  deeply  vaulted 
recess.  To  the  inner  side  of  the  fossa,  behind  and  above  the  entrance 
of  the  carotid  canal,  is  an  irregular  and  less  conspicuous  groove,8  which 
forms  part  of  the  jugular  foramen  giving  passage  to  the  ninth,  tenth, 
and  eleventh  cerebral  nerves.  Opening  into  the  commencement  of 
this  groove  at  the  posterior  border  of  the  pyramid  is  a  pyramidal  pit, 
from  which  a  fine  canal,  the  cochlear  aqueduct,9  proceeds  to  the 
labyrinth.  Externally  from  the  jugular  fossa  there  is  a  commonly 
quadrate  facet,  which  is  joined  by  cartilage  to  the  jugular  process  of 
the  occipital  bone. 

In  the  partition  between  the  carotid  canal  and  jugular  fossa  a  fine 
canal  ascends  to  the  tympanum  for  the  passage  of  the  tympanic  nerve. 
In  the  course  of  the  carotid  canal  there  are  several  small  foramina 
communicating  with  the  tympanum  for  the  transmission  of  vessels 
and  nerves.  From  the  jugular  fossa  a  fine  canal  is  directed  outwardly 


1  P.  auditorius.  2  Canal  of  Huguier.        3  P.  styloideus  ;  stylo-hyal  bone 

4  Tympano-hyal  bone.     5  F.  stylo-mastoideum.  6  Canalis  caroticus. 

7  F.  jugularis  ;  incisura  jugularis  lateralis. 

8  Incisura  jugularis  medialis.  '  Aquaeductus  cochleae. 


114 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


to  open  in  the  fissure  back  of  the  auditory  meatus  for  the  transmission 
of  the  auricular  branch  of  the  vagus.  Beneath  the  apex  of  the  pyra- 
mid and  the  horizontal  portion  of  the  carotid  canal  is  a  quadrate,  rough 
surface,  which  gives  attachment  to  the  pharynx ;  and  behind  this  is  a 
rougher  space,  which  articulates  with  the  basilar  process  of  the  occip- 
ital bone. 

In  the  notch  between  the  apex  of  the  pyramid  and  the  squama  is 
the  orifice  of  the  osseous  portion  of  the  eustachian  tube,1  which 
communicates  outwardly  with  the  tympanum.  It  is  formed  above  by 
the  tegmen  of  the  pyramid  and  below  by  the  tympanic  plate. 

The  auditory  meatus,2  or  outer  passage  of  the  ear,  is  situated  in 
a  deep  archway  between  the  glenoid  fossa  and  mastoid  process.  It  is 
a  short,  wide  canal,  which  in  the  prepared  bone  opens  inwardly  into 
the  cavity  of  the  tympanum.  Its  roof  is  formed  by  the  auditory 
plate,  which  extends  from  beneath  the  squama  inward  to  the  tym- 
panum, and  its  floor  and  sides  are  formed  by  the  tympanic  plate,  the 
outer  lip  of  which  is  the  auditory  process. 

A  more  particular  description  of  the  parts  of  the  temporal  bone 
relating  to  the  ear,  including  the  tympanum,  labyrinth,  and  mastoid 
sinuses,  will  be  given  in  the  account  of  the  organ  of  hearing. 

The  squama  of  the  temporal  bone  is  chiefly  composed  of  compact 
substance.  The  mastoid  portion  of  the  bone  is  thicker  than  the  for- 
mer, and  pervaded  throughout  with 
spongy  substance,  which,  however, 
for  the  most  part,  is  empty  or  con- 
tributes to  the  vacuities  of  the  mas- 
toid sinuses.  The  petrous  portion 
of  the  bone,  thus  named  from  its 
supposed  comparative  hardness, 
contains  the  labyrinth,  to  which 
it  forms  a  dense  wall  of  compact 
substance.  It  also  contributes  to 
form  the  tympanic  cavity ;  but  its 
apex  is  occupied  with  spongy  sub- 
stance filled  with  marrow. 

Near  the  period  of  birth  the 
temporal  bone  consists  of  three 
distinct  osseous  pieces,  which  are 
named  the  squamosal,  petrosal, 
and  tympanal.  Usually  at  birth 
these  are  partially  ankylosed,  but 
are  readily  separated  from  one  another.  In  many  animals  they  re- 
main in  part  or  all  permanently  separated,  or  become  variously  united. 
Thus,  in  the  hog  the  squamosal  and  petrosal  coalesce  and  the  tym- 


TEMPORAL  BONE  NEAR  THE  TIME  OF  BIRTH.  1, 
squamosal ;  2,  its  mastoid  portion ;  3,  petrosal ; 
4,  its  mastoid  portion ;  5,  notch  remaining 
from  the  early  separation  into  two  parts ;  6, 
petro-squamosal  suture;  7,  tympanal  or  tym- 
panic ring. 


1  Tuba. 


2  External  auditory  meatus  ;  m.  auditorius  extemus. 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


115 


FIG.  52. 


panal  remains  separate,  and  in  the  horse  the  latter  two  unite  and  the 
former  remains  distinct.  The  mastoid  portion  of  the  mature  bone  is  an 
outgrowth  from  both  the  squamosal  and  the  petrosal,  and  is  compara- 
tively but  little  produced  at  birth. 

The  squamosal '  is  a  nearly  circular  upright  plate,  which  joins  the 
petrosal  by  the  petro-squamosal  suture.  This  descends  externally 
behind  the  position  of  the  ear  from  the  upper  notch  between  the 
squamosal  and  petrosal,  and  internally  extends  from  the  upper  to 
the  lower  notch  between  the  same.  The  zygomatic  process  pro- 
jects obliquely  forward,  with  almost  no  curvature.  The  articulation 
of  the  mandible  deviates  but  little  from  the  general  vertical  plane  of 
the  squamosal,  and  it  is  a  shallow  concavity,  with  scarcely  any  distinc- 
tion of  glenoid  fossa  and  articular  eminence.  The  mastoid  portion  of 
the  squamosal  appears  as  a  triangular  plate,  which  outwardly  closes  the 
upper  part  of  the  tympanum.  Below,  it  forms  the  upper  margin  of 
the  entrance  of  the  latter,  to 
which  is  attached  the  tym- 
panic membrane.  Internally, 
it  is  separated  from  the  up- 
right plate  of  the  squamosal 
by  a  slanting  shelf,  which 
supports  the  contiguous 
border  of  the  tympanic  teg- 
men.  Below  the  shelf  is  a 
smooth  surface,  which  forms 
part  of  the  tympanic  cavity ; 
and  above  and  behind  this 
is  a  cellular  surface,  which 
forms  part  of  the  mastoid 
antrum. 

The    petrosal2    displays 
the    labyrinth,     already    of 

mature  size   and   bounded  by    tympanic  tegmen.    B.  Upper  view  of  the  right  petrosal. 

Compact  walls,   partially   em-  l'  ^  teg™en;  2'  ««?>«*  canal ;   f-  internal  auditory 

'  meatus ;  4,  supra-semicircular  canal ;  5,  recess  included 

bedded   in   more   spongy  Sub-  by  the  canal ;  6,  similar  recess  of  the  post-semicircular 

Stance,    from    which    it    may  canal ;  7,  hiatus  of  the  facial  canal.    C.  Tympanal.   1, 

J  glenoid  canals ;  2,  groove  for  the  tympanic  membrane. 

be    easily    excavated.      The 

supra-semicircular  canal  is  especially  conspicuous,  and  includes  a  con- 
siderable recess,3  which  subsequently  is,  for  the  most  part,  filled  up. 
The  tympanic  tegmen  appears  as  a  distinct  triangular  plate  projecting 
from  the  petrosal,  and  resting  by  its  outer  border  on  the  shelf  of  the 
squamosal.  The  cavity  of  the  tympanum  and  mastoid  antrum  are  well 


2      7 


THE  THREE  PIECES  OF  THE  TEMPORAL  BONE  SEPA- 
RATED. A.  Inner  view  of  the  right  squamosal.  1,  its 
squama ;  2,  mastoid  portion ;  3,  shelf  of  support  for  the 


1  Os  squamosum  ;  pars  squamosa ;  p.  squamo-zygomatica. 

2  Os  petrosum  ;  pars  petrosa ;  p.  petro-mastoidea  ;  periotic  bone. 
8  Fossa  arcuata ;  periotic  fenestra. 


116  SPECIAL,   ANATOMY    OF   THE   SKELETON. 

produced.  The  mastoid  portion  of  the  petrosal  is  connected  in  front 
with  that  of  the  squamosal,  and  is  often  already  partially  ankylosed 
with  it.  Its  upper  border  usually  exhibits  a  notch,  which  remains 
from  the  original  separation  of  the  petrosal  into  two  parts.  The  mas- 
toid process  is  yet  undeveloped. 

The  tympanal1  at  birth  is  a  slender  osseous  ring,  incomplete  for 
a  short  extent  above,  and  is  commonly  ankylosed  at  the  ends  with  the 
extremities  of  the  tympanic  margin  of  the  mastoid  portion  of  the 
squamosal.  It  slants  in  a  plane  from  the  ends  downward  and  inward, 
and  is  suturally  connected  along  the  back  and  lower  border  with 
the  petrosal.  It  is  grooved  along  its  inner  border  for  the  insertion 
of  the  tympanic  membrane ;  and  its  anterior  crus  is  also  obliquely 
grooved  internally  to  form  part  of  the  glenoid  canals,  for  the  accom- 
modation of  the  long  process  of  the  malleus  and  the  tympanic  nerve. 
At  this  period  the  osseous  auditory  meatus  is  undeveloped,  and  its 
tympanic  orifice  is  on  a  plane  almost  continuous  inwardly  from  the 
outer  surface  of  the  squamosal. 

In  the  development  of  the-  temporal  bone,  the  squamosal  and  tym- 
panal are  produced  from  nbro-connective  tissue,  and  the  petrosal  and 
styloid  process  from  cartilage.  Ossification  commences  in  the  squa- 
mosal of  the  foetus  about  the  end  of  the  second  month,  a  centre  ap- 
pearing at  its  lower  part  and  extending  in  the  squama,  the  mastoid 
portion,  and  in  the  zygomatic  process.  In  the  third  month  an  ossific 
centre  appears  in  the  lower  part  of  the  tympanal,  and  grows  to- 
wards the  extremities.  Ossification  commences  in  the  petrosal  near 
the  middle  of  foetal  life,  two  chief  centres  appearing  and  extending  in 
the  walls  of  the  labyrinth,  and  named  from  their  relative  positions  the 
prootic  and  opisthotic.  These  quickly  coalesce  to  form  the  osseous 
labyrinth,  which,  by  subsequent  continuous  growth,  produces  the  pyra- 
mid and  mastoid  portion  of  the  petrosal.  The  prootic  gives  rise  to  all 
that  part  of  the  pyramid  which  is  visible  within  the  cranium  except 
the  portion  contiguous  to  and  forming  the  jugular  fossa;  the  opisthotic 
to  all  that  part  visible  beneath  the  cranium,  including  the  jugular  fossa. 
The  mastoid  portion  is  produced  subsequent  to  the  ossification  of  the 
labyrinth  by  outgrowth  from  the  post-  and  ecto-semicircular  canals. 
The  production  from  the  post-semicircular  canal  first  makes  its  appear- 
ance as  an  elliptical  islet2  in  the  cartilage  which  occupies  the  interval 
between  the  squamosal  and  the  occipital  and  parietal  bones.  Later  the 
outgrowth  from  the  ecto-semicircular  canal  appears  as  a  quadrate  islet 
between  the  former  islet  and  the  squamosal.  The  two  islets  quickly 
unite,  and  thus  establish  the  mastoid  portion  of  the  petrosal ;  and  it  is 


1  Os  tympanicum ;  pars  tympanica ;  tympanic  ring. 

2  Epiotic ;  regarded  by  Prof.  Huxley  as  a  distinct  ossiflc  centre ;   but  accord- 
ing to  my  observations  in  the  human  temporal  bone,  a  continuous  outgrowth  from 
the  opisthotic. 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


117 


from  that  part  which  forms  the  quadrate  islet,  together  with  the  mas- 
toid  portion  of  the  squamosal,  that  the  mastoid  process  is  subsequently 
developed. 

The  squamosal  and  petrosal  commonly  begin  to  ankylose  shortly 
before  the  time  of  birth,  commencing  in  the  external  portion  of  the 
petro-squamosal  suture,  which,  in  this  position,  is  commonly  obliterated 
in  the  course  of  the  first  year.  Occasionally  traces  of  this  part  of  the 
suture  remain  as  short,  irregular  chinks,  and  rarely  as  a  continuous 
fissure  which  descends  from  the  notch  behind  the  squamosal  above  to 
the  end  of  the  mastoid  process,  as  represented  in  Fig.  53.  Such  a  speci- 
men indicates  that  the  anterior  third  of  the  mastoid  portion  of  the 
mature  temporal  bone  pertains  to  the  squamosal,  while  the  remainder 
belongs  to  the  petrosal.  The  mastoid  process,  scarcely  marked  at  birth, 
becomes  more  or  less  conspicuous  only  after  a  year  or  more.  The  mas- 
toid antrum  is  produced  at  birth,  but  the  contiguous  mastoid  sinuses 
undergo  little  development  until  much  later,  on  the  approach  of  puberty 
and  subsequently. 

The  auditory  meatus  is  produced  after  birth,  at  which  time  the 
tympanic  orifice  is  nearly  on  the  same  plane  as  the  outer  surface  of 
the  temporal  bone.  In  the  development  of  the  meatus  the  auditory- 
plate  is  gradually  differentiated  from  the  mastoid  portion  of  the  squa- 
mosal, and  at  the  same  time  the  tympanic  ring  grows  outwardly.  The 
sides  of  the  ring  grow  most  rapidly  and  expand  at  the  outer  ends, 
which  conjoin  to  form  the  auditory  process,  leaving  a  central  aperture 
in  the  tympanal  closed  by  fibrous  membrane,  and  directed  towards 
the  mandibular  articulation.  The  aperture  gradually  diminishes,  and 
commonly  disappears  about  the  fourth  or  fifth  year,  but  occasionally 
is  not  completely  obliterated. 

The  styloid  process  commences  to 
ossify  after  birth,  but  remains  in  great 
part  in  a  cartilaginous  condition  until 
after  puberty,  and  usually  does  not  anky- 
lose with  the  petrosal  until  approaching 
middle  age  or  later. 

In  the  mature  temporal  bone,  to  the 
squamosal  belongs  the  so-called  squa- 
mous  portion,  with  the  anterior  third  of  the 
mastoid  portion,  and  the  auditory  plate, 
which  forms  the  roof  of  the  auditory 
meatus ;  to  the  petrosal  belongs  the 
petrous  portion,  with  the  posterior  two- 
thirds  of  the  mastoid  portion,  excluding 
the  tympanic  plate,  which  belongs  to  the 
tympanal.  The  styloid  process  is  a  distinct  element  from  the  other 
osseous  pieces  of  the  temporal  bone ;  and  as  the  stylo-hyal  remains 
permanently  separated  in  many  lower  animals. 


FIG.  53. 


ADULT  TEMPORAL  BONE,  with  the 
external  portion  of  the  petro-squa- 
mosal suture  permanently  retained, 
from  a  specimen  in  the  museum  of 
the  University.  1,  squamosal ;  2,  pe- 
trosal ;  3,  tympanal. 


118 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


THE    MAXILI^E. 


The  maxillae,  or  maxillary  bones,1  are  the  largest  of  the  face, 
except  the  lower  jaw,  and  form  together  the  upper  jaw,  besides  con- 
tributing to  form  the  nasal  cavities  and  the  orbits.  Each  maxilla 
consists  of  a  hollow  portion,  the  body,  with  four  other  portions, 
named  the  malar,  alveolar,  palate,  and  nasal  processes. 


FIG.  54. 


"14  T5  16 
MAXILLA  OF  THE  LEFT  SIDE,  outer  view.  1, 
body ;  2,  tuberosity  ;  3,  alveolar  process ;  4,  or- 
bital plate ;  5,  nasal  process ;  6,  nasal  notch ;  7, 
nasal  spine;  8,  lachrymal  groove;  9,  entrance 
of  the  infraorbital  canal;  10,  infraorbital  fora- 
men ;  11,  orifices  of  the  posterior  dental  canals; 
12,  malar  process;  13,  articulation  for  the  in- 
ternal angular  process  of  the  frontal  bone ;  14, 
incisor  teeth ;  15,  canine  tooth  ;  16,  premolar 
teeth ;  17,  molar  teeth. 


17" 


MAXILLA  OF  THE  LEFT  SIDE,  inner  view.  1, 
nasal  surface  of  the  body;  2,  surface  for  the 
palate  bone;  3,  alveolar  process;  4,  orbital 
plate  ;  5,  nasal  process ;  6,  ridge  for  the  articu- 
lation of  the  turbinal  bone  ;  7,  nasal  spine; 
8,  lachrymal  groove ;  9,  antrum  ;  10,  palate 
process;  11,  incisive  foramen;  12,  tuberosity; 
13,  articular  extremity  for  the  internal  angular 
process  of  the  frontal  bone ;  14,  incisor  teeth ; 
15,  canine  tooth ;  16,  premolar  teeth ;  17,  molar 
teeth. 


The  body  has  nearly  the  shape  of  a  short  half-cylinder,  with  the 
convex  part  directed  outward  and  the  plane  surface  directed  inward, 
and  forming  a  large  part  of  the  outer  wall  of  the  nasal  cavity.  It  is 
occupied  by  a  large  air-chamber,  the  antrum,'2  which  opens  into  the 
latter  by  a  large,  irregular  aperture,  much  reduced  in  the  articulated 
bone  by  the  apposition  of  the  ethmoid,  palate,  and  turbinal  bones.  The 
smooth  surface  below  and  in  front  of  the  aperture,  curving  to  the  floor 
of  the  nasal  cavity,  forms  the  greater  portion  outwardly  of  the  inferior 
nasal  meatus ;  and  the  roughened  surface  behind  articulates  with  the 
nasal  plate  of  the  palate  bone. 

From  the  outer  part  of  the  body  projects  a  stout  pyramidal  offset, 
the  malar  process,3  which  terminates  in  an  oblique,  triangular,  rough 


1  Superior  maxillary  bones  ;    supermaxillary  bones  ;    superior  maxillae ;    upper 
jaw  bones  ;  ossa  maxillaria ;  o.  maxilla* 

2  A.  maxillare ;  a.  of  Highmore ;   a.  Highmorianum ;   maxillary  sinus  ;   super- 
maxillary  cavity. 

3  Processus  malaris  ;  p.  jugalis  ;  p.  zygomaticus  ;  p.  zygomatico-orbitalis. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  119 

surface  for  articulation  with  the  malar  bone.  The  fore  part  of  the 
body  extending  outwardly  on  the  malar  process  is  variably  depressed, 
forming  the  canine  fossa,1  above  which  is  the  infraorbital  foramen.2 
The  back  part  of  the  body  is  swollen,  and  its  convex  surface,  continu- 
ous outwardly  with  the  posterior  concave  surface  of  the  malar  process, 
forms  the  anterior  boundary  of  the  zygomatic  fossa,  while  its  upper 
inner  corner  forms  that  of  the  spheno-maxillary  fossa.  The  portion 
below  the  latter  extending  to  the  back  end  of  the  alveolar  process 
is  the  maxillary  tuberosity,3  which  is  impressed  with  a  rough  area 
or  pit  articulating  with  the  pyramidal  process  of  the  palate  bone. 
From  above  the  tuberosity  a  groove  descends  inwardly  to  form  part 
of  the  posterior  palatine  canal.  Near  the  centre  of  the  posterior  sur- 
face there  are  usually  two  small  foramina  of  the  posterior  dental 
canals,*  which  descend  in  the  outer  wall  of  the  antrum  and  transmit 
the  posterior  dental  vessels  and  nerves.  The  upper  part  of  the  body 
is  the  orbital  plate,5  forming  the  floor  of  the  orbit  and  the  roof  of 
the  antrum.  It  is  triangular  and  variably  concave  or  nearly  flat,  and 
slopes  more  or  less  outward.  Inwardly,  it  articulates  with  the  ethmoid 
and  lachrymal  bones  ;  at  the  apex  behind,  with  the  orbital  process  of 
the  palate  bone  ;  and  at  the  fore  part  outwardly,  with  the  malar  bone. 
In  front  it  is  defined  by  a  portion  of  the  infraorbital  margin,  within 
which  may  sometimes  be  seen  the  impression  of  the  origin  of  the 
inferior  oblique  muscle  of  the  eye.  Its  posterior  outer  border  is  a 
wide,  obtusely  rounded  notch,  which  forms  the  lower  margin  of  the 
spheno-maxillary  foramen.  From  this  a  groove  communicates  with 
the  infraorbital  canal,6  which  proceeds  forward  through  the  orbital 
plate  and  descends  to  its  outlet,  the  infraorbital  foramen.  The 
fore  part  of  the  canal  projects  from  the  roof  of  the  antrum,  and  gives 
off  the  anterior  dental  canal,7  which  descends  in  the  anterior  wall 
of  the  antrum,  and  gives  passage  to  the  anterior  dental  vessels  and 
nerve. 

The  alveolar  process 8  occupies  the  inferior  border  of  the  maxilla, 
and  with  its  fellow  forms  a  strong  arch  with  slightly  divergent  or  nearly 
parallel  sides;  but  occasionally  slightly  convergent,  so  that  the  arch 
assumes  a  horseshoe  shape.  It  is  the  thickest  and  most  spongy  portion 
of  the  bone,  and  is  pierced  with  a  series  of  conical  pits,  the  alveoli,  or 
sockets  for  the  teeth.  The  posterior  two-thirds  of  the  process  are  be- 
neath the  body,  and  form  the  floor  of  the  antrum,  into  which,  usually, 
the  bottoms  of  some  of  the  molar  alveoli  project.  The  anterior  part 
of  the  process  is  below  the  fore  part  of  the  nasal  cavity,  projecting 
more  or  less  obliquely  downward  and  forward.  The  external  or  facial 
surface  of  the  alveolar  process,  especially  in  advance,  is  marked  by 

1  F.  canina ;  f.  maxillaris.  8  F.  infraorbitale.  8  Tuberositas  maxillae. 

4  Canales  alveolares  posteriores.     6  Planum  orbitale.         6  Canalis  infraorbitalis. 
7  C.  alveolaris  anterius.  8  P.  alveolaris  ;  p.  dentalis. 


120  SPECIAL   ANATOMY  OF   THE   SKELETON. 

vertical  prominences  due  to  the  projection  of  the  alveoli.  That  of 
the  canine  alveolus,  usually  the  most  prominent,  separates  the  canine 
fossa  from  a  shallow  depression,  the  incisive  fossa,1  situated  in 
front  of  the  incisive  alveoli.  The  two  fossa3  are  variable,  usually 
slight,  but  sometimes  conspicuous,  and  to  some  extent  are  propor- 
tioned with  the  prominence  of  the  canine  and  contiguous  pair  of 
alveoli.  The  internal  surface  of  the  alveolar  process,  rough  and 
porous,  contributes  to  form  the  vaulted  hard  palate,  or  roof  of  the 
mouth.  The  anterior  extremity  ends  in  a  thick,  flat,  and  roughened 
border,  which  articulates  with  that  of  the  opposite  bone.  Above  the 
extremity  is  the  nasal  notch,  which  curves  from  the  median  line  out- 
ward and  upward  to  the  nasal  process,  and  forms  the  lateral  and  lower 
boundary  of  the  entrance  to  the  nasal  cavity.  Its  margin  above  is 
thin,  but  below  it  forms  a  thicker  acute  ridge,  which  rises  above  the 
level  of  the  floor  of  the  nasal  cavity.  The  inner  end  of  the  ridge  pro- 
jects forward  in  a  pointed  process,  which  joins  that  of  the  opposite 
side  to  form  the  nasal  spine.2  From  this  another  ridge  extends  back- 
ward, and  articulates  with  that  of  the  opposite  side  to  form  the  in- 
cisive crest,3  which  articulates  behind  with  the  end  of  the  vomer, 
and  is  grooved  above  for  the  accommodation  of  the  cartilage  of  the 
nasal  septum. 

The  palate  process  *  is  a  strong  horizontal  plate,  which  extends  in 
a  shelf-like  manner  from  the  base  of  the  alveolar  border  inward  and 
about  two-thirds  the  way  back.  Its  inner  border  is  produced  in  a  rising 
ridge,  which  is  roughened,  and  articulates  with  that  of  the  opposite 
maxilla  to  form  the  nasal  crest.5  This  articulates  above  with  the 
vomer,  and  forms  the  lower  border  of  the  nasal  partition.  The  upper 
surface  of  the  process  forms  part  of  the  floor  of  the  nasal  cavity,  is 
depressed  below  the  level  of  the  nasal  notch,  and  is  transversely  con- 
cave and  smooth.  The  lower  surface  is  flat,  rough,  and  porous,  and 
forms  part  of  the  palate  or  roof  of  the  mouth.  The  posterior  border 
is  transverse  and  straight,  and  is  serrated  for  articulation  with  the 
palate  plate  of  the  palate  bone.  At  the  fore  part  of  the  palate  pro- 
cess, contiguous  to  the  incisive  crest,  is  the  anterior  palatine  canal,6 
which  descends  from  the  nasal  cavity  and  joins  its  fellow  in  the  inter- 
mediate suture  of  the  maxillse,  to  end  in  the  incisive  foramen7  of 
the  palate,  a  short  distance  behind  the  incisor  alveoli. 

The  nasal  process 8  ascends  from  the  fore  part  of  the  maxilla, 
above  the  anterior  nasal  notch,  and  ends  in  a  thickened  serrated  ex- 
tremity, which  articulates  with  the  internal  angular  process  of  the  frontal 


1  F.  incisiva ;  f.  myrtiformis.  2  Spina  nasalis  anterius. 

8  Crista  incisiva.  *  P.  palatintas.  5  Crista  nasalis. 

6  Incisor  foramen  or  canal ;  canalis  incisivus  ;  foramen  of  Stenson. 

7  F.  incisivum  ;  f.  palatinum  anterius  ;  anterior  palatine  canal. 

8  P.  nasalis,  or  frontalis. 


SPECIAL   ANATOMY  OF   THE   SKELETON.  121 

bone.  Its  inner  anterior  border,  thick  above  and  narrow  below,  is 
roughened  to  articulate  with  the  nasal  bone.  Its  outer  surface  forms 
part  of  the  side  of  the  nose  in  front  of  the  orbit,  and  is  longitudinally 
grooved  behind  to  form  part  of  the  lachrymal  fossa  and  the  nasal 
duct  descending  from  it.  The  inner  surface  forms  part  of  the  outer 
wall  of  the  nasal  cavity,  and  is  defined  below  by  a  fore  and  aft  ridge, 
the  turbinal  crest,1  for  the  attachment  of  the  turbinal  bone.  The 
posterior  surface  is  irregular,  and  articulates  with  the  ectethmoid,  so 
as  to  close  in  front  the  ethmoidal  sinuses.  The  outer  border  defining 
this  surface  is  a  narrow  ridge,  which  articulates  with  the  lachrymal 
bone. 

The  maxilla,  with  the  exception  of  the  alveolar  process,  which  is 
largely  composed  of  spongy  substance,  consists  mainly  of  plates  of 
compact  substance. 

The  maxilla  commences  ossification  about  the  seventh  week  of  foetal 
life  from  several  points ;  according  to  Sappey,  five ;  but  these  quickly 
coalesce,  and  are  not  regarded  as  distinct  ossific  centres.  That  part  of 
the  bone  which  subsequently  contains  the  incisor  teeth  is  considered  to 
be  independent  of  the  rest,  from  the  fact  that  in  the  other  animals  it 
ordinarily  remains  as  a  permanently  distinct  bone,  which  is  named  the 
premaxilla.2  One  of  the  most  remarkable  differences  in  the  skull 
of  man  from  that  of  all  other  animals  is  the  apparent  absence  of  the 
latter ;  and  even  in  those  most  nearly  allied  to  him,  as  the  monkeys,  it 
remains  to  maturity  as  a  completely  distinct  and  conspicuous  bone 
containing  the  incisor  teeth.  It  originates  in  the  human  embryo  from 
a  distinct  centre,  but  so  quickly  coalesces  with  the  maxilla  that  its 
independent  existence  is  scarcely  recognized.  At  birth  and  later,  even 
to  adult  age,  a  fissure  is  observed  on  the  palate  process,  directed  out- 
ward from  the  incisive  foramen  to  the  alveolar  border,  indicating  the 
original  separation  of  the  premaxilla,  but  no  trace  of  such  a  separation 
is  visible  on  the  facial  surface  as  it  is  seen  in  other  animals.  The 
abnormal  condition  of  harelip  is  at  times  associated  with  a  separate 
premaxilla.  At  birth  the  alveolar  border  of  the  maxilla  is  occupied 
by  a  series  of  receptacles  enclosing  the  developing  teeth.  The  an- 
trum,  already  of  considerable  size,  begins  to  appear  near  the  middle 
of  foetal  life.  The  infraorbital  canal  is  open  by  a  fissure  along  its 
inner  side. 

After  birth  the  alveolar  process  is  gradually  developed,  and  acquires 
its  mature  condition  in  conformity  with  the  development  and  protru- 
sion of  the  teeth.  With  the  loss  of  the  latter  it  is  proportionately 
reduced,  and  finally  may  appear  as  a  narrow  arched  ridge  projecting 
comparatively  little  below  the  level  of  the  palate  process,  as  is  com- 
monly observed  in  old  age. 

1  Crista  turbinalis. 

2  Premaxillary.  intermaxillary,  or  incisive  bone ;  os  incisivum. 


122 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


THE  PALATE   BONES. 

The  palate  bones  1  are  situated  behind  the  maxilhe,  between  these 
and  the  sphenoid  bone.  They  enter  into  the  construction  of  the  hard 
palate,  the  nasal  cavities,  the  orbits,  and  the  spheno-maxillary  and 
pterygoid  fossae.  Each  bone  consists  of  an  inferior  palate  plate,  an 
external  nasal  plate,  and  three  conspicuous  processes. 


FIG.  56. 


FIG.  57. 


10     3 

POSTERIOR  VIEW  OF  THE  RIGHT  PALATE  BONE. 
1,  palate  plate;  2,  nasal  plate;  3,  pyramidal  pro- 
cess; 4,  articular  border  for  the  left  palate  bone; 
5,  posterior  nasal  spine;  6,  turbinal  crest;  7, 
spheno-palatine  notch,  between  8,  the  orbital, 
and  9,  the  sphenoidal  process;  10,  groove  for 
the  entopterygoid  process  of  the  sphenoid 
bone;  11,  position  of  the  posterior  palatine 
canal. 


EXTERIOR  VIEW  OF  THE  RIGHT  PALATE  BONE. 

1,  rough  surface  articulating  with  the  maxilla, 
and  diminishing  the  aperture  of  the  antrum ; 

2,  posterior  palatine  canal;  completed  by  the 
maxilla;    3,   spheno-palatine   notch;    4,  5,  6, 
orbital   process;   4,  surface  directed  towards 
the  spheno-maxillary  fossa ;  5,  orbital  surface ; 
6,  maxillary  border;  7,    sphenoidal  process; 
8,  pyramidal  process. 


The  palate  plate 2  is  horizontal  and  nearly  square,  and  serves  to 
extend  the  floor  of  the  nasal  cavity  and  the  hard  palate  behind  the 
palate  process  of  the  maxilla.  The  anterior  border,  slightly  thickened, 
is  serrated  to  articulate  with  the  latter  process.  The  posterior  border 
is  concave  and  sharp,  forms  the  inferior  margin  of  the  posterior  nasal 
orifice,  and  gives  attachment  to  the  soft  palate.  The  internal  border 
is  constructed  like  that  of  the  palate  process  of  the  maxilla,  and,  with 
that  of  the  opposite  side,  extends  the  nasal  crest  for  articulation  with 
the  vomer.  The  crest  behind  is  produced  in  a  pointed  process,  the 
posterior  nasal  spine,3  to  which  the  uvula  is  attached.  The  upper 
surface  of  the  palate  plate  extends  the  floor  of  the  nasal  cavity,  and 
is  transversely  concave  and  smooth.  The  lower  surface  extends  the 
hard  palate,  and  is  for  the  most  part  occupied  by  a  broad,  shallow 
groove,  which  curves  inward  and  forward  from  the  posterior  palatine 
canal,  and  is  usually  defined  behind  by  a  variable  ridge  for  the  attach- 
ment of  the  palatal  tensor  muscle. 

The  nasal  plate,4  thinner  and  longer  than  the  palate  plate,  ascends 

1  Ossa  palati ;  o.  pal^tina. 

2  Pars  palatina  ;  horizontal  plate  ;  pars  horizontals.          s  Spina  nasalis  postica. 
4  Pars  nasalis  ;  p.  perpendicularis  ;  p.  ascendens ;  vertical  plate. 


SPECIAL    ANATOMY  OF    THE   SKELETON.  123 

from  this  at  the  outer  back  part  of  the  nasal  cavity,  and  has  its  external, 
slightly  roughened  surface  articulating  with  the  maxilla.  It  contributes 
in  this  position  to  reduce  the  aperture  of  the  antrum.  Its  fore  part, 
extended  below  in  an  angle,  terminates  in  a  thin,  irregular  margin, 
which  is  partially  received  in  a  fissure  of  the  inferior  border  of  the 
aperture.  The  posterior  concave  border,  thin  and  irregular,  artic- 
ulates with  the  anterior  border  of  the  entopterygoid  process.  Out- 
ward from  the  posterior  border  is  a  smooth  surface,  which  extends 
above  on  the  sphenoidal  and  orbital  processes  and  forms  the  inner 
boundary  of  the  spheno-maxillary  fossa,  and  continues  below  in  a 
groove,  which,  by  apposition  with  the  maxilla,  forms  the  posterior 
palatine  canal,  for  the  transmission  of  the  corresponding  vessels  and 
nerve. 

The  internal  surface  is  smooth,  and  is  crossed  near  the  middle  by  a 
ridge,  the  turbinal  crest,1  with  which  the  posterior  extremity  of  the 
turbinal  bone  articulates.  A  similar  but  less  marked  ridge2  at  the 
upper  border  of  the  plate  articulates  with  the  nasal  mesoturbinal, 
which  belongs  to  the  ethmoid  bone. 

From  the  upper  border  of  the  nasal  plate  proceed  the  sphenoidal 
and  orbital  processes,  separated  by  a  circular  notch,  which  by  apposi- 
tion of  the  processes  to  the  sphenoid  bone  is  converted  into  the 
spheno-palatine  foramen.3  This  communicates  between  the  baok 
part  of  the  upper  nasal  meatus  and  the  spheno-maxillary  fossa,  and 
transmits  the  posterior  nasal  vessels  and  nerves. 

The  sphenoidal  process,*  the  posterior  and  smaller,  is  a  little 
plate,  of  which  the  upper  border  is  expanded  and  applied  to  the  under 
part  of  the  body  of  the  sphenoid  bone  within  the  fore  part  of  the  root 
of  the  entopterygoid  process.  Its  external  surface  forms  part  of  the 
inner  boundary  of  the  spheno-maxillary  fossa,  and  its  internal  surface 
part  of  the  outer  wall  of  the  nasal  cavity.  The  upper  border  applied 
to  a  narrow  groove  beneath  the  vaginal  process  of  the  sphenoid  bone 
forms  with  it  the  pterygo-palatine  canal.5 

The  orbital  process,6  situated  in  advance  of  the  former,  is  not 
only  much  larger  but  more  elevated,  and  projects  more  outwardly, 
expands  above,  and  commonly  encloses  a  considerable  cavity.  H 
presents  six  faces,  of  which  three  articulate  with  contiguous  faces  of 
the  ectethmoid,  sphenoid,  and  maxilla.  Of  the  others,  the  nasal  sur- 
face is  directed  into  the  upper  nasal  meatus,  the  orbital  surface  forms 
the  posterior  angle  of  the  floor  of  the  orbit,  and  the  spheno-maxillary 
surface  contributes  to  the  corresponding  fossa.  The  latter  two  sur- 
faces are  defined  by  a  smooth  border,  which  forms  the  inner  part  of 
the  inferior  margin  of  the  spheno-maxillary  foramen.  The  cavity  of 


1  Crista  turbinalis  ;  inferior  turbinal  crest. 

2  C.  ethmoidalis  ;  superior  turbinal  crest.  3  F.  spheno-palatinum. 
4  P.  sphenoidalis.                6  Canalis  pterygo-palatinus.  6  P.  orbitalis. 


124  SPECIAL,   ANATOMY   OF   THE   SKELETON. 

the  process,  of  variable  extent,  commonly  communicates  with  the  pos- 
terior ethmoidal  sinuses,  and  occasionally  with  the  sphenoidal  sinus. 
Sometimes  an  additional  recess  back  of  the  main  cavity  opens  back- 
ward into  the  latter. 

The  pyramidal  process  '  projects  backward  and  outward  from  the 
nasal  plate,  extending  to  its  conjunction  with  the  palate  plate,  and  is 
the  thickest  portion  of  the  bone.  Its  outer  surface,  extending  back- 
ward and  outward  from  that  of  the  nasal  plate,  is  triangular  and 
rough,  and  articulates  with  the  inner  back  part  of  the  maxillary  tuber- 
osity.  Between  it  and  the  nasal  plate  is  the  deep  groove  which  forms 
part  of  the  posterior  palatine  canal,  descending  to  the  under  sur- 
face of  the  palate  plate.  The  posterior  surface  is  triangular,  with  the 
apex  continuous  upward  into  the  posterior  border  of  the  nasal  plate. 
It  is  divided  into  three  vertical  grooves,  of  which  the  outer  and  inner 
are  divergent  and  roughened  to  articulate  with  the  lower  extremities 
of  the  sphenoid  pterygoid  processes,  while  the  intermediate  smooth 
one  occupies  the  notch  between  the  latter  and  completes  the  pterygoid 
fossa.  The  base  of  the  process-  forms  an  irregular,  oblique  ridge,  of 
which  the  outer  end  extends  beneath  the  ectopterygoid  process  of  the 
sphenoid,  and  the  inner  end  extends  under  the  palate  plate  and  gives 
attachment  to  the  palatal  tensor  muscle.  About  the  middle  of  the  ridge, 
behind  the  exit  of  the  posterior  palatine  canal,  are  usually  from  one 
to  three  small  palatine  canals,2  which  descend  through  the  anterior 
border  of  the  pyramidal  process  from  the  spheno-maxillary  fossa. 

The  palate  bone  is  composed  of  thin  plates  of  compact  substance, 
except  the  pyramidal  process,  which  contains  some  spongy  substance. 
It  is  developed  from  a  single  centime,  which  makes  its  appearance,  near 
the  end  of  the  second  month  of  foetal  life,  at  the  conjunction  of  the 
nasal  and  palate  plates. 

THE   TURBINAL   BONES. 

The  turbinal  bone 3  projects  along  the  outer  wall  of  the  nasal 
cavity  below  the  position  of  the  ethmoid  bone  and  overhangs  the 
inferior  nasal  meatus.  It  is  an  elongated,  elliptical,  scroll-like  plate, 
slightly  narrowed  and  rounded  in  front,  and  tapering  to  a  point 
behind.  The  inner  surface  is  convex,  irregularly  pitted,  grooved,  and 
porous.  The  outer  surface,  for  the  most  part  composing  the  roof  of  the 
inferior  nasal  meatus,  is  concave  and  less  rough  than  the  former.  The 
lower  free  border,  the  thickest  portion  of  the  bone,  is  obtuse,  everted, 
spongy,  and  rough.  The  upper  border  is  attached  the  entire  length  of 
the  bone,  and  gives  off  three  processes.  Its  fore  part  slants  downward, 

1  Pterygoid  process  ;  tuberosity  ;  apophysis  pterygoideus. 

2  Posterior  and  external,  small  palatine  canals. 

3  Inferior  turbinated  bone ;  os  turbinatum  inferius  ;  spongy  bone  ;  os  spongio- 
sum  ;  concha  inferior ;  maxillo-turbinal. 


SPECIAL   ANATOMY    OF    THE   SKELETON. 


125 


FIG.  58. 


and  articulates  with  the  turbinal  crest  of  the  maxilla  ;  and  its  back  part, 
also  slanting  downward,  articulates  with  the  turbinal  crest  of  the  palate- 
bone.  In  an  intermediate  position,  two  thin 
processes  ascend,  or  a  thin  plate  dividing 
into  two.  Of  these  the  anterior,  lachry- 
mal process,1  articulates  with  the  maxilla 
and  the  lachrymal  bones,  and  forms  with 
them  the  nasal  duct.  The  posterior,  eth- 
moidal  process,2  joins  the  uncinate  pro- 
cess of  the  ethmoid  bone,  and  with  it  par- 
tially closes  the  irregular  aperture  of  the 
antrum.  From  between  the  former  a  thin, 
angular  or  semicircular  plate,  the  maxil- 
lary process,3  curves  inward  and  down- 
ward, and  is  inserted  into  a  notch  at  the 
lower  part  of  the  aperture  of  the  antrum, 
between  the  maxilla  and  the  nasal  plate  of  the  palate  bone. 

The  turbinal  bone  originates  in  a  cartilaginous  matrix,  the  only  one 
of  the  face  that  does  so.  It  is  developed  from  a  single  centre  of  ossi- 
fication, which  does  not  make  its  appearance  until  several  months  after 
birth.  The  turbinals  are  often  unequally  produced,  and  are  frequently 
otherwise  unsymmetrical. 


EXTERNAL  VIEW  OF  THE  RIGHT  TUR- 
BINAL BONE.  1,  anterior  extremity 
articulating  with  the  maxilla;  2, 
posterior  extremity  articulating  with 
the  palate  bone;  3,  hook-like  plate 
articulating  with  the  lower  border 
of  the  maxillary  antrum.  Above 
are  the  lachrymal  and  ethmoidal 
processes ;  4,  inferior  obtuse  border. 


THE   LACHKYMAL   BONES. 

The  lachrymal  bone  4  is  the  smallest  of  those 
a  thin,  upright,  quadrate  plate  situated  at  the  fore 
part  of  the  inner  wall  of  the  orbit.  Externally,  it 
is  divided  by  a  sharp  descending  crest5  into  two 
surfaces,  of  which  the  usually  larger,  posterior  one, 
the  orbital  surface,  is  rectangular,  and  occupies 
the  same  plane  as  the  orbital  surface  of  the  ethmoid 
bone ;  while  the  anterior  surface  forms  a  groove,6 
which  joins  that  of  the  nasal  process  of  the  maxilla 
to  complete  the  lachrymal  fossa.  A  descending 
process  from  the  groove  unites  -with  the  turbinal 
bone  and  maxilla  to  form  the  nasal  duct ;  and  a  hook- 
like  process 7  from  the  bottom  of  the  crest  forms 
the  outer  edge  of  the  entrance  of  the  latter. 

The  internal  surface  of  the  lachrymal  bone  is 
applied  to  the  ectethmoid  in  advance  of  the  orbital 
plate,  and  in  this  position  completes  the  anterior 
ethmoidal  sinuses.  The  extension  of  the  same  sur- 


of  the  face,  and  is 


EXTERNAL  VIEW  OF 
THE  RIGHT  LACHRYMAL 
BONE.  1,  orbital  surface; 

2,  lachrymal    groove ; 

3,  small  process  bound- 
ingthe  latter  inferiorly ; 

4,  frontal  border ;  5,  eth- 
moidal border ;  C,  max- 
illary border ;  7,  process 
articulating   with    the 
turbinal  bone. 


1  P.  lachrymalis  ;  p.  nasalis.  *  P.  ethmoidalis. 

3  P.  auricularis  ;  p.  maxillaris.         *  Os  lachrymale  ;  os  unguis ;  unguiform  bone. 

5  Crista  lachrymalis.  6  Sulcus  lachrymalis.  *  Hamulus  lachrymalis. 


126  SPECIAL    ANATOMY    OF   THE   SKELETON. 

face  on  the  descending  process  of  the  nasal  duct  forms  part  of  the  outer 
wall  of  the  middle  nasal  meatus. 

The  anterior  border  of  the  lachrymal  bone  articulates  with  the  nasal 
process  of  the  maxilla;  its  superior  border,  with  the  internal  angular 
process  of  the  frontal  bone  ;  its  posterior  and  inferior  borders,  with  the 
orbital  plates  of  the  ethmoid  and  maxillary  bones.  The  inner  surface 
articulates  with  the  ethmoid  ;  and  the  descending  process,  with  the 
turbinal  bone. 

The  lachrymal  bone  is  variable,  especially  in  its  proportions  ;  and 
sometimes  it  is  perforated  or  imperfectly  ossified  ;  and  occasionally  the 
hook-like  process  is  separate  or  may  be  absent.  It  is  a  thin  plate  of 
compact  substance,  and  is  produced  from  a  single  centre,  which  appears 
about  the  end  of  the  second  month  of  foetal  life. 

THE   NASAL   BONES. 

The  nasal  bones  1  articulate  with  each  other  and  with  the  nasal 
processes  of  the  maxillae  to  form  the  bridge  of  the  nose.     They  vary 
considerably  in  size  and  shape  in  different  races  and  individuals,  and 
are  commonly  larger  and  best  produced  in  the  white  race.     They  vary 
not  only  in  size  but  in  proportions,  in  the  degree  of  prominence  and 
curvature,  and  in  being  more  or  less  fan-shaped  to  nearly  rectangular. 
They  project  downward   and  forward  from  the  nasal  notch   of  the 
frontal  bone,  and  form  the  upper  part  of  the  anterior  nasal  orifice. 
The  nasal  bone  is  commonly  thickest  and  narrowest  at  the  upper 
extremity,  and  becomes  gradually  wider  and  thinner 
in  its  descent  ;  but  sometimes,  especially  in  the  lower 
races,  it  becomes  narrower  in  the  upper  third  of  its 
descent  and  then  widens  to  the  lower  border.      It 
presents    two  principal    surfaces,    defined   by   four 
borders. 

The  anterior  surface  slants  downward  and  for- 
ward and  also  laterally  from  the  inner  border,  is 
for  the  most  part  concave  longitudinally,  but  be- 

comes  convex   below,  and   is  convex  transversely. 
ANTERIOR  VIEW  OF      -^         th     centre  •  u  aperture    the  nasal  fora_ 

THE  LEFT  NASAL  BONE.  ' 

i,  frontal  border;  2,     men,  which  transmits  a  little  vein  descending  from 


nasal  border;  3,  max-     ^ne  interior.   Tne  posterior  surface  above  is  narrow 

illary  border  ;  4,  lower 

border;  5,  nasal  fora-     and  rough,  and  with   the   upper  strongly  serrated 
men-  border  of  the  bone  articulates  with  the  nasal  notch 

of  the  frontal  bone.  The  surface  widens  below,  where 
it  is  smooth  and  concave,  and  forms  the  anterior  slope  of  the  roof  of 
the  nasal  cavity.  It  is  marked  by  a  groove,  which  is  occupied  by  a 
branch  of  the  nasal  nerve.  The  internal  border  above  is  nearly  as 
thick  as  the  bone  is  wide  in  the  same  position,  but  after  about  a  third 

1  Ossa  nasalia;  o.  nasi. 


SPECIAL   ANATOMY    OF   THE   SKELETON.  127 

of  the  length  gradually  tapers  below  to  a  point.  It  forms  a  somewhat 
uneven  plane,  which  conforms  to  its  fellow  so  as  to  interlock  with  it, 
and  projects  behind  in  a  slightly  roughened  ridge,  which  articulates 
with  the  nasal  spine  of  the  frontal  bone.  The  external  longest  border, 
mostly  thin  and  outwardly  bevelled  and  roughened,  articulates  with 
the  overlapping  edge  of  the  nasal  process  of  the  maxilla.  The  inferior, 
thin,  expanded  border  is  sometimes  entire  and  curved  to  accord  with 
the  nasal  notch  below,  and  sometimes  is  divided  by  one  or  two  clefts 
of  variable  depth. 

The  nasal  bone  is  mainly  composed  of  compact  substance,  but  usually 
contains  a  small  quantity  of  spongy  substance  in  its  thicker  upper  part. 
It  originates  in  a  single  ossific  centre,  which  appears  about  the  end  of 
the  second  month  of  foetal  life. 


THE   VOMEK. 

The  vomer,1  a  single  bone,  is  a  thin,  vertical,  irregularly  lozenge- 
shaped  plate,  which  occupies  the  back  lower  portion  of  the  nasal  par- 
tition.    Its  sides  are  smooth,  and  con- 
tribute to  form  the  inner  wall  of  the 
nasal   cavities.     Of  the  four  borders 
the  longer  ones  extend  forward,  while 
the  shorter  ones   are   directed   back- 
ward.   The  posterior  border  curves 

from  above   downward  and  forward,  2 

and  forms  the  dividing  line  between       LEFT  SIDE  OP  THE  VOMEK.    i,  broad 

,        .„  T,    .     ,,  .   ,        groove  receiving  the  rostrum  of  the  sphe- 

the  posterior  nasal  orifices.   It  is  thick     noid  ^^  2>  inferior  border  articula. 

and    notched   at   the   upper  extremity,      ting  with  the  palate  plates  of  the  maxillae 
1    ,  ,  i  .  j      i.  i,   i     '         an(i  palate   bones ;   3,  posterior  border, 

and  becomes   thin   and  sharp   below.     the  ^.^  llne  of  ^  posterjor  nasa[ 

The  Superior  border,  about  as  long  as      orifices;   4,  grooved  border  receiving  a 

thp  former   i<*  expanded    and   includes      narrow  slip  of  cartilage,  situated  between 
rmer,  is  expan  ea,  an  the  yomer  and  the  nagal  late  of  the  eth 


an    angular    gutter     from    which     the      moid  bone ;  5,  border  for  the  cartilagi- 

sides  project  in  a  pair  of  semi-ellipti-  j£™  septum  of  the  nose;  6'  nasal  sur' 
cal  ledges,  the  alae.2  These  articulate 

with  the  under  surface  of  the  sphenoidal  body  and  embrace  the  rostrum, 
and  by  their  edges  join  those  of  the  vaginal  processes  of  the  sphenoid 
bone  and  the  sphenoidal  processes  of  the  palate  bones.  The  anterior 
border,  about  twice  the  length  of  either  of  the  former,  slants  down- 
ward and  forward,  and  for  two-thirds  of  its  extent  articulates  with 
the  contiguous  border  of  the  ethmoidal  nasal  plate.  It  is  commonly 
cleft  to  a  variable  depth,  and  encloses  a  prolongation  of  the  septal 
cartilage  extending  to  the  sphenoidal  rostrum.  The  inferior  border, 
nearly  as  long  as  the  former,  is  horizontal,  and  articulates  with  the 
nasal  crest  of  the  maxillae  and  palate  bones.  The  anterior  angle  of  the 

1  Os  vomeris.  2  Alae  vomeris. 


128 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


FIG.  62. 


vomer  is  truncated,  and  articulates  with  the  back  part  of  the  incisive 
crest  of  the  maxillae.  The  vomer  is  a  plate  of  compact  substance. 

The  bone  is  frequently  unsymmetrical  and  variably  bent  from  the 
median  position  to  one  or  the  other  side,  and  especially  is  it  irregular 
in  its  articulation  with  the  ethmoidal  nasal  plate,  the  union  commonly 
projecting  into  one  nasal  cavity  more  than  into  the  other. 

At  birth  the  vomer  is  proportionately  longer  and  wider,  and  con- 
sists of  two  thin  plates,  which  are  united  along  the  lower  border,  and 
include  the  contiguous  portion  of  the  septal  cartilage  of  the  nose.  In 
the  subsequent  growth  of  the  bone  it  is  mainly  produced  below,  while 
the  plates  above  form  the  sides  of  the  cleft  of  the  anterior  border  of 
the  mature  bone  and  expand  as  the  alae  of  its  superior  border.  The 
vomer  originates  in  two  ossific  centres,  about  the  sixth  month  of  foetal 
life,  appearing  in  the  perichondrium  at  the  sides  of  the  septal  cartilage 
and  quickly  coalescing  beneath. 

THE  MALAK   BONES. 

The  malar  bones  occupy  the  prominent  part  of  the  cheeks,  and 
contribute  to  form  the  orbits  and  the  temporal  and  zygomatic  fossae. 
The  malar,1  or  cheek-bone,  terminates  at  its  lower  fore  part  in  a 
broad,  triangular,  rough  surface,  which  is 
supported  upon  and  articulates  with  the 
malar  process  of  the  maxilla.  Behind,  it 
is  prolonged  in  the  zygomatic  process, 
which  ends  in  a  serrated  border  slanting 
downward  and  backward,  and  articulating 
with  the  corresponding  process  of  the  tem- 
poral bone.  From  about  its  middle  the  bone 
is  extended  upward  in  the  frontal  process, 
which  forms  the  outer  boundary  between 
the  orbit  and  temporal  fossa,  and  ends  in  a 
strongly-serrated  extremity,  which  articu- 
lates with  the  external  angular  process  of 
the  frontal  bone. 

The  external  or  facial  surface  of  the 
malar  bone  is  vertical,  quadrilateral,  and  vari- 
ably convex,  and  forms  the  basis  of  the  promi- 
nence of  the  cheek.  Its  lower  front,  or  maxillary  border,  curves 
outward  and  downward  at  the  articulation  of  the  bone  with  the  malar 
process  of  the  maxilla.  The  lower  back,  or  zygomatic  border,  is 
convex,  contributes  more  than  half  to  the  length  of  the  zygomatic 
arch,  and  is  roughened  for  the  attachment  of  the  masseter  muscle. 
The  upper  front,  or  orbital  border,  is  a  smooth,  obtuse  arching  ridge, 
forming  about  one-third  of  the  circumference  of  the  orbital  entrance. 


OUTER  VIEW  OP  THE  BIGHT  MA- 
LAR BONE.  1,  external  or  facial 
surface  ;  2,  malar  foramen ;  3,  fron- 
tal process  ;  4,  5,  orbital  border  ; 
6,  maxillary  border ;  7,  zygomatic 
process;  8,  temporal  border;  9, 
zygomatic  border. 


10smalare;  osrnalae;  osjugale;  os  zygomaticum ;  os  jugamentum. 


SPECIAL   ANATOMY   OF    THE   SKELETON.  129 

The  upper  back,  or  temporal  border,  is  a  sigmoid  ridge,  which  ex- 
tends from  the  end  of  the  frontal  process  to  the  end  of  the  zygomatic 
process,  forms  the  anterior  boundary  of  the  temporal  fossa,  and  gives 
attachment  to  the  temporal  fascia. 

From  the  orbital  border  of  the  bone  a  curved  triangular  or  cres- 
centic  process,  directed  backward  and  inward,  is  the  orbital  plate,1 
which  separates  the  orbit  from  the  temporal  fossa.  Its  inner  surface 
is  concave,  and  forms  part  of  the  outer  wall  and  floor  of  the  orbit ; 
its  outer  surface  forms  the  adjacent  portion  of  the  temporal  and  zygo- 
matic fossae.  Its  lower  border  internally  joins  the  orbital  plate  of  the 
maxilla,  and  externally  the  posterior  border  of  the  malar  process  of 
the  same  bone.  Its  upper  border  articulates  with  the  orbital  plate  of 
the  frontal  bone,  and  its  back  border  with  the  great  wing  of  the 
sphenoid  bone.  Commonly,  a  small  portion  of  the  border,  between 
the  articulation  with  the  latter  and  the  maxilla,  forms  the  outer 
extremity  of  the  spheno-m axillary  foramen.  The  posterior,  or  tem- 
poral surface,  of  the  malar  bone  curves  from  the  back  of  the  orbital 
plate  outward  and  backward  within  the  zygomatic  process,  forming  the 
anterior  boundary  of  the  temporal  and  zygomatic  fossae. 

The  orbital  surface  of  the  orbital  plate  commonly  exhibits  several 
foramina,  the  entrance  of  the  malar  canals,2  which  terminate  varia- 
bly in  one  or  two  apertures  on  the  facial  and  temporal  surfaces  of  the 
bone,  and  transmit  the  branches  of  the  temporo-malar  nerve. 

The  malar  bone  is  variably  prominent  in  different  races,  and  also 
in  individuals  of  the  same  race.  It  is  developed  from  a  single  centre, 
which  appears  about  the  end  of  the  second  month  of  foetal  life. 


THE   MANDIBLE. 

The  mandible,  lower  jaw,  or  inferior  maxillary  bone,3  forms 
the  basis  of  the  lower  prominent  part  of  the  face,  of  which  it  is  the 
largest  and  strongest  piece.  It  is  the  only  movable  bone  of  the  skull, 
is  separated  from  all  others  of  the  face  by  the  intervening  teeth,  and 
articulates  with  the  temporal  bones  of  the  cranium.  It  consists  of  two 
lateral  portions,  which  are  separate  pieces  in  early  infancy,  and  which, 
in  many  animals,  remain  permanently  in  this  condition,  as,  for  example, 
in  the  dog,  cat,  and  sheep. 

The  horizontal  thicker  portion  of  the  mandible  containing  the 
teeth  is  named  the  body,  and  the  posterior  portion  on  each  side  ex- 
tending upward  is  the  ramus.  In  other  animals  it  is  usual  to  distin- 
guish each  half  of  the  jaw  under  the  latter  name. 

The  body  is  deepest  at  its  fore  part,  and  slightly  decreases  behind, 
is  produced  above  in  the  alveolar  process,  and  is  defined  below  by  a 


1  Pars  orbitalis  ;  orbital  process.          2  Canales  zygomatico-faciales  et  temporales. 
3  Mandibula  ;  os  maxillare  inferius  ;  inferior  maxilla. 

9 


130 


SPECIAL,   ANATOMY    OF   THE   SKELETON. 


FIG.  63. 


MANDIBLE.  1,  body :  2,  ramus ;  3,  sym- 
physis ;  4,  base ;  5,  angle ;  6,  mental  fora~ 
men;  7,  condyle;  8,  coronoid  process;  9, 
mandibular  notch ;  10,  mental  foramen ; 
11,  alveolar  process ;  12,  incisor  teeth ;  13, 
canine  tooth ;  14,  premolars ;  15,  molars. 


thick,  rounded  border,  named  the  base.  It  projects  in  front  in  a  tri- 
angular eminence,  the  mental  protuberance,1  which  is  of  variable 
prominence  and  breadth,  and  forms  the  basis  of  the  chin,  giving  to  it 
its  variety  of  shape,  narrow  or  broad,  rounded  or  square.  A  slight 

ridge  ascending  from  the  protuber- 
ance is  named  the  symphysis,2  as 
indicating  the  position  and  original 
character  of  union  of  the  two  halves 
of  the  bone. 

The  external  surface  of  the 
body,  for  the  most  part  vertical 
on  the  alveolar  process,  thence  in- 
clines slightly  forward  and  outward 
to  the  base.  Commonly  a  little  over 
an  inch  from  the  symphysis,  and 
nearer  the  base  than  the  upper  bor- 
der, is  the  mental  foramen,3  which 
opens  upward  and  outward  from  the 
dental  canal.  The  base  is  commonly 
somewhat  everted  at  the  chin,  and 
in  a  less  degree  laterally ;  is  convex 

in  its  course,  and  of  nearly  uniform  thickness  to  the  position  below 
the  second  molar  tooth,  whence  it  narrows  into  the  inferior  border 
of  the  ramus.  Above  the  base,  usually  below  the  second  molar  tooth, 
an  oblique  ridge  *  rises  from  the  outer  surface  of  the  body  and  curves 
backward  and  upward  into  the  anterior  border  of  the  ramus.  The 
internal  surface  of  the  body,  behind  the  position  of  the  mental  pro- 
tuberance, exhibits  a  variable  process,  the  mental  tubercle,5  which  is 
more  or  less  distinctly  divided  into  four  portions,  for  attachment  of 
the  genio-glossal  and  genio-hyoid  muscles.  The  tubercle  is  sometimes 
replaced  by  a  group  of  roughened  impressions,  or  presents  other  modifi- 
cations. Outwardly  from  it  there  is  usually  a  slight  depression,  some- 
times conspicuously  deepened,  the  sublingual  fossa,  which  accommo- 
dates the  sublingual  gland.  Below  the  fossa,  on  the  everted  base,  is 
an  oval,  rough  impression  for  the  insertion  of  the  digastric  muscle. 
Below  the  position  of  the  molar  teeth  is  a  conspicuous  ridge,  which 
divides  the  internal  surface  obliquely,  and  gives  attachment  to  the 
mylo-hyoid  muscle,  whence  its  name  of  the  mylo-hyoid  ridge.  Its 
fore  part,  less  prominent,  descends  below  the  sublingual  fossa  to  the 
mental  tubercle.  The  surface  above  the  ridge  is  smooth  and  invested 
with  the  mucous  membrane  of  the  gums.  Below  its  more  prominent 

1  Protuberantia  mentalis  ;  tuberculum  mentale  externum  ;  spina  mentalis  externa  ; 
mental  prominence  ;  mental  process. 

2  S.  mandibulee.  8  F.  mentale  ;  f.  maxillare  ant. 
4  Linea  obliqua ;  external  oblique  line. 

6  Spina  mentalis  interna  ;  mental  spines  ;  genial   tubercles. 


SPECIAL   ANATOMY   OF  THE   SKELETON.  131 

part  is  an  elongated  depression,  the  submaxillary  fossa,  which  par- 
tially lodges  the  submaxillary  gland. 

The  alveolar  process l  of  the  jaw  forms  a  thick,  horizontal  arch, 
into  which  the  teeth  are  inserted,  and  nearly  conforms  to  the  arch 
above.  Its  fore  part  is  vertical,  and  the  lateral  portions  occupy  a 
position  extending  backward  and  inward  along  the  sides  of  the  body. 
The  external  surface  in  advance  is  variably  marked  by  the  projection 
of  the  alveoli,  though  usually  to  a  less  degree  than  in  the  upper  jaw. 
On  each  side  of  the  symphysis  it  is  variably,  and  mostly  slightly, 
depressed  as  the  incisive  fossa.2 

The  ramus 3  is  a  quadrilateral  plate,  thinner  than  the  body,  ascend- 
ing more  or  less  obliquely  backward,  and  diverging  from  the  line  of  the 
alveolar  process.  It  divides  above  into  the  coronoid  and  condyloid  pro- 
cesses, which  are  separated  by  a  large  semicircular  interval,  the  man- 
dibular  notch.4  The  conjunction  of  the  posterior  and  inferior  borders 
of  the  ramus  forms  the  so-called  angle  of  the  jaw,5  is  convex,  and 
usually  projects  more  or  less  downward,  and  is  everted.  Occasionally 
it  is  simply  rounded,  and  does  not  project  downward,  and  sometimes 
it  is  nearly  or  quite  straight,  or  even  slightly  inverted.  The  external 
surface  of  the  ramus  is  a  broad,  vertical, "slightly  depressed,  and  un- 
even plane,  more  or  less  ridged  on  the  angle,  and  for  the  most  part 
serves  to  give  attachment  to  the  masseter  muscle.  The  internal  sur- 
face exhibits  a  central  depression,  communicating  below  with  the 
dental  foramen,6  the  commencement  of  the  dental  canal,  bounded 
inwardly  by  a  sharp-notched  border,  the  fore  part  of  which  is  produced 
in  a  thin,  tongue-like  process.  From  the  notch  a  groove  proceeds 
towards  the  submaxillary  fossa,  serving  to  lodge  the  mylo-hyoid  vessels 
and  nerve.  Behind  the  groove,  the  surface  extending  to  the  angle  is 
usually  more  or  less  strongly  ridged  for  the  attachment  of  the  internal 
pterygoid  muscle. 

The  dental  canal7  descends  obliquely  within  the  lower  part  of 
the  ramus,  and  thence  proceeds  forward  within  the  body,  beneath 
the  alveoli,  and  gives  an  outward  fork  to  the  mental  foramen,  while 
a  smaller  one  ends  in  the  incisive  alveoli.  It  gives  passage  to  the 
inferior  dental  vessels  and  nerve,  branches  of  which  traverse  short 
passages  communicating  with  the  bottoms  of  the  alveoli. 

The  coronoid  process,8  of  variable  size  and  proportions,  is  a 
flattened  conical  eminence,  ascending  and  slightly  divergent  from  the 
fore  part  of  the  ramus,  and  usually  curving  more  or  less  backward. 
Its  anterior  convex  border  continues  that  of  the  ramus,  forming  a 

1  Alveolar  border ;  limbus  alveolaris  ;  juga  alveolaria. 

2  Fossa  mentalis.  s  K.  adscendens  ;  r.  perpendicularis. 

4  Sigmoid,  or  semilunar  notch  ;  incisura  mandibularis,  sigmoidea,  or  semilunaris. 

5  Angulus  mandibulae.  6  Inferior  dental  foramen. 
1  Inferior  dental  canal ;  canalis  maxillaris,  or  alveolaris  inf. 

8  Processus  coronoideus. 


132  SPECIAL    ANATOMY   OF   THE   SKELETON. 

strongly  sigmoid  ridge  descending  to  the  body  outside  the  alveolar 
process.  Its  posterior  concave  border  forms  part  of  the  mandibular 
notch.  A  ridge  from  the  inner  surface  descends  to  the  inner  margin 
of  the  alveolar  process,  and  defines  an  anterior  triangular  grooved 
area,  which  descends  to  the  last  molar,  and  opens  externally  to  it.  The 
lower  part  of  the  ridge  gives  attachment  to  the  pterygo-maxillary  liga- 
ment and  buccinator  muscle.  The  outer  surface  of  the  coronoid  pro- 
cess, continuous  with  that  of  the  ramus,  gives  attachment  to  the  tem- 
poral and  masseter  muscles.  The  anterior  border  and  internal  surface 
also  give  attachment  to  the  temporal  muscle. 

The  condyloid  process,1  stouter  and  commonly  shorter  than  the 
former,  ascends  from  the  back  part  of  the  ramus  and  ends  in  a  trans- 
verse, elliptical  knob,  the  condyle,2  which  is  convex,  and  invested  with 
cartilage,  and  articulates  with  the  glenoid  fossa  of  the  temporal  bone. 
Its  transverse,  longer  axis  inclines  from  without  slightly  downward 
and  backward.  From  the  condyle,  the  process  narrows  in  the  neck, 
which  is  compressed  from  before  backward,  and  is  strengthened  by 
three  buttress-like  ridges,  of  which  two  descend  from  the  extremities 
of  the  condyle  and  converge  to  the  posterior  sigmoid  border  of  the 
ramus,  and  the  third  descends  from  the  outer  fore  part  of  the  condyle 
to  the  border  of  the  mandibular  notch.  The  inner  fore  part  of  the 
neck  presents  a  roughened,  shallow  fossa,  into  which  the  external  ptery- 
goid  muscle  is  inserted. 

The  mandible  is  composed  of  thick  layers  of  compact  substance 
enclosing  a  strong  layer  of  spongy  substance,  which  predominates  in 
the  body,  and  has  excavated  in  it  the  alveoli  for  the  teeth.  .  The  dental 
canal,  for  the  most  part,  lies  next  the  posterior  compact  layer. 

At  birth  the  mandible  consists  of  two  pieces,  which  are  united  at 
the  symphysis  by  cartilage.  At  this  period  the  body  appears  propor- 
tionately shallow  and  thick,  in  consequence  of  the  absence  of  the  alve- 
olar process,  which  is  subsequently  produced  in  accordance  with  the 
development  of  the  teeth.  It  is  chiefly  occupied  by  a  capacious  hollow 
divided  into  receptacles,  which  contain  the  developing  teeth.  The 
ramus  ascends  more  obliquely  than  subsequently  after  the  protrusion 
of  the  teeth.  Two  dental  canals  commence  on  its  inner  surface,  of 
which  the  upper  and  larger  proceeds  as  an  open  groove  beneath  the 
position  of  the  molar  teeth,  and  communicates  with  the  mental  fora- 
men, while  the  other  is  closed  along  its  course,  and  proceeds  beneath 
the  former.  The  larger  canal  accommodates  the  vessels  and  nerves  of 
the  temporary  teeth,  while  the  smaller  one  accommodates  those  of-  the 
succeeding  teeth. 

The  pieces  of  the  mandible  commence  ossification  in  the  sixth  or 
seventh  week  of  foetal  life,  and  each  is  reputed  to  start  in  several  points, 
which,  however,  quickly  coalesce,  so  that  each  is  regarded  as  being  de- 

1  P.  condyloideus.  2  Condylus. 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


133 


FIG.  64. 


rived  from  a  single  ossific  centre.  Ossification  occurs  in  the  perichon- 
drium,  investing  a  slender  rod  of  cartilage,  the  tympano-mandibular 
cartilage,1  which  extends  from  the  malleus  of  the  ear  along  the  course 
of  the  mandible,  but  subsequently  atrophies  and  disappears.  The  two 
pieces  of  the  mandible  ankylose  during  the  first  year  after  birth,  and 
leave  but  little  trace  of  the  original  separation. 

In  the  advance  of  age  with  the  loss  of  the  teeth  the  alveolar  process 
disappears,  and  the  fore  part  of  the  mandible  is  proportionately  reduced 
in  depth  and  is  surmounted  by  a  narrow  ridge,  which  occupies  the  former 
position  of  the  process. 

THE   ENTIRE   SKULL. 

The  skull  differs  remarkably  from  other  chief  parts  of  the  skeleton  in 
the  fact  that  all  the  bones  are  immovably  articulated  together,  with  the 
exception  of  the  mandible. 
Its  upper  part,  the  cra- 
nium, is  commonly  ovoid, 
with  the  narrower  extrem- 
ity forward,  but  it  varies  to 
a  more  oval  or  spheroidal 
form.  Its  anterior  extrem- 
ity is  the  forehead,  its  pos- 
terior broader  extremity  the 
occiput,  its  highest  part 
the  crown  or  vertex,  and 
its  under  part  the  base. 
The  face,  exclusive  of  the 
forehead,  is  placed  beneath 
the  anterior  half  of  the  cra- 
nium, from  which  it  projects 
in  front  to  a  variable  degree. 

The  cranium  conforms 
in  general  shape  to  that  of 
the  brain  it  contains,  but 
the  exterior  surface  does  not 
in  all  positions  accord  with 
the  interior  surface,  which 
appears  closely  moulded  to 
the  brain.  Its  walls  not 
only  vary  in  thickness  ac- 
cording to  the  age  and  sex, 
but  ordinarily  at  maturity 
it  varies  considerably  in 

different  individuals,  and  often  most  notably  in  different  races,  being 
generally  thicker  in  the  barbarous  or  lowest  races.  Commonly  in  the 

1  Cartilage  of  Meckel. 


THE  SKULL,  SEEN  PARTLY  IN  FKONT  AND  ON  THE  EIGHT 

SIDE.  1,  frontal  bone ;  2,  parietal  bone ;  3,  temporal  bone, 
its  squamous  portion ;  4,  sphenoid  bone,  temporal  sur- 
face of  its  great  wing;  5,  ethmoid  bone,  its  orbital 
surface ;  6,  maxilla ;  7,  malar  bone ;  8,  lachrymal  bone ; 
9,  nasal  bone ;  10,  mandible ;  a,  orbital  plate  of  the 
frontal  bone ;  b,  temporal  surface ;  c,  orbital  surface  of 
the  great  wing  of  the  sphenoid  bone;  d,  mastoid  por- 
tion of  the  temporal  bone ;  e,  orbital  surface  of  the  malar 
bone;  /,  orbital  plate  of  the  maxilla;  g,  infraorbital 
foramen ;  h,  mental  foramen ;  i,  symphysis ;  j,  ramus ; 
k,  coronoid  process ;  I,  condyloid  process ;  m,  angle ;  n, 
lachrymal  fossa. 


134  SPECIAL   ANATOMY    OF   THE   SKELETON. 

white  race  it  ranges  from  one-sixth  to  one-fourth  of  an  inch,  and  not 
unfrequently  in  the  negro  reaches  double  these  measurements.  It  also 
varies  in  different  positions,  independent  of  ridges  and  processes,  and 
is,  for  the  greatest  extent,  thickest  and  most  uniform  at  the  upper 
part,  and  thinnest  in  parts  protected  by  muscular  masses,  as  in  the 
temples  and  lower  part  of  the  occiput,  .where  it  often  is  scarcely  half 
a  line  in  thickness. 

The  upper  portion  of  the  cranium,  divided  horizontally  about  the 
middle,  is  called  the  vault,1  while  the  lower  portion  is  distinguished  as 
the  base  of  the  cranium.  On  each  side  of  the  cranium  is  the  broad 
depression  called  the  temporal  fossa,  defined  below  by  the  zygoma. 

The  face,  conjoined  with  the  cranium,  consists  of  a  series  of  recepta- 
cles :  the  orbits  for  the  eyes  and  their  accessory  parts,  the  nasal  cavi- 
ties with  their  accessory  sinuses,  and  the  cavity  of  the  mouth.  It  varies 
in  proportionate  size  and  prominence  in  comparison  with  the  cranium ; 
is  usually  larger  in  the  male,  and  is  largest  and  most  projecting  in  the 
lower  races  and  in  individuals  of  coarse  habits,  due  mainly  to  the 
greater  proportionate  production  of  the  jaws. 

Most  of  the  bones  of  the  cranium,  except  in  the  thinner  parts,  are 
composed  of  two  layers  of  compact  substance,  with  an  intervening 
layer  of  strong,  spongy  substance,  named  the  diploe,  and  it  is  upon 
the  variable  thickness  of  this  that  the  different  thickness  of  the  bones 
mainly  depends.  The  exterior  compact  layer  is  generally  thicker  than 
the  interior  layer,  which  is  less  tenacious  than  the  former,  and  from  its 
comparatively  greater  brittleness  has  been  distinguished  as  the  vitreous 
layer.  The  diploe  is  traversed  by  irregular  branching  channels,  named 
the  diploic  sinuses,  which  accommodate  veins. 

The  bones  of  the  face,  except  the  mandible,  are  mostly  much  thinner 
than  those  generally  of  the  cranium,  and  are  nearly  destitute  of  spongy 
substance. 

STJTUKES  OF   THE   SKULL. 

The  bones  of  the  skull,  except  the  mandible,  are  articulated  by  a 
mode  of  union  called  suture,  in  which  the  contiguous  borders  of  the 
bones  are  more  or  less  uneven,  roughened,  or  jagged,  and  mutually 
adapted  so  as  to  produce  the  closest  connection  short  of  actual  coales- 
cence. The  sutures  vary  in  character  from  those  in  which  the 
borders  are  slightly  roughened  to  those  in  which  the  borders  are 
jagged  with  irregular,  tooth-like  processes,  whence  they  are  called 
dentate  sutures.  In  some  of  the  sutures  the  contiguous  borders  of 
the  bones  are  bevelled  to  a  thin  edge,  and  mutually  overlap,  whence 
they  are  called  squamous  sutures,  from  the  resemblance  to  the  usual 
arrangement  of  the  scales  of  a  fish.  In  a  few  instances  the  suture  is 
formed  by  the  edge  of  one  bone  fitting  into  the  groove  of  the  border 
of  the  adjacent  bone. 

1  Calvaria ;  skull-cap. 


SPECIAL    ANATOMY    OF   THE   SKELETON.  135 

The  different  sutures  are  appropriately  named  from  the  bones  they 
unite,  but  the  most  conspicuous  ones  and  a  few  others  have,  besides, 
special  names. 

The  sutures  of  the  cranial  vault  are  the  most  conspicuous,  on  ac- 
count of  their  long,  tortuous  course  and  strongly  dentate  character. 
Their  tortuous  condition  is,  however,  mainly  confined  to  the  exterior 
of  the  cranium,  and  their  course  within  is  much  less  winding. 

The  coronal1  or  fronto-parietal  suture  crosses  the  fore  part  of 
the  cranium  between  the  summits  of  the  great  wings  of  the  sphenoid 
bone,  and  unites  the  frontal  with  the  parietal  bones.  It  is  more  deeply 
indented  laterally  than  above ;  and  it  is  slightly  bevelled  in  such  a 
manner  that  the  frontal  rests  on  the  parietals  above,  and  supports  them 
at  the  sides. 

The  lambdoid 2  or  occipito-parietal  suture  crosses  the  back  part 
of  the  cranium  between  the  mastoid  portions  of  the  temporal  bones, 
and  unites  the  occipital  with  the  parietal  bones.  It  is  the  most  intri- 
cate of  the  sutures,  is  deeply  dentate,  and  wonderfully  winding  in  its 
course. 

The  sagittal 3  or  interparietal  suture  unites  the  parietal  bones  in 
the  median  line  of  the  cranium  between  the  former  sutures.  It  is  also 
remarkably  tortuous  in  its  course. 

The  squamous  or  squamo-parietal  suture  is  formed  by  the 
deeply-bevelled  contiguous  borders  of  the  temporal  squama  and  the 
parietal  bone,  in  which  the  former  externally  overlaps  the  latter. 

The  squamo-sphenoid  suture  continues  in  the  circle  of  the  pre- 
ceding suture  to  the  cranium  beneath,  and  is  formed  between  the  tem- 
poral squama  and  the  great  wing  of  the  sphenoid  bone.  The  contiguous 
borders  are  somewhat  bevelled,  so  that  the  former  overlaps  the  latter 
above,  and  is  overlapped  by  it  below. 

The  parieto-mastoid  suture  unites  the  postero-inferior  angle  of 
the  parietal  with  the  upper  border  of  the  mastoid  portion  of  the  tem- 
poral bone.  It  is  short,  thick,  and  strongly  dentate,  and  forms  between 
the  latter  and  the  squama  a  grooved  notch,  which  receives  the  parietal 
angle. 

The  occipito-mastoid  suture,  likewise  thick  and  dentate,  descends 
in  a  curve  from  the  former,  and  is  extended  in  the  base  of  the  skull  to 
the  jugular  foramen.  It  is  sometimes  traversed  by  the  mastoid  foramen. 

At  the  side  of  the  cranium,  in  the  fore  part  of  the  temporal  fossa, 
the  spheno-parietal,  spheno-frontal,  and  spheno-malar  sutures 
are  continuous  in  succession,  and  descend  in  a  curve  from  the  summit 
of  the  sphenoid al  great  wing  to  the  spheno-maxillary  fissure.  The 
contiguous  borders  are  bevelled  in  such  a  way  that  the  sphenoid  over- 
laps the  parietal  and  frontal  bones. 

In  the  base  of  the  cranium  are  the  transverse  spheno-frontal 

1  Sutura  coronalis.  2  S.  lambdoidea.  8  S.  sagittalis. 


136  SPECIAL    ANATOMY   OF   THE   SKELETON. 

sutures,  uniting  the  sphenoidal  small  wings  with  the  frontal  orbital 
plates ;  and  between  them  is  the  spheno-ethmoid  suture. 

The  spheno-occipital  or  basilar  suture  is  formed  by  the  broad, 
roughened  contiguous  surfaces  united  by  a  thin  plate  of  cartilage,  which 
usually  ossifies  near  adult  age. 

The  petro-sphenoid  and  petro-occipital  sutures  are  continuous 
around  the  apex  of  the  temporal  pyramid ;  and  the  former  in  the  macer- 
ated skull  exhibits  a  large,  irregular  aperture,  the  lacerate  foramen,1 
which,  in  the  recent  state,  is  closed  beneath  by  cartilage. 

Occasionally  the  pair  of  frontal  bones  as  they  appear  at  birth  re- 
main permanently  separated,  and  are  united  by  the  frontal  suture, 
which  is  strongly  dentated,  and  continues  in  the  median  line  from  the 
sagittal  suture  to  the  root  of  the  nose. 

The  sutures  of  the  face  mostly  partake  of  the  serrated  character, 
but  are  generally  less  intricate  than  those  of  the  cranium. 

The  transverse  facial  suture  crosses  the  face  in  the  line  of  union 
with  the  cranium,  and  unites  the  frontal  bone  with  the  nasal,  maxillary, 
and  malar  bones.  The  middle  and  transverse  palate  sutures  cross- 
each  other  in  the  hard  palate. 

During  the  growth  of  the  skull  the  sutures  gradually  become  more 
intricate,  and  the  bones  more  closely  knit  together.  Commonly  at 
maturity  they  are  separable  with  moderate  force,  but  they  gradually 
become  more  intimately  and  firmly  united.  With  the  advance  of  life, 
but  in  no  regular  order,  they  become  more  or  less  ankylosed  and  insepa- 
rably united.  Frequently  late  in  life  many  or  most  of  the  sutures  are  ob- 
literated, and  occasionally  in  very  old  age  all  may  disappear,  so  that  the 
skull,  exclusive  of  the  mandible,  may  actually  form  but  a  single  bone. 

The  time  of  commencement  and  order  of  succession  of  disappear- 
ance of  the  sutures  are  very  variable.  In  those  of  the  cranium  they 
are  in  some  measure  related  with  the  cessation  of  growth  of  the  brain. 
With  the  exception  of  the  ankylosis  of  the  occipital  with  the  sphenoid 
bone,  and  sometimes  with  the  temporal  bone  at  an  earlier  period,  it 
usually  does  not  commence  until  after  thirty  years.  In  the  cranium 
the  coalescence  of  the  bones  mostly  commences  in  the  interior,  so  that 
the  sutures  may  appear  completely  obliterated  in  this  position  and  yet 
remain  open  on  the  exterior.  Succeeding  the  comparatively  early 
union  of  the  occipital  with  the  sphenoid  bone,  and  not  unfrequently 
with  the  mastoid  portion  of  the  temporal  bone,  commonly  the  earliest 
to  ankylose  are  the  parietals  at  their  back  part,  followed  by  their  union 
with  the  lower  part  of  the  frontal  bone,  and  later  with  the  occipital 
bone.  The  squamous  suture  is  usually  the  latest  to  be  obliterated ;  and 
when  the  frontal  suture  is  retained  to  maturity  it  is  one  of  the  most 
permanent.  Occasionally  the  parietals  ankylose  completely  at  the 
sagittal  suture  in  youth,  consequent  on  which  the  brain  meets  an  ob- 

1  Foramen  lacerum  ;  f.  1.  medium. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  137 

stacle  to  its  further  growth  in  the  transverse  direction  and  grows  pro- 
portionately fore  and  aft,  and  thus  gives  rise  to  an  unusual  elongated 
condition  of  the  cranium.  In  the  same  manner  the  premature  anky- 
losis  of  other  bones  produces  other  modifications  from  the  ordinary 
shape  of  the  latter.  More  or  less  complete  ankylosis  of  the  cranium 
occurs  in  youth  in  idiots,  while  the  process  is  greatly  retarded  or  is 
prevented  in  hydrocephalus. 

The  intervals  of  the  sutures  are  occupied  by  connective  or  carti- 
laginous tissue,  and  when  the  bone-earth  is  removed  by  macerating  the 
recent  skull  in  muriatic  acid,  the  contiguous  bones  appear  to  be  con- 
tinuous in  structure. 

SUPEKNUMEKAEY    BONES   OF   THE   SKULL. 

Frequently  there  occur  in  the  course  of  the  sutures,  especially  those 
of  the  cranial  vault,  little  islet-like  bones,  which  are  of  variable  size  and 
shape,  and  in  no  regular  position,  though  occasionally  a  pair  show  some 
disposition  to  symmetry  on  the  two  sides  of  the  skull.  These  sutural 
bones l  are  usually  single,  but  sometimes  there  are  several,  isolated  or 
together  in  a  row.  In  hydrocephalic  skulls  they  are  often  numerous 
and  large.  Ordinarily  they  are  most  frequently  found  in  the  lambdoid 
suture.  They  originate  in  distinct  centres  of  ossification,  but  have  no 
special  signification.  Sometimes  a  sutural  bone,2  or  a  pair,  replaces  to 
a  variable  extent  the  summit  of  the  occipital  bone.  Rarely,  also,  the 
upper  division  of  the  supraoccipital  of  the  embryo  remains  permanently 
separated,  and  connected  by  suture  with  the  rest  of  the  bone.  This 
condition  appears  to  have  been  a  more  frequent  one  in  some  of  the 
tribes  of  the  South  American  people.  The  isolated  portion  of  the 
supraoccipital  corresponds  with  the  interparietal  bone  of  some  of  the 
lower  animals,  as  in  the  rabbit.  Of  greater  rarity  is  a  supernumerary 
bone 3  occupying  the  former  position  of  the  anterior  fontanel. 

INTERIOR  OF  THE  CRANIUM. 

The  interior  of  the  cranium  conforms  to  the  brain  with  its  mem- 
branes. Its  upper  part,  or  vault,  forms  one  great  concavity,  which  is 
occupied  by  the  cerebrum,  and  its  lower  part,  or  base,  is  divided  into 
three  compartments,  the  pre-,  meso-,  and  postcranial  fossae.  The 
internal  surface  of  the  cranial  cavity,  except  in  the  postcranial  fossae, 
everywhere  exhibits  shallow  impressions  and  low  ridges,  which  con- 
form to  the  convolutions  and  fissures  of  the  cerebrum.  Besides  these, 
arborescent  channels  ascend  from  the  fossae  and  spread  upon  the  sides 
and  top  of  the  cranial  vault,  for  the  accommodation  of  the  meningeal 
blood-vessels.  In  many  skulls,  especially  those  of  old  people,  there 
are  often  to  be  observed  irregular  pits,  which  look  like  the  results 

1  Ossa  suturarum,  intercalaria,  triquetra,  rapho-geminata,  or  Wormiana ;  Wormian 
bones.  2  Epactal  bone.  3  Os  antiepileptium. 


138 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


FIG.  65. 


of  disease.  They  vary  in  number,  depth,  and  position,  and  are  more 
commonly  found  near  the  course  of  the  sutures  of  the  vault.  They 
are  produced  by  granular  growths,  named  Pacchionian  bodies, 

which  proceed  from  the  membranes  of 
the  brain,  and  are  regarded  as  morbid 
productions. 

Along  the  median  line  of  the  cranial 
vault  is  observed  a  shallow  groove  for  the 
accommodation  of  the  longitudinal  sinus 
of  the  dura.  Commencing  narrowly  at 
the  frontal  crest,  it  gradually  widens  as  it 
proceeds  backward  to  the  internal  occipi- 
tal protuberance,  where  it  becomes  con- 
tinuous usually  with  one  or  the  other  of 
the  grooves,  for  the  lateral  sinuses,  passing 
along  the  horizontal  limbs  of  the  occipital 
cross. 

The  three  pairs  of  cranial  fossse  widen 
in  a  divergent  manner  from  near  the 
centre  of  the  base  of  the  cranium  or  the 
position  of  the  sella,  and  they  expand 
above  in  the  cranial  vault.  From  in  front 
they  become  successively  deeper  and 
more  capacious. 

The  precranial  fossae,  most  elevated 
in  position,  are  occupied  by  the  frontal 
lobes  of  the  cerebrum.  Their  basis  is 
formed  by  the  orbital  plates  of  the  frontal 
bone',  with  the  intervening  cribriform 
plate  of  the  ethmoid  bone,  bounded  be- 
hind by  the  small  wings  of  the  sphenoid 
bone.  They  are  convex  on  the  orbital 
plates,  which  are  deeply  impressed  by  the 
cerebral  convolutions;  and  in  the  inter- 
mediate position  they  form  a  variably 
deep  concavity,  which  is  divided  by  the 
ethmoidal  crest.  On  each  side  of  the  latter 
is  the  olfactory  fossa,  for  the  lodgement 
of  the  olfactory  bulb,  a  fore  and  aft 
elongated,  narrow  depression  floored  by 
the  ethmoidal  cribriform  plate.  Opening 
laterally  into  the  olfactory  fossa  are  the 
little  pre-  and  postethmoidal  canals, 
communicating  with  the  orbit  between 
the  ethmoid  and  frontal  bones.  Between 
the  ethmoidal  crest  in  front  and  the  bottom  of  the  frontal  crest  is  a 


INTERNAL  VIEW  OF  THE  BASEOFTHE 
CRANIUM  OF  THE  LEFT  SIDE.  O,  6,  C, 
pre-,  meso-,  and  postcranial  fossae; 

1,  orbital  plate  of  the  frontal  bone; 

2,  small  wing  of  the  sphenoid  bone ; 

3,  great  wing  of  the  same ;  4,  squa- 
moiis  portion  of  the  temporal  bone ; 
5,  petrous  portion  of  the  same;  6, 
mastoid  portion ;    7,  parietal  bone ; 
8,  occipital  bone ;  9,  olfactory  fossa 
and  ethmoidal  crest ;  10,  sella ;  11,  pre- 
clinoid  process;  12,  basilar  groove ;  13, 
occipital  foramen ;  14,  optic  foramen ; 
15,  rotund  foramen;    16,    oval  fora- 
men ;  17,  spinous  foramen  and  groove 
from  it,  indicating  the  course  of  the 
great  meningeal  vessels ;  18,  lacerate 
foramen;  19,  internal  auditory  mea- 
tus;  20,  jugular  foramen ;  21,condylar 
foramen ;  22,  commencement  of  the 
groove   for  the   lateral  sinus.     The 
course  of  the  groove  is  observed  along 
the  horizontal  limb  of  the  occipital 
cross,  the  postero-inferior   angle  of 
the  parietal  bone,  the  mastoid  por- 
tion of  the  temporal,  and  the  jugular 
process  of  the  occipital,  terminating 
at  the  jugular  foramen. 


SPECIAL    ANATOMY   OF    THE   SKELETON. 

blind  pit1  or  a  canal,  which  communicates  below  with  the  nasal  cavities, 
and  transmits  a  vein  from  the  latter  to  the  commencement  of  the  longi- 
tudinal sinus. 

The  mesocranial  fossae  are  deeply  concave,  occupy  a  much  lower 
level  than  the  former,  and  receive  the  spheno-temporal  lobes  of  the 
cerebrum.  They  are  narrowest  inward  where  they  communicate 
through  the  sella,  and  they  expand  outwardly  to  the  parietal  region. 
In  front  they  are  defined  by  the  concave,  posterior  edges  of  the 
sphenoidal  small  wings,  and  between  these  by  the  anterior  margin 
of  the  optic  groove.  Behind  they  are  defined  by  the  upper  borders 
of  the  temporal  pyramids,  and  between  these  by  the  clivus.  Each 
fossa  is  formed  by  the  under  surface  of  the  sphenoidal  small  wing, 
the  cerebral  surface  of  the  great  wing,  the  inferior  parietal  angle, 
the  anterior  surface  of  the  temporal  pyramid,  and  the  inner  sur- 
face of  the  squama.  Most  of  the  important  foramina  of  the  sphenoid 
bone  communicate  with  it :  the  optic,  sphenoidal,  rotund,  oval,  and 
spinous  foramina.  At  its  inner  part,  in  the  macerated  skull,  is  a  large, 
irregular  hole,  the  lacerate  foramen,2  situated  between  the  fore  part 
of  the  apex  of  the  temporal  pyramid  and  the  sphenoidal  body.  In  the 
recent  state  the  hole  is  closed  below  by  cartilage,  and  is  occupied  above 
by  the  internal  carotid  artery  as  it  enters  the  cranium  from  the  carotid 
canal.  It  is  usually  extended  outwardly  by  the  incomplete  condition 
of  the  bony  canal,  which  in  the  recent  state  is  made  complete  by 
fibrous  membrane.  The  canal  opens  inwardly  and  forward  into  the 
lacerate  foramen,  and  ascends  at  the  side  of  the  sella,  on  the  lingule 
in  front.  Beneath  the  lingule  the  pterygoid  canal  opens  backward 
into  the  lacerate  foramen. 

The  groove  for  the  great  meningeal  vessels  starts  from  the  spinous 
foramen  in  the  apex  of  the  sphenoidal  angular  process,  and  turns  out- 
ward to  the  temporal  squama,  on  which  it  ascends  nearly  parallel  with 
the  anterior  border  and  divides  into  two  main  branches.  Of  these, 
one  continues  in  the  same  course  to  the  back  of  the  squama,  whence 
it  ascends  and  ramifies  on  the  back  part  of  the  parietal  bone  to  its 
upper  border ;  while  the  other  branch  leaves  the  squama,  crosses  the 
summit  of  the  sphenoidal  great  wing  to  the  adjoining  angle  of  the 
parietal  bone,  and  ascends  and  ramifies  on  the  fore  part  of  this  as  in 
the  former. 

The  postcranial  fossae,  more  capacious  and  on  a  lower  level  than 
the  preceding,  expand  outward  and  backward  from  the  clivus,  and  ac- 
commodate the  cerebellum,  the  pons,  and  the  medulla  oblongata.  Each 
is  defined  in  front  by  the  upper  border  of  the  temporal  pyramid  and 
behind  by  the  horizontal  limb  of  the  occipital  cross,  and  is  formed  by 
the  posterior  surface  of  the  pyramid  and  inner  surface  of  the  mastoid 
portion  of  the  temporal  bone  and  the  inner  surface  of  the  occipital 

1  Foramen  coecum.  2  F.  lacerum  medius. 


140  SPECIAL   ANATOMY   OF   THE   SKELETON. 

bone  below  the  horizontal  limb  of  the  occipital  cross.  The  two  fossae 
conjoin  in  front  on  the  basilar  groove,  which  slopes  from  the  clivus, 
near  the  centre  of  the  cranial  cavity,  downward  and  backward  to  the 
occipital  foramen.  The  inclined  surface  of  the  groove  is  nearly  flat  and 
variably  roughened  above,  and  is  wider,  concave,  and  smooth  below. 
It  gives  support  to  the  pons  and  medulla  oblongata.  The  occipital 
foramen  occupies  a  central  position  between  the  two  fossae,  and  on  each 
side  of  it  is  the  condylar  foramen  for  the  passage  of  the  hypoglossal 
nerve.  Behind  and  on  each  side  of  the  occipital  foramen  are  the  cere- 
bellar  fossae,  for  the  accommodation  of  the  cerebellar  hemispheres,  sep- 
arated by  the  occipital  crest.  At  the  outer  fore  part  each  postcranial 
fossa  is  crossed  by  the  continuous  masto-  and  petro-occipital  sutures, 
of  which  the  latter  is  interrupted  by  a  large  aperture,  the  jugular 
foramen.  This  is  formed  by  contiguous  notches  of  the  temporal 
pyramid  and  occipital  bone,  and  is  partially  divided  by  an  angular 
process  of  the  former.  In  the  recent  condition  the  division  is  com- 
pleted by  a  fibrous  band,  and  the  inner  portion  is  further  divided  by 
another  band,  so  that  three  distinct  passages  are  formed  in  the  jugular 
foramen.  The  outer  passage,  usually  the  largest,  is  the  outlet  of  the 
lateral  sinus,  and  accords  in  size  with  it  and  with  the  jugular  vein 
which  commences  in  it.  The  middle  passage  transmits  the  glosso- 
pharyngeal,  vagus,  and  accessory  nerves,  and  the  inner  passage  the 
infrapetrosal  sinus.  Into  the  latter  passage  opens  the  pyramidal  pit 
of  the  cochlear  aqueduct. 

At  the  back  boundary  of  each  postcranial  fossa  is  the  groove  for 
the  lateral  sinus,  which  commonly  varies  more  or  less  on  the  two  sides, 
one  being  proportioned  to  the  other.  The  larger  one  alone  is  commonly 
continuous  with  the  groove  for  the  longitudinal  sinus,  which  is  deflected 
to  one  side  of  the  internal  occipital  protuberance  to  join  it.  The  groove 
for  the  lateral  sinus,  after  proceeding  along  the  horizontal  limb  of  the 
occipital  cross,  sweeps  in  a  curve  forward  and  downward  on  the  mas- 
toid  portion  of  the  temporal  bone,  and  thence  turns  inward  and  for- 
ward across  the  occipital  jugular  process  to  terminate  in  the  outer 
passage  of  the  jugular  foramen,  with  which  it  is  related  in  size.  It 
is  deepest  in  its  course  on  the  temporal  bone,  and  in  this  position 
communicates  with  the  mastoid  foramen.  Near  its  termination  it 
often  communicates  with  a  postcondylar  foramen.  These  foramina 
are  very  variable  in  size,  are  proportioned  with  one  another  and  with 
the  jugular  foramen,  and  frequently  one  or  both  may  be  absent  on 
either  or  both  sides. 

In  a  skull  under  observation,  the  groove  of  the  left  lateral  sinus 
and  the  corresponding  passage  of  the  jugular  foramen  are  as  large  as 
the  last  joint  of  the  index  finger,  while  on  the  right  side  the  groove 
is  about  the  size  of  a  wheat  straw  and  discharges  through  the  mastoid 
foramen,  while  the  usual  passage  of  the  jugular  foramen  is  only  suf- 
ficient for  the  transmission  of  a  small  vein. 


SPECIAL   ANATOMY    OF   THE   SKELETON.  141 

LATEKAL   KEGION   OF  THE   SKULL. 

The  lateral  region  or  side  of  the  skull  has  a  general  triangular  out- 
line ;  the  lines  of  the  base  and  face  being  more  nearly  straight,  while 
the  line  of  the  vault  is  convex.  It  is  composed  above  and  behind  by 
the  cranium,  and  in  front  beneath  by  the  face.  Centrally,  it  exhibits 
a  broad  recess,  the  temporal  fossa,  which  is  occupied  by  the  tem- 
poral muscle,  and  forms  the  basis  of  the  temple.  Below,  the  fossa  is 
denned  by  the  zygoma,  and  behind  this  is  the  passage  of  the  ear,  or 
auditory  meatus.  Posterior  to  this  again  is  the  mastoid  process,  a 
peculiar  feature  of  the  human  skull.  From  the  zygoma  there  extends 
inwardly,  behind  the  maxilla,  a  deep  recess,  the  zygomatic  fossa,  and  at 
the  inner  corner  of  this  is  a  vertical,  wedge-shaped  cavity,  the  spheno- 
maxillary  fossa. 

The  temporal  fossa,  broad  and  shallow  above,  narrows  and  deepens 
inwardly  as  it  approaches  below  to  open  into  the  zygomatic  fossa.  It 
is  denned  above  by  the  temporal  ridge,  which  ascends  from  the  frontal 
external  angular  process,  curves  backward  across  the  side  of  the  frontal 
bone  and  the  parietal  to  its  posterior  fourth,  whence  it  descends  to  the 
back  of  the  temporal  squama,  and  turns  forward  to  the  root  of  the  zygo- 
matic process.  It  is  formed  by  the  lateral  surfaces  of  the  frontal  bone, 
the  sphenoidal  great  wing,  the  parietal  bone,  and  the  temporal  squama. 

The  zygoma  is  the  narrow,  horizontal  arch  which  extends  from 
the  temporal  bone  in  front  of  the  auditory  meatus  to  the  malar  bone. 
It  is  formed  by  the  conjunction  of  the  zygomatic  processes  of  the  two 
bones,  joined  by  an  oblique  serrated  suture.  The  anterior  abutment 
of  the  arch  extends  the  entire  depth  of  the  malar  bone  between  its 
frontal  and  maxillary  articulations.  It  encloses  an  ovoid  aperture, 
denned  inwardly  by  the  infratemporal  ridge,  which  proceeds  from 
the  root  of  the  temporal  zygomatic  process  across  the  lower  part  of 
the  squama,  and  thence  across  the  sphenoidal  great  wing  to  the 
spheno-maxillary  foramen.  The  aperture  of  the  zygoma  receives  near 
its  centre  the  tip  of  the  coronoid  process  of  the  mandible. 

The  zygomatic  fossa  is  the  irregular  cuboidal  space  below  the 
temporal  fossa,  extending  more  inwardly  in  the  base  of  the  cranium. 
It  is  bounded  in  front  by  the  tuber  of  the  maxilla ;  above  by  the  aper- 
ture of  the  zygoma,  the  under  surface  of  the  sphenoidal  great  wing, 
and  the  contiguous  under  surface  of  the  temporal  squama  in  advance 
of  the  articular  eminence;  outward  by  the  zygoma;  and  inward  by 
the  ectopterygoid  process.  It  is  occupied  by  the  coronoid  process  of 
the  mandible,  the  pterygoid  muscles,  the  internal  maxillary  blood- 
vessels, and  the  inframaxillary  nerve. 

The  spheno-maxillary  fossa  is  a  vertical,  wedge-shaped  cavity  at 
the  fore,  inner,  and  upper  corner  of  the  zygomatic  fossa,  into  which 
it  opens  outwardly.  Its  upper  wider  part1  is  situated  below  the 

1  Spheno-maxillary  fossa. 


142 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


FIG.  66. 


apex  of  the  orbit  into  which  it  opens,  and  is  thence  extended  outward 
as  the  spheno-maxillary  foramen.     Its  lower  part1  tapers  downward 

into  the  posterior  palatine  canal. 
It  is  bounded  in  front  by  the 
tuber  of  the  maxilla  and  the 
palate  orbital  process;  behind 
by  the  triangular  surface  in 
front  of  the  pterygoid  pro- 
cesses, and  the  surface  thence 
extended  outwardly  below  the 
orbital  surface  of  the  great 
sphenoidal  wing ;  and  internally 
by  the  upper  part  of  the  palate 
bone,  which  separates  it  from 
the  nasal  cavity. 

Communicating  with  the 
fossa  are  the  following :  the 
rotund  foramen,  behind  and 
about  midway  above ;  the 
pterygoid  canal,  below  and 
internal  to  the  former ;  and 
the  pterygo-palatine  canal, 
still  more  inwardly.  On  the 
inner  wall  above  is  the  spheno- 
palatine  foramen,which  opens 
into  the  nasal  cavity.  Below, 
the  fossa  tapers  into  the  post- 
palatine  canal  and  commu- 
nicates with  several  smaller 
canals.  The  fossa  is  chiefly  oc- 
cupied by  the  spheno-palatine  ganglion  and  the  nerves  connected  with 
it,  together  with  the  termination  of  the  internal  maxillary  artery. 

The  spheno-maxillary  foramen2  is  a  long  elliptical  aperture, 
which  extends  nearly  horizontally  outward  from  the  spheno-maxillary 
fossa  along  the  upper  fore  part  of  the  zygomatic  fossa,  from  which  it 
opens  into  the  orbit.  It  is  defined  above  by  the  lower  acute  border  of 
the  orbital  surface  of  the  sphenoidal  great  wing,  and  below  by  the  pos- 
terior margin  of  the  maxillary  orbital  plate  and  palate  orbital  process. 
The  inner  extremity  is  formed  by  a  notch  between  the  sphenoidal  body 
and  great  wing,  and  the  outer  extremity  by  the  malar  bone  or  the  con- 
junction of  the  sphenoid  with  the  maxilla.  The  foramen  represents 
the  large  and  free  communication  between  the  orbit  and  the  zygomatic 
and  temporal  fossae  in  other  orders  of  mammals. 


VIEW   OF  THE  EIGHT  SIDE    OF  A  PORTION    OF  THE 

FACE  AND  CRANIUM.  1,  frontal  bone ;  2,  malar  bone, 
a  portion  of  its  zygomatic  process  removed ;  3,  zygo- 
matic process  of  the  temporal  bone ;  4,  articular 
eminence,  and  back  of  it  the  glenoid  fossa;  5, 
squamous  portion  of  the  temporal  bone ;  6,  anterior 
inferior  angle  of  the  parietal  bone ;  7,  temporal  sur- 
face of  the  frontal  bone;  8,  temporal  surface  of  the 
great  wing  of  the  sphenoid  bone ;  9,  inferior  surface 
of  the  great  wing ;  10,  ectopterygoid  process ;  11, 
entopterygoid  process;  12,  maxilla;  13,  spheno- 
maxillary  fossa;  14,  spheno-palatine  foramen;  15, 
spheno-maxillary  foramen;  16,  oval  foramen ;  17, 
spinous  foramen ;  18,  infraorbital  foramen.  Fig- 
ures 5-8  occupy  the  fore  part  of  the  temporal  fossa ; 
the  space  between  9, 10,  and  14, 15,  is  the  zygomatic 
fossa. 


1  Pterygo-maxillary  fossa. 

2  Spheno-maxillary  fissure  ;  foramen  orbitalis  inferius. 


SPECIAL    ANATOMY    OF    THE   SKELETON. 


143 


FIG.  67. 


BASE   OF   THE   SKULL. 

The  inferior  region  or  base  of 
the  skull  is  ovoid  in  outline  with  the 
narrowed  extremity  formed  by  the 
chin,  and  the  broader  extremity  by 
the  occipital  protuberance  and  supe- 
rior semicircular  line.  Laterally  it 
is  bounded  by  the  jaws,  malar  bone, 
zygoma,  and  mastoid  process.  It 
is  divided  into  the  palatine,  gut- 
tural, and  occipital  regions. 

The  palatine  or  oral  region 
is  embraced  by  the  jaws  with  the 
teeth,  and  is  bounded  above  by  the 
palate.  It  is  chiefly  occupied  by 
the  tongue  and  muscular  floor  of  the 
mouth,  together  with  the  submax- 
illary  and  sublingual  glands.  It 
varies  greatly  in  depth  in  accord- 
ance with  the  presence  or  absence 
of  the  teeth  ;  in  the  former  case 
being  about  two  and  a  half  inches 
and  in  the  latter  less  than  an  inch. 
The  palate,  or  roof  of  the  mouth,  is 
formed  by  the  alveolar  processes  of 
the  maxilla3  and  the  palate  plates  of 
the  latter  and  of  the  palate  bones. 
It  is  strongly  vaulted,  and  is  divided 
by  the  middle  and  transverse  palate 
sutures.  The  surface  is,  for  the  most 
part,  roughened  and  porous,  but  is 
smoother  and  grooved  on  the  palate 

bones    and     contiguous    portion    Of     of  the  malar  bone ;  ll,  zygomatic  process  of 


EXTERNAL  VIEW  OF  THE  BASE  OF  THE 
SKULL,  RIGHT  SIDE.  1,  palate  plate  of  the 
maxilla ;  2,  palate  plate  of  the  palate  bone ; 
3,  vomer;  4,  5,  ento-  and  ectopterygoid  pro- 
cesses; 6,  pyramidal  process  of  the  palate 
bone ;  5, 6,  occupy  the  pterygoid  fossa ;  7,  under 
part  of  the  great  wing  of  the  sphenoid  bone, 
forming  part  of  the  zygomatic  fossa ;  8,  tem- 
poral surface  of  the  great  wing  of  the  sphe- 
noid bone ;  9,  zygoma ;  10,  zygomatic  process 


the  maxillae.  In  the  back  corner 
on  each  side  is  the  posterior  pal- 
atine canal,  which  descends  from 
the  spheno-maxillary  fossa  between 
the  palate  bone  and  maxilla,  and 
opens  on  a  smooth  grooved  surface, 
dividing  into  several  branches  on 
the  palate.  Near  it,  behind  and 
outwardly,  are  the  foramina  of  sev- 
eral smaller  palatine  canals  descend- 
ing from  the  same  fossa  through 
the  palate  pyramidal  process.  At 
the  fore  part  of  the  middle  palate 


the  temporal  bone ;  12,  squamous  portion  of 
the  temporal  bone;  13,  articular  eminence; 
14,  glenoid  fossa ;  15,  tympanic  plate ;  16,  sty- 
loid  process ;  17,  auditory  meatus ;  18,  mastoid 
process;  19,  digastric  fossa ;  20,  conjunction  of 
the  basilar  process  and  body  of  the  sphenoid 
bone;  21,  occipital- condyle;  22,  occipital  pro- 
tuberance, and  crest  leading  from  it  down- 
ward; 23,  24,  superior  and  inferior  semicir- 
cular lines ;  25,  occipital  foramen ;  26,  incisive 
foramen ;  27,  posterior  palatine  foramen ;  28, 
spheno-maxillary  foramen ;  29,  posterior  naris ; 
30,  oval  foramen;  31,  spinous  foramen;  32, 
lacerate  foramen;  33,  eustachian  tube;  34, 
entrance  of  the  carotid  canal ;  35,  jugular  fora- 
men ;  36,  stylo-mastoid  foramen ;  37,  pit  with  a 
posterior  condylar  foramen  ;  38,  mastoid  fora- 
men. 


144  SPECIAL    ANATOMY    OP   THE   SKELETON. 

suture  is  the  incisive  foramen,  which  is  formed  above  by  the  conjunc- 
tion of  the  naso-palatine  canals  descending  one  from  each  nasal  cavity. 

The  guttural  region,  or  the  region  of  the  pharynx  or  throat,  occu- 
pies the  central  portion  of  the  base  of  the  skull,  and  laterally  commu- 
nicates with  the  zygomatic  fossa,  and  behind  this  is  bounded  by  the 
articulation  of  the  mandible.  It  communicates  in  front  with  the  nasal 
cavities  by  the  posterior  nares,  and  is  limited  behind  by  the  occipital 
foramen  and  condyles. 

The  upper  median  portion  of  the  region  is  formed  by  the  basilar 
process  united  with  the  sphenoidal  body.  Its  surface  is  a  slightly 
prominent  quadrate  plane,  roughened  on  the  basilar  process  for  the 
attachment  of  the  prerecti  muscles  and  the  pharynx.  To  its  outer  side 
is  the  lacerate  foramen,  continuous  before  and  behind  with  the  petro- 
sphenoid  and  petro-occipital  sutures,  all  of  which,  in  the  recent  con- 
dition, are  closed  by  nbro-eartilage.  Below  the  petro-sphenoid  suture 
is  an  oblique  groove,  which  accommodates  the  cartilaginous  portion 
of  the  eustachian  tube,  and  communicates  outwardly  with  its  osseous 
portion.  .  In  advance  of  the  groove  are  the  oval  and  spinous  foramina 
of  the  sphenoid  bone,  and  behind  it  is  the  entrance  of  the  carotid 
canal.  Immediately  behind  this  is  the  jugular  foramen,  which,  in  the 
view  from  below,  exhibits  in  its  outer  portion  a  variably  large  and 
deep,  dome-like  fossa,  mainly  formed  by  the  temporal  pyramid.  The 
fossa  receives  the  commencement  of  the  jugular  vein,  and  has  opening 
into  it  behind,  from  above,  the  lateral  sinus.  It  accords  in  size  with 
these  vessels,  and,  with  them,  differs  in  a  proportionate  degree  on  the 
two  sides  of  the  skull.  The  inner  portion  of  the  foramen,  separated 
from  the  former  as  before  described,  transmits  the  accompanying  nerves, 
and  the  infrapetrosal  sinus  which  ends  in  the  jugular  vein.  To  the 
inner  side  of  the  jugular  foramen  is  the  exit  of  the  condylar  foramen 
for  the  hypoglossal  nerve. 

The  occipital  region  includes  the  occipital  foramen,  condyles, 
jugular  processes,  and  surface  extending  to  the  occipital  protuberance 
and  superior  semicircular  line.  To  its  outer  side  is  the  mastoid  process, 
with  the  digastric  fossa  and  groove  for  the  occipital  artery,  the  stylo- 
mastoid  foramen  or  exit  of  the  facial  canal,  and  the  styloid  process. 
The  mastoid  process  is  a  marked  feature  of  the  human  skull,  while  the 
jugular  process  is  a  rudiment  of  the  conspicuous  paroccipital  process 
of  many  lower  mammals,  as  in  the  hog  and  horse. 

THE    FACE. 

The  face  includes  the  fore  part  of  the  cranium,  or  forehead,  with 
the  bones  of  the  face.  It  is  occupied  by  the  orbits  and  nasal  cavities, 
all  situated  beneath  the  forehead,  and  is  formed  below  by  the  jaws.  Of 
variable  oval  outline,  its  length  extends  from  the  top  of  the  forehead 
to  the  chin,  and  its  breadth  between  the  malar  bones.  Near  its  centre 
is  the  nasal  aperture,  which  is  inverted  cordiform,  and  gives  attach- 


SPECIAL    ANATOMY   OF    THE   SKELETON. 


145 


ment  by  its  margin  to  the  nose.  Above  the  aperture  is  the  prominent 
bridge  of  the  nose,  formed  by  the  nasal  bones  and  nasal  processes  of 
the  maxillae.  On  each  side  is  the  orbit,  and  outwardly  from  this  the 
prominence  of  the  cheek  formed  by  the  malar  bone. 

THE   OKBITS. 

The  orbits,  or  eye-sockets,  are  four-sided  pyramidal  cavities,  directed 
fore  and  aft,  and  with  the  apex  behind.  They  are  separated  by  the 
breadth  of  the  ethmoid  bone,  in  great  measure  forming  their  inner  walls, 
which  are  parallel,  while  the  outer  walls  are  divergent.  The  entrance  of 
the  orbit  is  transversely  quadrate,  wider  than  high,  and  with  rounded 
angles.  It  inclines  slightly  and  variably  from  within  outward  and 
downward,  with  its  plane  vertical,  and  directed  forward  and  slightly 
outward.  It  is  formed 

above    by   the    supra-  FlG-  68- 

orbital  ridge  of  the 
frontal  bone,  inward 
and  below  by  the  max- 
illa, and  outward  and 
below  by  the  malar 
bone.  The  roof  is 
vaulted,  and  is  mainly 
formed  by  the  frontal 
orbital  plate,  but  re- 
ceives a  small  addition 
at  the  apex  from  the 
under  part  of  the  sphe- 
noidal  small  wing.  The 
floor,  less  concave,  va- 
riably slants  from  with- 
in outward  and  down- 
ward, and  is  mainly 
formed  by  the  orbital 
plate  of  the  maxilla, 
with  a  portion  of  the 
malar  bone  and  the 
orbital  process  of  the 
palate  bone.  The  inner 
wall,  nearly  vertical, 
inclines  somewhat  out- 
wardly behind  to  the 
floor,  forming  with  it  a  continuous  curve.  It  is  mainly  formed  by  the 
ethmoid  and  lachrymal  bones,  but  receives  a  contribution  from  the 
sphenoidal  body  behind  and  the  nasal  process  of  the  maxilla  in  front. 
The  outer  wall  is  also  nearly  vertical,' — a  plane  behind  on  the  orbital  sur- 
face of  the  sphenoidal  great  wing,  and  concave  in  front  on  the  malar  bone. 

10 


16  1718 


1514  13 


LEFT  SIDE  OP  FACE,  WITH  THE  OUTER  WALLS  OF  THE  ORBIT  AND 
ANTRUM  REMOVED.  1,  frontal  orbital  plate ;  2,  frontal  sinus ;  3, 
lachrymal  bone ;  4,  ethmoid  bone ;  5,  6,  ethmoidal  foramina ;  7, 
sphenoid  bone;  8,  optic  foramen;  9,  palate  bone;  10,  spheno- 
palatine  foramen ;  11,  rotund  foramen ;  12,  pterygoid  canal ;  13, 
pterygo-palatine  canal ;  14,  termination  of  the  spheno-maxillary 
fossa  in  the  posterior  palatine  canal ;  15,  posterior  dental  canal ; 
16,  inner  wall  of  antrum  formed  by  the  maxilla ;  17,  turbinal 
bone ;  18,  uncinate  process  of  the  ethmoid ;  19,  palate  bone ;  20, 
descending  process  of  the  lachrymal,  behind  which  is  the  open- 
ing of  the  antrum  into  the  nasal  cavity ;  21,  lachrymal  fossa. 


146  SPECIAL   ANATOMY    OF   THE   SKELETON. 

Opening  into  the  apex  or  back  end  of  the  orbit  is  the  optic  foramen, 
which  is  situated  nearest  the  conjunction  of  the  roof  and  inner  wall. 
External  to  it  is  the  large  sphenoidal  foramen,  which  ascends  from 
the  spheno-maxillary  fossa  between  the  inner  and  the  outer  wall  of  the 
orbit,  and  curves  outward  between  the  latter  and  the  roof.  In  the  floor, 
at  the  bottom  of  the  outer  wall,  is  the  spheno-maxillary  foramen,  which 
communicates  with  the  spheno-maxillary  and  zygomatic  fossae. 

The  separation  of  the  orbit  from  the  temporal  and  zygomatic  fossae 
by  a  complete  wall  is  a  characteristic  of  man  and  the  order  to  which 
he  belongs,  and  is,  for  the  most  part,  absent  in  other  animals.  The 
spheno-maxillary  foramen  is  the  contracted  representative  of  the  free 
communication  existing  in  the  latter  between  the  orbit  and  temporal 
fossa,  as  exemplified  in  the  dog. 

At  the  fore  part  of  the  inner  wall  of  the  orbit  is  a  half-cylindrical 
niche,  the  lachrymal  fossa,  which  is  formed  by  grooves  of  the  lachry- 
mal bone  and  the  nasal  process  of  the  maxilla,  and  accommodates  the 
lachrymal  sac.  It  is  continuous  below  with  the  nasal  duct,  a  short 
cylindrical  canal,  which  descends  to  end  in  the  inferior  nasal  meatus,  and 
conducts  the  tears  to  the  nose.  It  is  formed  by  the  conjunction  of  the 
nasal  process  of  the  maxilla  with  the  lachrymal  and  turbinal  bones. 

In  the  ethmo-frontal  suture,  along  the  junction  of  the  inner  wall 
and  roof  of  the  orbit,  are  the  pre-  and  postethmoidal  foramina,  the 
entrance  of  two  short  canals,  which  open  into  the  olfactory  fossa  of  the 
cranial  cavity. 

The  axis  of  the  orbit  passes  from  the  middle  of  the  sphenoidal 
foramen  to  the  centre  of  the  orbital  entrance. 

THE   NASAL   CAVITIES. 

The  nasal  cavities  are  two  large  air-spaces,  which  occupy  the  in- 
terior of  the  middle  of  the  face,  separated  by  a  vertical  fore  and  aft 
partition.  In  the  prepared  skull  they  communicate  with  the  exterior 
in  front  of  the  face  by  the  anterior  nasal  orifice,  and  behind  with 
the  guttural  region  by  a  pair  of  orifices,  the  posterior  nares.  They 
are  of  greatest  extent  fore  and  aft  along  the  roof,  are  about  as  deep 
as  they  are  long  at  the  lower  part  or  floor,  and  are  little  over  half  an 
inch  where  widest,  between  the  partition  and  outer  wall.  Each  cavity 
communicates  with  a  number  of  accessory  air-chambers,  named  the 
maxillary  antrum,  and  the  frontal,  ethmoidal,  and  sphenoidal  sinuses. 

The  anterior  nasal  orifice  is  inverted  cordiform,  and  is  roofed 
over  by  the  bridge  of  the  nose,  which  is  composed  of  the  nasal  bones 
and  the  nasal  processes  of  the  maxillae ;  and  at  the  sides  is  formed  by 
the  conjunction  of  the  nasal  notches  of  the  latter.  The  border  of  the 
orifice  is  acute,  and  beneath  is  extended  in  a  pointed  process,  the 
nasal  spine,  which  gives  attachment  to  the  fore  part  of  the  nasal 
septum  and  column,  separating  the  nostrils.  In  the  negro  the  lower 
border  of  the  orifice  is  obtusely  rounded  off  to  the  alveolar  surface, 


SPECIAL    ANATOMY    OF   THE    SKELETON. 


147 


constituting  a  race  distinction,  which  also  finds  its  counterpart  in  other 
species  of  our  order. 

The  posterior  nares,  or  nasal  orifices,  are  vertically  rectangular, 
and  have  their  plane  di- 
rected backward  with  a  FIG.  69. 
slight  inclination  down- 
ward into  the  guttural 
region ;  and  they  are  sepa- 
rated by  the  posterior  bor- 
der of  the  votner.  Each 
naris  is  bounded  outwardly 
by  the  entopterygoid  pro- 
cess of  the  sphenoid  bone, 
and  below,  is  defined  by  the 
curved  edge  of  the  palate 
plate  of  the  palate  bone, 
which  unites  with  its  fellow, 
in  the  palate  spine,  for  the 
attachment  of  the  uvula. 
Above,  it  is  bounded  by  the 
ala  of  the  vomer,  connected 
with  the  vaginal  process  of 
the  sphenoid  bone. 

The  nasal  septum 
separates  the  nasal  cavi- 
ties in  the  median  line, 
extending  from  the  pos- 
terior nares  to  the  fore 

part  of  the  former,  where  it  presents  a  deep  angular  notch,  which 
accommodates  the  cartilaginous  portion  of  the  partition  of  the  nose. 
It  is  formed  above  by  the  ethmoidal  nasal  plate,  and  below  and  behind 
by  the  vomer,  which  alone  separates  the  posterior  nares.  The  notch 
in  front  for  the  septal  cartilage  is  formed  above  by  the  ethmoidal  nasal 
plate,  and  below  by  the  vomer  and  the  incisive  crest  of  the  maxillse. 
From  its  back  angle  a  canal  is  extended  between  the  anterior  grooved 
border  of  the  vomer  and  the  adjacent  border  of  the  ethmoidal  nasal 
plate  to  the  sphenoid  body.  The  canal  is  occupied  by  a  prolongation 
of  the  nasal  septal  cartilage. 

The  nasal  septum  forms  the  inner  wall  of  each  nasal  cavity,  and 
is  normally  median  and  vertical  in  position,  but  is  frequently  more  or 
less  bent  unsymmetrically  to  one  or  the  other  side. 

The  roof  of  each  nasal  cavity,  the  greater  part  of  its  length,  forms 
a  groove  or  narrow  space,  which  extends  from  in  front  of  the  nose  to 
the  sphenoid  bone,  and  then  turns  abruptly  down  to  the  bottom  of  the 
latter,  where  it  expands  to  the  width  of  the  cavity,  and  in  this  manner 
extends  to  the  posterior  naris.  It  is  formed  in  succession  by  the  nasal 


VERTICAL  SECTION  OF  THE  FACE,  exhibiting  the  osseous 
nasal  septum.  1,  frontal  bone;  2,  frontal  sinus;  3,  nasal 
spine  of  the  frontal  bone ;  4,  nasal  bone ;  5,  nasal  spine 
of  the  maxilla ;  6,  nasal  process  of  the  same  bone ;  7, 
border  of  the  palate  plate  of  the  same ;  8,  incisive  fora- 
men ;  9,  left  posterior  naris;  10,  palate  plate  of  the  palate 
bone ;  11,  nasal  plate  of  the  ethmoid  bone ;  12,  ethmoidal 
crest;  13,  vomer;  14,  left  turbinal  bone;  15,  sphenoidal 
sinus;  16,  entopterygoid  process;  17,  ectopterygoid  pro- 
cess. 


148 


SPECIAL   ANATOMY    OF   THE   SKELETON. 


FIG.  70. 


bone,  the  frontal  nasal  ala,  the  ethmoidal  cribriform  plate,  the  sphenoid 
body,  and  the  ala  of  the  vomer  with  the  sphenoidal  vaginal  process. 

The  floor  of  each  nasal  cavity,  depressed  below  the  level  of  the 
anterior  nasal  orifice,  is  horizontal,  nearly  flat  fore  and  aft,  moderately 
concave  transversely,  and  smooth.  It  is  formed  by  the  palate  plates 

of  the  maxillae  and  palate 
bones.  At  its  fore  part, 
between  the  nasal  and  in- 
cisive crests,  is  the  naso- 
palatine  canal,  which  de- 
scends to  join  its  fellow  in 
the  intermediate  suture 
and  end  in  the  incisive 
foramen. 

The  outer  wall  is  the 
most  extensive  and  com- 
plex portion  of  the  nasal 
cavity,  and  is  formed  by 
the  maxilla  and  palate 
bone,  the  ectethmoid  and 
turbinal  bone,  and  the  na- 
sal, lachrymal,  and  sphe- 
noid bones.  It  exhibits 
three  fore  and  aft  horizon- 
tal projections,  named  tur- 
binals,  which  successively 
increase  in  length  and 
overhang  equally  long  pas- 
sages, or  meatuses.  The 
supraturbinal,  a  process 
of  the  ectethmoid,  over- 
hangs the  superior  mea- 
tus, which  extends  about 
half  the  length  of  the 

latter  at  the  upper  back  part  of  the  nasal  cavity.  The  mesotur- 
binal,  a  process  hanging  from  the  ectethmoid,  extends  along  the 
middle  of  the  nasal  cavity  above  the  middle  meatus.  The  infra- 
turbinal,  a  distinct  bone,  extends  along  the  lower  third  of  the  nasal 
cavity  overhanging  the  inferior  meatus.  Not  unfrequently  above  the 
supraturbinal  there  is  a  smaller  one  overhanging  a  shallow  recess. 

Of  the  sinuses  communicating  with  the  nasal  cavity,  the  sphenoidal 
sinus  opens  by  a  circular  orifice  directed  forward  into  the  upper  back 
part  behind  the  contiguous  portion  of  the  ectethmoid.  The  pos- 
terior ethmoidal  sinuses  open  by  one  or  several  orifices  into  the  su- 
perior meatus.  The  frontal  sinus  and  the  anterior  ethmoidal  sinuses 
open  by  a  common  passage,  the  infundibulum,  into  the  fore  part  of 


VIEW  OF  THE  OUTER  WALL  OP  THE  RIGHT  NASAL  CAVITY. 

1,  frontal  bone ;  2,  its  orbital  plate ;  3,  its  nasal  spine ;  4, 
nasal  bone  ;  5,  ethmoid  bone ;  6,  supraturbinal ;  7,  meso- 
turbinal ;  8,  turbinal  bone ;  9,  descending  process  of  the 
lachrymal  bone,  within  the  position  of  which  is  the  nasal 
duct;  10,  nasal  spine  of  the  maxilla;  11,  naso-palatine 
canal ;  12,  palate  plate  of  the  maxilla ;  13,  nasal  pro- 
cess of  the  latter;  14,  ectopterygoid  process;  15,  ento- 
pterygoid  process;  16,  nasal  plate  of  the  palate  bone; 
17,  its  palate  plate  ;  18,  posterior  palatine  foramen ;  19, 
superior  meatus  of  the  nose;  20,  middle  meatus;  21, 
inferior  meatus;  22,  frontal  sinus;  23,  sphenoidal  sinus; 
24,  its  communication  with  the  upper  back  part  of  the 
nasal  cavity ;  25,  spheno-palatine  foramen ;  26,  orifice  of 
the  antrum. 


SPECIAL,   ANATOMY    OF   THE    SKELETON.  149 

the  middle  meatus.  The  maxillary  antrum,  mainly  formed  by  the 
maxilla,  at  the  inner  part  receives  contributions  from  the  palate, 
ethmoid,  lachrymal,  and  turbinal  bones.  It  communicates  with  the 
middle  meatus,  in  the  macerated  skull,  usually  by  two  apertures,  sep- 
arated by  the  union  of  the  uncinate  process  of  the  ethmoid  with  the 
ethmoidal  process  of  the  turbinal  bone. 

DEVELOPMENT  AND  GKOWTH  OF  THE  SKULL. 

The  skull  originates  in  a  partially  cartilaginous  and  a  partially  fibro- 
connective  tissue  basis.  The  bones  of  the  base  of  the  cranium,  to- 
gether with  the  turbinal  bones,  are  derived  from  cartilage.  The  ear 
ossicles  and  the  hyoid  bone,  not  included  with  the  description  of  the 
skull,  also  originate  in  cartilage.  The  bones  of  the  vault  of  the  cranium, 
including  the  squamosals,  the  tympanals,  the  upper  division  of  the 
supraoccipitals,  and  the  pterygoids,  together  with  all  the  bones  of  the 
face  except  the  turbinals,  are  produced  from  fibro-conneetive  tissue. 
Even  those  which  originate  in  cartilage  subsequently  grow  in  thick- 
ness from  their  periosteal  investment. 

Ossification  commences  in  most  of  the  bones  of  the  skull,  as  already 
mentioned,  from  the  sixth  to  the  eighth  week  of  foetal  life,  but  in  a 
few  instances  does  not  occur  until  near  the  middle  of  the  latter  period, 
as  in  the  ectethmoids  and  petrosals,  or  even  until  after  birth,  as  in  the 
mesethmoid  and  turbinal  bones. 

At  birth  the  chief  tabular  bones  of  the  cranium  consist  of  simple 
plates  with  conspicuous  central  prominences,  the  frontal,  parietal,  and 
occipital  eminences,  from  which  radiating  fibres  proceed  to  the  borders 
and  project  in  spicules.  The  borders  do  not  interlock  with  one  another 
in  the  manner  soon  after  produced,  but  one  parietal  bone  overlaps  the 
other,  and  both  of  these  overlap  the  frontals  and  occipital  bone.  This 
condition  renders  the  skull  more  yielding  under  pressure,  and  is  advan- 
tageous in  birth  in  facilitating  the  passage  of  the  head  of  the  child 
through  the  less  yielding  pelvis  of  the  mother. 

The  fibrous  appearance  observed  on  the  surface  of  young  bones 
indicates  the  chief  direction  of  the  nutritive  blood-vessels,  which 
determine  the  lines  of  ossification  or  deposition  of  the  bone-earth  in 
the  production  of  the  bones.  In  the  subsequent  growth  of  the  bones 
the  compact  layers  are  produced  from  the  periosteum,  while  the  origi- 
nal osseous  layer  and  many  of  those  superadded  by  the  periosteum  are 
resolved  into  the  intervening  diploe.  The  early  radiated  and  more 
porous  and  spongy  appearance  of  the  bones  gradually  disappears,  and 
the  surface  becomes  more  compact  and  smooth ;  and  the  eminences  of 
the  bones  of  the  cranial  vault  or  of  other  centres  of  ossification  become 
gradually  suppressed  or  less  obvious. 

In  the  tabular  bones  of  the  cranium,  at  or  near  the  time  of  birth, 
from  less  advanced  ossification  at  points  most  remote  from  the  centres, 
there  appear  certain  membranous  spaces,  which  are  named  the  fonta- 


150  SPECIAL,    ANATOMY   OF   THE   SKELETON. 

nels.  Of  these  the  largest  and  most  conspicuous  is  the  anterior 
fontanel,  situated  at  the  top  of  the  vertex,  at  the  intersection  of  the 
coronal  with  the  frontal  and  sagittal  sutures.  It  is  lozenge-shaped, 
with  the  sides  convex  inwardly,  and  with  the  antei'ior  angle  prolonged. 
It  enlarges  for  some  time  subsequent  to  birth,  and  during  life  pulsation 
is  perceptible  in  it,  due  to  the  action  of  the  arteries  of  the  brain.  It 
gradually  diminishes  from  the  continued  growth  of  the  borders  of  the 
bones,  and  usually  disappears  two  or  three  years  after  birth.  The 
posterior  fontanel  is  a  triangular  space  at  the  intersection  of  the 
sagittal  and  lambdoid  sutures  prior  to  the  last  month  of  foetal  life,  but 
is  commonly  closed  at  birth,  and  its  position  indicated  by  the  contigu- 
ous angles  of  the  parietal  bones  overlapping  the  summit  of  the  occipi- 
tal bone.  The  lateral  fontanels  are  similar  spaces  to  the  preceding, 
one  in  front,  between  the  parietal,  frontal,  temporal,  and  sphenoid 
bones ;  the  other  behind,  between  the  parietal,  occipital,  and  temporal 
bones.  These  commonly  disappear  during  the  year  after  birth.  The 
anterior  and  posterior  fontanels  serve  as  important  means  during  birth 
to  determine  by  the  touch  the  relative  position  of  the  head  of  the 
child  to  the  pelvis  of  the  mother. 

At  birth  the  skull  is  much  larger  in  proportion  to  the  rest  of  the 
skeleton  than  at  maturity.  The  cranium  is  also  much  larger  in  pro- 
portion to  the  face ;  indeed,  while  it  is  half  a  dozen  times  larger  than 
the  latter  in  the  infant,  it  is  scarcely  more  than  double  the  size  in  the 
adult.  There  is  also  a  greater  disproportion  in  the  breadth  of  the 
cranium,  the  forehead  being  relatively  narrower.  The  widest  part  of 
the  cranium  in  the  infant  is  at  the  parietal  eminences,  and  the  highest 
point  at  the  fore  part  of  the  parietal  bones.  In  the  adult  the  widest 
part  is  usually  in  a  more  advanced  and  lower  position,  and  the  highest 
point  at  the  summit  of  the  frontal  bone.  In  infancy  the  upper  part 
of  the  cranium,  together  with  the  brain,  grows  more  rapidly  than  the 
base.  The  forehead  at  first  is  more  nearly  vertical  in  front,  and  the 
frontal  eminences  are  commonly  a  conspicuous  feature  of  childhood. 
Later,  from  more  rapid  growth  in  advance,  with  the  production  of  the 
superciliary  ridges  and  the  frontal  sinuses,  the  forehead  appears  more 
receding  and  the  frontal  eminences  less  marked. 

As  previously  indicated,  the  face  at  birth  is  remarkably  small  in 
proportion  to  the  cranium  compared  with  that  of  the  adult.  It  is  also 
short  in  comparison  with  the  breadth,  and  is  not  prominent  from  want 
of  development  of  the  teeth  and  alveolar  processes.  The  upper  portion, 
including  the  orbits,  is  proportionately  better  developed  than  the  others. 
In  the  middle  portion,  of  the  accessory  cavities  of  the  nose  only  the 
maxillary  antra  and  the  ethmoidal  sinuses  are  produced.  From  the 
little  development  of  the  former  the  outer  part  of  the  floor  of  the 
orbits  rests  on  the  alveolar  border,  and  is  but  slightly  above  the  level 
of  the  floor  of  the  nasal  cavities.  The  alveolar  borders  of  the  jaws 
are  thick,  and  exhibit  rows  of  rounded  eminences,  corresponding  to  the 


SPECIAL   ANATOMY   OF   THE   SKELETON.  151 

recesses  of  the  dental  sacs  and  their  contained  teeth.  The  body  of  the 
mandible  is  but  little  produced  below  the  recesses  of  the  teeth,  and  the 
rami  are  very  oblique.  The  temporal  and  zygomatic  fossae  are  propor- 
tionately very  small.  The  temporal  ridge,  scarcely  produced,  with  the 
temporal  fossa,  extends  but  a  little  way  on  the  parietal  bone,  occupying 
only  its  anterior  inferior  angle  and  a  small  portion  of  the  surface  con- 
tiguous to  the  squamosa  of  the  temporal  bone.  The  guttural  region, 
the  pterygoid  fossae,  and  the  palatine  region  are  comparatively  small 
and  shallow,  the  latter  being  scarce  a  fourth  the  depth  it  is  after  the 
production  of  the  teeth  and  alveolar  processes. 

The  skull  continues  to  grow  more  or  less  obviously,  and  its  features 
become  more  distinctly  marked  to  maturity.  The  period  at  which  it 
ceases  to  grow  is  in  some  measure  variable,  and  not  very  evident. 
Ordinarily  after  adult  age  it  slowly  increases  to  thirty  or  forty  years, 
and  even  later  under  certain  circumstances,  as,  for  instance,  the  con- 
tinued growth  of  the  brain  promoted  by  the  active  exercise  of  its 
functions.  Commonly  the  bones  commence  to  ankylose  from  thirty  to 
forty-five  years,  but  sometimes  the  process  is  delayed  to  fifty  or  sixty 
years.  Later  than  this  the  bones  are  commonly  found  to  be  ankylosed 
and  the  sutures  more  or  less  obliterated,  though  even  to  the  latest  period 
of  life  the  lines  of  original  separation  often  remain  more  or  less  visible. 
In  very  old  age,  eighty  or  later,  but  sometimes  earlier,  the  bones  of  the 
cranium  and  face  are  found  to  be  so  completely  ankylosed  as  to  form, 
with  the  exception  of  the  mandible,  but  a  single  piece. 

After  maturity,  with  the  advance  of  life,  the  diploe  becomes  more 
open,  and  its  venous  channels  more  capacious,  and  the  various  sinuses 
also  gradually  become  enlarged.  In  very  old  age  the  walls  of  the 
cranium  become  thinner  and  more  brittle,  and  the  cerebral  impressions 
more  or  less  effaced,  but  the  vascular  grooves  become  more  marked, 
and  the  diploic  sinuses  more  freely  communicate  with  one  another. 
With  the  loss  of  the  teeth,  whether  prematurely  by  disease  or  acci- 
dent, or  as  usual  in  the  advance  of  life,  the  alveolar  processes  of  the 
jaws  disappear,  and  the  face  is  much  reduced  in  length  or  depth, 
thus  reverting  to  the  condition  of  infancy.  With  the  reduction  of  the 
fore  part  of  the  mandible  the  rami  gradually  assume  a  more  oblique 
position,  which  is  also  a  reversion  to  the  infantile  condition.  As  the 
arch  of  the  body  of  the  mandible  is  considerably  larger  than  the  arches 
of  the  alveolar  processes,  with  the  disappearance  of  these  the  mandible 
is  drawn  up  in  front  of  their  former  position,  and  thus  approximates 
the  prominent  chin  to  the  nose,  a  feature  so  characteristic  of  the  aged 
face. 

VAKIATIONS   OF   THE   SKULL. 

Sexual  differences  appear  in  many  skulls,  but  others  show  every 
grade  of  intermediate  variation,  so  that  there  is  no  certainty  in  their 
distinction.  Generally  the  skull  of  the  female  is  smaller  and  of  more 
delicate  construction,  with  its  processes,  ridges,  and  muscular  attach- 


152  SPECIAL   ANATOMY    OF   THE   SKELETON. 

ments  less  produced,  and  with  its  surfaces  more  even  and  smooth.  The 
cranium  is  proportionately  less  elevated,  more  regularly  rounded  or  oval, 
with  thinner  walls,  less  prominent  superciliary  ridges,  and  less  expanded 
sinuses.  The  face  is  smaller  in  proportion  to  the  cranium,  with  narrower 
and  less  prominent  jaws. 

The  skull  in  different  races  and  peoples  exhibits  certain  well-marked 
peculiarities,  but  they  are  of  inconstant  character,  and  between  extreme 
differences  every  shade  of  variation  is  to  be  found.  The  cranium  varies 
considerably  in  shape,  size,  proportions,  and  capacity.  The  face  also 
varies  in  size  and  proportions,  whether  viewed  separately  or  in  relation 
with  the  cranium.  The  cranium  is  comparatively  long  or  short,  broad 
or  narrow,  low  or  high,  and  is  more  or  less  conspicuously  oval,  spheroid, 
square,  conical,  and  roof-like  on  top.  The  face  is  comparatively  small 
and  receding,  large  and  protruding,  broad  or  narrow,  long  or  abort,  and 
centrally  depressed  or  prominent.  The  capacity  of  the  normal  adult 
cranium  ranges  from  sixty  to  one  hundred  and  ten  cubic  inches ;  and 
the  average  in  all  races  is  estimated  at  eighty-five  cubic  inches. 

The  comparatively  long  cranium  is  named  dolichocephalic ;  the 
short  cranium,  brachycephalic.  The  more  protruding  face  is  named 
prognathous  ;  the  least  protruding,  orthognathous  ;  and  the  broad 
face,  eurygnathous. 

Generally  the  skull  of  the  white  race  is  dolichocephalic  and  orthogna- 
thous, though  in  some  people,  as  the  Danes,  the  brachycephalic  form  pre- 
vails. The  English  are  commonly  dolichocephalic,  and  this  form  is  prev- 
alent in  the  United  States.  The  Germans  exhibit  both  forms  and  every 
intermediate  variety.  The  cranial  capacity  is  ordinarily  highest  in  the 
white  race,  especially  in  its  more  intellectual  representatives.  The  face 
in  the  white  race  is  mostly  comparatively  small,  narrow,  and  orthogna- 
thous. Frequently  it  is  more  or  less  conspicuously  prominent  mesially 
and  centrally.  In  the  Mongolian  race  generally  the  skull  is  brachyce- 
phalic and  prognathous,  and  the  face  is  eurygnathous  and  centrally 
depressed.  The  Esquimaux  pertaining  to  this  race  are  among  the 
most  dolichocephalic  of  people.  In  the  negro  race  the  skull  is  dolicho- 
cephalic and  prognathous,  and  the  cranial  capacity  small.  In  the  Aus- 
tralian these  conditions  reach  their  extreme. 

The  difference  in  the  angle  which  is  produced  by  variation  in  the 
proportion  and  relative  position  of  the  cranium  and  face  has  been  re- 
garded as  an  index  of  that  difference.  Distinguished  as  the  facial 
angle,  it  is  ascertained  by  drawing  a  horizontal  line  from  the  anterior 
nasal  spine  to  the  auditory  meatus,  and  a  second  line,  to  intersect  the 
former,  from  the  glabella  to  the  upper  alveolar  process.  In  the  white 
race  the  facial  angle  commonly  ranges  from  70°  to  85°  ;  in  the  Mon- 
golian race,  from  65°  to  80° ;  and  in  the  negro  race,  from  60°  to  75°. 
In  idiots  it  is  considerably  lower. 

The  skulls  of  most  monkeys,  compared  with  the  skull  of  man,  exhibit 
a  very  great  proportionate  reduction  in  the  cranium,  with  an  increase  of 


SPECIAL,    ANATOMY   OF   THE   SKELETON. 


153 


the  face,  so  that  the  facial  angle  is  reduced  in  a  corresponding  degree. 
In  most  other  animals  of  man's  class  the  proportionate  reduction  of 
the  cranium  to  the  face  is  observed  to  go  on,  often  with  an  increase  of 
the  latter,  so  that  in  the  lower  orders  the  face  assumes  a  position  almost 
entirely  in  advance  of  the  cranium.  The  human  skull,  in  comparison 
with  that  of  other  animals  generally,  is  especially  remarkable  for  the 
great  proportionate  capacity  of  the  cranium  and  the  smallness  of  the 
face,  especially  of  the  jaws,  and  of  the  recesses  and  attachment  of 
muscles  related  to  the  movements  of  the  mandible. 

A  want  of  complete  symmetry  in  the  shape  of  the  skull  is  of  fre- 
quent occurrence.  Deformity  is  readily  induced  in  the  cranium  during 
its  growth  from  continued  pressure  in  certain  positions,  and  thus  the 
occiput  is  observed  to  become  permanently  flattened  on  one  side  from 
the  sleeping  infant  habitually  lying  in  that  manner.  Remarkable  de- 
formities of  the  skull,  the  result  of  pressure  to  the  head  in  infancy, 
produced  by  the  application  of  splints  and  bandages,  are  exemplified 
in  the  ancient  Peruvians  and  in  the  Flathead  Indians. 

MECHANICAL   CONSTRUCTION   OF  THE   SKULL. 

The  mechanical  construction  of  the  skull  is  in  all  respects  ad- 
mirably adapted  to  its  various  purposes.  The  ovoid  shape  of  the 
cranium,  with  its  narrower  extremity  directed  in  the  position  most 
liable  to  shock  or  accident,  insures  the  protection  of  the  large  and 
delicate  brain  to  the  greatest  degree.  The  conspicuously  greater 


FIG.  71. 


FIG.  72. 


ANTEKO-POSTERIOR  SECTION  OF  THE  CRANIUM,  ex- 
hibiting the  mode  by  which  the  connection  of  the 
different  bones  contributes  to  preserve  its  integrity. 
1,  parietal  bone;  2,  frontal  bone;  3,  its  orbital 
plate ;  4,  frontal  sinus ;  5,  body  of  sphenoid  bone ; 
6,  sphenoidal  sinus ;  7,  occipital  bone ;  8,  marginal 
thickening  of  the  occipital  foramen. 


HORIZONTAL  SECTION  OF  THE  CRANIUM.  1, 
frontal  bone ;  2,  parietal  bone ;  3,  occipital 
bone. 


projection  of  the  different  eminences  in  the  infantile  cranium  is   a 
further  security  against  injuries  from  blows  at  a  time  when  the  brain 


154 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


is  proportionately  larger,  and  more  soft  and  delicate,  than  later.  Be- 
fore ankylosis  of  the  bones  of  the  skull  they  are  everywhere  so  in- 
timately and  fitly  articulated  that  no  ordinary  violence  is  sufficient 
to  derange  or  displace  them.  Sections  made  through  the  cranium  in 
any  direction,  as  illustrated  in  Figs.  71-76,  exhibit  the  varied  modes 
of  junction  of  the  borders  of  the  bones,  which  contribute  to  main- 


FIG.  73. 


TRANSVERSE  SECTION  THROUGH  THE  FRONT  OF 
THE  CRANIUM.  1,  transverse  arch  formed  by 
the  frontal  bone;  2,  great  wing  of  the  sphenoid 
bone,  including  or  overlapping  the  abutments 
of  the  frontal  arch ;  3,  body  of  the  sphenoid 
bone,  with  its  sinuses. 


FIG.  74. 


TRANSVERSE  SECTION  IN  ADVANCE  OF  THE 
MIDDLE  OF  THE  CRANIUM.  1,  parietal  bone  form- 
ing with  its  fellow  an  arch;  2,  great  wing  of 
the  sphenoid  bone  ;  3,  horizontal  portion  of  the 
wing;  4,  body,  with  the  sphenoidal  sinuses. 


tain  the  integrity  of  the  whole.  The  face  is  a  wedge-like  segment  of 
a  cylinder  inserted  beneath  the.  narrower  extremity  of  the  cranium, 
against  which  it  is  strongly  stayed  by  the  orbital  and  zygomatic  arches, 
the  pterygoid  processes,  and  the  rami  of  the  mandible.  The  middle  of 


FIG.  75. 


TRANSVERSE  SECTION  THROUGH  THE  MIDDLE  OF 
THE  CRANIUM.  1,  parietal  bone;  2,  squamous 
portion  of  the  temporal  bone  ;  3,  petrous  por- 
tion ;  4,  body  of  the  sphenoid  bone,  with  the 
sphenoidal  sinuses. 


FIG  76. 


TRANSVERSE  SECTION  POSTERIOR  TO  THE  MID- 
DLE OF  THE  CRANIUM.  1,  back  part  of  the  pa- 
rietal bones ;  2,  mastoid  portion  of  the  temporal 
bone ;  3,  mastoid  process  with  the  sinuses ;  4, 
petrous  portion  of  the  temporal ;  5,  sphenoidal 
body,  or  the  basilar  process. 


the  face  is  remarkable  for  its  lightness  combined  with  strength.  The 
bridge  of  the  nose,  the  entrances  of  the  orbits,  and  the  zygomatic 
arches  are  all  constructed  on  mechanical  principles,  giving  strength 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


155 


and  protection  to  the  parts.  The  jaws  are  strong  arches,  in  which  the 
teeth  are  securely  implanted.  The  upper  jaw,  like  the  nether  millstone 
in  purpose,  is  stationary  and  firmly  fixed,  and  is  maintained  in  position 
by  the  stays  of  the  face  above  mentioned.  The  mandible,  the  only 
movable  bone  of  the  skull,  through  its  extension  backward  to  articulate 
with  the  temporal  bones,  becomes  a  most  powerful  lever,  and,  under 
the  action  of  the  muscles  of  mastication,  performs  the  part  of  the 
moving  millstone  in  the  trituration  of  the  food. 

ARTICULATION   OF   THE   LOWER  JAW. 

The  articulation  of  the  lower  jaw,1  or  of  the  mandible,  is  formed 
between  the  condyle  of  this  bone  and  the  glenoid  fossa  and  articular 
eminence  of  the  temporal  bone.  The  opposed  surfaces  are  invested 
with  cartilage,  and  the  joint  is  enclosed  by  a  capsular  ligament  strength- 
ened by  lateral  ligaments,  and  is  divided  by  an  interarticular  ligament 
into  two  synovial  lined  cavities. 


FIG.  77. 


FIG.  78. 


VERTICAL  SECTION  OF  THE  AETICULATION  OF 
THE  LOWER  JAW.  1,  is  placed  above  the  glenoid 
fossa ;  2,  articular  eminence ;  3,  interarticular 
ligament  dividing  the  joint  into  two  cavities,  4 
and  5 ;  6,  an  interarticular  ligament  separated 
from  the  joint,  to  exhibit  its  form. 


EXTERNAL  VIEW  OP  THE  TEMPORO-MANDIBU- 
LAR  ARTICULATION.  1,  zygoma;  2,  preglenoid 
tubercle;  3,  ramus  of  the  mandible;  4,  mas- 
toid  process;  5,  external  lateral  ligament;  6, 
stylo-maxillary  ligament,  a  process  of  the  cer- 
vical fascia. 


The  capsular  ligament2  is  a  loose  fibrous  sac  attached  around  the 
margin  of  the  glenoid  fossa  and  articular  eminence  above,  and  to  the 
neck  of  the  mandible  below. 

The  external  lateral  ligament3  is  a  thin,  flat  band  extending  from 
the  outer  part  of  the  preglenoid  tubercle  downward  and  backward  to 
the  outer  part  of  the  neck  of  the  mandible.  The  internal  lateral 
ligament 4  is  a  thin  band  descending  from  the  entoglenoid  tubercle  to 
the  inner  side  of  the  neck  of  the  mandible. 


1  Temporo-maxillary  articulation.  *  L.  capsulare. 

3  Ligamentum  maxillare  externum ;  1.  accessorium  laterale. 

4  L.  accessorium  mediale. 


156  SPECIAL   ANATOMY   OF   THE   SKELETON. 

The  interarticular  ligament1  is  an  oval  disk  of  fibro-cartilage 
within  the  articulation,  coextensive  with  the  temporal  articular  sur- 
face, and  dividing  the  joint  horizontally  into  two  compartments.  In 
fore  and  aft  section  it  is  sigmoid,  and  is  thickest  in  the  position  of  the 
glenoid  fossa,  so  as  to  render  the  transition  from  the  concavity  of  the 
joint  behind  to  the  convexity  in  front  much  less  abrupt  below  the  disk 
than  it  is  above.  It  is  chiefly  composed  of  an  intertexture  of  hori- 
zontal, fibrous  bundles,  which  become  more  concentric  at  the  thickened 
circumference,  where  it  is  intimately  connected  with  the  capsular  and 
lateral  ligaments.  Occasionally  it  is  perforated,  when  the  two  cavities 
of  the  joint  communicate.  Several  accessory  ligaments  are  connected 
with  the  mandible,  independent  of  the  articulation  described, — the 
spheno-maxillary  and  the  stylo-maxillary  ligaments. 

The  spheno-maxillary  ligament2  is  a  long,  thin  band,  narrow 
above,  where  it  is  attached  to  the  sphenoid  spinous  process,  and  widen- 
ing below,  where  it  is  attached  to  the  inner  border  of  the  dental  fora- 
men. It  descends  between  the  pterygoid  muscles,  and  has  intervening 
between  it  and  the  ramus  of  the  mandible  the  internal  maxillary 
vessels  and  the  auriculo-temporal  and  inferior  dental  nerves. 

The  stylo-maxillary  ligament 3  is  a  band  of  fibres  connected  with 
the  cervical  fascia,  and  extending  from  the  styloid  process  to  the  lower 
part  of  the  posterior  border  of  the  ramus  of  the  mandible,  between  the 
internal  pterygoid  and  masseter  muscles. 

In  the  ordinary  opening  and  closing  of  the  mouth  the  condyles  of 
the  lower  jaw  rotate  on  their  long  axis  within  the  glenoid  fossae.  In 
the  forward  movement  of  the  lower  jaw  the  condyles  descend  from  the 
fossae  beneath  the  articular  eminences,  and  the  interarticular  ligaments 
glide  forward  with  them ;  in  the  backward  movement  the  reverse 
occurs.  In  mastication  the  same  movements  take  place  alternately 
on  each  side. 

THE   HYOID   BONE. 

The  hyoid  bone  *  is  situated  in  the  neck,  at  the  root  of  the  tongue, 
to  which  it  gives  attachment.  It  is  a  horizontal  arch,  which  usually, 
until  about  the  middle  of  life,  is  composed  of  five  osseous  pieces,  named 
the  body,  the  greater  cornua,  and  the  small  cornua. 

Tha  body,5  or  basihyal,  is  the  middle  front  piece,  to  which  the 
cornua  are  united  laterally  by  cartilage.  It  is  a  transverse  bar  of  variable 
proportionate  length  and  depth,  is  bowed  with  the  convexity  forward, 
and  has  obliquely  truncated  ends  directed  upward,  outward,  and  back- 
ward. The  anterior  surface,  convex  and  uneven,  is  directed  forward 


1  I.   fibro-cartilage ;   cartilage  interarticularis  ;  meniscus ;   operculum  cartilagi- 
neum.  2  Internal  lateral  ligament ;  1.  laterale  internum. 

3  L.  stylo-maxillare  ;  1.  stylo-myloideum. 

4  Os  hyoides  ;  os  linguae  ;  tongue-bone.  5  Basis. 


SPECIAL    ANATOMY   OF   THE   SKELETON.  157 

and  upward.  It  is  divided  by  a  transverse  ridge  and  a  variable  median 
prominence  into  four  somewhat  depressed  areas,  which  give  attachment 
to  muscles.  The  posterior  surface  is  deeply  and 
evenly  concave,  and  is  directed  backward  and 
downward.  The  upper  border,  nearly  straight 
across,  is  concave  behind.  The  lower  border, 
variably  concave  for  the  most  part,  turns  up 
convexly  at  the  sides  to  the  articulation  of  the 

greater  cornua. 

m,  ,       „.  THE  HYOID  BONE.  1,  body;  2, 

The  greater  cornua,1  or  thyrohyals,  longer  greater  cornu.  3)Small  cornu. 
than  the  body,  are  directed  backward  from  the 

ends  on  a  level  with  the  upper  border.  They  are  slightly  curved  or 
nearly  straight,  club-shaped,  flattened  obliquely  from  above  downward, 
tapering  behind,  and  end  in  a  rounded  knob. 

The  small  cornua,2  or  ceratohyals,  articulate  in  front  of  the 
union  of  the  greater  cornua  with  the  body,  and  are  directed  obliquely 
upward  and  backward,  to  be  connected  with  the  stylo-hyoid  ligament. 
They  are  conical,  of  variable  length, — from  a  line  or  two  in  youth  to 
half  an  inch  or  more  approaching  the  middle  of  life, — and  are  often 
more  or  less  cartilaginous. 

Ossification  commences  in  the  body  and  greater  cornua  in  the  last 
month  of  foetal  life  ;  in  the  small  cornua  at  variable  periods  during  the 
first  to  several  years  after  birth.  The  greater  cornua  mostly  become 
ankylosed  with  the  body  after  forty  or  fifty  years ;  and  sometimes  in 
old  age  the  small  cornua  also  co-ossify  with  the  rest  of  the  bone. 

The  hyoid  bone,  together  with  its  connections  with  the  temporal 
bone,  represents  the  complicated  branchial  arches  of  fishes,  and  is  very 
variably  developed  in  other  classes  of  animals. 

The  stylo-hyoid  ligament  is  a  long,  slender,  mostly  feeble  cord 
of  fibre-connective  tissue,  which  extends  between  the  styloid  process 
of  the  temporal  bone  and  the  small  cornu  of  the  hyoid  bone.  Occa- 
sionally it  is  itself  more  or  less  ossified,  and  in  this  condition  late  in 
life  may  be  ankylosed  with  either  the  styloid  process  or  the  hyoid 
bone,  and  sometimes  with  both.  In  some  animals,  as  the  dog,  it  is 
replaced  by  a  distinct  bone,  the  epihyal. 

BONES  OF   THE   UPPER  LIMBS. 

The  upper  limbs,  suspended  from  the  upper  part  of  the  thorax,  at 
the  sides  of  the  trunk,  consist  each  of  the  shoulder,  the  arm,  the  fore- 
arm, and  the  hand.  The  bones  of  the  shoulder  are  the  scapula  and  clav- 
icle, which,  with  those  of  the  opposite  side,  form  the  shoulder-girdle. 
The  arm  has  a  single  bone,  the  humerus ;  the  forearm  has  two  bones, 
the  radius  and  the  ulna ;  and  the  hand  is  composed  of  three  parts,  the 

1  C.  majora.  2  C.  minora ;  cornicula. 


158 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


carpus,  with  eight  bones,  the  metacarpus,  with  five  bones,  and  the 
digits,  of  which  there  are  five,  each  of  three  bones  or  phalanges,  ex- 
cept the  first,  which  has  two  phalanges,  and  in  addition  two  sesamoid 
bones. 

SCAPULA. 

The  scapula,1  or  shoulder-blade,  is  placed  at  the  upper  back  part 
of  the  thorax,  extending  from  the  position  of  the  second  to  the  seventh 
rib.  It  consists  of  a  broad,  thin,  triangular  plate,  with  thickened  bor- 
ders, the  body,  from  which  spring  two  conspicuous  processes,  named 
the  spine  and  the  coracoid  process. 


FIG.  80. 


FIG.  81. 


THE  SCAPULA  OF  THE  LEFT  SIDE,  posterior 
view.  1,  supraspinous  fossa ;  2,  infraspinous 
fossa ;  3,  superior  border ;  4,  coracoid  notch ;  5, 
inferior  border;  6,  glenoid  cavity;  7,  inferior 
angle;  8,  neck  of  the  scapula;  9,  posterior 
border  or  base;  10,  spine;  11,  its  triangular 
commencement,  upon  which  the  tendon  of 
the  trapezius  muscle  moves ;  12,  acromion ;  13, 
one  of  the  nutritious  foramina;  14,  coracoid 
process. 


ANTERIOR  VIEW  OF  THE  SCAPULA.  1,  ridges 
crossing  the  subscapular  fossa:  2,  attachment 
of  the  serratus  muscle;  3,  superior  border;  4, 
superior  angle ;  5,  coracoid  notch ;  6.  coracoid 
process ;  7,  acromion ;  8,  spine  of  the  scapula ;  9, 
articular  surface  for  the  clavicle;  10,  glenoid 
cavity ;  11,  elevated  margin  of  the  same ;  12, 
neck;  13,  inferior  border;  14,  inferior  angle; 
15,  base ;  16,  position  at  which  the  spine  com- 
mences. 


The  anterior  surface,2  directed  towards  the  ribs,  presents  a  broad, 
uneven  concavity,  the  subscapular  fossa,3  which  is  occupied  by  the 
subscapular  muscle.  The  deepest  part  of  the  fossa  corresponds  with 
the  position  behind,  of  the  spine  of  the  scapula,  and  is  named  the  sub- 
scapular  angle.  At  the  outer  border  of  the  fossa  is  a  thick  convex 
ridge,  descending  from  the  neck  to  the  inferior  angle  ;  and  the  fossa  is 
also  crossed  by  several  narrow  ridges,4  converging  towards  the  neck, 


1  Scapulum  ;  omoplata ;  blade-bone. 
3  F.  subscapularis. 


2  Venter. 

4  Costse  scapulares. 


SPECIAL   ANATOMY   OF    THE   SKELETON.  159 

• 

for  the  attachment  of  tendinous  intersections  of  the  muscle  occupying 
it.  At  the  superior  and  inferior  angles  are  narrow,  flattened  surfaces, 
conjoined  by  a  variable  ridge  along  the  vertebral  border,  for  the  attach- 
ment of  the  great  serratus  muscle. 

The  posterior  surface 1  of  the  scapula  is  divided  near  its  upper 
third  by  the  spine  into  two  recesses,  of  which  the  upper,  smaller  one 
is  the  supraspinous  fossa,2  and  the  lower  one  is  the  infraspinous 
fossa,3  both  being  occupied  by  corresponding  muscles.  The  infraspi- 
nous fossa  is  bulging  at  the  middle,  and  most  depressed  along  the  outer 
border,  which  forms  a  prominent  obtuse  ridge,  descending  from  the 
neck  to  the  inferior  angle  of  the  bone,  and  giving  attachment  to  an 
aponeurosis  separating  the  infraspinous  from  the  teres  muscles.  Out- 
wardly from  the  ridge  above,  is  a  narrow  grooved  surface  for  the  origin 
of  the  small  teres  muscle,  and  below,  a  wider  convex  surface  for  the 
origin  of  the  greater  teres  muscle. 

Of  the  three  borders  of  the  scapula,  the  superior  border  is 
shortest,  and  has  springing  from  its  outer  part  the  coracoid  process. 
Its  inner  two-thirds  are  thin,  and  slant  downward  and  outward 
from  the  superior  angle  to  the  root  of  the  coracoid  process,  where  it 
ends  in  a  semicircular  notch,4  which  is  converted  by  a  transverse 
ligament5  into  the  coracoid  foramen6  for  the  passage  of  the  supra- 
scapular  nerve.  Sometimes  the  ligament  is  replaced  by  a  bridge  of  bone. 
The  internal  or  vertebral  border,  also  called  the  base,  is  the  longest, 
and  extends  between  the  superior  and  inferior  angles.  It  is  convex  and 
somewhat  wavy  in  its  course,  and  is  abruptly  directed  more  outward 
above  the  position  of  the  spine.  It  is  slightly  thickened,  and  gives 
attachment  to  the  scapular  elevator  and  rhomboid  muscles.  The  ex- 
ternal or  axillary  border  is  the  thickest  part  of  the  bone  except  the 
head,  which  it  serves  to  sustain  in  a  bracket-like  manner.  It  is  formed 
by  the  prominent  ridges  at  the  outer  part  of  the  subscapular  and  infra- 
spinous fossae,  which  descend  from  the  front  and  back  of  the  neck  to 
the  inferior  angle.  From  it  projects  a  narrow  intermediate  ridge,  which 
gives  attachment  to  an  aponeurosis  separating  the  subscapular  from 
the  teres  muscles.  The  upper  extremity  of  the  ridge  beneath  the 
glenoid  fossa  is  thick  and  roughened,  and  gives  origin  to  the  long  head 
of  the  brachial  triceps  muscle. 

Of  the  angles  of  the  scapula,  the  superior  angle,  formed  by  the 
conjunction  of  the  superior  and  vertebral  borders,  is  thin,  smooth, 
rounded  angular,  and  slightly  prolonged  upward.  The  inferior  angle, 
formed  by  the  conjunction  of  the  axillary  and  vertebral  borders,  is 
thick,  roughened,  and  rounded  angular.  The  external  angle  expands 
upward  and  outward  into  the  head,  the  thickest  part  of  the  bone, 


1  Dorsum.  2  F.  supraspinata.  3  F.  infraspinata. 

4  Coracoid  notch  ;  incisura  coracoidea  ;  i.  semilunaris. 

5  Ligamentum  coracoideum.  6  F.  coracoideum. 


160  SPECIAL   ANATOMY   OF    THE   SKELETON. 

terminating  in  the  glenoid  cavity,1  which  forms  the  upper  and  inner 
articulating  surface  of  the  shoulder-joint.  The  cavity  is  a  vertical, 
ovoid,  shallow,  concave  fossa,  invested  with  cartilage,  and  is  directed 
outward  with  an  inclination  forward  and  slightly  upward.  The  narrow 
extremity  above  forms  a  low  tuberosity,  which  gives  origin  to  the  long 
head  of  the  brachial  biceps  muscle.  The  prominent  margin  gives  at- 
tachment to  the  glenoid  ligament.  Within  the  position  of  the  head, 
the  narrower  portion  of  the  bone  is  the  neck,2  defined  by  the  scap- 
ular notch  between  the  head  and  spine  behind  and  the  coracoid  notch 
above. 

The  coracoid  process 3  springs  by  a  broad  base  from  the  upper 
part  of  the  head,  curves  upward,  forward,  and  outward,  and  terminates 
in  a  compressed  rounded  end  above  the  front  of  the  shoulder-joint.  Its 
upper  fore  part  is  unevenly  convex,  and  at  the  base  inwardly  presents 
a  broad,  low  tuberosity,  which  gives  attachment  to  the  coraco-clavicular 
ligament.  Its  lower  fore  part  forms  with  the  front  of  the  neck  a 
groove,  which  is  directed  outward  and  upward  from  the  subscapular 
fossa,  and  serves  to  conduct  the  subscapular  muscle  to  its  inser- 
tion. 

The  spine  is  a  thick,  triangular  shelf  projecting  behind  the  body 
between  the  supraspinous  and  infraspinous  fossse.  It  springs  by  a 
wide  base  stretching  from  the  vertebral  border  to  about  the  middle  of 
the  neck,  and  thence  extends  backward  and  upward,  and  is  prolonged 
outward  and  forward  to  form  the  acromion.  Its  upper  surface  extends 
outward  beneath  the  acromion,  and  forms  part  of  the  supraspinous 
fossa ;  and  its  under  surface  forms  the  upper  part  of  the  infraspinous 
fossa.  The  anterior  border  is  thick  and  rounded,  curves  backward,  out- 
ward, and  upward,  and  expands  in  the  inferior  surface  of  the  acromion. 
Between  it  and  the  head,  at  the  back  of  the  neck,  is  the  scapular  notch, 
through  which  the  supraspinous  and  infraspinous  fossae  communicate. 
The  posterior  border  is  the  longest,  and  is  obvious  as  a  ridge,  which 
may  be  felt  beneath  the  skin,  and  extends  from  the  vertebral  border 
of  the  scapula  outwardly  to  the  top  of  the  shoulder.  It  presents  a 
bowed  surface  of  varying  breadth  ;  starting  at  the  vertebral  border  in 
a  triangle,  it  narrows  outwardly,  then  expands,  narrows  again,  and 
once  more  expands  upon  the  acromion.  The  tendon  of  the  trapezius 
muscle  glides  over  its  triangle,  and  is  then  inserted  along  its  upper 
lip ;  and  from  the  lower  lip  arises  the  deltoid  muscle.  The  acromion  * 
is  prolonged  from  the  spine  upward  and  forward,  overhangs  the  back 
of  the  shoulder-joint,  and  ends  at  the  top  of  the  shoulder,  whence  the 
name.  It  is  elliptical,  flattened  from  above  downward,  and  contributes 
by  its  upper  convex  surface,  which  is  subcutaneous,  to  the  rounded 

1  Fossa  glenoidea ;  cavitas  glenoidea  ;  acetabulum  humeri ;  omocotyle. 

2  Cervix.  3  Processus  coracoideus ;  p.  uncinatus. 
4  Akron,  the  top  or  summit  >  oraos,  the  shoulder  ;  acromion  process. 


SPECIAL    ANATOMY   OF   THE   SKELETON.  161 

form  of  the  shoulder;  while  the  lower  surface  is  contiguous  to  the 
shoulder-joint.  The  outer  roughened  border  gives  attachment  to  the 
deltoid  muscle,  extending  from  the  lower  lip  of  the  spine ;  and  its 
anterior  extremity  gives  attachment  to  the  coraco-acromial  ligament. 
Just  within  the  latter  it  exhibits  a  flat,  elliptical  facet,  directed  inward 
and  upward,  for  articulation  with  the  clavicle. 

The  scapula,  for  the  most  part,  is  a  comparatively  thin  bone,  is 
thicker  at  the  borders,  and  thickest  at  the  head  and  processes,  where 
it  is  composed  of  a  proportionate  quantity  of  spongy  substance.  In 
the  position  of  the  supraspinous  and  infraspinous  fossae  it  consists  of  a 
plate  of  compact  substance  so  thin  as  to  be  translucent,  and  in  pre- 
pared specimens,  from  contraction  in  drying,  it  often  appears  broken 
in  these  parts.  Occasionally,  also,  the  ossification  is  incomplete  in  this 
position,  leaving  one  or  more  apertures,  which  in  the  recent  condition 
are  closed  by  the  periosteum.  Among  the  nutritious  foramina,  sev- 
eral, conspicuous  for  their  size,  ai*e  to  be  observed  at  the  base  of  the 
spine. 

Ossification  commences  in  the  scapula,  in  the  latter  part  of  the 
second  month  of  foetal  life,  from  a  principal  centre  appearing  in  the 
body  and  thence  extending  into  the  spine.  At  birth  the  chief  part 
of  the  bone  is  ossified,  but  the  coracoid  process,  the  acromion,  the 
base  and  inferior  angle,  and  the  margin  of  the  glenoid  cavity  are  yet 
cartilaginous.  Ossification  occurs  in  the  coracoid  process  during  the 
first  year  after  birth,  and  continues  until  about  puberty,  when  the 
process  ankyloses  with  the  body ;  contributing  a  small  portion  to  the 
upper  extremity  of  the  glenoid  cavity.  At  the  same  time  ossification 
begins  in  the  acromion,  usually  from  two  centres,  which  speedily  unite, 
when  the  epiphysis  continues  to  increase  till  maturity,  and  then  coa- 
lesces with  the  spine.  Between  sixteen  and  eighteen  years,  epiphyses 
appear  at  the  inferior  angle,  along  the  base,  in  the  tuberosity  of  the 
coracoid  process,  and  at  the  upper  part  of  the  glenoid  cavity,  all  of 
which  unite  with  the  rest  of  the  bone  between  twenty-two  and  twenty- 
five  years,  when  the  scapula  is  rendered  complete. 

The  coracoid  process  represents  a  permanently  distinct  and  well- 
developed  bone  in  other  classes  of  animals  than  our  own,  as,  for 
instance,  in  birds,  in  which,  like  the  clavicle,  it  extends  between  and 
articulates  with  both  scapula  and  sternum.  In  the  hoofed  mammals, 
as,  for  example,  the  ox,  the  process  is  rudimental.  The  cartilage  and 
epiphyses  of  the  base  of  the  immature  scapula  represent  the  more 
largely  developed  cartilaginous  or  partially  ossified  suprascapula  of 
many  lower  animals,  such  as  lizards  and  amphibians. 

Rarely,  the  completely  ossified  epiphysis  of  the  acromion  re- 
mains permanently  separated,  and  is  united  with  the  spine  by  a 
ligament. 

11 


162  SPECIAL   ANATOMY   OF    THE   SKELETON. 

CLAVICLE. 

The  clavicle,1  or  collar-bone,  is  placed  at  the  upper  part  in  front 
of  the  thorax,  and  extends  nearly  horizontally  from  the  sternum  out- 
ward over  the  first  rib  to 
the  acromion  of  the  scap- 
ula. It  is  a  long  bone  of 
irregular  cylindroid  form 
and  sigmoid  curvature, 

CLAVICLE  OF  THE  EIGHT  SIDE,  upper  view.    1,  sternal  end;  m  ^ich  ^e  sternal  6X- 

2,  portion  which  joins  the  cartilage  of  the  first  rib ;  3,  an-  tremity    18    Convex    for- 

teriorconvexityandlineofattachmentofthegreater pectoral  Ward  and  the  acromial 
muscle ;  4,  upper  surface  of  the  acromial  end ;  5,  its  articular 

surface ;  6,  anterior  concavity,  giving  attachment  to  the  del-  extremity       is        Convex 

toid  muscle ;  7,  posterior  convexity,  giving  attachment  to  the  backward  while  the  COn- 
trapezius  muscle  ;  8,  position  of  origin  of  the  sterno-mastoid 

muscle.  cavities     are     reversed. 

The  sternal  extremity 

is  trilateral,  and  ends  in  a  vertical,  uneven,  articular  surface,  which 
is  variably  rounded  triangular,  with  the  base  upward  and  the  apex 
directed  downward  and  backward  ;  and  with  the  greater  width  in  the 
same  direction.  For  the  most  part,  the  surface  is  somewhat  depressed, 
looks  inward,  and  is  connected  with  the  sternum  by  an  intervening 
fibre-cartilage ;  while  the  lower  fore  part  is  convex,  and  articulates 
with  the  first  costal  cartilage.  The  acromial  extremity  curves  out- 
ward and  backward,  is  cylindroid  and  flattened  from  above  downward, 
and  is  widest  fore  and  aft.  It  is  defined  in  front  and  behind  by  narrow 
borders,  which  are  more  or  less  roughened,  and  afford  attachment  to 
the  deltoid  and  trapezius  muscles.  It  ends  in  a  variable  transverse 
oval  facet,  which  is  directed  outward,  with  a  slight  inclination  forward 
and  downward,  and  articulates  with  the  extremity  of  the  acromion. 

The  upper  surface  of  the  clavicle,  partly  subcutaneous,  along  the 
inner  two-thirds  is  convex  and  directed  both  upward  and  forward,  and 
at  the  outer  third  is  variably  flattened,  sometimes  convex  and  some- 
times depressed,  and  is  directed  upward.  At  its  inner  part,  in  front,  it 
is  impressed  by  the  attachment  of  the  greater  pectoral  muscle,  and 
at  the  outer  part,  in  front,  by  the  deltoid  muscle,  and  behind,  by  the 
trapezius  muscle.  The  inferior  surface,  at  the  inner  two-thirds,  is 
directed  obliquely  downward  and  backward,  and  at  the  outer  third 
is  directed  downward.  Along  the  middle  it  is  feebly  depressed  or 
grooved  for  the  attachment  of  the  subclavius  muscle,  and  is  defined  in 
front  by  the  inferior  prominent  border  of  the  bone,  to  which  is  attached 
the  subclavian  fascia.  Beneath  the  sternal  extremity  it  exhibits  a 
variable,  irregular,  elliptical,  roughened  impression  for  the  attachment 
of  the  costo-clavicular  ligament ;  and  beneath  the  acromial  extremity 
an  equally  variable,  oblique,  roughened  ridge  for  the  attachment  of  the 
coraco-clavicular  ligament. 

1  Clavicula. 


SPECIAL,   ANATOMY   OF   THE   SKELETON.  163 

The  clavicle  has  nearly  the  same  construction  as  the  long  bones  of 
the  limbs  generally,  but  does  not  possess  the  distinct  central  medullary 
cavity.  It  is  composed  within  of  coarse,  spongy  substance,  commonly 
with  traces  of  a  narrow,  irregular  medullary  cavity  along  the  middle 
back  part.  The  compact  substance  predominates  along  the  posterior 
part  of  the  bone,  and  is  comparatively  thin  in  front,  except  in  the 
outer  concavity.  One  or  two  medullary  nutritious  foramina  occupy 
the  posterior  concavity,  with  the  canals  directed  outwardly  and  com- 
municating with  the  interior. 

In  the  female  the  clavicle  is  usually  more  slender,  less  curved,  and 
less  marked  by  muscular  and  ligamentous  attachments.  In  men  habit- 
uated to  the  most  active  muscular  exercise,  the  clavicle  is  generally 
shorter,  more  robust  and  curved,  and  more  strongly  marked  by  the 
muscular  and  ligamentous  attachments. 

It  is  a  remarkable  fact  that  ossification  begins  in  the  clavicle  earlier 
than  in  any  other  bone  of  the  skeleton.  It  commences  in  the  shaft 
about  the  sixth  week  of  foetal  life,  and  an  epiphysis  makes  its  appear- 
ance at  the  sternal  extremity  from  the  eighteenth  to  the  twentieth  year, 
and  ankyloses  with  the  shaft  a  few  years  subsequently.  The  clavicle 
is  the  only  medium  of  articulation  of  the  upper  limb  with  the  rest  of 
the  skeleton.  In  those  animals,  of  our  class,  in  which  the  fore  limbs 
are  used  alone  for  locomotion  and  support,  the  clavicle  is  absent,  as  in- 
stanced in  the  horse,  ox,  and  elephant.  It  is  a  most  important  means 
in  maintaining  an  outward  position  to  the  shoulder-joint,  so  as  to  give 
the  widest  range  of  movement  to  the  limb. 

THE   HUMERUS. 

The  humerus,  or  arm-bone,1  is  directed  downward  from  the 
scapula,  with  a  slight  inward  inclination,  at  the  side  of  the  thorax. 
It  is  nearly  straight,  but  has  a  slight  curvature  forward  at  the 
lower  extremity.  The  shaft  is  trilateral,  cylindroid  above,  more  com- 
pressed fore  and  aft  and  laterally  expanded  below,  and  exhibits  three 
surfaces  separated  by  three  borders.  Its  upper  extremity  is  expanded 
and  thickest,  and  terminates  obliquely,  at  an  angle  of  about  forty-five 
degrees,  in  the  head.2  This  is  a  smooth,  hemispherical,  articular  emi- 
nence, which  is  directed  inward,  upward,  and  backward,  and  partially 
overhangs  the  back  of  the  shaft,  which  projects  behind  in  a  bracket-like 
manner  to  sustain  it.  The  contracted  union  of  the  shaft  with  the  head 
is  the  neck,3  which  in  front  and  outward  appears  as  a  shallow  groove 
separating  the  head  from  a  pair  of  conspicuous  tuberosities,  also  sepa- 
rated from  each  other  by  the  commencement  of  the  bicipital  groove. 
The  small  tuberosity 4  is  situated  below  the  front  of  the  head,  and 
is  an  obtuse  process  impressed  inwardly  above,  with  a  facet  for  the 

1Oshumeri;  o.  brachii;  o.  brachiale.  2  Caput. 

3  Cervix ;  collum.  4  Lesser  luberosity  ;  tuberculum  minus. 


164 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


10  H; 


insertion  of  the  subscapular  muscle.  The  greater  tuberosity1  is 
situated  below  the  outer  part  of  the  head  on  a  level  with  the  former, 
but  rises  a  little  higher  in  front,  and  is  thrice  the  size.  It  is  a  broad, 

convex  process  impressed  above  with  three 
facets,  in  succession  for  the  insertion  of  the 
supraspinous,  infraspinous,  and  small  teres 
muscles. 

The  surgeon  finds  it  convenient  to  apply 
the  name  of  neck2  to  the  narrowed  portion 
of  the  shaft  below  the  head  and  tuberosities, 
where  the  bone  is  often  accidentally  frac- 
tured, while  the  accident  is  rare  in  the  po- 
sition of  the  neck  as  distinguished  by  the 
anatomist. 

The  internal  border3  of  the  shaft  de- 
scends from  the  small  tuberosity  to  the  in- 
ternal epicondyle,  and  separates  the  antero- 
internal  surface  from  the  posterior  surface. 
Its  upper  third4  is  obtuse,  and  forms  the 
inner  boundary  of  the  bicipital  groove,  at 
the  lower  part  of  which  it  is  roughened  for 
the  insertion  of  the  latissimus  and  greater 
teres  muscles.  The  lower  two-thirds  are 
more  prominent  and  narrow ;  about  the 
middle  the  shaft  is  roughened  for  the  in- 
sertion of  the  coraco-brachial  muscle,  and 
below  forms  the  internal  supracondylar 
ridge,  which  descends  and  curves  to  the 
end  of  the  epicondyle. 

The  external  border5  descends  from 
the  back  part  of  the  great  tuberosity  to  the 
external  epicondyle,  and  separates  the  antero- 
external  surface  from  the  posterior  surface. 
Its  upper  half  is  obtuse,  and,  for  the  most 
part,  is  somewhat  roughened  for  the  origin 
of  the  external  head  of  the  brachial  triceps  muscle.  Below  this  it  is 
crossed  by  a  slight  oblique  depression,  the  musculo-spiral  groove, 
which  descends  from  within  on  the  posterior  surface  to  the  antero-ex- 
ternal  surface,  and  indicates  the  course  of  the  superior  profunda  vessels 
and  musculo-spiral  nerve.  Below  the  groove  the  border  becomes  gradu- 
ally more  prominent,  and  forms  the  external  supracondylar  ridge, 
which  is  roughened,  and  gives  origin  to  the  long  supinator  and  long 


16 


riT 

HUMERUS    OF    THE     LEFT    SIDE, 

viewed  in  front.  1,  shaft ;  2,  head ; 
3,  neck;  4,  greater  tuberosity; 
5,  small  tuberosity;  6,  bicipital 
groove;  7,  8,  ridges  bounding 
the  latter  and  giving  attachment 
to  muscles ;  9,  position  of  inser- 
tion of  the  deltoid  muscle;  10, 
principal  nutritious  foramen ;  11, 
capitulum  for  the  radius;  12, 
trochlea  for  the  ulna ;  13, 14,  ex- 
ternal and  internal  epicondyles ; 
15,  16,  supracondylar  ridges;  17, 
fossa  for  the  coronoid  process  of 
the  ulna. 


1  Tuberculum  majus. 
3  Angulus  medialis. 
5  Angulus  lateralis. 


1  Collum  chirurgicum. 
Spina  tuberculi  minoris. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  165 

radio-carpal  extensor  muscles.  The  anterior  border l  starts  from  the 
fore  part  of  the  greater  tuberosity,  and  descends  in  front  of  the  shaft 
to  its  lower  extremity.  Its  upper  part 2  forms  the  anterior  boundary 
of  the  bicipital  groove,  at  the  lower  portion  of  which  it  is  produced  in 
a  rough  ridge3  for  the  insertion  of  the  greater  pectoral  muscle.  Below 
this,  to  about  the  middle  of  the  shaft,  it  forms  the  anterior  limit  of  a 
superficial  triangular  rough  eminence,  which  is  situated  on  the  aritero- 
external  surface  and  gives  insertion  to  the  deltoid  muscle.  From  this 
the  border  proceeds  as  the  median  convex  prominence  of  the  front  of 
the  shaft  to  its  lower  extremity. 

The  anterior  surface,  at  its  upper  part,  presents  the  bicipital 
groove/  so  named  from  its  being  occupied  by  the  longer  tendon  of 
the  brachial  biceps  muscle.  The  groove  commences  between  the  tuber- 
osities,  descends  for  several  inches  along  the  shaft,  and  is  bounded  ex- 
ternally and  internally  by  roughened  borders,  the  bicipital  ridges, 
which  receive  the  insertion  of  the  greater  pectoral,  latissimus,  and 
teres  muscles.  In  the  recent  condition  it  is  invested  with  fibro-carti- 
lage,  and  lined  with  a  prolongation  of  the  synovial  membrane  of  the 
shoulder-joint.  The  outer  portion  of  the  surface  of  the  shaft  at  its 
upper  third  is  smooth,  and  is  covered  by  the  deltoid  muscle.  The  sur- 
face on  each  side  of  the  'deltoid  insertion,  and  below  this  extending  to 
the  distal  extremity  of  the  bone,  is  covered  by  the  brachialis  muscle. 
The  posterior  surface  of  the  shaft  above  is  half  cylindrical,  con- 
verges outwardly  below  to  the  musculo-spiral  groove,  and  is  occupied 
by  the  long  head  of  the  brachial  triceps  muscle.  Outwardly,  from  the 
latter  groove,  the  surface  gradually  widens  to  the  distal  extremity  in  a 
flattened  triangle,  which  gives  attachment  to  the  internal  head  of  the 
brachial  triceps  muscle. 

The  distal  extremity  of  the  humerus  is  the  widest  portion  of  the 
bone,  and  the  thinnest  fore  and  aft ;  and  it  ends  in  a  broad  articular 
surface  supported  on  two  processes,  the  capitulum  and  the  trochlea. 

The  capitulum,5  or  radial  head,  is  the  outer  process,  and  articulates 
with  a  circular  concavity  on  the  head  of  the  radius.  The  articular  sur- 
face occupies  its  anterior  and  inferior  aspect,  and  is  continuous  in- 
wardly with  that  of  the  trochlea,  from  which  it  is  defined  by  a  groove. 

The  trochlea 6  articulates  with  the  ulna,  and  is  a  transverse  cylin- 
der widely  and  deeply  grooved  like  a  pulley-wheel,  with  the  inner  side 
more  expanded.  It  is  directed  downward,  with  an  oblique  inclination 
from  behind  forward  and  from  without  inward.  The  articular  surface 
extends  fore  and  aft  between  two  fossae  situated  immediately  above  at 


1  Angulus  anterior.  2  Spina  tuberculi. 

3  Anterior  bicipital  ridge ;  pectoral  ridge. 

4  Sulcus  bicipitalis ;  s.  intertubercularis  ;  semicanalis  humeri. 

5  Capitellum ;  eminentia  capitata ;  tuberculum ;  small  head ;  humeral  condyle. 

6  Rotula ;  pulley. 


166  SPECIAL    ANATOMY    OP   THE   SKELETON. 

the  front  and  back  of  the  shaft.  The  anterior  or  coronoid  fossa l  is 
a.  trilateral  concave  recess,  which  receives  the  apex  of  the  coronoid 
process  of  the  ulna  in  extreme  flexure  of  the  forearm.  The  posterior 
or  olecranon  fossa,2  a  much  larger  recess,  like  the  former  receives.the 
summit  of  the  olecranon  in  extension  of  the  forearm.  The  fossae  at 
bottom  are  separated  by  a  thin,  translucent  plate,  which  occasionally 
is  perforated.  In  the  recent  condition  they  are  lined  by  extensions  of 
the  synovial  membrane  of  the  elbow-joint,  and  their  upper  margins 
give  attachment  to  the  capsular  ligament.  Above  the  capitulum  in 
front  there  is  usually  a  slight  depression,3  which  accommodates  the 
border  of  the  head  of  the  radius  in  extreme  flexion  of  the  forearm. 

Above  the  trochlea  inwardly  is  a  prominent  tuberosity,  the  in- 
ternal epicondyle,4  continuous  with  the  internal  supracondylar  ridge, 
and  impressed  by  the  attachment  of  the  internal  lateral  ligament  of 
the  elbow-joint.  '  Its  back  part  is  commonly  impressed  with  a  feeble 
groove,5  which  indicates  the  course  of  the  ulnar  nerve.  Above  the 
capitulum  outwardly  is  a  less  prominent  tuberosity,  the  external  epi- 
condyle,6 which  is  continuous  with  the  external  supracondylar  ridge, 
and  is  impressed  by  the  attachment  of  the  external  lateral  ligament  of 
the  elbow-joint. 

The  humerus  is  constructed  like  other  long  bones  of  the  limbs  gen- 
erally, the  shaft  being  occupied  by  a  large  medullary  cavity,  with 
thick  compact  walls  thinning  away  towards  the  extremities  of  the 
bone,  which  are  composed  of  spongy  substance  with  a  thin  investment 
of  compact  substance.  The  principal  medullary  nutritious  foramen  is 
commonly  situated  at  the  lower  third  of  the  humerus  on  the  internal 
border,  and  has  the  canal  directed  downward.  Sometimes  a  second 
foramen  occupies  a  higher  position  on  or  near  the  same  border. 

Ossification  commences  in  the  humerus  towards  the  end  of  the 
second  month  of  foetal  life,  the  chief  centre  appearing  near  the  middle 
of  the  shaft,  which  alone  is  ossified  at  birth.  A  centre  starts  in  the 
head  near  the  middle  of  the  first  year  or  later,  and  another  starts  in 
the  greater  tuberosity  at  the  end  of  the  second  year  or  early  part  of  the 
third.  About  the  same  time  a  centre  appears  in  the  capitulum,  and 
others  follow  in  the  small  tuberosity  and  internal  epicondyle  in  the 
fourth  or  fifth  year.  The  centres  of  the  head  and  tuberosities  coalesce 
about  the  latter  period  and  grow  into  a  large  epiphysis,  which,  though 
the  first  to  ossify,  is  the  last  to  ankylose  with  the  shaft,  occurring,  as 
it  does,  in  the  female  about  the  twenty-second  year,  and  in  the  male 

1  F.  anterior  major  ;  fossa  supratrochlearis  anterior. 

2  F.  olecrani ;  f.  posterior;  fossa  supratrochlearis  posterior;  sinus  maximus. 
8  Fossa  anterior  minor. 

4  Internal  condyle  ;  condylus  flexorius  ;  epicondylus  medialis  ;  epitrochlea  ;  in- 
ternal tuberosity.  6  Sulcus  ulnaris. 

6  External  condyle  ;  epicondyle  ;  epicondylus  lateralis ;  nodus  externus  ;  external 
tuberosity ;  condylus  extensorius. 


SPECIAL   ANATOMY    OF   THE   SKELETON. 


167 


FIG.  84. 


11 


approaching  the  twenty-fifth  year.  A  centre  does  not  appear  in  the 
trochlea  until  about  the  twelfth  year,  and  that  of  the  external  epi- 
condyle  the  following  year.  The  centres  of  the  capitulum,  trochlea, 
and  external  epicondyle  unite  about  the  sixteenth  year,  and  shortly 
after  ankylose  with  the  shaft ;  to  which,  also,  the  centre  of  the  internal 
epicondyle  ankyloses  a  year  later. 

THE  ULNA. 

The  ulna '  is  the  inner,  more  posterior,  and  longer  bone  of  the  fore- 
arm. It  is  trilaterally  prismatic,  with  the 
upper  extremity  the  larger,  and  articulating 
with  the  humerus  and  radius,  with  which  it 
forms  the  elbow-joint,  whence  it  gradually 
tapers  to  the  lower  extremity,  where  it  also 
articulates  with  the  radius  and  forms  part 
of  the  wrist-joint.  It  is  not  quite  straight, 
but  from  the  upper  extremity  is  slightly 
bent  forward  to  near  its  middle,  whence  it 
pursues  a  straighter  course  to  the  lower 
extremity,  which  is  slightly  bent  outwardly. 

The  upper  extremity  terminates  in 
two  conspicuous  eminences,  the  olecranon 
and  coronoid  process,  separated  by  the  sig- 
moid  fossa. 

The  olecranon,2  situated  at  the  upper 
back  part  of  the  ulna,  forms  the  promi- 
nence of  the  elbow.  It  is  a  thick,  strong 
process,  ascending  from  the  back  of  the 
shaft  above  the  position  of  the  coronoid 
process,  and  curving  forward  at  the  sum- 
mit, which,  in  the  extended  condition  of 
the  forearm,  is  received  into  the  olecranon 
fossa  of  the  humerus.  Its  posterior  sur- 
face converges  downward  and  forms  a  tri- 
angle, which  is  flattened,  convex,  and  sub- 
cutaneous. The  anterior  surface  forms 
the  upper  division  of  the  sigmoid  fossa. 
The  upper  surface  is  trilateral  and  convex, 
gives  attachment  to  the  brachial  triceps 
muscle  contiguous  to  the  posterior  surface, 
and  is  covered  with  a  synovial  bursa  next 
the  summit. 


THE    TWO    BONES    OF  THE   EIGHT 

FOREARM,  viewed  in  front;  the 
ulna  to  the  right  'and  the  radius  to 
the  left  of  the  figure.  1,  shaft  of 
the  ulna;  2,  sigmoid  fossa;  3,  ar- 
ticulation of  the  head  of  the  ra- 
dius with  the  ulna ;  4,  olecranon ; 
5,  coronoid  process;  6,  nutritious 
foramen ;  7,  sharp  ridges  of  both 
bones  of  the  forearm  for  the 
attachment  of  the  interosseous 
membrane  ;  8,  head  of  the  ulna ;  9, 
styloid  process;  10,  shaft  of  the 
radius  ;  11,  head  of  the  same ;  12, 
neck ;  13,  tuberosity ;  14.  roughened 
attachment  of  the  terete  pronator 
muscle ;  15,  carpal  extremity  of  the 
bone ;  16,  its  styloid  process. 


The  coronoid  process 3  is  a  broad  py- 


ramidal eminence,  which  is  directed  forward  from  the  shaft  in  advance 


1  Cubitus  ;  focile  majus  ;  canna  major. 

2  Olecranon  process  ;  processus  anconaeus. 


s  Processus  coronoideus. 


168  SPECIAL   ANATOMY   OF    THE   SKELETON. 

of  the  position  of  the  olecranon,  and  curves  upward  at  the  apex.  Its 
upper  surface  forms  the  lower  division  of  the  •  sigmoid  fossa  ;  and  its 
anterior  surface  slopes  downward,  and  at  the  base  inwardly  exhibits  a 
rough  area l  for  the  attachment  of  the  brachialis  muscle. 

The  sigmoid  fossa  2  is  formed  between  the  olecranon  and  coronoid 
process,  and  conforms  to  the  trochlea  of  the  humerus,  with  which  it 
articulates.  It  is  semicircular  fore  and  aft,  and  is  divided  into  two 
articular  facets  by  a  slight  transverse  ridge  extending  between  a  pair 
of  notches.  The  upper  or  olecranon  facet  is  directed  forward,  is 
somewhat  cordiform,  broader  than  long,  transversely  convex,  and  ver- 
tically concave.  The  lower  or  coronoid  facet  is  horizontal,  irregu- 
larly transverse  oval,  inwardly  concave,  outwardly  convex,  and  fore 
and  aft  concave.  From  the  coronoid  facet,  another,  the  radial  facet,3 
extends  downward  on  the  outer  side  of  the  base  of  the  coronoid  pro- 
cess. It  is  fore  and  aft  irregularly  oval  and  concave,  and  articulates 
with  the  lateral  border  of  the  head  of  the  radius.  Internally,  the 
sigmoid  fossa  is  bordered  by  a  ridge,  which  gives  attachment  to  the 
internal  lateral  ligament  of  the  elbow-joint,  and  at  its  thickened  fore 
part  affords  an  origin  to  the  superficial  digital  flexor  muscle.  Else- 
where the  margins,  contiguous  to  the  sigmoid  fossa,  are  more  or  less 
roughened  for  the  attachment  of  the  capsular  ligament,  and  the  bor- 
ders in  front  and  behind  the  radial  articular  facet  are  in  like  manner 
roughened  for  the  attachment  of  the  orbicular  ligament. 

The  tapering  distal  extremity  of  the  ulna  expands  in  a  rounded 
eminence,  the  head,4  from  the  inner  side  of  which  projects  the  styloid 
process.5  The  head  exhibits  a  smooth  convex  surface,6  which  is  di- 
rected outward  and  forward  for  articulation  with  the  radius ;  and  is 
continued  beneath,  where  it  is  opposed  to  an  interarticular  ligament, 
which  separates  the  head  from  the  cavity  of  the  wrist-joint.  Between 
the  articular  surface  and  the  base  of  the  styloid  process  is  a  pit  for  the 
insertion  of  the  ligament.  The  styloid  process  is  a  nipple-shaped  promi- 
nence, which  extends  a  little  lower  than  the  head,  and  gives  attach- 
ment to  the  internal  lateral  ligament  of  the  wrist.  Between  it  and 
the  head  behind  is  a  groove,  descending  from  the  back  of  the  shaft, 
for  the  passage  of  the  tendon  of  the  ulno-carpal  flexor. 

The  prismatic  shaft  of  the  ulna  presents  three,  for  the  most  part, 
flattened  surfaces,  defined  by  three  more  or  less  prominent  borders. 

The  internal  border  descends  from  the  inner  side  of  the  coronoid 
process  to  the  fore  part  of  the  styloid  process,  and  separates  the  inter- 
nal from  the  anterior  surface.  For  the  greater  part  of  its  length  it  is 

1  Tuberositas  ulnae ;  tubercle  of  the  ulna. 

2  Fossa  sigmoidea ;  greater  sigmoid  cavity ;  f.  sigmoidea  major ;  f.  semilunaris 
major. 

3  Lesser  or  small  sigmoid  cavity  ;  fossa  sigmoidea  minor  ;  incisura  semilunaris ; 
sinus  lunatus. 

4  Capitulum.  5  Processus  styioideus.  6  Circumferentia  articularis. 


SPECIAL   ANATOMY   OP   THE   SKELETON.  169 

obtusely  rounded  and  smooth,  and  gives  attachment  to  the  deep  digital 
flexor  muscle ;  its  lower  fourth  forms  the  inner  limit  of  a  superficial 
roughened  ridge,  which  gives  attachment  to  the  quadrate  pronator 
muscle.  The  external  border  descends  from  the  back  of  the  radial 
articular  facet  to '  the  fore  part  of  the  head,  separates  the  anterior 
from  the  posterior  surface,  and  gives  attachment  to  the  interosseous 
membrane,  which  extends  between  the  ulna  and  radius.  Its  upper 
three-fourths  are  prominent  and  acute,  especially  along  the  middle 
of  the  shaft,  but  the  lower  part  is  rounded  and  scarcely  defined.  The 
posterior  border  descends  from  the  outer  margin  of  the  olecranon  to 
the  back  of  the  styloid  process,  and  separates  the  internal  from  the 
posterior  surface.  Its  upper  three-fourths  are  acute,  and  the  lower 
obtuse  and  scarcely  defined. 

The  anterior  surface  of  the  ulna,  rounded  in  front  above  and  flat- 
tened or  slightly  depressed  along  the  middle,  gives  attachment  to  the 
deep  digital  flexor.  At  its  upper  part,  outwardly,  it  is  concave,  and 
gives  attachment  to  the  short  supinator  muscle  ;  and  at  its  lower  fourth 
is  rounded,  and  marked  by  a  superficial  rough  ridge,  for  the  attachment 
of  the  quadrate  pronator.  The  internal  surface,  slightly  concave 
at  its  commencement,  but  slightly  convex  the  greater  part  of  its  length 
and  becoming  more  narrow  and  rounded  below,  for  its  upper  three- 
fourths  gives  attachment  to  the  deep  digital  flexor  muscle,  and  is  sub- 
cutaneous at  the  lower  fourth.  The  posterior  surface,  at  its  upper 
third,  presents  a  triangular  concave  area,  which  gives  attachment  to 
the  anconeus  muscle.  Below  this  it  is  divided  by  a  longitudinal  ridge, 
the  narrower  area  next  the  posterior  border  accommodating  the  ulno- 
carpal  extensor  muscle,  and  the  broader  depressed  one  next  the  external 
border  accommodating  the  extensor  muscles  of  the  thumb. 

The  ulna  has  the  usual  construction  of  other  long  bones.  Its  chief 
medullary  nutritious  foramen  is  situated  at  the  upper  third  of  the 
anterior  surface  of  the  shaft,  and  has  the  canal  directed  upward.  Ossi- 
fication begins  near  the  middle  of  the  shaft  about  the  end  of  the  second 
month  of  foetal  life.  A  centre  for  the  lower  epiphysis  appears  about 
the  fifth  year,  and  another  for  an  epiphysis  of  the  extremity  of  the 
olecranon  about  the  tenth  year  ;  the  former  uniting  with  the  shaft  about 
the  sixteenth  year,  and  the  latter  about  the  twentieth  year. 

THE   EADIUS. 

The  radius l  lies  to  the  outer  side  of  the  ulna,  parallel  with  it ;  is 
more  forward,  shorter,  and  articulates  with  it  at  both  extremities.  It 
is  cylindroid,  and  in  greater  part  trilaterally  prismatic,  is  slightly 
bowed  forward  and  inward,  is  smallest  at  the  upper  extremity,  where 
it  articulates  with  the  humerus,  and  is  largest  at  the  lower  extremity, 

1  Focile  minus  ;  canna  minor. 


170  SPECIAL,   ANATOMY   OF   THE   SKELETON. 

where  it  articulates  with  the  carpus,  and  contributes  largely  to  the 
construction  of  the  wrist-joint. 

The  upper  extremity  ends  in  the  head,1  which  is  a  horizontal,  cir- 
cular disk,  with  a  smooth  surface  above  and  around  the  edge,  in  the 
recent  state  invested  with  cartilage.  The  upper  surface  is  concave, 
and  articulates  with  the  capitulum  of  the  humerus,  and  the  marginal 
surface,2  widest  within,  articulates  with  the  radial  facet  of  the  ulna, 
and  also  moves  on  the  orbicular  ligament,  embracing  the  head. 

Below  the  head,  the  contracted  cylindrical  commencement  of  the 
shaft  forms  the  neck.3  Beneath  this,  inwardly  and  forward,  is  a 
rounded  eminence,  the  tuberosity,4  the  back  of  which  is  impressed  by 
the  insertion  of  the  tendon  of  the  biceps  muscle,  and  is  more  convex 
in  front,  where  a  synovial  bursa  is  interposed. 

The  inner  border  of  the  shaft  is  prominently  acute  along  the 
middle  of  the  bone,  and  gives  attachment  to  the  interosseous  mem- 
brane, and  separates  the  anterior  and  posterior  surfaces.  The  outer 
border,  or  surface,  of  the  shaft  is  convex,  and  for  the  most  part 
undefined  from  the  anterior  and  posterior  surfaces.  Extending  from 
about  its  middle  upward  is  an  oval  rough  impression,  for  the  insertion 
of  the  terete  pronator  muscle.  Its  upper  third,  extending  around  the 
front  and  back,  is  embraced,  by  the  short  supinator  muscle.  On  the 
anterior  surface  an  oblique  line  descends  from  the  tuberosity  to  the 
middle  of  the  outer  border,  and  gives  attachment  to  the  superficial 
digital  flexor.  The  surface  below  the  ridge  to  the  lowest  fourth  of  the 
shaft  is  convex  outwardly  and  depressed  inwardly,  and  affords  attach- 
ment to  the  deep  digital  flexor.  Its  lowest  part  is  wider  and  flatter, 
and  gives  attachment  to  the  quadrate  pronator  muscle.  The  posterior 
surface  above  forms  part  of  that  embraced  by  the  short  supinator ; 
along  the  middle  is  depressed  inwardly,  for  the  attachment  of  the  ex- 
tensor muscles  of  the  thumb ;  and  below  is  covered  with  the  extensor 
tendons  directed  to  the  grooves  at  the  lower  extremity. 

The  lower  extremity  of  the  radius  is  the  broadest  part  of  the  bone, 
and  about  as  thick  as  the  head ;  is  narrowest  outwardly,  and  is  quad- 
rilateral ;  and  terminates  in  the  carpal  articular  surface  and  styloid 
process. 

The  carpal  articular  surface,  directed  downward,  is  concave  and 
triangular,  widest  transversely,  and  with  its  apex  extended  on  the  sty- 
loid process.  It  articulates  with  the  scaphoid  and  semilunar  bones 
of  the  carpus,  and  is  inwardly  defined  by  a  ridge  from  the  ulnar  ar- 
ticular surface.5  This  is  a  concave  facet  on  the  inner  side  of  the 
radius  for  articulation  with  the  head  of  the  ulna ;  and  the  ridge  be- 
tween the  two  surfaces  gives  attachment  to  the  interarticular  ligament, 
which  separates  the  radio-carpal  from  the  radio-ulnar  articulation. 

1  Capitulum.  2  Circumferentia  articularis.  3  Collum. 

4  Bicipital  tuberosity  ;  tuberositas.  5  Sigmoid  cavity  ;  sinus  lunatus. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  171 

The  styloid  process :  is  a  pyramidal  downward  projection  at  the 
outer  part  of  the  shaft,  which  gives  attachment  at  its  base  to  the 
tendon  of  the  long  supinator,  and  by  its  apex  to  the  external  lateral 
ligament  of  the  wrist ;  and  outwardly  is  grooved  for  the  tendons  of 
the  extensor  muscles  of  the  thumb. 

The  front  of  the  distal  extremity  of  the  radius  is  defined  from  the 
carpal  articular  facet  by  a  ridge,  which  gives  attachment  to  the  cap- 
sular  ligament  of  the  wrist.  Behind  it  is  prominent,  and  is  traversed 
by  three  descending  grooves,  of  which  the  outer  broadest  one  gives 
passage  to  the  tendons  of  the  radio-carpal  extensors,  the  inner  one  to 
the  digital  extensor  tendons,  and  the  intermediate  narrowest  one  to  the 
tendon  of  the  second  pollical  extensor. 

The  radius  is  constructed  like  the  ulna,  and  its  chief  medullary 
nutritious  foramen  holds  a  corresponding  position  and  course.  Ossifi- 
cation, likewise,  commences  as  in  the  ulna.  A  centre  appears  for  an 
epiphysis  of  the  distal  extremity  about  the  end  of  the  second  year, 
and  one  for  the  head  in  the  fifth  year.  The  latter  ankyloses  with 
the  shaft  about  the  eighteenth  year,  and  the  former  in  the  twentieth 
year. 

THE   HAND. 
The  hand 2  consists  of  the  carpus,  the  metacarpus,  and  five  digits. 

THE   CARPUS. 

The  carpus,3  or  wrist,  is  composed  of  eight  small  bones  closely 
articulated  together  and  ranged  in  two  transverse  rows,  the  upper  row 
articulating  with  the  bones  of  the  forearm,  the  lower  row  with  the 
metacarpus.  Mostly  named  from  some  supposed  resemblance,  those 
of  the  first  or  upper  row,  from  the  outer  or  radial  side  inwardly,  are 
the  scaphoid,  lunar,  cuneiform,  and  pisiform  bones,  and  those  of  the 
second  or  lower  row  in  the  same  order  are  the  trapezium,  trapezoid, 
magnum,  and  unciform  bones.  In  common,  their  posterior  or  dorsal 
surface  and  their  anterior  or  palmar  surface  is  somewhat  roughened 
for  ligamentous  attachment,  while  the  other  surfaces  are  articular 
and  smooth,  and  in  the  recent  state  are  invested  with  cartilage.  The 
superior  articular  surfaces  are  generally  convex,  the  inferior  ones  con- 
cave, and  the  opposed  lateral  ones  mostly  flat. 

The  scaphoid  bone,*  the  largest  of  the  first  row  of  the  carpus, 
occupies  its  outer  side.  It  is  somewhat  boat-shaped,  as  expressed  by 
the  name,  and  has  its  length  directed  obliquely  from  behind,  forward, 
downward,  and  outward.  Its  narrow  end  in  front  forms  a  blunt  tuber- 
osity,  to  which  the  anterior  annular  and  external  lateral  ligaments  of 
the  wrist  are  attached.  Its  posterior  higher  and  wider  extremity  ex- 

1  Processus  styloideus.  2  Manus. 

8  Ossa  carpi.  *  Os  scaphoideum  ;  os  naviculare. 


172 


SPECIAL   ANATOMY    OF   THE   SKELETON. 


FIG.  85. 


hibits  a  trilateral  convex  facet,  directed  upward,  backward,  and  outward 
to  articulate  with  the  radius.  Inwardly,  it  has  a  flat,  crescentic  facet 
for  the  lunar  bone,  and  below  the  latter  a  longer  concave  facei  for  the 

magnum.  Beneath  its  anterior  extremity 
it  presents  a  convex  surface  divided  into 
two  facets  for  the  trapezium  and  trapezoid 
bones. 

The  lunar  bone,1  succeeding  the  former 
inwardly,  is  crescentic  fore  and  aft,  thickest 
above,  and  convex  where  it  articulates 
with  the  radius,  and  concave  below,  and 
divided  into  two  facets  for  articulation 
with  the  magnum  and  unciform  bones. 
Outwardly  it  has  a  flat  crescentic  facet  for 
the  scaphoid,  and  inwardly  a  quadrate  facet 
for  the  cuneiform  bone. 

The  cuneiform  bone,2  next  the  pre- 
ceding inwardly,  is  nearly  as  large.  It  is 
wedge-like,  with  the  base  presenting  a 
quadrate  facet,  which  articulates  with  the 
lunar  bone,  and  with  the  apex  blunt  and 
forming  a  tubercle,  at  the  inner  border  of 
the  wrist,  giving  attachment  to  the  internal 
lateral  ligament.  Upward  and  backward 
it  presents  a  convex  facet,  which  enters 
into  the  wrist-joint,  and  is  separated  from 
the  head  of  the  ulna  by  the  interarticular 
ligament.  Below  and  outward  it  presents  the  longest  facet,  which 
is  sinuous,  and  articulates  with  the  unciform  bone.  In  front  of  its 
apex  it  presents  an  oval  facet,  which  articulates  with  the  pisiform 
bone. 

The  pisiform  bone,3  the  smallest  of  the  carpus,  is  oval,  and  pos- 
sesses a  single  oval  facet,  which  articulates  in  front  of  the  apex  of  the 
cuneiform  bone. 

The  trapezium,4  the  first  bone  outwardly  of  the  second  row  of  the 
carpus,  is  intermediate  to  the  scaphoid  and  first  metacarpal  bone.  It 
is  of  irregular  shape,  has  its  thicker  part  upward  at  the  outer  side  of 
the  wrist,  and  its  narrower  part  directed  between  the  bases  of  the  first 
and  second  metacarpal  bones.  Its  fore  part  presents  a  laterally  com- 
pressed tubercle,  which  affords  attachment  to  the  anterior  annular  lig- 
ament, and  borders  a  deep  groove  within  for  the  tendon  of  the  ulno- 


BONES  OF  THE  CARPUS,  and  those 
with  which  they  articulate;  right 
hand,  posterior  view.  Of  the  upper 
bones  U  is  the  lower  end  of  the  ulna, 
and  R  is  the  lower  end  of  the  ra- 
dius. Of  the  bones  of  the  carpus, 
in  the  first  row,  S  is  the  scaphoid, 
L  the  lunar,  C  the  cuneiform,  and 
P  the  pisiform  bone ;  and  in  the 
second  row,  T  T  are  the  trapezium 
and  trapezoid,  M  the  magnum, 
and  U  the  unciform  bones.  1,  the 
metacarpal  bones. 


1  Semilunar  bone  ;  os  semilunare  ;  os  lunare  ;  os  lunatum. 

2  Os  cuneiforme  ;  os  pyramidale  ;  os  triangulare  ;  os  triquetrum. 

3  Os  pisiforme  ;  os  orbiculare ;  os  rotundum  ;  os  subrotundum. 

4  Os  multang-ulum  majus  ;  os  rhomboides. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  173 

carpal  flexor.  Upward  and  inward  it  presents  a  concave  facet,  which 
articulates  with  the  scaphoid ;  and  below  this  a  surface  divided  into  two 
facets,  which  articulate  with  the  trapezoid  and  second  metacarpal  bone. 
Outward  and  downward  it  presents  its  most  considerable  facet,  which 
is  convex  fore  and  aft  and  concave  from  side  to  side,  and  articulates 
with  the  first  metacarpal  bone. 

The  trapezoid  bone,1  succeeding  the  former,  is  the  smallest  of  the 
second  row,  and  is  wedge-like,  with  its  broad  extremity  forming  the 
dorsal,  and  its  narrow  extremity  the  palmar  surface.  Its  upper  sur- 
face presents  a  small  quadrate  facet  for  the  scaphoid  bone ;  its  outer 
surface,  a  larger  convex  facet  for  the  trapezium ;  its  inner  surface,  a 
concave  facet  for  the  magnum  ;  and  its  lower  surface  forms  a  large 
facet,  fore  and  aft  concave  and  transversely  convex,  for  articulation 
with  the  second  metacarpal  bone. 

The  magnum,2  the  third  bone  of  the  second  row,  and  the  largest  of 
the  carpus,  has  an  irregular  quadrate  base  below,  supporting  a  rounded 
head  which  occupies  the  centre  of  the  wrist  in  a  concavity  formed  by 
the  scaphoid  and  lunar  bones.  The  palmar  and  dorsal  surfaces  are 
large,  and  occupy  the  middle  of  the  wrist.  The  superior  convex  surface 
articulates  with  the  scaphoid  and  lunar  bones.  The  inferior  surface  of 
the  base  is  divided  into  three  facets,  of  which  the  middle,  longer  one 
articulates  with  the  middle  metacarpal  bone,  and  the  others  articulate 
with  the  adjacent  metacarpals.  The  inner  surface  at  the  base  articu- 
lates with  the  trapezoid  bone,  and  above  with  the  scaphoid  bone.  The 
outer  surface  articulates  with  the  cuneiform  bone,  and  is  roughened 
below  at  the  fore  part  for  the  attachment  of  an  interosseous  liga- 
ment. 

The  unciform  bone,3  the  second  in  size,  and  the  last  of  the  second 
row  of  the  carpus,  is  remarkable  for  its  conspicuous  hook-like  process, 
which  is  directed  forward,  and  gives  attachment  to  the  anterior  annu- 
lar ligament.  The  dorsal  and  palmar  surfaces  are  large,  and  the  latter 
contributes  considerably  to  the  anterior  concavity  of  the  carpus.  The 
upper  part  of  the  bone  presents  a  sinuous  surface,  which  articulates 
with  the  lunar  and  cuneiform  bones ;  its  outer  surface  articulates  with 
the  magnum ;  and  the  broad  base  presents  two  facets,  which  articulate 
with  the  fourth  and  fifth  metacarpal  bones. 

The  bones  of  the  carpus  are  composed  of  spongy  substance  invested 
with  a  thin  layer  of  compact  substance,  which  on  the  dorsal  and  palmar 
surfaces  exhibits  variable,  more  or  less  conspicuous  nutritious  foramina 
communicating  with  the  interior.  At  birth  they  are  all  in  a  cartilagi- 
nous condition,  and  each  is  subsequently  ossified  from  a  single  centre. 
Ossification  commences  in  the  magnum  in  the  first  year,  in  the  unci- 


1  Os  trapezoides  ;  os  multangulum  minus  ;  os  pyramidale ;  os  trapezium  minus. 

2  Os  magnum  ;  os  capitatum  ;  capitate  bone. 

3  Os  unciforme  ;  os  hamatum  ;  os  cuneiforme. 


174  SPECIAL   ANATOMY    OF   THE    SKELETON. 

form  in  the  early  part  of  the  second  year,  in  the  cuneiform  in  the  third 
year,  in  the  lunar  and  trapezium  in  the  fourth  or  fifth  year,  in  the 
scaphoid  and  trapezoid  in  the  sixth  year,  and  in  the  pisiform  from  the 
eighth  to  the  twelfth  year. 

The  carpus,  composed  of  the  associated  bones  above  described,  forms 
the  basis  of  the  wrist.  Its  dorsal  surface  is  transversely  convex,  and 
its  palmar  surface  is  concave.  The  sides  of  the  concavity  are  formed 
externally  by  the  tubercles  of  the  scaphoid  and  trapezium ;  internally 
by  the  pisiform  bone  and  the  hook-like  process  of  the  unciform  bone. 
The  lateral  prominences  thus  produced  give  attachment  to  the  anterior 
annular  ligament,  which  converts  the  concavity  of  the  carpus  into  a 
canal  for  the  passage  of  the  tendons  of  the  flexor  muscles  accompanied 
by  the  median  nerve.  The  upper  part  of  the  carpus,  composed  of  the 
bones  of  the  first  row,  exclusive  of  the  pisiform  bone,  is  convex,  and 
forms  the  lower  part  of  the  radio-carpal  articulation,  or  wrist-joint. 
The  pisiform  holds  an  advanced  position,  and  is  excluded  from  the  joint. 
The  intermediate  articulation  of  the  two  rows  of  carpal  bones  is  hinge- 
like  ;  the  first  row  forming  a  median  concavity,  which  receives  a  median 
convex  prominence  of  the  second  row,  produced  by  the  magnum  and 
unciform  bone.  The  lower  border  of  the  carpus  forms  an  uneven, 
transverse  plane  articulating  with  the  metacarpus. 

THE  METACARPUS. 

The  metacarpus1  consists  of  five  bones  in  a  transverse  row,  ex- 
tending from  the  carpus  to  the  digits,  and  forming  the  basis  of  the 
palm  and  back  of  the  hand.  The  metacarpal  bones2  are  numbered 
from  the  outer  or  radial  side,  and  are  designated  by  number  or  from 
the  digit  appended  to  each.  They  are  of  different  lengths,  and  are 
slightly  bowed  with  the  concavity  forward,  and  their  expanded  ex- 
tremities are  most  produced  in  front,  so  as  to  contribute  to  the  concavity 
of  the  palm.  Their  upper  or  carpal  extremity  is  also  named  the  base,3 
and  their  lower  or  digital  extremity  the  head.4  The  first  metacarpal 
bone,  or  that  of  the  thumb,  is  most  unlike  the  others,  is  more  divergent 
from  the  carpus,  and  has  its  anterior  surface  directed  inwardly  towards 
the  others.  The  metacarpal  bones  of  the  fingers  are  slightly  divergent 
from  the  carpus,  where  they  articulate  with  each  other,  and  they  are 
alike  except  at  the  base,  which  varies  in  each  case. 

The  metacarpal  bones  of  the  fingers  are  proportionately  of  more 
slender  proportions  than  that  of  the  thumb ;  are  longer,  have  a  narrower 
more  cylindrical  shaft,  and  a  thicker  and  more  prominent  convex  head. 
The  shaft  is  somewhat  prismatic  and  expanded  towards  the  extremities. 
The  posterior  surface  exhibits  at  the  base  a  narrow  ridge,  gradually 
expanding  below  to  the  width  of  the  shaft  in  a  nearly  flat,  -triangular 

1  Middle-hand  bones.  2  Ossa  metacarpi. 

3  Basis.  *  Capitulum  ;  caput ;  condylus. 


SPECIAL,   ANATOMY   OF   THE   SKELETON. 


175 


PIG.  86. 


10 


area,  which  is  covered  by  the  expanded  extensor  tendons  as  they  pro- 
ceed to  the  fingers.  From  the  ridge  and  triangular  area  the  surface 
slopes  away  on  each  side,  and  is  slightly  depressed  to  accommodate  the 
dorsal  interosseous  muscles.  The  an- 
terior surface  presents  a  slight  me- 
dian ridge,  from  which  the  sides  incline 
to  the  lateral  borders  for  the  accom- 
modation of  the  palmar  interosseous 
muscles.  The  base  is  irregularly  cu- 
boidal,  is  tuberous  and  roughened 
for  ligamentous  and  tendinous  attach- 
ments, and  is  furnished  with  smooth 
facets,  which  articulate  with  the  carpus 
and  adjoining  metacarpal  bones.  The 
head  is  quadrate,  depressed  at  the 
sides  and  in  front,  and  ends  in  a  sphe- 
roidal eminence  which  articulates  with 
the  first  phalanx.  The  articulating 
surface  is  narrow  and  square  behind, 
widens  forward  beneath  and  in  front, 
and  in  this  position  is  prolonged  on 
a  pair  of  lateral  tubercles,  upon  which 
the  lateral  ligaments  play  in  the  flexion 
of  the  fingers.  Behind  the  lateral  de- 
pressions of  the  head  is  another  pair 
of  less  prominent  tubercles,  which  give 
attachment  to  the  lateral  ligaments. 

The  first  metacarpal  bone,1  or  that  of  the  thumb,  is  shorter  and 
broader  than  the  others,  and  of  more  robust  proportions.  The  shaft 
is  fore  and  aft  compressed  cylindrical,  and  more  prominent  laterally 
than  in  the  others.  Its  posterior  surface  is  flattened  convex,  the  an- 
terior surface  demi-cylindroid,  and  slightly  more  prominent  in  the 
median  line.  The  base  above  presents  a  large,  transversely  oval  facet, 
convex  from  side  to  side,  and  slightly  concave  fore  and  aft,  for  articu- 
lation with  the  trapezium.  The  head  is  less  prominently  convex  than 
in  the  other  metacarpals,  and  is  proportionately  less  thick  compared 
with  its  width. 

The  second  metacarpal  bone  is  the  longest  of  the  series,  and 
is  otherwise  slightly  larger  than  the  succeeding  ones.  The  base  is 
divided  above  by  a  notch  into  two  lateral  angular  portions,  which  are 
received  in  corresponding  intervals  of  the  trapezium,  trapezoid,  and 
magnum.  The  notch  forms  the  chief  carpal  facet,  is  fore  and  aft  con- 
vex and  transversely  concave,  and  articulates  with  the  trapezoid  bone, 
while  the  smaller  lateral  facets  articulate  with  the  trapezium  and  mag- 


THE  LEFT  HAND,  viewed  in  front,  or  on 
the  palmar  surface.  1,  scaphoid  bone ; 
2,  semilunar ;  3,  cuneiform  ;  4,  pisiform  ; 
5,  trapezium ;  6,  groove  in  the  latter ;  7, 
trapezoid ;  8,  magnum ;  9,  unciform ;  10, 
the  five  metacarpal  bones;  11,  first  row 
of  phalanges  of  the  fingers ;  12,  second 
row;  13,  last  row;  14,  15,  phalanges  of 
the  thumb. 


1  Os  metacarpi  pollicis. 


176  SPECIAL   ANATOMY  OP   THE   SKELETON. 

num.  Another  facet  on  the  inner  side  articulates  with  the  base  of  the 
third  metacarpal  bone.  A  transverse  tubercle  in  front  of  the  base  is 
the  point  of  insertion  of  the  tendon  of  the  radio-carpal  flexor,  and  a 
more  depressed  one,  outward  and  behind,  receives  the  tendon  of  the 
longer  radio-carpal  extensor. 

The  third  metacarpal  bone,  a  little  shorter  and  smaller  than  the 
former,  has  its  base  considerably  narrower  in  front  than  behind,  where 
it  exhibits  a  pyramidal  tubercle 1  fitting  into  an  angular  interval  of  the 
magnum  and  second  metacarpal  bone.  The  upper  surface  forms  a 
quadrate  facet  articulating  with  the  magnum ;  the  outer  side  presents 
a  fore  and  aft  concave  facet  for  the  second  metacarpal ;  and  the  inner 
side  two  oval  facets  for  the  fourth  metacarpal  bone.  Below  the  pyram- 
idal tubercle  is  a  slightly  roughened  prominence,  which  receives  the 
insertion  of  the  shorter  radio-carpal  extensor. 

The  fourth  metacarpal  bone,  shorter  and  smaller  than  the  pre- 
ceding, has  a  more  regular  quadrate  base,  the  upper  part  of  which 
presents  a  large  facet  for  articulation  with  the  unciform  bone,  and  a 
small  one  behind  for  the  magnum.  On  the  outer  side  it  presents  two 
oval  facets  for  the  third  metacarpal,  and  on  the  inner  side  a  concave 
facet  for  the  fifth  metacarpal  bone. 

The  fifth  metacarpal  bone,  the  shortest  except  that  of  the  thumb, 
and  otherwise  the  smallest,  has  the  back  of  the  shaft  with  but  one 
sloping  side  from  the  triangular  area.  The  base  exhibits  a  carpal  facet, 
fore  and  aft  convex  and  transversely  concave,  for  articulation  with  the 
unciform  bone,  and  a  smaller  facet  on  the  outer  side  for  the  fourth 
metacarpal  bone.  On  the  inner  side  it  exhibits  a  low  tuberosity, 
which  receives  the  tendon  of  insertion  of  the  ulno-carpal  flexor. 

The  metacarpal  bones  have  the  same  general  construction  as  the 
larger  long  bones,  and  like  them  include  a  medullary  cavity,  which  is 
shortest  in  the  metacarpal  bone  of  the  thumb.  Usually,  a  principal 
medullary  nutritious  foramen  is  to  be  observed  in  a  position  related 
with  that  in  which  it  exists  in  larger  bones.  In  the  metacarpal  of 
the  thumb  it  occupies  the  inner  side  of  the  shaft  below  the  middle,  and 
is  directed  downward.  In  the  other  metacarpals  it  usually  occupies 
the  outer  side  of  the  shaft  above  the  middle,  and  is  directed  upward. 
Not  unfrequently,  in  the  second  metacarpal,  it  occupies  a  position  on 
the  inner  side,  but  directed  upward. 

The  shaft  of  the  metacarpals  commences  ossification  near  the  end 
of  the  second  month  of  foetal  life,  and  is  ossified  throughout  at  birth. 
Epiphyses  are  formed  for  the  base  of  the  first  metacarpal  and  for  the 
head  of  the  other  metacarpals  from  the  third  to  the  fifth  year,  and 
ankylose  with  the  shaft  about  adult  age. 

1  Apophysis  pyramidalis  ;  processus  styloideus. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  177 

THE   DIGITS. 

The  digits  1  succeed  the  metacarpal  bones,  with  which  they  artic- 
ulate, and  consist  of  the  thumb,  or  pollex,2  and  fingers,  the  latter 
being  named,  in  order,  the  index,3  middle,4  ring,5  and  little  fingers.6 
The  thumb  consists  of  two  bones  or  phalanges,  and  in  addition  includes 
two  little  ones  named  sesamoid  bones :  the  fingers  each  consist  of  three 
phalanges. 

The  phalanges,7  or  joints,  of  the  digits  are  long  bones,  generally 
demi-cylindroid,  slightly  bent  forward,  tapering  below,  convex  behind, 
and  flattened  in  front.  They  end  in  expanded  extremities,  most  pro- 
duced forward  and  laterally,  and  with  the  upper  one  the  larger,  and 
named  the  base.  In  each  digit  they  successively  decrease,  and  are 
named  numerically ;  and  the  last  one,  from  its  supporting  the  nail, 
is  also  called  the  ungual  phalanx. 

The  first  phalanx  8  is  the  longest  and  otherwise  the  largest.  Its 
base  is  transversely  rounded  rectangular ;  it  is  nearly  flat  above,  with  a 
shallow,  concave  facet  for  articulating  with  the  head  of  the  metacarpal 
bone,  and  forms  an  obtuse,  somewhat  roughened,  ridge  at  the  sides  and 
front  for  the  attachment  of  the  anterior  and  lateral  ligaments  and 
tendons  of  the  interosseous  muscles.  The  lower  extremity  is  a  trans- 
verse cylinder,  grooved  like  a  pulley,  and  thus  forms  a  trochlea  for 
articulating  with  the  second  phalanx.  The  articular  surface  is  narrow 
and  half  oval  behind,  expands  to  the  width  of  the  trochlea  beneath, 
and  ascends  higher  in  front,  where  it  is  defined  by  a  transverse,  con- 
cave margin.  At  the  sides  is  a  slight  depression,  above  and  behind 
which  is  a  tubercle  for  the  attachment  of  a  lateral  ligament. 

O 

The  first  phalanx  of  the  thumb  is  not  bent  forward,  but  is  even 
slightly  concave  in  the  length  behind,  instead"  of  convex  as  in  the 
fingers;  and  the  fore  part  of  the  shaft  is  less  expanded  and  more 
obtuse  at  the  lateral  borders. 

The  second  phalanx9  of  the  fingers  has  a  transverse  oval  base 
ascending  from  the  sides  to  the  middle,  and  has  its  articulating  surface 
conforming  to  the  trochlea  of  the  first  phalanx,  with  a  pair  of  shallow 
concavities  separated  by  a  median  fore  and  aft  ridge.  The  shaft  and 
lower  extremity  are  like  those  of  the  first  phalanx,  except  that  in  the 
former  the  lateral  borders  are  more  strongly  impressed  for  the  attach- 
ment of  the  corresponding  tendon  of  the  superficial  digital  flexor. 

The  last,  or  ungual  phalanx,10  has  its  base  like  that  of  the  second 
phalanx  of  the  fingers,  but  is  flat  in  front  to  a  level  with  the  fore  part 
of  the  shaft,  and  roughened  for  the  insertion  of  the  corresponding 

1  Digiti ;  dactyli.  2  Digitus  primus. 

3  D.  secundus  ;  d.  index.  *  D.  medius  ;  d.  tertius  ;  d.  impudicus. 

5  D.  annularis  ;  d.  quartus.  6  D.  parvus  ;  d.  minimus  ;  d.  quintus. 

7  Nodi ;  internodia ;  articuli  ;  condyli.  8  Procondylus. 

9  Mesocondylus.  10  Metacondylus. 

12 


178 


SPECIAL   ANATOMY   OP   THE   SKELETON. 


tendon  of  the  flexor  muscle.  The  shaft  is  proportionately  more  taper- 
ing than  in  the  other  phalanges,  is  less  prominent  at  the  lateral 
borders,  and  ends  in  a  discoid  expansion l  with  a  wide  horseshoe-shaped 
roughness  on  the  front  surface. 

The  phalanges  of  the  middle  finger  are  successively  longer  than 
those  of  the  other  fingers ;  those  of  the  index  and  ring  fingers  differ 
but  slightly;  and  those  of  the  little  finger  are  shortest.  The  first 
phalanx  of  the  thumb  is  proportionately  the  most  robust,  but  is  no 
longer  than  that  of  the  little  finger ;  the  ungual  phalanx  is  the  most 
robust  and  the  longest. 

The  phalanges  have  the  same  construction  as  other  long  bones,  even 
to  the  possession  of  a  medullary  cavity.  The  medullary  nutritious 
foramen,  frequently  not  distinct  among  other  foramina,  is  commonly 
situated  at  the  outer  border  of  the  front  surface,  and  is  directed  down- 
ward. The  development  and  completion  of  the  phalanges  are  the  same 
as  in  the  first  metacarpal  bone. 

The  sesamoid  bones2  are  two  nodules  of  oval  shape  with  a 
smooth  facet  which  articulates  with  the  anterior  tubercle  on  each  side 
in  front  of  the  metacarpal  bone  of  the  thumb. 

AKTICULATIONS   OF  THE   UPPEE  LIMBS. 
The  upper  limb  articulates  with   the  rest   of   the   skeleton  only 
through  the  sternal  extremity  of  the  clavicle,  and  in  such  animals  as 
do  not  possess  the  latter,  as,  for  example,  the  horse,  it  has  no  liga- 
mentous  union  with  the  former. 


FIG.  87. 


THE  STEKNO-CLAVICULAK   AKTICULATION. 

This  is  formed  by  the  sternal 
end  of  the  clavicle  in  union  with  the 
upper  lateral  angle  of  the  sternum 
and  the  contiguous  portion  of  the 
first  costal  cartilage.  The  opposed 
surfaces  of  the  bones  are  invested 
with  cartilage,  and  a  disk  of  fibro- 
cartilage  is  interposed,  dividing  the 
joint  into  two  synovial  cavities.  The 
interarticular  fibro-cartilage 3  is 
thickest  at  the  margin,  especially 
above  and  behind,  where  it  is  at- 
tached to  the  clavicle ;  and  below  is  at- 
tached to  the  junction  of  the  sternum 
and  costal  cartilage,  and  elsewhere 
to  the  enclosing  ligaments.  A  loose  capsular  ligament  envelops  the 
joint,  connected  with  the  margins  of  the  articular  surfaces,  and 


STERNO-CLAYICULAR,  COSTO-CLAVICULAB, 
AND  COSTO-STERNAL  ARTICULATIONS.  1,  Cap- 
sular  ligament  of  the  sterno-clavicular  ar- 
ticulation; 2,  interclavicular  ligament;  3, 
costo-clavicular  ligament ;  4,  interarticular 
fibro-cartilage ;  5,  anterior  costo-sternal  liga- 
ments. 


1  Tuberositas  unguicularis. 

3  Cartilage  interarticularis  ;  c.  meniscoidea. 


2  Ossa  sesamoidea. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  179 

strengthened  by  accessory  bands.  The  two  stronger  of  these  are  the 
anterior  and  posterior  sterno-clavicular  ligaments,  passing  be- 
tween the  bones. 

A  variable  and  weaker  band,  the  interclavicular  ligament,1  is 
extended  between  the  clavicles  at  the  upper  border  of  the  sternum,  to 
which  it  is  connected.  Additional  strength  is  given  to  the  articulation 
by  the  costo-clavicular  ligament,2  a  short,  strong  band,  which  as- 
cends from  the  costal  cartilage  obliquely  outward  to  the  usually  well- 
marked  impression  beneath  the  sternal  extremity  of  the  clavicle. 

The  sterno-clavicular  articulation  is  the  centre  of  movement  of  the 
upper  limb  on  the  trunk,  and  admits  of  motion  in  all  directions.  The 
upward  and  forward  movements  are  limited  by  the  costo-clavicular 
ligament;  the  downward  and  backward  movements,  by  the  clavicle 
coming  into  contact  with  the  first  rib. 

THE  SCAPULO-CLAVICULAR  ARTICULATION. 

The  outer  end  of  the  clavicle  articulates  with  the  end  of  the  acro- 
mion  of  the  scapula,  the  joint  having  a  synovial  cavity  enclosed  by  a 
capsular  ligament,  of  which  two  stronger  bands  passing  between  the 
bones  above  and  below  form  the  superior  and  inferior  acromio- 
clavicular  ligaments.  The  joint  sometimes  includes  a  partial  or 
complete  interarticular  nbro-cartilage.  It  exhibits  limited  motion, 
consisting  of  gliding  of  the  clavicle  on  the  acromion,  and  a  backward 
and  forward  rotation  of  the  scapula. 

The  articulation  of  the  two  bones  is  greatly  strengthened  and  the 
motion  restrained  by  the  coraco-clavicular  ligament.3  This  consists 
of  two  bands,  which  ascend  from  the  tuberosity  at  the  root  of  the 
coracoid  process  of  the  scapula  to  the  rough,  oblique  impression  on  the 
under  surface  of  the  acromial  end  of  the  clavicle.  The  bands  widen 
and  diverge  in  their  ascent,  are  united  outwardly,  and  include  an 
angular  space  inwardly.  The  ligament  especially  limits  the  forward 
and  backward  movements  of  the  scapula  on  the  clavicle. 

THE   SHOULDER-JOINT. 

This  is  a  ball-and-socket  joint,  and  remarkable  for  its  great  range  of 
movement  in  every  direction.  It  has  for  its  basis  the  shallow  glenoid 
cavity  of  the  scapula,  upon  which  moves  the  large  hemispherical  head 
of  the  humerus.  The  articular  surfaces  of  both  bones  are  invested 
with  cartilage,  which  becomes  thicker  from  the  centre  to  the  circum- 
ference in  the  glenoid  cavity,  and  does  the  reverse  on  the  head  of  the 
humerus.  The  glenoid  cavity  is  further  deepened  by  the  glenoid 
ligament,  a  prismatic  fibre-cartilaginous  band  attached  around  the 
margin  of  the  glenoid  cavity  and  continuous  above  with  the  tendon  of 
origin  of  the  longer  head  of  the  brachial  biceps  muscle.  The  joint  is 

1  L.  interclaviculare.  2  Rhomboid  ligament. 

3  L.  coraco-claviculare  internum  et  externum  ;  conoid  and  trapezoid  ligaments. 


180 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


FIG.  88. 


enclosed  by  a  long,  loose  capsular  ligament,  attached  above  to  the  neck 
of  the  scapula  adjacent  to  the  glenoid  cavity,  and  below  to  the  neck  and 

tuberosities  of  the  humerus.  It  is 
thickest  above,  and  is  strengthened  in 
this  position  by  the  coraco-humeral 
ligament,  a  broad  band,  which  de- 
scends from  the  outer  border  of  the 
coracoid  process  to  the  front  of  the 
greater  tuberosity  of  the  humerus. 
The  looseness  of  the  capsular  ligament 
is  such  that  when  the  surrounding 
muscles  are  detached  the  head  of  the 
humerus  falls  an  inch  from  its  articu- 
lation with  the  glenoid  cavity.  When 
the  limb  is  in  the  usual  position  of 
rest,  the  ligament  forms  a  fold  at  the 
axillary  border  of  the  joint.  It  is 
greatly  strengthened  by  the  muscles 
in  contact  with  it,  the  supraspinous 
above,  the  infraspinous  and  small  teres 
behind,  the  subscapular  in  front,  and 
the  long  head  of  the  triceps  beneath. 
The  joint  is  further  strengthened  by 
the  tendon  of  the  longer  head  of  the 
biceps,  which  starts  from  the  summit 
of  the  glenoid  cavity,  descends  through  the  upper  part  of  the  joint, 
and  emerges  from  an  aperture  of  the  capsular  ligament  into  the  bi- 
cipital  groove  of  the  humerus.  The  synovial  membrane  lines  the 
capsular  ligament,  invests  the  glenoid  ligament,  is  reflected  in  a  tubular 
sheath  on  the  biceps  tendon  within  the  joint,  and  is  thence  prolonged 
upon  it  down  the  bicipital  groove.  A  synovial  bursa  between  the 
tendon  of  the  subscapular  muscle  and  the  capsular  ligament  commonly 
communicates  with  the  synovial  cavity  of  the  joint,  and  sometimes  a 
second  one  between  the  infraspinous  muscle  and  the  capsular  ligament. 
Greater  security  is  given  to  the  shoulder-joint  by  the  coraco-acromial 
arch  forming  the  upper  part  of  the  shoulder,  and  composed  of  the  acro- 
mion  united  to  the  coracoid  process  by  the  coraco-acromial  liga- 
ment,1 which  is  a  strong  triangular  band  attached  by  its  base  to  the 
outer  border  of  the  coracoid  process,  and  by  its  apex  to  the  end  of  the 
acromion.  Between  the  arch  and  the  supraspinous  muscle  is  placed  a 
synovial  bursa.2 

Motion  in  the  shoulder-joint  is  limited  when  the  limb  is  raised  from 
the  greater  tuberosity  coming  into  contact  with  the  acromion,  any  further 
elevation  being  due  to  movement  in  the  sterno-clavicular  articulation. 


SCAPT7LO-CLAVICULAR    AND     SCAPULO-HU- 
MERAL     ARTICULATIONS.       1,     ECrOmiO-Cla- 

vicular  articulation,  surrounded  by  its 
capsular  ligament ;  2,  coraco-clavicular 
ligament;  3,  coraco-acromial  ligament; 
4,  coracoid  ligament  converting  the  notch 
into  a  foramen ;  5,  capsular  ligament  of 
the  shoulder-joint ;  6,  coraco-humeral  lig- 
ament; 7,  tendon  of  the  brachial  biceps 
muscle. 


1  L.  triangulate  ;  1.  triquetrum. 


2  Subacromial  bursa. 


SPECIAL   ANATOMY    OF   THE   SKELETON.  181 


THE   ELBOW-JOINT. 

The  articulation  of  the  elbow  is  hinge-like,  and  in  the  flexion  and 
extension  of  the  forearm  the  bones  of  the  latter  move  upon  the 
humerus;  the  ulna,  with  its  sigmoid  fossa,  on  the  trochlea,  and  the 
head  of  the  radius  on  the  capitulum.  The  ulna  moves  only  in  this 
manner,  but  in  the  pronation  and  supination  of  the  hand,  the  head  of 
the  radius  rotates  both  on  the  capitulum  of  the  humerus  and  the  radial 
facet  of  the  ulna.  The  articular  cavity  between  the  humerus  and  the 
radius  and  ulna  communicates  with  that  between  the  latter  bones. 
There  is  no  direct  ligamentous  attachment  between  the  humerus  and 
radius,  but  the  capsular  and  external  lateral  ligaments  from  the  former 
are  connected  with  the  orbicular  ligament,  which  embraces  the  head  of 
the  radius  and  retains  it  in  position  without  interfering  with  its  move- 
ment of  rotation. 

The  orbicular  ligament *  is  a  strong  fibrous  band,  which  passes 
transversely  around  and  beneath  the  border  of  the  head  of  the  radius, 
and  is  fixed  by  its  ends  to  the  ulna  in  front  and  behind  the  radial  artic- 
ular facet. 

The  capsular  ligament2  of  the  elbow-joint  is  attached  to  the 
humerus,  in  front  and  behind,  between  the  epicondyles,  and  includes 
the  coronoid  and  olecranon  fossas  ;  and  below  it  is  attached  to  the  coro- 
noid  process  and  olecranon  bordering  the  sigmoid  cavity  of  the  ulna, 
and  to  the  orbicular  ligament  enclosing  the  head  of  the  radius.  The 
anterior  portion3  of  the  ligament  is  stronger  than  the  posterior  portion,4 
and  it  is  reinforced  by  strong  lateral  ligaments.  The  synovial  mem- 
brane of  the  joint  lines  the  capsular  ligament,  invests  the  coronoid  and 
olecranon  fossae,  and  extends  into  the  radio-ulnar  articulation,  where  it 
lines  the  orbicular  ligament  to  the  neck  of  the  radius. 

The  internal  lateral  ligament 5  is  a  broad  triangular  band,  with 
its  narrower  extremity  connected  with  the  fore  part  of  the  internal 
epicondyle,  and  with  its  fibres  radiating  below  to  be  fixed  along  the 
inner  side  of  the  olecranon  and  coronoid  process. 

The  external  lateral  ligament6  is  a  shorter  and  narrower  band, 
fixed  above  to  the  fore  part  of  the  external  epicondyle,  and  radiating 
below  to  become  continuous  with  the  orbicular  ligament  surrounding 
the  head  of  the  radius,  and  to  be  attached  behind  to  the  outer  part  of 
the  ulna. 

In  extension  of  the  forearm  the  fore  part  of  the  internal  lateral 
ligament  is  put  on  the  stretch  while  the  back  part  is  relaxed,  and  in 
flexion  the  condition  of  the  ligament  is  reversed. 

1  L.  orbiculare,  annulare,  or  coronarium.  2  Membrana  sacciformis. 

3  Anterior  ligament ;  1.  rectum  anticum. 

4  Posterior  ligament ;  1.  rectum  posticum  ;  1.  cubiti  posticum. 

5  L.  laterale  internum.  6  L.  laterale  externum  ;  1.  brachio-radiale. 


182 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


THE   RADIO-ULNAE  ARTICULATION. 

The  superior  radio-ulnar  articulation,  formed  between  the  head 
of  the  radius  and  the  contiguous  radial  articular  facet  of  the  ulna,  forms 
part  with  the  elbow-joint,  as  already  described. 

The  inferior  radio-ulnar  articulation,  formed  between  the  ulnar 
articular  surface  of  the  lower  extremity  of  the  radius  and  the  head  of 
the  ulna,  is  completely  separated  from  the  cavity  of  the  wrist-joint  by 


FIG.  89. 


FIG.  90. 


THE  ELBOW- JOINT,  LEFT  side,  viewed  antero- 
internally.  1,  the  capsular  ligament  in  front ; 
2,  internal  lateral  ligament ;  3,  orbicular  liga- 
ment ;  4,  oblique  ligament ;  5,  interosseousmem- 
brane ;  6,  internal  epicondyle. 


THE  SAME  ELBOW-JOINT,  viewed  externally. 
1,  external  supracondylar  ridge  of  the  hume- 
rus ;  2,  ulna ;  3,  radius ;  4,  external  lateral  liga- 
ment; 5,  6,  orbicular  ligament;  7,  8,  capsular 
ligament ;  9,  interosseous  membrane. 


a  triangular  nbro-cartilage.  This  is  attached  by  its  apex  to  the  pit 
beneath  the  head  of  the  ulna  at  the  root  of  the  styloid  process,  and  by 
its  base  to  the  ridge  defining  the  ulnar  articular  surface  of  the  radius 
from  the  carpal  articular  surface.  The  joint  is  enclosed  by  a  loose  cap- 
sular ligament,  which  is  attached  to  the  roughened  borders  contiguous 
to  the  articular  surfaces  of  the  ulna  and  radius,  and  to  that  of  the 
triangular  fibro-cartilage.  It  is  strengthened  in  front  and  behind  by 
narrow,  thin,  oblique  bands,  forming  the  anterior  and  posterior  liga- 
ments. It  is  lined  with  a  synovial  membrane,  which  is  usually  sepa- 
rate from  that  of  the  wrist-joint. 

The  wide  interval  of  the  bones  of  the  forearm  is  occupied  by  the 
interosseous  membrane,1  a  thin  aponeurosis,  which  is  mainly  com- 
posed of  bundles  of  fibres  descending  obliquely  from  the  acute  inner 

1  Interosseous  ligament;  membrana  interossea  ;  1.  interosseum. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  183 

border  of  the  radius  to  the  contiguous  border  of  the  ulna.  While  con- 
tributing strength  to  the  union  of  the  two  bones,  by  its  broad  surfaces 
it  affords  attachment  to  the  deeper  flexor  and  extensor  muscles  of  the 
forearm.  Above  the  membrane  is  a  large  opening,  which  permits  the 
play  of  the  tuberosity  of  the  radius  in  the  rotation  of  the  bone  on  the 
ulna.  The  lower  margin  of  the  opening  formed  by  the  interosseous 
membrane  is  commonly  reinforced  by  a  narrow  band,  the  oblique 
ligament,1  which  descends  from  the  base  of  the  coronoid  process  of 
the  ulna  to  the  radius  below  its  tuberosity.  Beneath  the  oblique  liga- 
ment an  aperture  in  the  interosseous  membrane  gives  passage  to  the 
posterior  interosseous  vessels ;  and  another  aperture  at  the  lower  ex- 
tremity of  the  membrane  transmits  the  anterior  interosseous  vessels  to 
the  back  of  the  forearm. 

In  rotation  of  the  radius  it  moves  on  the  capitulum  of  the  humerus 
and  on  the  upper  radial  articular  surface  and  the  head  of  the  ulna,  while 
the  latter  two  bones  remain  passive.  The  hand  accompanies  the  move- 
ment of  the  radius,  the  palm  alternately  assuming  a  backward  and  a 
forward  position,  or,  in  the  flexed  condition  of  the  forearm,  a  down- 
ward and  an  upward  position.  The  motion  in  which  the  palm  is 
turned  downward  or  backward  is  called  pronation,  and  is  produced  by 
the  rotation  of  the  radius  inwardly  and  obliquely  across  the  ulna. 
The  reverse  motion,  in  which  the  palm  is  turned  forward  or  upward, 
is  that  of  supination,  and  is  produced  by  the  rotation  of  the  radius 
outwardly  when  it  assumes  its  usual  position  parallel  with  the  ulna. 

ARTICULATIONS   OF   THE   HAND. 

The  hand 2  in  the  ordinary  position  occupies  the  same  plane  as  the 
forearm,  and  retains  this  in  the  rotation  of  the  radius,  but  in  the  move- 
ment of  the  wrist-joint  may  assume  a  nearly  right  angle  forward  or  back- 
ward, and  may  bend  to  a  less  degree  laterally.  The  dorsal  surface  of 
the  hand  is  slightly  convex,  the  palmar  surface  concave,  and  becomes  so 
in  greater  degree  in  flexion  of  the  fingers.  The  fore  part  of  the  meta- 
carpus forms  the  basis  of  the  palm  or  hollow  of  the  hand.  The  inter- 
spaces of  the  metacarpus,  named  interosseal,  are  occupied  by  the  inter- 
osseous muscles.  When  the  fingers  are  flexed  and  the  hand  closed,  as  in 
the  fist,  the  heads  of  the  metacarpal  bones  and  contiguous  bases  of  the 
phalanges  are  rendered  prominent  as  the  knuckles,  the  position  of  which 
accords  with  a  flexure  or  crease  at  the  anterior  third  of  the  palm.  The 
fingers  may  be  flexed  to  nearly  a  right  angle  with  the  metacarpus,  but 
extended  only  to  the  same  plane ;  and  when  extended  they  are  readily 
moved  laterally  or  from  and  to  one  another.  The  joints  or  phalanges 
of  the  fingers  are  readily  flexed  and  extended  in  the  same  manner  as 
these  are  on  the  metacarpus,  but  have  no  lateral  movement.  From  the 
construction  of  the  carpo-metacarpal  articulation  of  the  first  digit,  in 

1  Round  ligament ;  1.  obliquum  ;  1.  teres ;  1.  cubito-radiale  teres ;  chorda  trans- 
versalis,  transversa,  or  obliqua.  2  Manus. 


184 


SPECIAL   ANATOMY   OF   THE   SKELETON. 


FIG.  91. 


its  movements  it  is  rendered  readily  opposable  to  the  other  digits,  and 

is  thus  distinguished  as  the  thumb,  which  gives  to  the  hand  its  quality 

as  a  prehensile  organ. 

All  the  articulations,  including  the  lower  extremities  of  the  bones 

of  the  forearm,  the  carpus,  and  the  base  of  the  metacarpus,  appear  to 

be  invested  with  a  common  capsular 
ligament,  which  is,  nevertheless,  com- 
posed of  a  number  of  distinct  capsules, 
more  or  less  blended  on  account  of 
their  proximity  to  one  another. 

THE    WRIST-JOINT. 

This  is  formed  by  the  radio-carpal 
articulation,  consisting  above  of  the 
concave  articular  surface  of  the  radius 
continuous  with  the  triangular  fibro- 
cartilage  inwardly,  and  below  by  the 
scaphoid,  lunar,  and  cuneiform  bones, 
which  together  present  a  continuous 
convex  articular  surface.  The  joint  is 
closed  from  the  radio-ulnar  articulation 
by  the  intervening  fibro-cartilage,  and 
from  the  intercarpal  articulation  by 
short  interosseous  ligaments  between 
the  carpal  bones.  It  is  invested  with 
a  strong  capsular  ligament  lined  by 
synovial  membrane.  The  capsular  liga- 
ment is  regarded  as  consisting  of  the 
anterior  and  posterior  and  two  lateral 
ligaments. 

The  external  lateral  ligament  is  a 
short,  thick,  half-conoid  band,  attached 
by  its  apex  to  the  styloid  process  of  the 
radius,  and  by  the  base  to  the  outer 
tuberous  portion  of  the  scaphoid  bone, 
partially  extending  to  the  ridge  of  the 
trapezium  and  the  anterior  annular  liga- 
ment. 

The  internal  lateral  ligament  is  a 
rounded  cord,  longer  and  narrower  than 
the  former,  attached  above  to  the  styloid 
process  of  the  ulna,  and  below  to  the 
tuberous  inner  portion  of  the  cunei- 
form bone,  partially  extending  to  the 
pisiform  bone  and  the  anterior  annular  ligament. 

The  anterior  ligament  is  thick  and  strong,  and  consists  of  ob- 


LlGAMENTS  OF  THE  WRIST  AND  HAND, 

anterior  view.  1,  lower  part  of  the  inter- 
osseous  membrane ;  2,  lower  radio-ulnar 
articulation  enclosed  by  a  capsular  liga- 
ment; 3,  fore  part  of  the  radio-carpal 
joint  enclosed  by  a  capsular  ligament; 

4,  external  lateral  ligament  of  the  wrist ; 

5,  internal  lateral  ligament ;  6,  palmar 
portion  of  the  capsular  ligament  of  the 
carpus ;  7,  pisiform  bone  with  its  capsu- 
lar ligament ;  8,  palmar  portion  of  the 
capsular  ligament  connecting  the  car- 
pus with  the  base  of  the  metacarpus;  9, 
capsular  ligament  of  the  trapezium  and 
metacarpal   bone   of    the   thumb;    10, 
anterior    ligament  of    the   metacarpo- 
phalangeal  articulation  of  the  thumb; 
11,  external    lateral    ligament   of    the 
same ;  12,  anterior  ligament  of  the  cor- 
responding joint  of  the  index  finger, 
represented  as  removed   in   the  other 
fingers;  13,  lateral  ligaments  of  thesame 
articulation ;    14,    transverse    ligament 
connecting  the  heads  of  the  contiguous 
metacarpal  bones;  15,  16,  anterior  and 
lateral  ligaments  of  the  phalangeal  ar- 
ticulations. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  185 

liquely  intersecting  membranous  bands,  attached  above  to  the  anterior 
marginal  ridge  and  styloid  process  of  the  radius,  and  fibro-cartilage  con- 
necting this  with  the  ulna,  and  below  to  the  palmar  surface  of  the  carpus, 
mainly  to  the  bones  of  the  first  row.  The  posterior  ligament,  of  less 
strength  than  the  former,  likewise  consists  of  intersecting  membranous 
bands,  attached  above  to  the  posterior  marginal  ridge  of  the  radius,  and 
the  fibro-cartilage  connecting  this  with  the  ulna,  and  below  to  the  dorsal 
surface  of  the  carpus,  especially  to  the  bones  of  the  first  row. 

The  radio-carpal  articulation  permits  flexion  and  extension,  abduc- 
tion and  adduction,  and  also  circumduction,  but  not  rotation. 

THE  INTERCARPAL  AND  CARPO-METACARPAL  ARTICULATIONS. 

The  carpal  bones,  together  with  the  bases  of  the  metacarpal  bones, 
in  their  articulation  together  include  three  distinct  synovial  cavities, 
and  occasionally  a  fourth. 

The  principal  articular  cavity  is  formed  between  the  two  rows 
of  carpal  bones,  and  between  these  and  the  metacarpal  bones,  exclusive 
of  the  pisiform  bone  and  the  first  metacarpal  bone.  From  between 
the  two  rows  of  carpal  bones  the  cavity  extends  upward  between  the 
scaphoid  and  lunar  bone,  and  between  this  and  the  cuneiform  bone ; 
downward  between  the  carpal  bones  of  the  second  row  to  the  interval 
between  this  and  the  metacarpal  bones ;  and  thence  downward  between 
the  bases  of  these.  The  cavity  is  closed  above  from  the  wrist-joint  by 
two  short  interosseous  ligaments,  connecting  the  upper  contiguous 
portions  of  the  scaphoid  and  lunar  bone,  and  of  this  and  the  cuneiform 
bone ;  and  below  by  three  interosseous  ligaments,  connecting  the 
contiguous  metacarpal  bones.  Of  three  other  interosseous  liga- 
ments, connecting  the  carpal  bones  of  the  second  row,  a  small  one 
is  situated  between  the  lower  part  of  the  trapezium  and  trapezoid ; 
a  second  between  the  back  part  of  the  trapezoid  and  magnum ;  and 
the  third  and  largest  in  the  interval  in  front  of  the  latter  and  the 
unciform  bone,  and  connected  with  the  contiguous  portion  of  the  fourth 
metacarpal  bone.  Sometimes  an  interosseous  ligament  connects  the 
median  ridge  of  the  unciform  bone  below  with  the  contiguous  ridge  of 
the  fifth  metacarpal  bone,  and  separates  the  cavity  between  these  two 
bones  from  the  principal  one.  The  joint  is  invested  with  a  capsular 
ligament  lined  throughout  with  synovial  membrane.  The  capsular 
ligament  is  composed  of  short  bands,  which  pass  in  different  directions 
between  the  adjoining  bones  of  the  carpus  and  metacarpus  in  front  and 
behind,  where  the  bands  are  named  the  palmar  and  dorsal  ligaments. 
Thus  they  are  extended  transversely  between  the  bones  of  each  row  of 
the  carpus,  and  between  the  bases  of  those  of  the  metacarpus,  and 
longitudinally  and  obliquely  between  the  two  rows  of  carpal  and  the 
metacarpal  bones.  The  transverse  ligaments  are  stronger  than  the 
others,  and  the  dorsal  ligaments  are  also  generally  stronger  than  the 
palmar  ligaments.  Lateral  ligaments,  continuous  with  those  of  the 


186  SPECIAL  ANATOMY   OF   THE   SKELETON. 

wrist-joint,  occupy  the  sides  of  the  carpus ;  the  internal  extending 
from  the  cuneiform  to  the  unciform  bone,  partially  to  its  unciform 
process  and  to  the  base  of  the  last  metacarpal  bone  ;  the  external, 
from  the.  scaphoid  to  the  trapezium,  and  partially  extended  to  the  base 
of  the  first  metacarpal  bone. 

The  pisiform  bone  forms  an  independent  articulation  with  the  cunei- 
form bone,  the  opposed  surfaces  being  invested  with  cartilage,  and  the 
joint  enclosed  with  a  thin,  loose  capsular  ligament.  This  is  strength- 
ened by  a  dorsal  and  a  palmar  band,  and  the  articulation  is  further 
secured  by  the  partial  attachment  of  the  internal  lateral  ligament  of 
the  wrist  to  the  pisiform  bone  and  annular  ligament;  and  by  two  addi- 
tional bands  extending  from  the  pisiform  bone  to  the  process  of  the 
unciform  bone  and  to  the  base  of  the  fifth  metacarpal  bone. 

The  metacarpal  bone  of  the  thumb  likewise  forms  an  independent 
articulation  with  the  trapezium ;  the  joint  being  enclosed  in  a  loose  cap- 
sular ligament  extended  between  the  roughened  adjacent  surfaces  of 
the  two  bones,  and  lined  by  synovial  membrane. 

The  articulation  between  the  two  rows  of  carpal  bones  admits  of 
considerable  motion,  contributing  to  the  capability  of  flexion  and  ex- 
tension of  the  hand.  The  movements  of  the  other  articulations  of  the 
carpal  bones  with  each  other  and  with  the  metacarpus  are  of  a  very 
limited  character,  except  that  between  the  trapezium  and  the  first 
metacarpal  bone,  which  especially  provides  for  the  flexion  and  extension 
and  abduction  and  adduction  of  the  thumb. 

THE   METACARPO-PHALANGEAL  AND   THE   PHALANGEAL 
ARTICULATIONS. 

The  articulation  between  the  fingers  and  the  metacarpus  is  formed 
between  the  head  of  the  metacarpal  bones  and  the  base  of  the  first 
phalanges.  The  opposed  surfaces  of  the  bones  are  invested  with  car- 
tilage, and  each  joint  is  enclosed  in  a  capsular  ligament  lined  with  syno- 
vial membrane,  and  greatly  strengthened  fore  and  aft  by  the  closely- 
applied  flexor  and  extensor  tendons,  and  laterally  by  the  attachment 
of  the  tendons  of  the  interosseous  muscles. 

The  lateral  ligaments  are  strong  rounded  bands,  one  on  each  side, 
attached  above  to  the  posterior  tubercle  of  the  head  of  the  metacarpal 
bone,  and  below  to  the  ridge  at  the  side  of  the  base  of  the  first  pha- 
lanx. In  flexion  of  the  joint  they  move  on  the  anterior  articular 
tubercles,  and  become  tightly  stretched.  The  anterior  ligament  is  a 
fibro-cartilaginous  band  intimately  connected  with  the  former,  and 
grooved  in  front  for  the  passage  of  the  flexor  tendons  to  the  phalanges. 
It  is  thin  above,  where  it  is  connected  with  the  metacarpal  bone,  and 
gradually  thickens  below  to  its  attachment  with  the  base  of  the  pha- 
lanx. The  posterior  portion  of  the  capsular  ligament  is  a  thin  layer 
of  connective  tissue,  and  is  mainly  substituted  by  the  adjacent  extensor 
tendon  passing  over  the  joint.  The  synovial  membrane  lining  the  cap- 


SPECIAL   ANATOMY    OF   THE   SKELETON.  187 

sule  is  reflected  upward  in  front  between  the  articular  tubercles  of  the 
head  of  the  metacarpal  bone.  The  anterior  ligaments  of  the  meta- 
carpo-phalangeal  articulations  are  united  in  the  intervals  by  strong 
bands,  the  transverse  ligaments. 

The  movements  in  the  metacarpo-phalangeal  articulations  are  those 
of  flexion  and  extension  and  abduction  and  adduction  of  the  fingers. 

The  articulations  between  the  phalanges  are  formed  by  the  trochlea 
of  the  bones  above  with  the  paired  concave  surface  of  the  bones  below, 
and  are  provided  with  ligaments  closely  according  with  those  of  the 
metacarpo-phalangeal  articulations.  The  phalangeal  articulations  are 
hinge-like  joints,  and  admit  only  of  flexion  and  extension. 

BONES   OF   THE  LOWER  LIMBS. 

The  lower  limbs,  succeeding  the  bottom  of  the  trunk,  consist  each 
of  the  thigh,  the  leg,  and  the  foot.  The  hip-bone,  which  together 
with  its  fellow  and  the  sacrum  forms  the  ipelvis,  is  an  element  of  the 
lower  limb.  The  thigh  has  a  single  bone,  the  femur;  and  another, 
the  patella,  occupies  the  front  of  the  knee.  The  leg  has  two  bones, 
the  tibia  and  fibula;  and  the  foot  is  composed  of  three  parts,  corre- 
sponding with  those  of  the  hand :  the  tarsus  with  seven  bones ;  the 
metatarsus  of  five  bones ;  and  the  five  digits,  each  with  three  phalanges, 
except  the  first,  which,  like  the  thumb,  has  two  phalanges,  and  in  addi- 
tion a  pair  of  sesamoid  bones. 

THE  HIP  BONES. 

The  hip,  haunch,  or  innominate  bone  '  forms  part  of  the  pelvis, 
and  holds  the  same  relation  to  the  lower  limbs  that  the  scapula  does 
to  the  upper  limb.  It  is  immovably  articulated  with  the  sacrum  be- 
hind and  with  its  fellow  in  front,  and  just  in  advance  of  its  middle 
outwardly  it  forms  the  socket  of  the  hip-joint.  It  is  a  large,  broad, 
thick  bone,  constricted  at  the  middle,  and  in  shape  has  the  outline  of  a 
figure  of  eight.  It  is  usually  described  in  three  parts,  named  the  ilium, 
ischium,  and  pubis,  corresponding  with  the  separation  of  the  bone  in 
infancy  into  three  principal  portions,  which  subsequently  become  com- 
pletely ankylosed. 

The  ilium 2  is  the  upper  and  largest  portion  of  the  hip-bone,  and 
is  situated  below  the  lateral  wall  of  the  abdomen.  It  is  a  broad  plate, 
which  inclines  from  the  rest  of  the  bone  upward,  outward,  and  back- 
ward, and  terminates  above  in  an  expanded  and  thickened  border,  the 
crest.3  This  is  subcutaneous,  and  produces  the  prominence  of  the 
hip.  It  is  semicircular  and  sigmoid  in  its  course,  curving  inward  at 
the  fore  part  and  outward  at  the  back  part.  It  is  rounded,  and  is 
roughened  for  the  attachment  of  the  abdominal  and  erector  spinal 
muscles.  It  is  thicker  at  the  extremities,  and  especially  back  of  the 

1  Os  innominatum,  coxae,  anonymum,  or  pelvis  lateralis;  pelvic  bone. 

2  Os  ilium,  ilei,  or  ilion  ;  haunch  or  hip-bone.  3  Crista  ilei. 


188 


SPECIAL   ANATOMY    OF    THE   SKELETON. 


anterior  fourth,  where  it  forms  a  variable  angular  prominence  directed 
outward.  The  projecting  ends  of  the  crest  and  a  similar  pair  of 
processes  below,  separated  from  the  former  by  a  notch,  are  named 
the  iliac  spines,1  of  which  the  anterior  are  more  prominent  and 
tuberous  than  the  posterior.  The  anterior  superior  spine  2  gives 


FIG.  93. 


18 

INNER  VIEW  OF  THE  LEFT  HIP-BONE.  The  dotted 
line  indicates  its  division  into  three  parts:  1,  the 
ilium,  2,  the  pubis,  and  3,  the  ischium.  (1,  iliac 
fossa :)  4,  crest  of  the  ilium ;  5,  6,  anterior  superior 
and  inferior  spines ;  7,  8,  posterior  superior  and 
inferior  spines ;  9,  articular  surface  for  the  sacrum ; 
10,  rough  surface  for  the  attachment  of  ligaments. 
(2,  body  of  the  pubis:)  11,  symphysis;  12,  hori- 
zontal, and  13,  descending  ramus;  14,  pubic  crest; 
15,  pubic  spine ;  16,  pectineal  line.  (3,  plane  of 
the  ischium  :)  17,  ramus  of  the  ischium ;  18,  tu- 
berosity ;  19,  spine  of  the  ischium :  20,  ilio-pubic 
eminence ;  21,  obturator  foramen  ;  22,  great  sciatic 
notch ;  23,  small  sciatic  notch. 


OUTER  VIEW  OF  THE  LEFT  HIP-BONE.  1, 
ilium ;  2,  ischium ;  3,  pubis.  (1,  dorsal  sur- 
face of  the  ilium :)  4,  crest  of  the  ilium ;  5,  6, 
7,  middle,  inferior,  and  superior  curved 
lines;  8,  9,  anterior  superior  and  inferior 
spines;  10,  11,  posterior  superior  and  in- 
ferior spines.  (2,  body  of  the  ischium :)  12, 
spine  of  the  ischium ;  13,  great  sciatic  notch ; 
14,  small  sciatic  notch ;  15,  tuberosity  of  the 
ischium ;  16,  ramus  of  the  ischium.  (3,  body 
of  the  pubis:)  17,  horizontal  ramus  of  the 
pubis;  18,  descending  ramus;  19,  acetabu- 
lum ;  20,  obturator  foramen. 


attachment  to  Poupart's  ligament  and  the  sartorius  tendon ;  the  an- 
terior inferior  spine 3  to  the  ilio-femoral  ligament  and  femoral  rectus 
tendon ;  and  the  corresponding  posterior  spines  to  the  posterior  sacro- 
iliac  and  great  sacro-sciatic  ligaments.  Below  the  anterior  inferior 
spine,  extending  over  the  acetabulum  to  the  pubis,  is  a  concave  notch, 
which  accommodates  the  ilio-psoas  muscle ;  and  below  the  posterior 
inferior  spine  4  is  a  deep  concavity,  the  great  sciatic  notch,5  which 
extends  to  the  spine  of  the  ischium. 

The  inner  surface  of  the  ilium  is  divided  into  three  unequal  por- 
tions.    Of  these  the  upper  anterior  is  the  iliac  fossa,  a  broad,  smooth, 


1  Spinous  processes. 
8  Ant.  inferior  sp.  pr. 


2  Anterior  superior  spinous  process. 
*  Post.  inf.  sp.  process.          5  Incisura  ischiadica  major. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  189 

shallow  concavity,  which  forms  the  lateral  wall  of  the  upper  part  of 
the  pelvis.  It  commences  above  at  the  iliac  crest,  and  converges  below 
to  the  notch  within  the  position  of  the  anterior  inferior  spine.  The 
back  portion  of  the  inner  surface  is  an  irregular  vertical  plane,  at  the 
fore  part  of  which  is  the  sacral  articular  surface,1  reniform  in  outline 
and  uneven.  Behind  the  articular  surface,  the  area  extending  to  the 
iliac  crest  is  more  uneven,  and  gives  attachment  to  the  posterior  sacro- 
iliac  ligament.  The  third  and  smallest  portion  of  the  inner  surface 
of  the  ilium  forms  part  of  the  pelvic  cavity,  and  is  separated  from 
the  iliac  fossa  by  a  ridge,  which  is  part  of  the  ilio-pectineal  line. 

The  outer  surface,  or  dorsum,  of  the  ilium  looks  obliquely  out- 
ward, backward,  and  downward,  and  forms  the  basis  of  attachment  of 
the  buttock.  It  is  bent  in  the  course  of  the  crest,  and  is  crossed  by 
three  feebly-marked  lines,2  which  define  the  spaces  of  attachment  of 
the  gluteus  muscles.  The  superior  curved  line 3  is  the  shortest,  and 
proceeds  from  about  the  posterior  fourth  of  the  iliac  crest  backward 
and  downward  to  the  great  sciatic  notch.  The  middle  curved  line, 
the  longest  and  usually  best  marked,  proceeds  from  near  the  anterior 
part  of  the  iliac  crest  to  the  upper  part  of  the  great  sciatic  notch.  The 
inferior  curved  line  proceeds  from  the  notch  between  the  anterior 
iliac  spines  to  the  fore  part  of  the  great  sciatic  notch.  To  the  outer  side 
of  the  anterior  inferior  spine  a  shallow  groove  curves  backward  above 
the  acetabulum  for  the  attachment  of  a  tendon  of  the  femoral  rectus 
muscle. 

The  ischium  4  occupies  a  position  beneath  the  ilium  and  pubis,  and 
is  hook-shaped,  with  the  thicker  portion,  or  body,  behind,  and  the 
narrower  portion,  or  rarnus,  turning  up  in  front  to  join  the  descending 
ramus  of  the  pubis.  The  body  above  joins  the  ilium  and  pubis  in  the 
construction  of  the  acetabulum,  and  below  the  latter  is  produced  in  a 
conspicuous  prominence,  the  tuberosity.5  This  presents  outwardly  an 
uneven  convex  surface,  elliptical  in  outline,  widest  above  and  behind, 
and  tapering  beneath  to  the  ramus.  The  upper  part  of  the  surface  ex- 
hibits two  impressions,  of  which  the  higher  and  more  anterior  gives 
origin  to  the  semimembranosus  muscle,  and  the  succeeding  one  to  the 
semitendinosus  and  femoral  biceps  muscles.  The  lower  part  of  the 
tuberosity  gives  origin  to  the  great  adductor  muscle,  and  its  inner 
prominent  lip  affords  attachment  to  the  great  sacro-sciatic  ligament. 

Internally,  the  body  of  the  ischium  presents  a  deep  vertical  plane, 
bent  a  little  forward  behind,  and  forming  the  chief  part  of  the  lateral 
wall  of  the  pelvic  cavity.  From  its  back,  inner  border,  near  the  middle, 
projects  a  compressed  angular  process,  the  ischial  spine,6  which  forms 


1  Auricular  surface.  'l  Lineae  arcuatse. 

3  L.  arcuata  externa  ;  1.  semicircularis. 

4  Os  ischii ;  o.  coxendicis  ;  o.  sedentarium  ;  seat-bone  ;  hip-bone  ;  knuckle-bone  ; 
pin-bone  ;  chance-bone.  5  Tuberositas,  or  tuber  ischii.  6  Spina  ischii. 


190  SPECIAL,    ANATOMY    OF   THE    SKELETON. 

the  lower  limit  of  the  great  sciatic  notch,  and  gives  attachment  to 
the  small  sacro-sciatic  ligament.  Below  the  spine,  between  it  and  the 
ischial  tuberosity,  is  a  concavity,  the  small  sciatic  notch,1  which  is 
transversely  convex  and  slightly  grooved  for  the  play  of  the  tendon 
of  the  internal  obturator  muscle. 

The  back  of  the  ischium  above  the  tuberosity  is  a  convex  surface 
behind  the  acetabulum  and  bordering  the  great  sciatic  notch.  The 
outer  surface  of  the  ischium  below  the  acetabulum  extends  to  the 
lower  end  of  the  tuberosity,  and  borders  the  lower  part  of  the  obtu- 
rator foramen. 

The  ramus  of  the  ischium  2  is  a  flattened  bar,  ascending  obliquely 
forward  from  the  tuberosity  to  join  the  descending  ramus  of  the  pubis. 
Its  outer  or  back  border  is  acute,  and  contributes  to  form  the  obturator 
foramen.  Its  inner  or  front  border  is  thickened,  and  more  or  less 
everted  and  roughened,  for  the  attachment  of  the  crus  of  the  cavernous 
body  of  the  penis. 

The  pubis 3  occupies  a  position  in  advance  of  the  ilium  and  in  ad- 
vance of  and  above  the  ischium,  and  articulates  with  its  fellow  in  the 
symphysis.  It  is  the  smallest  of  the  three  portions  of  the  hip-bone, 
and  .consists  of  a  broader  intermediate  body,  with  a  horizontal  and  a 
descending  ramus.  The  body  is  a  thick  quadrate  plate,  slanting  from 
above  downward  and  backward.  Its  posterior  surface  looks  backward 
and  upward,  is  smooth,  and  forms  part  of  the  anterior  wall  of  the 
pelvic  cavity.  The  anterior  surface  looks  downward  and  outward,  is 
depressed,  and  gives  origin  to  muscles.  The  upper  border  is  thickened 
and  convex,  and  is  everted  so  as  to  form  a  transverse  obtuse  ridge,  the 
pubic  crest,4  the  inner  end  of  which,  with  the  anterior  border  of  the 
pubis,  forms  the  pubic  angle,  and  the  outer,  more  prominent  end 
forms  the  pubic  spine.5  The  inner  border  of  the  pubis  is  thick, 
roughened,  and  somewhat  projecting  behind.  Internally  it  exhibits  a 
vertical,  elliptical  articular  facet,  which  is  uneven,  and  is  united  with 
that  of  the  opposite  pubis  by  fibro-cartilage,  together  forming  the 
pubic  symphysis.6 

The  horizontal  ramus 7  proceeds  directly  outward  from  the  body 
to  join  the  ilium  and  ischium,  with  which  it  contributes  to  form  the 
acetabulum.  It  is  prismatic,  and  expands  outwardly  to  its  junction 
with  the  ilium,  with  which  it  forms  the  ilio-pubic  eminence,8  a  con- 
spicuous convex  prominence  above  the  fore  part  of  the  acetabulum. 
The  upper  surface  of  the  ramus  forms  a  transversely  concave  triangle, 
with  the  pubic  spine  as  its  apex  and  the  ilio-pubic  eminence  as  its  base. 
It  slopes  from  behind  downward  and  forward,  and  is  bounded  in  front 


1  Incisura  ischiadica  minor.  2  Kamus  ascendens. 

3  Os  pubis  ;  o.  pectinis  ;  pubic  bone  ;  share-bone.  *  Crista  pubis ;  pecten. 

5  Tuberculum  pubis.  6  S.  pubis.  '  Body  of  the  pubis. 

8  Tuberculum  ilio-pubicum  ;  ilio-pectineal  eminence. 


SPECIAL    ANATOMY  OF    THE   SKELETON.  191 

by  an  obtuse  ridge,  which  proceeds  from  the  pubic  spine  to  the  anterior 
border  of  the  acetabulum ;  and  behind  is  defined  by  a  more  acute  ridge, 
the  pectineal  line,1  which  proceeds  from  the  pubic  spine  outward  and 
backward  to  become  continuous  with  a  ridge  of  the  ilium,  forming 
together  the  ilio-pectineal  line.2  The  posterior  surface  of  the  ramus 
below  the  pectineal  line  forms  part  of  the  pelvic  cavity.  The  inferior 
surface  forms  the  upper  part  of  the  obturator  foramen,  and  is  outwardly 
grooved  obliquely  for  the  accommodation  of  the  obturator  vessels  and 
nerve. 

The  descending  ramus 3  of  the  pubis,  shorter  than  the  other,  is 
prolonged  from  the  body  downward  and  outward  to  join  the  ascending 
ramus  of  the  ischium,  to  which  it  conforms  in  shape.  The  outer 
border  of  the  pubis  between  its  rami  is  narrow,  and  forms  the  upper 
anterior  portion  of  the  obturator  foramen. 

The  acetabulum,4  or  socket  of  the  hip-joint,  is  situated  at  the 
outer  part  of  the  hip-bone,  in  the  thickest  portion  of  which  it  appears 
as  a  large  hemispherical  excavation,  looking  outward,  downward,  and 
forward.  It  is  bounded  by  a  prominent  acute  border,  which  is  inter- 
rupted at  its  inner  part  by  the  cotyloid  notch 5  communicating  with  an 
irregular  fossa6  at  the  bottom  of  the  acetabulum.  The  surface  of  the 
latter  extending  to  the  notch  and  embracing  the  fossa  is  smooth,  and 
is  invested  with  cartilage.  The  fossa  accommodates  a  cushion  of  con- 
nective and  adipose  tissue,  and  the  sides  of  the  communicating  notch 
give  attachment  to  the  round  ligament  of  the  hip-joint.  The  upper 
outer  portion  of  the  acetabulum,  comprising  two-fifths,  is  formed  by 
the  ilium,  the  lower  portion  about  the  same  extent  by  the  ischium,  and 
the  remaining  front  portion  by  the  pubis.  Before  ankylosis  of  the 
three  pieces  of  the  hip-bone,  their  conjunction  in  the  acetabulum  ap- 
pears as  a  triradiate  fissure  occupied  by  cartilage,  but  in  the  mature 
bone  the  fissure  is  commonly  completely  obliterated. 

Traces  of  the  original  separation  of  the  three  pieces  of  the  hip- 
bone are  frequently  to  be  observed  as  slightly  roughened  lines  crossing 
the  ilio-pubic  eminence,  and  internally  at  the  conjunction  of  the  ilium, 
ischium,  and  pubis. 

At  the  fore  part  of  the  hip-bone  is  a  large  opening,  the  obturator 
foramen,7  which  is  formed  by  the  pubis  and  ischium.  In  the  male  it 
is  obliquely  ovoid,  with  the  broader  pole  upward  and  forward  between 
the  rami  of  the  pubis,  and  the  narrow  pole  directed  to  the  lower  end 
of  the  ischial  tuberosity.  In  the  female  the  foramen  commonly  appears 
proportionately  shorter  and  wider  and  more  triangular  in  shape,  with 
the  base  of  the  triangle  between  the  rami  of  the  pubis. 

In  accordance  with  the  ordinary  sexual  differences,  the  hip-bone 


1  Linea  pectinea  ;  1.  arcuata.         2  Linea  ilio-pectinea.          3  Ramus  of  the  pubis. 

4  Cotyloid  cavity  ;  cotyle.  5  Incisura  acetabuli. 

6  Fossa  acetabuli.  7  F.  obturatorium,  or  obturatum  ;  f.  ovale. 


192  SPECIAL   ANATOMY   OF    THE   SKELETON. 

of  the  female  is  of  more  delicate  proportions,  less  thick  and  strong, 
and  less  marked  by  muscular  attachments  than  in  the  male.  In  addi- 
tion it  presents  other  differences  peculiar  but  variable.  Commonly, 
the  ilium  is  of  greater  proportionate  breadth  but  less  depth,  more 
extended  outwardly,  with  the  iliac  fossa  more  shallow,  and  the  great 
sciatic  notch  wider.  The  body  of  the  ischium  is  shorter,  its  inner  sur- 
face more  vertical,  its  spine  less  bent  forward,  and  the  ramus  narrower, 
flatter,  and  more  tapering.  The  body  of  the  pubis  is  of  less  depth  but 
greater  width ;  the  horizontal  ramus  is  longer  and  narrower,  and  the 
descending  ramus  more  tapering.  The  obturator  foramen  is  shorter 
and  is  wider  above,  so  as  to  assume  a  triangular  shape  with  rounded 
angles.  The  acetabulum  is  further  removed  outwardly  from  the  posi- 
tion of  the  symphysis. 

The  hip-bone  is  the  thickest  of  the  broad  bones,  and  like  the  others 
is  composed  of  interior  spongy  substance  invested  with  plates  of  com- 
pact substance.  At  the  central  part  of  the  iliac  fossa  the  bone  is 
thinnest,  and  in  this  position  is  frequently  devoid  of  spongy  substance 
and  is  translucent.  It  is  likewise  thin  at  the  bottom  of  the  acetabu- 
lum. It  is  most  conspicuously  porous  and  roughened  contiguous  to 
the  iliac  crest,  the  margin  of  the  acetabulum,  and  the  pubic  symphy- 
sis. More  conspicuous  nutritious  foramina  are  observed  in  these  posi- 
tions, but  several  of  the  largest  are  commonly  to  be  seen  at  the  back 
part  of  the  iliac  fossa,  on  the  dorsum  of  the  ilium  and  on  the  inner 
surface  of  the  body  of  the  ischium. 

The  hip-bone  is  developed  from  three  primary  centres,  of  which  that 
of  the  ilium  appears  about  the  end  of  the  second  month  of  the  foetus, 
that  of  the  ischium  in  the  third  month,  and  that  of  the  pubis  in  the 
fourth  month.  At  birth  the  three  pieces  are  conjoined  by  cartilage  in 
the  position  of  the  acetabulum,  and  the  ramus  of  the  ischium  is  united 
in  the  same  manner  to  the  descending  ramus  of  the  pubis.  The  pieces 
continue  to  grow  until  about  the  eighth  year,  when  the  ramus  of  the 
ischium  becomes  ankylosed  with  the  descending  ramus  of  the  pubis ; 
but  all  remain  connected  in  the  acetabulum  through  a  triradiate  carti- 
lage. This  commences  to  ossify,  about  puberty,  in  three  points  which, 
together  with  the  three  chief  pieces  of  the  bone,  become  ankylosed 
about  the  eighteenth  year.  After  puberty  osseous  epiphyses  make 
their  appearance  in  the  cartilaginous  crest  of  the  ilium,  on  the  anterior 
superior  and  inferior  iliac  spines,  the  ischial  tuberosity,  and  on  the 
pubic  symphysis  and  spine,  and  these  coalesce  with  the  rest  of  the 
bone  from  about  the  time  of  adult  age  to  twenty-five  years. 

THE   PELVIS. 

The  hip  bones,  together  with  the  sacrum,  including  the  coccyx,  com- 
pose the  pelvis,1  which  forms  the  basin-like  lower  portion  of  the  trunk. 

1  Gr.  pelus,  a  basin. 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


193 


FIG.  94. 


In  the  erect  position  of  the  body  the  pelvis  is  bent  obliquely  backward 
from  the  vertebral  column  above,  so  that  the  crest  of  the  pubis  descends 
nearly  to  a  level  with  the  end  of  the  sacrum.  It  is  divided  into  two  parts 
by  a  prominent  rim,  named  the  brim  of  the  pelvis,1  which  is  formed  on 
each  side  by  the  ilio-pectineal  line  continued  behind  the  crest  of  the  pubis 
and  by  the  curved  ridge  and  promontory  of  the  sacrum.  The  upper  part 2 
is  formed  by  the  ilia,  and  includes  the  widest  space  of  the  pelvis,  which 
pertains  to  the  abdom- 
inal cavity.  The  lower 
part  is  distinguished  as 
the  true  pelvis,3  and 
encloses  the  cavity  of 
the  pelvis.  It  is  a 
complete  bony  girdle, 
formed  by  the  sacrum 
and  coccyx,  the  is- 
chium  and  pubis,  and 
a  small  portion  of  the 
ilium.  The  upper  ex- 
tremity of  the  pelvic 
cavity,  corresponding 
with  the  brim,  is  the 
inlet,  or  superior 
strait ;  *  the  lower  ex- 
tremity is  the  outlet, 
or  inferior  strait.5 
In  consequence  of  the 
curvature  of  the  sa- 
crum and  coccyx,  the 
pelvic  cavity  appears 
as  a  curved  cylinder, 
slightly  narrowed  to- 
wards the  outlet.  It  is  longest  behind,  and  shortest  at  the  pubic  sym- 
physis.  Its  lateral  wall  is  deep  and  vertical,  and  constitutes  the  plane 
of  the  ischium  of  the  obstetrician.  It  extends  from  the  ilio-pectineal 
line  to  the  end  of  the  ischial  tuberosity,  and  is  mainly  formed  by  the 
body  of  the  ischium  with  small  portions  of  the  ilium  and  pubis. 

The  pelvic  inlet  is  cordiform,  with  the  notched  base  conforming 
with  the  base  of  the  sacrum,  and  the  rounded  apex  with  the  pubes. 
Its  transverse  diameter  is  greater  than  that  fore  and  aft,  and  its  plane 
inclines  forward  and  downward  at  an  angle  of  about  sixty  degrees. 

1  Linea  innominata;  1.  terminalis  ;  labrum  pelvis. 

2  Superior,  greater,  or  false  pelvis. 

3  Pelvis  vera  ;  p.  minor ;  inferior  pelvis. 

4  Apertura  pelvis  superior ;  angustia  abdominalis. 

5  A.  p.  inferior  ;  exitus  pelvis  ;  angustia  perinealis. 

13 


FRONT  VIEW  OF  A  FEMALE  PELVIS.  1,  last  lumbar  vertebra ; 
2,  intervertebral  ligaments;  3,  sacrum,  the  figure  being  placed 
below  its  promontory ;  4,  transverse  lines  indicating  the  original 
separation  of  the  sacrum  into  five  vertebral  segments ;  5,  end 
of  the  coccyx ;  6,  iliac  fossa ;  7,  8,  anterior  superior  and  infe- 
rior spines;  9,  acetabulum;  10,  cotyloid  notch;  11,  body 
of  the  ischium;  12,  tuberosity  of  the  ischium;  13,  spine  of 
the  ischium,  seen  through  the  obturator  foramen ;  14,  body 
of  the  pubis;  15,  symphysis  of  the  pubes;  16,  arch  of  the 
pubes ;  17,  crest  of  the  pubes ;  18,  spine  of  the  pubis ;  19,  pec- 
tineal  line ;  20,  ilio-pubic  eminence ;  21,  great  sacro-sciatic 
notch. 


194  SPECIAL    ANATOMY    OF   THE   SKELETON. 

The  outlet,  rather  smaller  than  the  inlet,  when  completed  by  the  great 
sacro-sciatic  ligaments,  has  the  same  shape,  with  the  notched  base 
formed  by  the  coccyx  and  the  apex  by  the  pubic  symphysis.  Its  fore 
part  is  the  pubic  arch,1  the  base  of  which  extends  between  the  ischial 
tuberosities ;  and  the  sides  are  formed  by  the  conjoined  rami  of  the 
pubes  and  ischia.  On  each  side  of  the  outlet  is  the  deep  sacro-sciatic 
notch,2  formed  in  front  by  the  ischium,  above  by  the  ilium,  and  behind 
by  the  sacrum  and  coccyx.  It  is  converted  into  the  great  and  small 
sciatic  foramina  by  the  sacro-sciatic  ligaments,  which  also  separate 
them  from  the  pelvic  outlet. 

The  axis  of  the  pelvis  conforms  to  the  curvature  of  the  pelvic  cavity. 
The  axis  of  the  inlet  is  directed  upward  and  forward  to  the  umbilicus ; 
that  of  the  outlet  is  directed  downward  and  forward. 

The  pelvis  of  the  female  not  only  differs  from  that  of  the  male  in 
accordance  with  the  usual  difference  in  other  parts  of  the  skeleton,  but 
also  exhibits  important  modifications  which  relate  to  the  sexual  func- 
tions. The  female  pelvis  is  proportionately  larger,  but  of  more  delicate 
construction.  It  is  proportionately,  and  often  absolutely,  of  greater 
breadth,  and  is  of  less  depth.  The  ilia  spread  more  laterally,  so  as  to 
produce  greater  breadth  or  prominence  of  the  hips  than  in  the  male. 
The  true  pelvis  has  greater  horizontal  capacity,  less  depth,  and  is  com- 
monly less  .curved  and  less  contracted  approaching  the  outlet.  The 
inlet  is  larger,  less  intruded  upon  by  the  sacral  promontory,  and  is 
more  circular  or  transversely  oval.  The  outlet  is  likewise  larger,  with 
the  ischial  tuberosities  less  convergent,  and  with  the  pubic  arch  wider, 
lower,  more  truly  arched,  and  with  the  sides  more  everted. 

In  the  male  the  sides  of  the  pubic  arch  are  much  stouter  than  in 
the  female,  and  are  strongly  ridged  at  the  anterior  border  for  the 
attachment  of  the  crura  of  the  penis.  In  the  female  they  are  nar- 
rower, more  flattened,  and  less  ridged  for  the  attachment  of  the 
clitoris. 

Great  variability  exists  in  the  size  and  conformation  of  the  pelvis  in 
different  individuals,  as  well  as  sexes.  Several  dried  and  usually  well- 
proportioned  male  and  female  pelves  exhibit  the  following  range  of 
measurements : 

Male.  Female. 

Breadth  of  pelvis  at  iliac  crests 10    to  11£  in.  9J  to  llf  in. 

Pore  and  aft  diameter  of  inlet 4     "    4£  <  4£  "    5     " 

Transverse  diameter  of  inlet 4|  "     5J  '  5J-  "    5J   " 

Oblique  diameter  of  inlet      5     "     5  '  6£  "    5i   " 

Depth  of  pelvic  cavity  behind 4£  "    4|  '  4J  "    4|   " 

Depth  of  pelvic  cavity  laterally 4J-  "    4|  '  3J  "    3|   " 

Depth  of  pelvic  cavity  in  front If  "     2  '  If  "    If-   " 

Fore  and  aft  diameter  of  outlet 3£  "    4£  '  3£  "    5     " 

Transverse  diameter  of  outlet 3£  "     4  '  3|  "    5     " 

1  Arcus  pubis.  *  Incisura  sacro-ischiadica. 


SPECIAL   ANATOMY   OP  THE   SKELETON. 


195 


AKTICULATIONS  OF  THE   PELVIS. 

The  hip  bones  are  immovably  articulated  with  the  sacrum  and  with 
each  other,  forming  the  sacro-iliac  articulation  on  each  side  behind, 
and  the  pubic  articulation  in  front. 

The  sacro-iliac  articulation  or  symphysis  is  formed  by  the 
lateral  articular  surface  of  the  sacrum  with  the  corresponding  surface 
of  the  ilium,  each  being  covered  by  a  thin  plate  of  fibre-cartilage.  The 
articulation  is  enclosed  by  ligamentous  bands,  which  form  the  sacro- 
iliac  ligaments. 

The  anterior  sacro-iliac  ligament *  is  thin,  and  is  composed  of 
short  fibrous  bands,  which  pass  between  the  contiguous  bones  in  front 
of  the  articulation. 


FIG.  95. 


FIG.  96. 


LIGAMENTS  OF  THE  PELVIS  AND  HIP-JOINT. 
1,  lower  part  of  the  anterior  vertebral  lig- 
ament ;  2,  pubic  symphysis ;  3,  ilio-lumbar 
ligament;  4,  sacro-iliac  symphysis,  with 
the  anterior  sacro-iliac  ligament;  5,  ob- 
turator membrane ;  6,  edge  of  the  tendon 
of  the  external  oblique  muscle  of  the  ab- 
domen, named  Poupart's  ligament ;  7,  ex- 
tension of  the  latter  along  the  pectineal 
line  named  Gimbernat's  ligament ;  8,  cap- 
sular  ligament  of  the  hip-joint;  9,  ilio- 
femoral  ligament. 


LIGAMENTS  OF  THE  PELVIS  AND  HIP-JOINT.  1,  pos- 
terior sacro-iliac  ligament ;  2,  great  sacro-sciatic 
ligament ;  3,  small  sacro-sciatic  ligament ;  4,  great 
sciatic  foramen ;  5,  small  sciatic  foramen ;  6,  coty- 
loid  ligament  surrounding  the  border  of  the  ace- 
tabulum ;  7,  round  ligament ;  8,  cut  edge  of  the 
capsular  ligament;  9,  obturator  membrane. 


The  posterior  sacro-iliac  ligament,2  much  thicker  and  stronger 
than  the  former,  is  composed  of  numerous  fibrous  bands,  which  pass 
between  the  contiguous  bones  in  the  deep  interval  behind  the  articu- 
lation. Several  of  the  bands  extend  between  the  iliac  crest  and  the 
irregular  surface  behind  the  sacrum,  and  others  descend  obliquely  from 
the  posterior  iliac  spines  to  the  latter. 


1  L.  sacro-iliacum  anterius ;  1.  pelvis  anticum. 

2  L.  sacro-iliacum  posterius ;   1.  sacro-iliacum  longum  et  breve ;    1.  ilio-sacrale 
interosseum. 


196  SPECIAL   ANATOMY   OF   THE   SKELETON. 

The  sacro-iliac  articulation  is  further  greatly  strengthened  by  the 
ilio-lumbar  and  sacro-sciatic  ligaments. 

The  ilio-lumbar  ligament l  is  a  strong  band  which  proceeds  from 
the  end  of  the  transverse  process  of  the  last  lumbar  vertebra  to  the 
contiguous  portion  of  the  crest  of  the  ilium,  the  base  of  the  sacrum, 
and  the  anterior  sacro-iliac  ligament. 

The  great  sacro-sciatic  ligament 2  springs  by  a  broad  expansion 
from  the  posterior  inferior  iliac  spine  and  the  margin  below  of  the 
sacrum  and  coccyx,  and  thence  converges  to  a  strong  band,  which 
descends  obliquely  outward  to  be  attached  by  a  narrow  expansion 
along  the  inner  lip  of  the  ischial  tuberosity  to  the  pubic  arch. 

The  small  sacro-sciatic  ligament3  springs  in  advance  of  the 
former  in  close  connection  with  it  from  the  margin  of  the  sacrum  and 
coccyx,  and  thence  converges  to  a  strong  band,  which  proceeds  out- 
ward and  forward  to  be  inserted  into  the  spine  of  the  ischium. 

The  sacro-sciatic  ligaments  convert  the  deep  sacro-sciatic  notch  into 
two  foramina.  Of  these  the  upper  is  the  great  sciatic  foramen/  a 
large,  oval  aperture,  formed  above  by  the  ilium,  in  front  by  the  ischium, 
and  behind  and  below  by  the  sacro-sciatic  ligaments.  Through  it  pass 
the  pyriformis  muscle,  and  the  gluteal,  sciatic,  and  pudic  vessels  and 
nerves.  The  small  sciatic  foramen,5  triangular  in  shape,  is  formed 
by  the  divergence  of  the  sacro-sciatic  ligaments  from  behind  and  the 
small  sciatic  notch  of  the  ischium  in  front.  It  gives  passage  to  the 
internal  obturator  tendon  and  the  pudic  vessels  and  nerves. 

The  articulation  of  the  pubes.  This  joint,  commonly  called  the 
pubic  symphysis,6  is  formed  by  the  union  of  the  pubes  through  a 
disk  of  fibre-cartilage,  which  is  connected  with  the  bones  by  means 
of  a  lamina  of  true  cartilage.  The  disk  has  a  disposition  to  divide,  as 
indicated  by  a  frequent  fissure  in  its  upper  back  part.  The  symphysis 
is  strengthened  by  short,  thin  fibrous  bands  passing  between  the  pubes, 
and  named" the  pre-,  post-,  supra-,  and  subpubic  ligaments,  the  last 
being  the  strongest,  and  rounding  off  the  summit  of  the  pubic  arch. 

The  obturator  membrane  T  closes  the  obturator  foramen,  except 
at  its  upper  outer  part,  where  it  leaves  a  considerable  aperture  for  the 
passage  of  the  obturator  vessels  and  nerve.  It  resembles  the  inter- 
osseous  membrane  of  the  forearm,  and  like  it  affords  an  attachment 
to  muscles. 

THE   FEMUK. 

The  femur,  or  thigh-bone,8  is  the  largest  and  longest  bone  of  the 
skeleton,  and  the  only  one  of  the  thigh.  In  the  erect  position  of  the 

1  L.  ileo-lumbale. 

2  L.  sacro-ischiaticum  majus  ;  1.  sacro-tuberosum  ;  1.  pelvis  posticum  magnum. 

3  L.  sacro-ischiaticum  minus  or  internum ;  1.  sacro-spinosum  ;  1.  pelvis  posticum 
parvum.  *  F.  ischiadicum.  6  F.  i.  minus. 

6  Synchondrosis  pubis.  7  Membrana  obturatoria.         8  Os  femoris. 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


197 


FIG.  97. 


body  it  inclines  from  its  articulation  with  the  hip-bone  inward  and 
slightly  backward  to  the  knee. 

The  shaft l  is  a  cylindrical  column  slightly  bent,  with  the  convexity 
forward,  and  moderately  expanded  at  the  extremities.     The  upper  ex- 
tremity terminates  in  the  neck,  surmounted  by  the  head,  and  in  two 
conspicuous  processes,  the  trochanters.     The 
lower  extremity,  more  expanded,  ends  in  a 
pair  of  large  articular   eminences,  the   con- 
dyles. 

The  intermediate  portion  of  the  shaft, 
narrowest  and  most  cylindrical,  is  produced 
behind  in  a  conspicuous  roughened  ridge,  the 
linea  aspera,2  along  the  sides,  or  lips,  of 
which  the  vasti  muscles  are  attached,  and 
between  them  the  adductor  muscles.  The 
projection  of  the  linea  aspera  and  the  slight 
flattening  of  the  shaft  in  front  give  to  this 
portion  of  the  bone  a  somewhat  prismatic 
form,  the  sides  of  which  are  completely 
covered  by  the  crureus  and  vasti  muscles. 
The  linea  aspera  forks  above  and  below  in 
a  pair  of  diverging,  less  prominent  ridges. 
Of  the  upper  ones,  the  outer  ridge  ascends 
to  the  great  trochanter,  and  for  several  inches 
of  its  course  is  conspicuously  roughened  for 
the  attachment  of  the  tendon  of  the  great 
gluteus  muscle.  The  upper  inner  ridge  as- 
cends in  advance  of  the  position  of  the  small 
trochanter,  and  marks  the  attachment  of  the 
internal  vastus  muscle.  Between  the  two 
upper  ridges,  a  less  conspicuous  one  below 
the  small  trochanter  gives  attachment  to  the 
pectineus  muscle.  The  lower  ridges  from 
the  linea  aspera  diverge  and  descend  to  the 
condyles,  whence  they  are  named  the  supra- 
condyloid  ridges.  They  include  a  triangular 
flat  surface,  which  forms  the  anterior  wall 3 

of  the  popliteal  space.  The  outer  ridge  is  the  more  prominent,  and 
the  inner  one  is  partially  interrupted  by  a  shallow  impression  which 
accommodates-the  femoral  artery. 

The  neck  of  the  femur  extends  from  the  proximal  extremity  of 
the  bone  obliquely  upward,  inward,  and  a  little  forward.  It  is  about 
as  long  as  it  is  broad,  cylindrical,  slightly  compressed  from  before 
backward,  and  narrowed  towards  the  middle.  It  is  widely  expanded 


FEMUE  OF  THE  RIGHT  SIDE, 
front  view.  1,  the  shaft ;  2,  head ; 
3,  neck ;  4,  great  trochanter ;  5, 
anterior  inter-trochanteric  ridge; 
6,  small  trochanter ;  7,  external, 
and  8,  internal  condyles;  9, 
external  epicondyle;  10,  groove 
for  the  popliteal  tendon ;  11,  in- 
ternal epicondyle. 


1  Body. 


2  Crista  femoris. 


3  Floor ;  planura  popliteum. 


198  SPECIAL   ANATOMY    OF    THE   SKELETON. 

at  the  base,  where  it  joins  the  shaft,  extending  between  the  trochanters. 
It  is  shortest  above  and  in  front,  and  is  longest  below.  The  posterior 
surface  is  somewhat  flattened,  and  is  commonly  crossed  horizontally  by 
a  feeble  groove,  which  accommodates  the  tendon  of  the  external  obtu- 
rator muscle. 

The  head 1  forms  the  greater  part  of  a  sphere  which  terminates 
the  neck,  and  is  the  highest  part  of  the  bone.  Its  surface,  most  ex- 
tensive above,  in  the  recent  state  is  covered  with  cartilage.  Below  and 
behind  its  centre  is  a  little  pit,2  which  gives  attachment  to  the  round 
ligament. 

The  great  trochanter s  is  the  stout,  irregular  quadrate  eminence 
which  terminates  the  shaft  outside  the  base  of  the  neck.  Its  upper 
posterior  angle  is  its  most  projecting  point,  or  summit,  and  curves  in- 
ward and  backward,  so  as  to  overhang  the  trochanteric  fossa,4  which 
is  a  deep  pit,  behind  the  trochanter,  for  the  insertion  of  the  tendon  of 
the  internal  obturator  muscle.  The  outer  surface  of  the  trochanter  is 
prominent,  convex  and  uneven,  is  impressed  at  its  fore  part  by  the 
insertion  of  the  small  gluteus,  and  from  the  summit  along  its  middle  by 
the  middle  gluteus.  Behind  the  latter  it  is  smooth,  for  the  play  over  it 
of  the  great  gluteus.  The  upper  border  forms  a  rough  ridge,  which 
curves  forward  and  inward  above  the  neck  to  its  fore  part,  where  it 
forms  a  more  prominent  eminence,  the  femoral  tubercle.  In  advance 
of  the  summit  the  ridge  is  impressed  by  the  insertions. of  the  pyriformis, 
external  obturator,  and  geminus  muscles.  The  posterior  border  of  the 
trochanter  is  a  thick  ridge  which  forms  the  upper  extremity  of  the  pos- 
terior inter-trochanteric  line. 

The  small  trochanter5  is  a  conical  eminence,  situated  behind  the 
shaft  below  the  neck.  Its  roughened  summit,  directed  inward,  gives 
insertion  to  the  psoas  muscle. 

In  front  of  the  femur  the  shaft  is  defined  from  the  neck  by  a  low, 
roughened  ridge,  the  anterior  inter-trochanteric  line,6  which  de- 
scends obliquely  from  the  femoral  tubercle  to  the  bottom  of  the  neck, 
in  advance  of  the  small  trochanter.  The  line  gives  attachment  to  the 
capsular  ligament  of  the  hip-joint,  and  to  the  upper  extremity  of  the 
conjoined  crureus  and  internal  vastus  muscles. 

Behind  the  femur  the  shaft  is  defined  from  the  neck  by  the  pos- 
terior inter-trochanteric  line,7  a  thick,  prominent,  and  smooth  ridge, 
which  curves  from  the  summit  of  the  great  trochanter  downward  and 
inward  to  the  small  trochanter. 

The  lower  extremity  of  the  femur,  more  expanded  than  the  upper, 
terminates  in  a  pair  of  large  articular  eminences,  the  condyles,  which, 

1  Caput  femoris.  2  Fossa  capitis.        3  T.  major. 

4  F.  trochanterica  ;  digital  fossa.  5  T.  minor. 

6  Linea  intertrochanterica  anterior  ;  1.  obliqua  femoris  ;  spiral  line. 

7  L.  i.  posterior ;  crista  intertrochanterica. 


SPECIAL    ANATOMY    OF   THE    SKELETON.  199 

in  the  normal  position,  are  on  the  same  level,  but  when  the  femur  is 
perpendicular  the  internal  condyle *  appears  longest,  or  extends  lowest. 
The  external  condyle 2  is  the  wider,  and  more  prominent  in  front,  and 
the  internal  condyle  is  more  prominent  internally.  The  condyles  pro- 
ject most  behind,  and  are  there  separated  by  a  deep,  square  notch,  the 
inter-condyloid  fossa,3  the  sides  of  which  are  impressed  by  the  attach- 
ment of  the  crucial  ligaments  of  the  knee-joint.  Below  and  behind,  the 
condyles  form  the  smooth,  convex  tibial  articular  surfaces,  which 
inwardly  incline  towards  each  other.  In  front  they  unite  with  the 
trochlea,4  which  is  a  broadly-grooved  articular  surface,  on  which  the 
patella  moves  upward  and  downward  in  the  extension  and  flexion  of 
the  leg.  The  trochlea  is  placed  bet  ween, the  condyles,  but  extends  more 
on  the  external  condyle,  both  vertically  and  transversely.  The  remote 
lateral  surfaces  of  the  condyles  are  convex  and  conspicuously  porous, 
and  are  produced  into  a  more  central  prominence,  the  epicondyle,5 
which  is  impressed  by  the  attachment  of  the  lateral  ligaments  of  the 
knee.  Below  the  outer  epicondyle  is  a  fossa,  which  is  prolonged  in  a 
groove  to  the  back  of  the  condyle.  In  the  recent  state  the  fossa  gives 
origin  to  the  tendon  of  the  popliteus  muscle,  and  the  groove,  invested 
with  cartilage,  accommodates  the  continuation  of  the  tendon.  Above 
the  inner  epicondyle  is  a  roughened  tubercle,  which  forms  the  lower 
extremity  of  the  corresponding  supracondyloid  ridge,  and  gives  in- 
sertion to  the  tendon  of  the  great  adductor  muscle.  Above  the  con- 
dyles behind  are  the  roughened  impressions  which  give  origin  to  the 
heads  of  the  gastrocnemius  muscle. 

The  chief  medullary  nutritious  foramen  is  commonly  situated  on 
the  linea  aspera,  about  the  upper  third  of  the  bone,  from  which  the 
canal  is  directed  very  obliquely  upward  to  open  into  the  medullary 
cavity.  Occasionally  a  second  foramen  is  situated  about  the  middle  of 
the  linea  aspera. 

The  shaft  of  the  femur  is  completely  enveloped  in  the  muscles  of 
the  thigh,  and  the  head  and  neck  are  deeply  situated.  The  great 
trochanter  is  covered  by  the  aponeurosis  of  the  great  gluteus  muscle, 
and  forms  the  most  prominent  part  of  the  hip.  The  condyles  at  the 
sides  of  the  knee  are  subcutaneous,  and  the  inner  is  the  more  promi- 
nent. The  trochlea  is  covered  by  the  patella,  but  becomes  covered  by 
the  extensor  muscles  when  the  limb  is  flexed. 

Ossification  commences  in  the  shaft  of  the  femur  in  the  seventh 
week  of  the  embryo.  A  centre  also  appears  for  the  lower  epiphysis 
before  birth,  and  another  for  that  of  the  head  during  the  first  year 
subsequently.  Centres  further  appear  in  the  trochanters, — about  the 
fourth  year  in  the  great  one,  and  about  puberty  in  the  small  one.  The 


1  Condylus  interims  or  medialis.  2  Condylus  externus  or  lateralis. 

3  F.  intercondyloidea.  *  Fossa  patellas ;  f.  intercondyloidea  anterior. 

5  Tubercle. 


200  SPECIAL   ANATOMY    OF    THE   SKELETON. 

small  trochanter  fuses  with  the  shaft  about  the  seventeenth  year,  and 
the  great  trochanter  a  year  later.  The  epiphysis  of  the  head  ankyloses 
with  the  shaft  about  the  eighteenth  year,  and  that  of  the  distal  ex- 
tremity near  adult  age. 

THE   PATELLA. 

The  patella,  or  knee-pan,1  is  a  chestnut-shaped  bone,  situated  in 
front  of  the  knee-joint,  which  it  contributes  to  form.     The  upper  border, 
or  base,  is  thick,  and  is  impressed  by  the  attachment  of  the  tendon  of 
the  quadriceps  extensor.     The  lower  border  is 
FIG.  98.  prolonged  in  an  obtuse   angular  process,  the 

apex,  which  gives  attachment  to  the  strong 
ligament  of  the  patella.  The  anterior  surface 
is  convex  and  longitudinally  striate,  for  the 
attachment  of  the  extension  of  the  quadriceps 
tendon.  The  posterior  surface,  except  on  the 
apex,  forms  a  transversely  oval  articular  facet, 
which  conforms  to  the  trochlea  of  the  femur, 

its  outer  Portion  being  the  more  extensive, 
facet  for  the  trochlea  of  the  The  base,  apex,  lateral  borders,  and  anterior 
femur;  3  apex  of  the  bone  f .  f  th  t  n  embedded  in  the 

roughened  for  the  attachment 

of  its  ligament.  tendon  of  the  quadriceps  extensor,  of  which 

the  patellar  ligament  is  a  continuation.     The 

articular  facet  is  invested  with  cartilage.  The  bone  is  composed  of 
uniform  spongy  substance,  with  a  thin  layer  of  compact  substance, 
especially  perforated  in  front  for  the  passage  of  nutrient  vessels. 

At  birth  the  patella  is  in  a  cartilaginous  state,  and  it  does  not  com- 
mence to  ossify  until  the  third  year.  It  commonly  is  developed  from 
a  single  centre. 

THE   HIP-JOINT. 

The  hip-joint,  formed  between  the  acetabulum  and  the  head  of  the 
femur,  is  a  ball-and-socket  joint,  and  is  one  of  the  most  movable  and 
strongest  of  the  articulations.  The  opposed  articular  surfaces  of  the 
bones  are  invested  with  cartilage,  which  is  thicker  centrally  on  the 
head  of  the  femur,  and  thinnest  at  the  circumference,  and  exhibits  the 
reverse  condition  in  the  acetabulum. 

The  acetabulum  is  rendered  deeper  and  is  somewhat  contracted  at 
the  mouth  by  the  cotyloid  ligament,  which  is  a  prismatic  fibre-carti- 
laginous band  attached  around  its  margin.  The  ligament  bridges  over 
the  cotyloid  notch,  where  it  is  reinforced  by  additional  fibres ; 2  and  it 
converts  the  notch  into  a  foramen,  which  communicates  with  the  joint, 
and  transmits  nutrient  vessels.  The  fossa  at  the  bottom  of  the  ace- 

1  Rotula ;  knee-cap  ;  os  scutiforme,  disciforme,  or  sesamoideum  magnum  ;  olecra- 
non  mobile. 

2  Transverse  ligament. 


SPECIAL   ANATOMY    OF   THE   SKELETON. 


201 


FIG.  99. 


tabulum,  extending  to  the  cotyloid  notch,  is  occupied  by  a  cushion 
of  connective  with  adipose  tissue,  invested  by  the  lining  synovial 
membrane  of  the  joint. 

The  capsular  ligament 
is  a  dense,  membranous,  cy- 
lindrical capsule,  enclosing 
the  joint.  Above,  it  is  at- 
tached around  the  margin 
of  the  osseous  acetabulum, 
enclosing  the  cotyloid  liga- 
ment, and  leaving  this  free, 
except  at  the  cotyloid  notch, 
where  it  is  connected  with 
it,  and  with  the  contiguous 
border  of  the  obturator  fora- 
men. Extending  downward 
and  enclosing  the  neck  of 
the  femur,  it  is  attached  be- 
low to  the  anterior  inter- 

•      T  u  LIGAMENTS  OF  THE  HIP.    1,  portion  of  the  posterior 

trochanteric  line,  the  root  sacro-iliac  ligament;  2,  the  great  sacro-sciatic  liga- 
ment ;  3,  the  small  sacro-sciatic  ligament ;  4,  the  great 
sciatic  foramen ;  5,  the  small  sciatic  foramen ;  6,  the 
cotyloid  ligament  surrounding  the  acetabulum ;  7,  the 
round  ligament;  8,  attachment  of  the  capsular  liga- 
ment of  the  hip-joint  to  the  neck  of  the  femur ;  9,  obtu- 


rator membrane. 


of  the  great  trochanter  at 

its  fore  part,  and  to  the  back 

of  the  neck  below  its  middle. 

It  is  much   thicker  at   the 

upper  and  fore  part  of  the 

joint,  where  the  greatest  strength  is  required,  and  is  longer  and  thin 

and  loose  at  its  lower  part.     It  is  chiefly  composed  of  longitudinal 

fibre-bundles,  with  others  both  oblique  and  transverse,  and  is  reinforced 

by  a  stout  accessory  band,  the  ilio-femoral  ligament,  which  extends 

from  the  anterior  inferior  iliac  spine  to  the  anterior  inter-trochanteric 

line. 

The  round  ligament *  is  a  strong  fibrous  cord,  which  is  attached  to 
the  pit  on  the  head  of  the  femur,  proceeds  inwardly,  and  expands  to  be 
attached  to  the  sides  of  the  cotyloid  notch.  It  is  enveloped  in  a  sheath 
of  the  synovial  membrane  extending  from  the  cushion  at  the  bottom 
of  the  acetabulum.  The  round  ligament  checks  the  outward  rotation 
of  the  femur,  and  also  its  adduction  in  the  flexed  position  of  the 
thigh. 

The  synovial  membrane  of  the  hip-joint,  starting  from  the  margin 
of  the  articular  cartilage  of  the  head  of  the  femur,  invests  the  neck, 
and  thence  lines  the  capsular  ligament,  invests  the  cotyloid  ligament  and 
the  cushion  of  the  acetabulum,  and  sheathes  the  round  ligament. 

The  hip-joint  is  closely  enveloped  with  muscles.  In  front  are  the 
psoas  and  iliacus,  with  a  synovial  bursa  between  them  and  the  capsular 


Ligamentum  teres. 


202 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


FIG.  100. 


ligament ;  above  are  the  femoral  rectus  and  small  gluteus ;  behind,  the 
pyriformis,  external  obturator,  geminus,  and  quadrate  femoral  muscles. 
The  arteries  of  the  joint  are  furnished  by  the  obturator,  sciatic, 
internal  circumflex,  and  gluteal  arteries.  The  nerves  are  derived  from 
the  sacral  plexus,  the  great  sciatic,  and  the  obturator  nerves. 

THE    BONES   OF   THE   LEG. 

These  consist  of  the  tibia  and  fibula,  which  in  the  erect  position  are 
placed  perpendicularly  side  by  side,  extending  from  the  knee  to  the 
ankle,  and  articulated  almost  immovably  together. 

THE   TIBIA. 

The  tibia,  or  shin-bone,1  the  larger  of  the  leg  bones,  and  next  in 
size  to  the  femur,  is  placed  in  front  and  at  the  inner  side  of  the  leg.  It 
has  a  prismatic  columnar  shaft,  with  the  upper, 
larger  extremity  or  head  articulating  with  the 
femur  and  forming  part  of  the  knee-joint,  and 
the  lower  extremity  articulating  with  the  foot 
at  the  ankle-joint. 

The  shaft  is  trilateral  prismatic  and  straight, 
expands  above  in  the  head,  and  gradually  nar- 
rows below  to  the  lower  fourth,  where  it  enlarges 
to  the  distal  extremity.  Its  three  surfaces  are 
defined  by  as  many  borders. 

The  anterior  border,  called  the  crest  or 
shin,2  commences  near  the  head  in  the  tuber- 
cle, whence  it  descends  as  a  prominent,  acute, 
flexuose  ridge  to  the  lower  fourth  of  the  shaft, 
where  it  subsides  in  a  smooth,  convex  surface 
extending  to  the  position  of  the  instep.  The 
ridge  curves  outwardly  above  and  inwardly 
below ;  and  it  serves  to  give  attachment  to  the 
deep  crural  fascia.  The  tubercle 3  is  an  oblong, 
obtuse  eminence  terminating  the  crest  above. 
Its  lower  part  is  roughened  for  the  attachment 
of  the  patellar  ligament ;  and  its  upper  portion 
is  impressed  with  a  smooth  facet,  which  accom- 
modates a  bursa  intervening  between  the  tuber- 
cle and  the  ligament.  The  internal  border 
of  the  shaft,  obtuse  and.  less  prominent  than 
the  former,  defines  the  internal  from  the  pos- 
terior surface.  Its  upper  expanded  extremity 
gives  attachment  to  the  internal  lateral  liga- 
ment of  the  knee-joint,  and  its  lower  extremity  subsides  in  a  con- 


n 


TIBIA  AND  FIBULA  OF  THE 

LEFT  LEG.  1,  shaft  of  the 
tibia;  2,  3,  tuberosities ;  4, 
spine ;  5,  tubercle ;  6,  crest 
or  shin ;  7,  lower  extremity 
of  the  bone ;  8,  internal 
malleolus;  9,  shaft  of  the 
fibula;  10,  its  head;  11,  ex- 
ternal malleolus. 


1  Focile  inajus  ;  canna  major.    "  Crista ;  spina.    3  Tuberculum ;  tuberositas ;  spina. 


SPECIAL,   ANATOMY    OF   THE   SKELETON.  203 

tinuous  convex  surface  common  to  the  outer  side  and  back  of  the 
shaft.  The  external  border  separates  the  external  from  the  pos- 
terior surface  of  the  shaft.  It  forms  an  acute  ridge,1  less  prominent 
than  that  of  the  crest,  and  subsiding  at  the  extremities.  It  gives  at- 
tachment to  the  interosseous  membrane,  which  is  extended  between 
the  tibia  and  fibula. 

The  internal  surface  of  the  shaft  is  nearly  flat  along  the  middle, 
and  wider  and  transversely  convex"  at  the  extremities.  Its  lower 
fourth  is  continuous  in  front  to  the  instep.  It  is,  for  the  most  part, 
subcutaneous,  except  at  the  upper,  broader  extremity,  where  it  is 
covered  by  the  tendons  of  the  sartorius,  gracilis,  and  semitendinosus 
muscles.  The  external  surface,  for  the  most  part  above,  is  directed 
outwardly,  and  is  depressed  along  the  posterior  border  approaching 
the  middle.  Its  lower  part  is  continuous  in  front  with  the  external 
surface  descending  to  the  instep,  and  is  covered  by  the  extensor  tendons. 
Its  upper  part  gives  origin  to  the  anterior  tibial  muscle.  The  posterior 
surface  is  transversely  convex,  and  at  the  lower  extremity  is  continu- 
ous with  the  external  surface.  Its  upper  part  is  crossed  by  a  slight 
ridge,  the  popliteal  line,2  which  descends  obliquely  from  the  fibular 
articulation  to  the  inner  border,  and  defines  a  triangular  space  above, 
for  the  attachment  of  the  popliteus  muscle.  Along  the  middle  of  the 
surface  is  an  obtuse  ridge,  which  defines  the  attachment  inwardly  of 
the  long  hallucal  flexor,  and  outwardly  of  the  posterior  tibial  muscle. 
The  lower  part  of  the  surface  is  covered  by  the  long  digital  flexor, 
long  pollical  flexor,  and  posterior  tibial  muscles. 

The  upper  extremity,  or  head,3  of  the  tibia  appears  as  a  hori- 
zontal, transverse  oval  disk  projecting  laterally  and  behind.  It  has  a 
thick,  porous  border,  and  its  convex  lateral  prominences  form  the  tu- 
berosities.4  Above  these  are  two  smooth  fore  and  aft  oval  facets, 
which  articulate  with  the  condyles  of  the  femur.  The  inner  somewhat 
narrower  facet  is  a  shallow  concavity,  while  the  outer  one  is  slightly 
concave  centrally  and  nearly  flat  or  convex  approaching  the  outer 
border.  They  are  separated  by  an  irregular  tract,  which  widens  in 
front,  and  back  of  the  middle  is  elevated  in  an  eminence  called  the 
spine.5  This  is  notched,  and  its  more  prominent  sides  form  the  most 
elevated  portion  of  the  contiguous  articular  facets,  and  give  attach- 
ment to  the  ends  of  the  semilunar  cartilages.  In  front  and  behind 
the  spine  is  a  rough  impression  for  the  attachment  of  the  ends  of  the 
crucial  ligaments  and  semilunar  cartilages.  The  front  of  the  head 
forms  a  flattened,  porous,  triangular  surface  extending  to  the  tubercle. 
Behind  the  head  the  tuberosities  are  separated  by  a  wide,  shallow  de- 
pression, the  popliteal  notch,6  which  is  impressed  by  the  posterior 

1  Crista  interossea.  2  Linea  poplitea  ;  1.  obliqua.  3  Caput  tibiae. 

4  Condyli  tibiae.      8  Spinous  process  ;  spina  media  ;  eminentia  intercondyloidea. 

6  Incisura  poplitea. 


204  SPECIAL   ANATOMY    OF   THE   SKELETON. 

crucial  ligament.  Behind  the  inner  tuberosity  is  a  transverse  depres- 
sion, which  gives  attachment  to  the  tendon  of  the  semimembranosus 
muscle.  Below  the  back  of  the  outer  tuberosity  is  a  smooth,  flat,  and 
nearly  circular  facet,  looking  downward  and  outward,  for  the  articula- 
tion of  the  fibula. 

The  lower  extremity  of  the  tibia,  much  the  smaller,  from  nearly 
cylindrical  becomes  quadrilateral,  and  on  the  inner  side  is  prolonged 
in  a  strong,  compressed  mammillary  process,  the  internal  rnalleo- 
lus.1  Below,  it  forms  a  smooth,  concave,  quadrate  surface,  with  a 
slight  fore  and  aft  ridge,  for  articulating  with  the  astragalus.  The 
articular  surface  is  narrower  inwardly,  and  is  there  extended  down- 
ward on  the  malleolus  to  articulate  with  the  inner  side  of  the  as- 
tragalus. The  front  surface  ends  in  an  obtuse  ridge  bordering  the 
ankle,  and  depressed  at  the  margin  for  the  attachment  of  the  capsular 
ligament.  The  back  surface  ends  in  a  similar  ridge,  which  is  slightly 
grooved  for  the  tendon  of  the  long  hallucal  flexor.  The  outer  surface 
forms  a  rough  depression,  to  which  is  attached  the  interosseous  liga- 
ment connecting  it  with  the  fibula,  and  the  depression  is  bounded  in 
front  and  behind  by  ridges,  which  give  attachment  to  the  correspond- 
ing tibio-fibular  ligaments.  The  lower  part  of  the  depression  is  some- 
times smooth,  and  in  the  recent  state  covered  with  cartilage,  for  articu- 
lation of  the  fibula.  The  inner  surface  of  the  tibia  is  prolonged  on  the 
malleolus,  and  is  there  prominently  convex  and  subcutaneous.  The 
malleolus  has  a  thick-ridged  border  for  ligamentous  attachment ;  and 
behind,  it  is  grooved  for  the  tendons  of  the  posterior  tibial  and  long 
digital  flexor  muscles.  Its  apex  outwardly  presents  a  depression,  for 
the  attachment  of  the  internal  lateral  ligament  of  the  ankle-joint. 

The  principal  medullary  nutritious  foramen  is  usually  found  at  the 
upper  third  of  the  tibia  below  the  popliteal  line,  with  its  canal  directed 
downward.  It  is  larger  than  the  corresponding  foramen  of  any  other 
bone. 

The  shaft  of  the  tibia  commences  to  ossify  about  the  seventh  week 
of  embryonic  life.  The  centre  of  the  epiphysis  of  the  head  appears 
about  birth,  and  that  for  the  lower  extremity  of  the  tibia  in  the  second 
year.  An  ossific  centre  sometimes  appears  for  the  tibial  tubercle.  The 
inferior  epiphysis  ankyloses  with  the  shaft  about  the  eighteenth  year, 
and  that  of  the  head  about  maturity. 

THE    FIBULA. 

The  fibula 2  is  a  slender  bone  nearly  as  long  as  the  tibia,  with  which 
it  articulates  at  the  outer  side  of  the  leg.  It  is  slightly  bent,  with  the 
convexity  backward  and  outward,  and  its  upper  extremity  or  head 
is  less  advanced  in  position  than  the  lower  extremity.  The  head  ar- 
ticulates with  that  of  the  tibia  behind  and  below  the  outer  tuberosity, 

1  Malleolus  internus  ;  m.  medialis  ;  inner  ankle-bone. 

2  Os  perone  ;  peroneum;  peroneal  bone  ;  splint- or  splinter-bone. 


SPECIAL,    ANATOMY    OF   THE   SKELETON. 


205 


FIG.  101. 


and  does  not  enter  into  the  formation  of  the  knee-joint.  The  lower 
extremity  articulates  with  that  of  the  tibia  externally,  and  is  prolonged 
below  it  in  a  conspicuous  process,  the  external  malleolus,  or  outer 
ankle,  which  contributes  to  form  the  ankle-joint. 
The  shaft  of  the  fibula  is  half  cylindroid  and 
prismatic,  and  presents  three  chief  borders  and 
surfaces.  The  anterior  border,  for  the  most 
part  acutely  prominent  and  obtusely  rounded  in 
front  of  the  head,  descends  from  this  to  the  fore 
part  of  the  external  malleolus.  The  external 
border,  least  prominent,  is  obtusely  rounded 
above,  and  becomes  acute  below.  Commencing 
at  the  outer  side  of  the  head,  about  the  middle 
of  the  shaft  it  turns  behind  inward  and  de- 
scends to  the  back  of  the  external  malleolus. 
The  internal  border,  for  the  most  part  promi- 
nently acute,  but  especially  along  the  middle  of 
the  shaft,  is  obtusely  rounded  at  the  extremities. 

The  internal  surface,  most  flattened  and 
depressed  the  greater  part  of  its  extent,  is 
crossed  very  obliquely  by  the  interosseous 
ridge,1  which  gives  attachment  to  the  in- 
terosseous membrane  extending  between  the 
fibula  and  tibia.  The  ridge  commences  above 
as  the  upper  part  of  the  anterior  border  of 
the  shaft,  and  below  is  continuous  as  the  lower 
part  of  the  internal  border.  The  depressed 
surface  behind  the  ridge  above  gives  attach- 
ment to  the  posterior  tibial  muscle,  and  the 
narrower  depressed  surface  in  front  and  below 
gives  attachment  to  the  extensors  of  the  toes. 
The  external  surface  of  the  shaft  is  convex, 
and  at  the  upper  half  is  continuous  with  the 
posterior  surface,  but  is  defined  from  it  below 
by  the  more  prominent  portion  of  the  exter- 
nal border.  It  is  for  the  most  part  covered  by 
and  gives  origin  to  the  peronei  muscles.  Its 
lower  extremity  exhibits  a  flattened,  triangular 
space,  which  is  subcutaneous,  and  is  defined  behind  by  a  line  descend- 
ing from  the  anterior  border  to  the  end  of  the  external  malleolus.  The 
posterior  surface  of  the  shaft  above,  continuous  with  the  external 
surface,  gives  attachment  to  the  soleus  muscle,  and  its  lower  part, 
directed  inward,  gives  origin  to  the  long  hallucal  flexor. 

The  head 2  of  the  fibula  is  rounded  quadrate,  and  presents  above 


TIBIA    AND    FIBULA    OF   THE 

EIGHT  LEG,  posterior  view.  1, 
2,  articular  surfaces  for  the 
condyles  of  the  femur  sepa- 
rated by  the  tibial  spine;  3, 
the  inner  tuberosity;  4,  sur- 
face occupied  by  the  popliteal 
muscle  defined  by  the  pop- 
liteal line,  5 ;  6,  nutritious  fora- 
men; 7,  surface  covered  by 
the  flexors  of  the  toes ;  8,  in- 
ternal malleolus;  9,  grooves 
for  tendons;  10,  interosseous 
ridge;  11,  head;  12,  subcuta- 
neous surface  at  the  lower 
part  of  the  bone ;  13,  external 
malleolus ;  14,  groove  for  ten- 
dons. 


1  Crista  interossea. 


2  Capitulum. 


206  SPECIAL    ANATOMY   OF   THE   SKELETON. 

an  oval,  flat  facet,  in  the  recent  state  invested  with  cartilage,  for  artic- 
ulating with  the  tibia.  The  border  of  the  head  is  obtusely  rounded  for 
attachment  of  the  tibio-fibular  ligaments,  and. externally  and  behind  it 
is  produced  in  a  conical  eminence,  the  styloid  process,1  which  gives 
attachment  to  the  external  lateral  ligaments  of  the  knee  and  the  tendon 
of  the  femoral  biceps  muscle. 

The  external  nialleolus 2  is  longer  and  more  prominent  than  the  in- 
ternal malleolus,  and  forms  the  outer  boundary  of  the  ankle-joint.  Ex- 
ternally, it  is  convex  and  subcutaneous,  and  is  continuous  with  the  trian- 
gular space  of  the  external  surface  of  the  shaft.  Internally,  it  presents  a 
triangular  smooth  facet,  which  is  covered  with  cartilage,  and  articulates 
with  the  outer  side  of  the  astragalus.  Behind  the  facet  is  a  concave  fossa 
extending  to  the  apex  of  the  malleolus,  which  gives  attachment  to  the 
external  lateral  ligament  of  the  ankle.  Behind,  the  malleolus  is  marked 
by  a  shallow  groove  for  the  tendons  of  the  peronei  muscles.  Above 
the  malleolus  internally  is  a  roughened  surface  for  articulation  with 
the  tibia ;  sometimes  partially  smooth  and  covered  with  cartilage. 

The  foramen  for  the  principal  medullary  artery  is  situated  on  the 
posterior  surface  of  the  shaft  above  the  middle,  its  canal  being  directed 
upward. 

The  head  of  the  fibula  is  prominent  at  the  outer  back  part  of  the 
knee ;  the  shaft  is  enveloped  by  muscles,  except  over  the  triangular 
surface  below  extending  on  the  external  malleolus,  which  is  also  promi- 
nently subcutaneous. 

In  the  ossification  of  the  fibula  a  centre  appears  in  the  shaft  in  the 
seventh  week  of  the  foetus ;  rather  later  than  in  the  tibia.  A  centre 
for  a  lower  epiphysis  appears  in  the  second  year  after  birth,  and  an- 
other for  an  upper  epiphysis  in  the  third  or  fourth  year.  The  lower 
epiphysis  ankyloses  with  the  shaft  about  the  twenty-first  year,  and  the 
upper  one  about  the  twenty-fourth  year. 

THE    KNEE-JOINT. 

This  is  the  largest  and  most  complicated  articulation  of  the  body, 
and  moves  as  a  hinge-joint.  The  articular  surfaces  of  the  bones  are 
those  of  the  femur,  the  tibia,  and  the  patella.  A  continuous  plate  of  car- 
tilage invests  the  condyles  and  trochlear  surface  of  the  femur,  and  sepa- 
rate plates  for  each  of  the  articular  surfaces  of  the  head  of  the  tibia 
and  of  the  patella.  The  head  of  the  fibula  does  not  enter  into  the 
construction  of  the  knee-joint,  though  it  affords  attachment  to  the 
external  lateral  ligament  of  the  latter.  The  surrounding  ligaments  of 
the  knee-joint  are  reinforced  by  a  superficial  fibrous  covering,  derived 
from  the  contiguous  tendons  and  fascia. 

The  function  of  an  anterior  ligament  to  the  knee-joint  is  performed 

1  Processus  styloideus. 

2  M.  externus ;  m.  lateralis  ;  outer  ankle-bone  ;  coronoid  process. 


SPECIAL,    ANATOMY   OF    THE   SKELETON. 


207 


FIG.  102. 


by  the  common  tendon  of  the  quadriceps  extensor  muscle,  which  is 
inserted  into  the  base  of  the  patella,  thence  envelops  this  bone,  except 
its  articular  surface,  and  forms  the  patellar  ligament.1  This  is  a 
strong,  flattened  cylindrical  band,  which  is  composed  of  longitudinal 
fibrous  bundles,  and  descends  from  the  apex 
of  the  patella,  to  be  inserted  into  the  lower 
part  of  the  tibial  tubercle.  Between  the 
upper  part  of  the  latter  and  the  ligament 
there  is  interposed  a  synovial  bursa,  which 
does  not  communicate  with  the  knee-joint. 

Interposed  between  the  articular  sur- 
faces of  the  femoral  condyles  and  those  of 
the  tibia  are  two  fibro-cartilages,  which  are 
named,  from  their  shape,  the  semilunar 
cartilages.2  These  are  crescentic,  and  thin 
away  from  their  exterior  border  to  a  sharp 
interior  edge,  which,  together  with  the 
upper  and  lower  surfaces,  is  free  and 
smooth,  and  conforms  to  the  articular  sur- 
faces of  the  femur  and  tibia.  Their  thick 
exterior  border  is  attached  to  the  contigu- 
ous part  within  of  the  capsular  and  lateral 
ligaments.  Their  extremities  assume  a  dis- 
tinctly fibrous  character,  and  are  firmly 
attached  in  the  interval  between  the  articu- 
lar surfaces  of  the  tibia,  and  they  are  conjoined  in  front  by  a  variable 
band,  the  transverse  ligament. 

The  external  semilunar  cartilage 3  forms  nearly  a  circle,  and  is 
of  greater  width  than  the  internal ;  and  its  extremities  are  fixed  in 
front  and  behind  the  tibial  spine,  between  the  ends  of  the  internal 
cartilage.  The  anterior  extremity  is  continuous  with  the  anterior  cru- 
cial ligament,  and  the  posterior  extremity  is  fixed  to  the  inner  tuber- 
osity  of  the  tibia  in  front  and  behind  the  attachment  of  the  posterior 
crucial  ligament.  The  external  semilunar  cartilage  externally  is  grooved 
by  the  passage  over  it  of  the  tendon  of  the  popliteal  muscle. 

The  internal  semilunar  cartilage,*  nearly  semicircular,  by  its 
anterior,  narrower  extremity  is  attached  in  front  of  the  inner  articular 
surface  of  the  tibia,  and  by  its  posterior  extremity  back  of  the  tibial 
spine,  between  the  attachment  of  the  external  cartilage  and  the  pos- 
terior crucial  ligament. 

The  crucial  ligaments 5  are  two  strong  fibrous  cords,  which  cross 


FRONT  VIEW  OF  THE  RIGHT 
KNEE-JOINT.  1,  tendon<of  the  quad- 
riceps extensor  muscle ;  2,  patella ; 
3,  ligament  of  the  patella,  or  ten- 
dinous insertion  of  the  muscle  just 
mentioned ;  4,  capsular  ligament ; 
5,  6,  internal  and  external  lateral 
ligaments ;  7,  superior  tibio-fibular 
articulation. 


1  Ligamentum  patellae. 

2  Cartilagines  semilunares  ;  c.  lunatse ;  c.  falcatse  or  falciformes  ;  fibre-cartilages  ; 
menisci. 

*  Meniscus  medialis. 


3  Meniscus  lateralis. 

5  L.  cruciata,  interossea,  or  obliqua. 


208 


SPECIAL    ANATOMY   OF   THE   SKELETON. 


each  other  near  the  centre  of  the  cavity  of  the  knee-joint,  and  con- 
nect the  femur  and  tibia.  They  are  extended  between  the  sides  of  the 
intercondylar  fossa  of  the  former,  and  the  tibia  in  front  and  behind  its 
spine. 

FIG.  103.  FIG.  104. 


THE  EIGHT  KNEE-JOINT,  laid  open  from 
the  front.  1,  articular  surface  of  the  femur ; 
2,  3,  crucial  ligaments ;  4,  insertion  of  the 
anterior  ligament  into  the  tibia ;  5,  attach- 
ment of  the  suspensory  ligament  to  the 
femur;  6,  7,  internal  and  external  semi- 
lunar  cartilages ;  8,  ligament  of  the  patella 
turned  down,  so  as  to  exhibit  the  synovial 
bursa,  9 ;  10,  superior  tibio-flbular  articu- 
lation ;  11,  interosseous  membrane. 


LONGITUDINAL  SECTION  OF  THE  KNEE-JOINT.  1, 
femur;  2,  tendon  of  the  quadriceps  extensor;  3, 
patella ;  4,  ligament  of  the  patella ;  5,  tibia ;  6,  syno- 
vial bursa ;  7,  cushion  of  fat  occupying  the  angular 
interval  between  the  patella  and  head  of  the  tibia ; 
******  reflections  of  the  synovial  membrane ; 
8,  pouch  of  this  membrane  extending  upward  be- 
tween the  tendon  of  the  quadriceps  extensor  and 
the  front  of  the  femur ;  9,  the  outer  alar  fold  of  the 
synovial  membrane ;  10,  suspensory  ligament ;  11, 
crucial  ligament ;  12,  posterior  ligament. 


The  anterior  crucial  ligament,1  the  smaller  one,  is  attached  to  the 
inner  back  part  of  the  external  condyle,  and  descends  outward  and  for- 
ward to  be  attached  to  the  depression  in  front  of  the  tibial  spine. 

The  posterior  crucial  ligament2  is  attached  to  the  outer  fore 
part  of  the  internal  condyle,  and  descends  backward  to  the  inner  side 
of  the  former  ligament,  to  be  attached  behind  the  tibial  spine. 

The  internal  lateral  ligament 3  is  a  long  band,  thicker  behind,  and 
is  situated  nearer  the  back  of  the  joint.  It  is  attached  above  to  the 
inner  epicondyle  of  the  femur,  and  below  to  the  inner  side  of  the  shaft 
and  tuberosity  of  the  tibia  for  several  inches.  It  is  intimately  con- 
nected with  the  internal  semilunar  cartilage. 

The  external  lateral  ligament 4  consists  of  a  short  band  of  fibres, 
reinforcing  the  capsular  ligament,  and  extending  from  the  lower  part  of 
the  outer  epicondyle  to  the  styloid  process  of  the  fibula.  The  tendon  of 
the  popliteal  muscle  passes  beneath  it.  The  accessory  lateral  liga- 


1  External  crucial  ligament ;  1.  cruciatum  anticum. 

2  Internal  crucial  ligament ;  1.  cruc.  posticum  or  medium. 

3  L.  laterale  internum.  *  L.  laterale  externum  breve. 


SPECIAL   ANATOMY   OF    THE    SKELETON.  209 

ment l  is  a  strong  round  cord,  attached  above  to  the  outer  epicondyle 
of  the  femur,  and  below  to  the  outer  part  of  the  head  of  the  fibula. 
It  divides  the  tendon  of  insertion  of  the  femoral  biceps  into  two  parts. 

The  capsular  ligament  of  the  knee-joint  in  front  is  mainly  substi- 
tuted by  the  tendon  of  the  quadriceps  extensor,  together  with  the 
patella  and  its  ligament.  In  the  intervals  of  these  and  the  lateral 
ligaments  it  is  thin,  and  is  formed  by  membranous  offsets2  from  the 
tendon  of  the  quadriceps,  which  extend  downward  and  backward,  to 
be  attached  to  the  condyles  of  the  femur,  the  semilunar  cartilages,  the 
lateral  ligaments,  and  the  heads  of  the  tibia  and  fibula.  These  lateral 
offsets  are  intimately  blended  with  the  investing  femoral  fascia.  The 
inner  offset  is  continuous  with  the  edge  of  the  patellar  ligament ;  but 
the  outer  offset  passes  behind  the  ligament,  to  be  attached  to  the  head 
of  the  tibia. 

The  posterior  portion  of  the  capsular  ligament,  usually  described  as 
distinct  under  the  name  of  the  posterior  ligament,3  is  a  strong  mem- 
branous intertexture  enclosing  the  back  of  the  joint  in  the  interval  of 
the  lateral  ligaments.  It  is  connected  to  the  femur  above  the  condyles 
and  intercondylar  fossa,  and  below  to  the  head  of  the  tibia,  and  is  inti- 
mately connected  with  the  semilunar  cartilages.  It  is  reinforced  by  a 
strong  fasciculus  derived  from  the  tendon  of  the  semimembranosus 
muscle,  proceeding  from  the  inner  tuberosity  of  the  tibia  to  the  cap- 
sule covering  the  external  condyle  of  the  femur. 

The  interval  at  the  fore  part  of  the  knee-joint,  between  the  head  of 
the  tibia  and  the  patellar  ligament,  is  occupied  by  a  cushion  of  con- 
nective and  adipose  tissue.  From  this  a  narrow  fibrous  band,  the 
suspensory  ligament,*  proceeds  upward  and  backward,  to  be  fixed 
to  the  fore  part  of  the  intercondylar  fossa. 

The  synovial  membrane  of  the  knee-joint  is  remarkable  for  its  ex- 
tent and  complexity.  Excepting  the  articular  surfaces  of  the  bones, 
it  invests  all  parts  of  the  cavity,  including  the  crucial  ligaments  and 
semilunar  cartilages.  From  the  capsular  ligament  behind  it  is  reflected 
upon  the  crucial  ligaments,  and  with  them  forms  a  partial  partition, 
separating  the  sides  of  the  cavity  of  the  joint.  At  the  upper  part  of 
the  latter,  in  front,  it  forms  a  large,  loosely-attached  pouch,  which,  in 
the  extended  condition  of  the  leg,  reaches  several  inches  above  the 
patella  and  femoral  trochlea,  beneath  the  tendon  of  the  quadriceps  ex- 
tensor, on  the  shaft  of  the  femur.  The  pouch,  being  attached  by  con- 
nective tissue  to  the  contiguous  structures,  is  drawn  down  in  the  flexion 
of  the  leg.  The  subcrureus  muscle  is  inserted  into  the  pouch.  At  the 
lower  part  of  the  joint  the  synovial  membrane  does  not  extend  below 

1  L.  laterale  externum  longum ;  1.  accessorium  laterale. 

2  L.  patellare  laterale  et  mediale. 

3  L.  posticum  Winslowi ;  1.  popliteum  or  obliquum. 

4  L.  mucosum  or  adiposum ;  1.  suspensorium  marsupii ;  1.  plicae  synov.  patellaris. 

14 


210  SPECIAL   ANATOMY   OF   THE   SKELETON. 

the  level  of  the  articular  surfaces  of  the  head  of  the  tibia.  In  this 
position  in  front  it  invests  the  connective-tissue  cushion  and  its  suspen- 
sory ligament.  From  this  the  membrane  is  reflected  on  each  side  in  a 
pair  of  conspicuous  falcate  and  irregularly-fringed  processes,  the  alar 
folds,1  which  extend  upward  on  the  capsular  ligament  at  the  sides 
of  the  patella,  sometimes  encircling  it.  Frequently  a  pair  of  semilunar 
folds  extend  from  the  same  point  horizontally  to  the  sides  of  the  joint. 
The  inner  surface  of  the  knee-cushion  and  the  pouch  above  the  femoral 
trochlea  are  more  or  less  conspicuously  villous,  and  often  to  a  remark- 
able degree.  From  the  back  of  the  joint  the  synovial  membrane  ex- 
tends into  a  groove  between  the  external  tuberosity  of  the  tibia  and 
head  of  the  fibula,  and  is  thence  reflected  on  the  tendon  of  the  popliteus 
muscle,  which  occupies  the  groove. 

The  ordinary  motion  of  the  knee-joint  is  hinge-like,  as  in  flexion 
and  extension  of  the  leg.  In  the  flexed  or  partially-flexed  condition 
of  the  leg  the  joint  allows  of  some  rotation,  inwardly  through  the 
action  of  the  popliteal  muscle,  outwardly  by  the  femoral  biceps.  The 
semilunar  cartilages  adjust  the  inequalities  of  the  femur  and  tibia,  and 
facilitate  the  movements  between  these  bones.  Incidentally  they  are 
of  service  in  moderating  the  jar  produced  in  jumping  or  falling  on  the 
feet.  The  crucial  ligaments,  while  firmly  uniting  the  femur  and  tibia, 
serve  also  to  restrict  the  movements  of  the  bones  in  different  directions. 
The  patella  gives  leverage  to  the  quadriceps  muscle  in  its  action  on  the 
tibia,  and  further  protects  the  knee-joint.  In  extreme  extension  of  the 
leg,  the  fore  part  of  the  condyles  of  the  femur  is  in  contact  with  the 
semilunar  cartilages  and  head  of  the  tibia ;  in  extreme  flexion,  the  back 
part.  In  the  act  of  flexion  the  tibia  and  semilunar  cartilages  together 
glide  back  on  the  condyles  of  the  femur.  In  extension,  the  patellar 
ligament  and  posterior  crucial  ligament  are  relaxed,  while  the  other 
chief  ligaments  are  rendered  tense ;  in  flexion,  the  former  are  put  on 
the  stretch,  and  the  latter  are  relaxed. 

AKTICULATIONS  OF  THE   TIBIA  AND  FIBULA. 

The  tibia  and  fibula  are  articulated  together  almost  immovably, 
are  connected  at  the  extremities  by  synovial  joints,  and  in  the  interme- 
diate position  by  an  interosseous  membrane,  which  also  serves  to  give 
attachment  to  the  muscles  of  the  leg. 

The  upper  tibio-fibular  articulation 2  is  formed  between  the  flat- 
tened, oval  articular  surfaces  of  the  head  of  the  fibula  and  external 
tuberosity  of  the  tibia.  It  is  enclosed  by  a  capsular  ligament,  re- 
inforced by  oblique  bands,  which  are  the  upper  anterior  and  poste- 
rior tibio-fibular  ligaments.3  The  synovial  membrane  of  the  joint 

1  Alar  ligaments  ;  lig.  alaria  externum  and  internum  or  minus  and  majus  ;  pro- 
cessus  aliforrnes  marsupium  patellare.  2  Superior  peroneo-tibial  articulation. 

3  L.  capituli  fibulae  ant.  et  post. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  211 

usually  communicates  with  that  of  the  knee-joint,  through  the  groove 
for  the  popliteal  tendon,  above  and  behind  the  head  of  the  fibula. 

The  lower  tibio-fibular  articulation1  is  formed  between  the 
lower  extremities  of  the  tibia  and  fibula.  The  opposed  surfaces  of  the 
bones,  for  the  most  part  roughened,  are  connected  by  short  intervening 
fibres,  which  form  the  interosseous  ligament.  They  are  smooth  at 
their  lower  border,  and  invested  with  cartilage  continuous  with  that 
of  the  ankle-joint.  Strong  flat  bands  descend  obliquely  from  the  emi- 
nences in  front  and  behind  the  tibia  to  the  external  malleolus,  forming 
the  lower  anterior  and  posterior  tibio-fibular  ligaments."  The 
latter  is  much  stronger  than  the  former,  and  is  inserted  into  the  fossa 
within  the  malleolus,  as  well  as  into  its  back  part.  The  synovial  cavity 
of  the  joint  ascends  as  a  narrow  cleft  from  the  ankle-joint  to  the  at- 
tachment of  the  interosseous  ligament. 

The  interosseous  membrane 3  is  a  strong,  bluish-white  aponeu- 
rosis,  extended  between  the  contiguous  borders  of  the  tibia  and  fibula, 
and  is  composed  mainly  of  parallel  fibres,  descending  obliquely  from 
the  tibia  to  the  fibula,  a  few  crossing  in  the  opposite  direction.  At  its 
upper  part  is  a  large  opening  for  the  transmission  of  the  anterior 
tibial  vessels,  and  its  lower  part  is  continuous  with  the  interosseous 
ligament  of  the  corresponding  tibio-fibular  articulation. 

THE  FOOT. 

The  foot  consists  of  three  divisions :  the  tarsus,  the  metatarsus,  and 
five  digits. 

THE    TARSUS. 

The  tarsus  forms  the  back  part  of  the  foot  and  the  instep,  and  con- 
sists of  seven  bones, — the  astragalus,  calcaneum,  scaphoid,  cuboid,  and 
three  cuneiform  bones. 

The  astragalus,  or  ankle-bone,4  is  the  uppermost  bone  of  the 
tarsus,  the  second  in  size,  and  the  only  one  of  the  foot  which  articu- 
lates with  the  bones  of  the  leg.  It  rests  beneath  on  the  calcaneum,  and 
articulates  in  front  with  the  scaphoid  bone.  Its  long  axis  is  fore  and 
aft,  and  it  is  of  less  height  than  transverse  breadth.  Its  posterior 
portion,  or  body,  is  irregularly  quadrate,  and  is  embraced  above  and 
at  the  sides  by  the  tibia  and  fibula,  with  which  it  forms  the  ankle-joint. 
The  upper  articular  surface,  for  the  tibia,  is  fore  and  aft  convex  and 
feebly  grooved,  and  is  transversely  nearly  straight.  Articular  sur- 
faces also  extend  downward  upon  the  sides  for  the  malleoli,  the  depth 
on  the  outer  side  being  more  than  double  that  on  the  inner  side. 

1  Inferior  peroneo-tibial  articulation. 

2  L.  malleoli  lateralis,  anterior  and  posterior. 

3  Membrana  interossea;  ligamentum  interosseum. 

4  Talus  ;  os  tessera  or  balista  ;  sling-bone  ;  huckle-bone. 


212 


SPECIAL    ANATOMY    OP   THE   SKELETON. 


Beneath  the  body  is  an  articular  surface  for  the  calcaneura,  concave 
obliquely  from  behind  forward  and  outward,  and  nearly  straight  in 
the  opposite  direction.  In  advance  of  the  body  a  conspicuous  pro- 
cess is  the  head,  which  is  separated  from 
the  former  by  a  somewhat  narrowed  and 
roughened  portion,  the  neck.  The  front 
of  the  head  presents  a  convex  articular  sur- 
face for  the  scaphoid  bone,  and  continuous 
with  it  beneath  is  a  narrower  articular  facet 
for  the  sustentacle  of  the  calcaneum.  Be- 
neath the  body  a  groove,1  widening  out- 
wardly in  a  fossa,  separates  the  two  calca- 
nean  articular  surfaces,  and  accommodates 
the  intertarsal  ligament,  which  connects 
the  astragalus  with  the  calcaneum.  The 
posterior  extremity  of  the  body  forms  a 
transverse  ridge,  which  is  grooved  for  the 
passage  of  the  tendon  of  the  long  hallucal 
flexor.  The  inner  side  of  the  body,  extend- 
ing forward  and  upward  on  the  head,  ex- 
hibits a  roughened  porous  surface  for  liga- 
mentous  attachment. 

The  calcaneum,  or  heel-bone,2  the 
largest  bone  of  the  tarsus,  forms  the  pos- 
terior extremity  of  the  foot,  at  its  fore  part 
above  supports  the  astragalus,  and  in  front 
articulates  with  the  cuboid  bone.  It  is  irreg- 
ularly oblong,  with  its  long  axis  fore  and 
aft,  and  its  depth,  for  the  most  part,  greater 
than  its  width. 

The  posterior  half  of  the  bone  forms  its  tuberosity,3  which  projects 
behind  the  ankle-joint  and  forms  the  prominence  of  the  heel.  The 
tuberosity  is  laterally  compressed,  cylindroid  and  quadrilateral,  and  ter- 
minates in  a  thickened  convex  knob,  which  is  roughened  below  for  the 
insertion  of  the  tendon  of  Achilles,  while  it  is  sloped  off  above  and 
smooth  for  the  reception  of  a  bursa  intervening  between  the  tendon 
and  the  bone.  Beneath,  the  tuberosity  is  produced  into  a  pair  of  emi- 
nences, the  internal  and  external  tubercles,4  of  which  the  former  is 
much  larger  than  the  latter.  The  upper  part  of  the  tuberosity  is  nar- 
rowest, is  convex  transversely,  and  concave  fore  and  aft,  and  corre- 
sponds with  the  interval  between  the  ankle-joint  and  the  Achilles 
tendon. 

The  calcaneum  above,  in  advance  of  its  tuberosity,  presents  a  large 


DORSAL  SURFACE  OF  THE  RIGHT 
FOOT.  1,  body  of  the  astragalus ; 
2,  its  head ;  3.  calcaneum ;  4,  sca- 
phoid bone ;  5,  6,  7,  ento-,  meso-, 
and  ectocuneiform  bones ;  8,  cu- 
boid bone;  9,  metatarsal  bones; 
10, 11,  phalanges  of  the  great  toe ; 
12, 13,  14,  phalanges  of  the  other 
toes. 


1  Sulcus  tali ;  s.  interarticularis. 
8  Tuberositas  ;  tuber  calcis. 


2  Os  calcis  ;  calcaneus  ;  calcar  pedis. 
4  Tuberosities. 


SPECIAL   ANATOMY    OF   THE   SKELETON. 


213 


FIG.  106. 


fossa  partially  resting  on  a  process,  the  sustentacle,1  which  overhangs 
the  inner  side  of  the  bone.  The  fossa  exhibits  two  articular  facets, 
separated  by  a  roughened  tract,  which  descends  obliquely  on  the 
sustentacle  and  widens  on  the  fore  part 
of  the  bone.2  The  posterior  larger  facet 
slopes  in  front  of  the  tuberosity  down- 
ward, forward,  and  outward,  is  convex  in 
its  descent,  and  nearly  flat  transversely, 
and  articulates  with  the  under  part  of  the 
body  of  the  astragalus.  The  anterior 
facet,  longer  and  much  narrower,  slopes 
in  the  same  direction  on  the  sustentacle, 
is  concave  in  its  descent,  and  flat  trans- 
versely, and  articulates  with  the  under 
part  of  the  head  of  the  astragalus.  The 
tract3  separating  the  facets  corresponds 
with  that  of  the  astragalus,  and  accom- 
modates the  strong  intertarsal  ligament 
connecting  the  two  bones. 

The  anterior  extremity  of  the  calca- 
neum  in  front  presents  a  vertical,  trilat- 
eral facet,  which  articulates  with  the 
cuboid  bone.  It  is  concave  from  above 
downward,  and  convex  transversely. 

The  outer  surface  of  the  calcaneum 
forms  an  uneven  vertical  plane,  which, 
for  the  most  part,  is  subcutaneous.  The 
inner  surface,  less  of  a  plane  vertically 
than  the  former,  between  the  tuberosity 
and  the  sustentacle,  forms  a  deep  con- 
cavity,4 which  is  directed  obliquely  down- 
ward and  forward,  and  accommodates  the 

flexor  tendons,  vessels,  and  nerves  in  their  course  from  the  back  of  the 
leg  to  the  sole.  At  the  fore  part  of  the  concavity,  beneath  the  sus- 
tentacle, is  a  curved  groove,  which  gives  passage  to  the  tendon  of  the 
long  hallucal  flexor. 

The  inferior  part  of  the  calcaneum  forms  a  thick,  transversely  con- 
vex ridge,  which  converges  from  the  tubercles  beneath  the  tuberosity 
to  an  anterior  tubercle,  which  gives  attachment  to  the  long  plantar 
ligament. 

The  scaphoid  bone 5  occupies  the  inner  part  of  tlfe  tarsus  in  front 


15 


15          16 
SOLE  OP  THE  LEFT  FOOT.     1,  COHCav- 

ity  of  the  calcaneum ;  2,  outer  face 
of  the  same ;  3,  groove  for  the  tendon 
of  the  long  hallucal  flexor;  4,  head 
of  the  astragalus ;  5,  scaphoid  hone ; 
6,  its  tuberosity ;  7,  8,  9,  ento-,  meso-, 
and  ectocuneiform  bones ;  10,  cuboid 
bone;  11,  its  groove  for  the  tendon 
of  the  long  peroneal  muscle ;  12, 
metatarsal  bones;  13,  first  row  of 
phalanges ;  14,  second  row ;  15,  third 
row;  16,  last  phalanx  of  the  great 
toe. 


1  Sustentaculum  tali ;  processus  lateralis  ;  lateral  or  lesser  process. 

2  Greater  process. 

8  Sulcus  calcanei ;  s.  interarticularis. 

4  Sinuosity.         5  Os  scaphoideum  or  scaphoides  ;  os  naviculare  ;  navicular  bone. 


214  SPECIAL   ANATOMY   OF   THE   SKELETON. 

of  the  astragalus  and  with  the  cuneiform  bones  in  front  of  it.  It  is 
transversely  ovoid  in  outline,  with  a  posterior,  elliptical  concave  artic- 
ular surface  for  the  head  of  the  astragalus,  and  a  convex  articular  sur- 
face in  front  divided  into  three  facets  for  the  cuneiform  bones.  The 
upper  and  lower  surfaces  are  roughened  for  ligamentous  attachment. 
The  outer  extremity,  usually  roughened  for  attachment  to  the  adjacent 
cuboid  bone,  occasionally,  also,  exhibits  a  small  facet  for  articulating 
with  the  latter.  The  inner  extremity  is  formed  by  a  thickened  tuber- 
osity,  which  is  directed  downward,  and  receives  the  insertion  of  the 
tendon  of  the  posterior  tibial  muscle. 

The  cuboid  bone l  occupies  the  outer  fore  part  of  the  tarsus,  ex- 
ternally to  the  scaphoid  and  cuneiform  bones,  and  in  advance  of  the 
calcaneum.  Behind,  it  presents  a  vertical,  trilateral  articular  surface 
for  the  latter,  and  in  front  another,  divided  into  two  facets  for  the  outer 
two  metatarsal  bones.  The  inner  surface  is  broad  and  uneven,  and  at 
its  upper  middle  portion  presents  an  articular  facet  for  the  ectocunei- 
form  bone.  The  remaining  roughened  portion  of  the  surface  gives 
attachment  to  interosseous  ligaments.  Sometimes  its  upper  portion 
presents  a  small  facet  for  articulation  with  the  scaphoid  bone.  The 
upper  surface  forms  a  roughened  plane  inclining  downward,  forward, 
and  outward.  The  inferior  surface,  broad  and  uneven,  is  crossed 
obliquely  from  without  inward  and  forward  by  a  ridge-like  tuber- 
osity,2  which  is  more  prominent  and  smooth  at  the  outer  extremity. 
In  advance  of  the  tuberosity  is  a  groove,3  which  accommodates  the 
tendon  of  the  long  peroneal  muscle,  while  a  patella-like  thickening 
of  the  tendon  plays  on  the  smooth  prominence  of  the  tuberosity.  Be- 
hind the  tubercle  the  surface  is  depressed,  and  gives  attachment  to  liga- 
ments. The  outer  shortest  border  of  the  bone  presents  a  notch,  which 
is  the  commencement  of  the  groove  beneath. 

The  cuneiform  bones,  named  from  their  wedge  shape,  form  a 
transverse  row  at  the  inner  fore  part  of  the  tarsus,  in  which  they 
occupy  the  most  advanced  position,  and  articulate  with  the  inner  four 
metatarsal  bones.  Their  upper  surface,  roughened  planes,  contributes 
to  form  the  convex  back  of  the  instep.  Their  posterior  border  forms 
a  transverse  curved  line ;  their  anterior  border  an  irregular  line,  most 
forward  with  the  entocuneiform  and  least  with  the  mesocuneiform 
bone. 

The  entocuneiform  bone,4  the  largest  of  the  series,  is  the  most 
advanced  in  position  of  the  tarsal  bones.  The  narrow  border  of  the 
wedge  is  directed  upward,  and  the  base  downward,  where  it  forms  a 
thick,  convex  tuberosity,  which  is  situated  at  the  inner  border  of  the 
tarsus  and  gives  insertion  to  the  tendons  of  the  tibial  muscles.  The 

1  Os  cuboideum  or  cuboides. 

2  Tuberositas  cuboidei.  3  Sulcus  peronei. 

4  Internal  cuneiform  bone ;  os  cuneiforme  internum  or  primum. 


SPECIAL   ANATOMY   OF   THE   SKELETON.  215 

upper  surface  looks  inwardly,  and  the  lower  surface  is  directed  out- 
wardly in  the  sole.  The  posterior  surface  presents  a  trilateral  concave 
facet,  which  articulates  with  the  scaphoid  bone ;  the  anterior  surface  a 
large  reniform  facet,  convex  from  above  downward  and  nearly  straight 
transversely,  for  articulating  with  the  first  metatarsal  bone.  The  sur- 
face just  beneath  the  upper  outer  border  exhibits  an  elliptical  articular 
facet  divided  into  two  portions  for  the  mesocuneiform  and  second  meta- 
tarsal bones. 

The  mesocuneiform  bone,1  the  smallest  of  the  series  and  less 
advanced  in  position,  has  its  nearly  square  base  upward,  and  its  narrow 
border  downward  in  the  sole.  The  opposite  sides  are  uneven,  and 
exhibit  smooth  facets  above  for  articulation  with  the  contiguous  cunei- 
form bones.  The  anterior  and  posterior  surfaces  exhibit  triangular 
vertical  facets  for  articulation  behind  with  the  scaphoid  bone,  and  in 
front  with  the  second  metatarsal  bone. 

The  ectocuneiform  bone 2  resembles  the  former  in  shape  and 
relative  position  of  the  wedge.  Its  base  above  presents  an  oblong 
rectangular  plane,  and  the  lower  narrow  border  of  the  bone  forms  in 
the  sole  a  thick  fore  and  aft  ridge  for  tendinous  and  ligamentous  attach- 
ment. Behind,  the  bone  presents  a  quadrate,  vertical  articular  surface 
for  the  scaphoid  bone.  A  similar  surface  in  front  articulates  with  the 
third  metatarsal  bone,  and  is  continuous  at  the  upper  angles  laterally 
with  small  facets  for  the  adjoining  metatarsal  bones.  The  lateral  sur- 
faces of  the  bone  are  broad,  uneven  planes,  which  present  an  articular 
facet  at  their  upper  back  portion  for  the  contiguous  cuboid  and  meso- 
cuneiform bones. 

THE  METATARSUS. 

The  five  bones  of  the  metatarsus  are  arranged  in  a  row  parallel 
with  one  another,  and  are  distinguished  by  number  according  to  their 
position  from  within  outward.  They  have  the  same  general  construc- 
tion as  the  metacarpal  bones,  with  a  trilateral  shaft,  in  each  case  a  dif- 
ferent base,  and  a  quadrate  hemispheroidal  head,  impressed  at  the  sides 
by  the  attachment  of  lateral  ligaments. 

The  first  metatarsal  bone,  shorter  than  the  others,  is  much  more 
thick  or  robust.  It  extends  farthest  forward,  but  not  so  far  back  as 
the  others.  It  is  much  longer  and  thicker  than  the  corresponding 
metacarpal  bone.  Its  shaft  is  trilateral  cylindroid,  and  is  less  com- 
pressed laterally  than  in  the  other  metatarsals.  Its  most  prominent 
borders  are  below,  external  and  internal.  The  upper  and  outer  surfaces 
are  transversely  convex  and  more  continuous ;  the  lower  surface  is  more 
flattened  and  inclines  inwardly.  The  base  forms  the  larger  extremity, 
is  vertically  oval,  and  presents  behind  a  reniform,  somewhat  concave, 


1  Middle  cuneiform  bone ;  os  cuneiforme  medium  or  secundum. 

2  External  cun.  bone  ;  os  cun.  externum  or  tertium. 


216  SPECIAL   ANATOMY   OF   THE   SKELETON. 

articular  surface  for  the  scaphoid  bone.  Its  lower  extremity  outwardly 
is  produced  in  a  tuberosity,  which  receives  the  insertion  of  the  ten- 
don of  the  long  peroneal  muscle.  The  head  is  square  hemispherical, 
with  its  convex  articular  surface  in  front  for  the  first  phalanx.  Below, 
the  articular  surface  presents  a  median  ridge,  and  on  each  side  a  pro- 
longation for  the  play  of  the  sesamoid  bones. 

The  remaining  four  metatarsal  bones,  larger  and  of  much  more 
slender  proportions  than  the  first  one,  are  also  more  nearly  like  one  an- 
other. They  slightly  and  successively  decrease  in  length,  and  extend 
farther  back,  but  not  so  far  forward  as  the  first  one.  In  comparison 
with  the  corresponding  metacarpal  bones,  they  are  of  more  nearly  the 
same  length,  more  slender,  and  have  the  shaft  more  tapering,  and  ending 
in  a  smaller,  laterally  compressed  head.  They  are  thickest  at  the  base, 
and  the  shaft  narrows  forward  to  within  a  short  distance  of  the  head. 
The  more  prominent  borders  of  the  shaft  are  above  and  below,  and 
the  lateral  surfaces  are  flattened  for  the  accommodation  of  the  inter- 
osseous  muscles.  The  base  is  larger  than  the  head,  and  deepest  verti- 
cally except  in  the  last  one,  in  which  the  greater  diameter  is  trans- 
verse. Beneath,  it  is  produced  in  a  roughened  tubercle  for  ligamen- 
tous  attachment.  The  head  is  quadrate,  deeper  than  wide,  and  with  a 
convex  articular  surface  notched  beneath. 

The  second  and  third  metatarsals  are  more  nearly  alike  than  they 
are  to  the  succeeding  ones,  which  also  more  nearly  resemble  each  other. 
The  base  is  unlike  in  all,  but  the  rest  of  the  bone  is  the  same,  except 
that  in  the  former  two  the  shaft  is  more  uniform,  and  in  the  latter  it  is 
more  spread  outwardly  approaching  the  base. 

The  second  metatarsal  has  a  triangular  base,  with  an  articular  facet 
behind  for  the  mesocuneiform  bone,  another  at  the  upper  angle  on 
the  inner  side  for  the  entocuneiform  bone,  and  a  pair  on  the  outer 
side,  each  usually  subdivided,  for  articulating  with  the  contiguous 
borders  of  the  ectocuneiform  and  third  metatarsal  bones. 

The  third  metatarsal  has  a  more  quadrate  base,  with  a  large  facet 
behind  for  the  ectocuneiform  bone,  and  usually  two  small  ones  on  the 
inner  side,  and  a  considerable  one  on  the  outer  side,  for  the  contiguous 
metatarsals. 

The  fourth  metatarsal  also  has  a  quadrate  base,  with  a  facet  behind 
for  the  cuboid  bone,  and  lateral  ones  nearly  as  large,  the  inner  for  the 
ectocuneiform  and  third  metatarsal,  and  the  outer  for  the  last  meta- 
tarsal. 

The  fifth  metatarsal  has  a  transversely  ovoid  base,  with  the  narrow 
extremity  produced  in  a  roughened  tuberosity,  which  is  directed  out- 
ward and  upward,  and  affords  insertion  to  the  short  peroneal  tendon. 
Internal  to  the  tuberosity  is  a  flat  facet  for  articulation  with  the  cuboid 
bone,  and  continuous  with  it  on  the  inner  side  another  facet  for  the 
contiguous  metatarsal  bone. 


SPECIAL   ANATOMY    OF   THE   SKELETON.  217 

THE   DIGITS. 

The  digits  of  the  foot  are  constructed  like  those  of  the  hand,  the 
first  one  of  two  phalanges,  with  a  pair  of  sesamoid  bones,  the  others 
each  of  three  phalanges.  The  digits  of  the  foot,  or  toes,  are  distin- 
guished by  number  in  succession.  The  phalanges  in  general  conform 
to  those  of  the  hand,  but  are  less  well  developed. 

The  phalanges  of  the  first  or  great  toe,  or  hallux,  differ  but 
slightly  in  length  from  those  of  the  thumb,  but  are  otherwise  of  much 
more  robust  proportion.  The  phalanges  of  the  other  toes  are  much 
smaller  than  those  of  the  fingers.  Those  of  the  first  row  have  their 
shaft  of  less  proportionate  width  to  their  depth,  so  that  they  appear 
more  narrowed  between  the  extremities.  In  the  succeeding  rows  the 
shaft  of  the  phalanges  is  generally  so  little  produced  as  to  appear 
but  little  more  than  a  constriction  between  the  extremities.  This  is 
especially  the  case  in  the  outer  two  toes;  and  sometimes  in  the  fifth, 
or  little  toe,  the  two  phalanges  are  ankylosed. 

The  sesamoid  bones  consist  of  a  pair  of  little  oval  bones,  which 
are  placed  beneath  the  head  of  the  first  metatarsal  bone,  with  which 
they  articulate,  and  enter  into  the  formation  of  the  first  joint  of  the 
great  toe.  They  are  embedded  in  the  tendons  of  the  short  hallucal 
flexor,  but  their  articular  surface  is  invested  with  cartilage.  Occasion- 
ally smaller  sesamoid  bones  are  found  in  a  corresponding  position  of 
the  other  toes.  They  also  occur  in  other  positions  in  the  tendons. 
Thus,  not  unfrequently  one  is  found  in  the  long  peroneal  tendon  where 
it  plays  over  the  tuberosity  of  the  cuboid  bone,  and  another  in  the 
tendon  of  the  posterior  tibial  muscle  near  its  insertion. 

THE   FOOT. 

The  foot  is  placed  at  a  right  angle  to  the  leg,  with  which  it  articu- 
lates at  the  posterior  third  to  form  the  ankle-joint,  and  thence  projects 
behind  to  form  the  heel.  It  is  narrowest  in  the  latter  position,  highest 
at  the  ankle-joint,  and  thence  spreads  laterally  and  slants  off  to  the 
toes. 

The  dorsurn,  or  back  of  the  foot,  is  convex,  and  inclines  chiefly 
forward  and  outward  from  in  front  of  the  ankle-joint,  or  instep,  which 
corresponds  with  the  fore  part  of  the  tarsus.  The  plantar  surface, 
or  sole,  extends  the  entire  length  and  breadth  of  the  foot,  and  is  con- 
cave or  arched.  The  extremities  of  the  arch  and  its  outer  part,  formed 
successively  by  the  calcaneum,  cuboid,  last  metatarsal  bone,  and  pha- 
langes, nearly  reach  a  level,  or  rest  on  the  ground.  The  inner  part  of  the 
arch  is  open,  and  forms  the  hollow  of  the  foot.  A  large,  irregular, 
funnel-like  passage,  the  tarsal  sinus,  traverses  the  tarsus  from  the 
outer  side  inward  and  backward,  between  the  astragalus  and  calcaneum. 
Its  fore  part  communicates,  between  the  two  latter  and  the  scaphoid 
and  cuboid  bones,  with  the  sole.  It  is  occupied  by  the  intertarsal  liga- 


218 


SPECIAL,   ANATOMY   OF   THE   SKELETON. 


merit.  A  large  interval  in  the  sole,  between  the  sustentacle  of  the 
calcaneum  and  the  scaphoid,  leaves  exposed  a  portion  of  the  anterior 
articular  surface  of  the  head  of  the  scaphoid  bone,  and  is  closed  by  the 
inferior  calcaneo-scaphoid  ligament. 

OSSIFICATION   OF   THE    BONES   OF  THE   FOOT. 

In  the  development  of  the  bones  of  the  foot,  the  centres  of  ossifi- 
cation make  their  appearance  at  different  periods.  A  centre  appears  in 
the  calcaneum  about  the  sixth  month  of  foetal  life,  and  one  appears 
for  an  epiphysis  to  the  extremity  of  the  tuberosity  not  until  about  the 
ninth  year  subsequently.  A  centre  for  the  astragalus  appears  about 
the  seventh  month ;  one  for  the  cuboid  about  the  time  of  birth ;  for 
the  ectocuneiform  in  the  first  year ;  for  the  entocuneiform  in  the  third 
year ;  and  for  the  mesocuneiform  and  scaphoid  about  the  fourth  year. 
The  epiphysis  of  the  calcaneum  coalesces  about  the  sixteenth  year. 
The  metatarsals  and  phalanges  accord  in  their  development  with  the 
corresponding  bones  of  the  hand,  though  the  ossification  and  coales- 
cence of  epiphyses  may  occur  a  little  later. 

ANKLE-JOINT. 

The  ankle-joint,1  or  ankle,  is  formed  by  the  distal  ends  of  the 
tibia  and  fibula,  embracing  the  upper  and  lateral  articular  surfaces  of 
the  body  of  the  astragalus.  It  is  a  hinge-joint,  which  only  permits  of 
flexion  and  extension  of  the  foot  on  the  leg.  It  is  enclosed  by  a  cap- 
sular  ligament,  reinforced  by  strong  lateral  ligaments. 

FIG.  108. 


EXTERNAL  VIEW  OF  THE  RIGHT  ANKLE-JOINT. 
1,  tibia ;  2,  external  malleolus  of  the  fibula ;  3, 
astragalus ;  4,  calcaneum  ;  5,  cuboid  bone ;  6, 
7,  8,.  three  bands  of  the  external  lateral  liga- 
ment; 9,  front  of  the  capsular  ligament. 


INTERNAL  VIEW  OF  THE  ANKLE-JOINT.  1,  in- 
ternal malleolus  of  the  tibia;  2,  astragalus;  3, 
calcaneum ;  4,  scaphoid  bone ;  5,  internal  cunei- 
form bone ;  6,  internal  lateral  ligament ;  7,  cap- 
sular ligament ;  8,  Achilles  tendon. 


The  fore  part  *  of  the  capsular  ligament  is  a  broad,  thin  membrane, 
attached  above  to  the  lip  of  the  articular  surfaces  of  the  tibia  and 
fibula,  and  below  to  the  neck  of  the  astragalus.  It  is  loose  in  the 


Articulatio  pedis  ;  a.  talo-cruralis. 


2  Anterior  or  tibio-tarsal  ligament. 


SPECIAL   ANATOMY  OF   THE  SKELETON. 


219 


FIG.  109. 


flexed  condition  of  the  foot,  and  is  rendered  tense  when  this  is  ex- 
tended. It  is  greatly  strengthened  by  the  tendons  of  the  digital  exten- 
sors, the  anterior  tibial  and  third  peroneal  muscles,  which  lie  in  front 
of  it.  The  back  part *  of  the  ligament  is  a  short  membrane  extending 
between  the  contiguous  borders  of  the 
articular  surfaces  of  the  tibia  and  fibula 
above  and  the  ridge  of  the  astragalus  below. 

The  internal  lateral  ligament 2  is  a 
strong,  triangular,  membranous  band,  the 
fibres  of  which  descend  and  radiate  from 
the  border  of  the  internal  malleolus  to  the 
inner  side  of  the  astragalus,  the  sustentacle 
of  the  calcaneum,  and  the  scaphoid  bone. 
It  is  crossed  by  the  tendons  of  the  poste- 
rior tibial  and  long  digital  flexor  muscles. 

The  external  lateral  ligament 3  con- 
sists of  three  widely-divergent  bands,4 
which  proceed  from  the  apex  and  fossa 
of  the  external  malleolus :  one  in  advance 
to  the  neck  of  the  astragalus,  the  second 
behind  to  the  posterior  ridge  of  the  lat- 
ter, and  the  third  obliquely  downward  and 
backward  to  the  outer  side  of  the  calca- 
neum near  its  middle. 

The    synovial   membrane,   besides   in- 
vesting the  ankle-joint  in  the  usual  manner,  gives  an  offset  to  the  in- 
ferior tibio-fibular  articulation. 

ARTICULATIONS  OF   THE  TARSUS. 

The  astragalus  forms  with  the  rest  of  the  tarsus  two  distinct  joints, 
separated  by  the  intertarsal  ligament,  and  distinguished  from  the  bones 
which  enter  into  their  formation,  as  the  astragalo-calcanean  and  as- 
tragalo-calcaneo-scaphoid  articulations.  Each  forma  a  distinct  synovial 
cavity. 

The  intertarsal  ligament5  forms  a  broad,  thick  partition  occu- 
pying the  tarsal  sinus,  and  consists  of  fibrous  bundles,  which  extend 
between  the  contiguous  grooves  of  the  astragalus  and  calcaneum  and 
connect  the  two  bones  firmly  together. 

The  astragalo-calcanean  articulation,6  situated  behind  the  in- 
tertarsal ligament,  is  formed  by  the  concave  articular  facet  of  the  body 
of  the  astragalus  and  the  convex  facet  of  the  calcaneum  below  and 
behind.  From  the  position  of  the  intertarsal  ligament  in  front  it  is 


POSTERIOR  VIEW  OF  THE  INFERIOR 
TIBIO-FIBULAR  AND  ANKLE-JOINTS.  1, 
interosseous  membrane ;  2,  3,  two 
bands  of  the  posterior  tibio-flbular 
ligament;  4,  internal  lateral  liga- 
ment of  the  ankle-joint ;  5,  6,  pos- 
terior and  middle  bands  of  the  ex- 
ternal lateral  ligament ;  7,  capsular 
ligament  of  the  ankle-joint;  8,  cal- 
caneum. 


1  Posterior  ligament.  2  Internal  lateral  or  deltoid  lig. ;  1.  calcaneo-tibiale. 

3  External  lateral  1.  4  L.  fibulare  tali  ant.,  post.,  et  calcanei. 

5  L.  intertarseum ;  1.  talo-calcaneum  interosseum.  6  Art.  talo-calcanea. 


220 


SPECIAL    ANATOMY    OF   THE   SKELETON. 


FIG.  110. 


enclosed  by  a  short  capsular  ligament  behind,  and  is  strengthened  at 
the  sides  by  the  lateral  ligaments  of  the  ankle. 

The   astragalo-calcaneo-scaphoid   articulation1  is  a  ball-and- 
socket  joint,  of  which  the  ball  is  formed  by  the  head  of  the  astragalus 

and  the  socket  by  the  sustentacle  of  the 
calcaneum  behind,  the  scaphoid  in  front, 
and  the  inferior  calcaneo-scaphoid 
ligament 2  beneath.  The  latter  is  a  thick, 
dense  membrane,  partially  fibro-cartilagi- 
nous,  and  rarely  partially  ossified,  bridg- 
ing over  the  interval  between  the  inner 
border  of  the  sustentacle  of  the  calcaneum 
and  the  under  part  of  the  scaphoid  bone. 
It  articulates  with  the  under  part  of  the 
head  of  the  astragalus,  and  is  internally 
connected  with  the  internal  lateral  liga- 
ment of  the  ankle.  The  tendon  of  the 
posterior  tibial  muscle  passes  over  it  be- 
neath. The  external  calcaneo-scaphoid 
ligament 3  consists  of  interosseous  bundles 
passing  obliquely  between  the  inner  border 
of  the  anterior  extremity  of  the  calcaneum 
and  the  contiguous  outer  border  of  the 
scaphoid  bone.  The  upper  part  of  the 
articulation  is  closed  by  the  astragalo- 
scaphoid  ligament,*  a  thin  membrane 
which  passes  between  the  neck  of  the  as- 
tragalus and  the  upper  surface  of  the 
scaphoid  bone. 

The  calcaneo-cuboid  articulation  is 
formed  between  the  fore  part  of  the  cal- 
caneum and  the  cuboid  bone,  and  has  a 
synovial  cavity  enclosed  by  a  capsular 
ligament  reinforced  by  the  following : 

The  superior  calcaneo-cuboid  liga- 
ment,5 a  thin,  narrow  band  passing  be- 
tween the  contiguous  surfaces  above  of 
the  calcaneum  and  cuboid  bone. 

The  inferior  calcaneo-cuboid  liga- 
ment,6 a  broad,  strong  band  which  extends  from  the  anterior  tubercle 
beneath  the  calcaneum  to  the  contiguous  under  surface  and  tuberosity 
of  the  cuboid  bone. 


LIGAMENTS  OF  THE  SOLE  OF  THE 
FOOT.  1,  calcaneum ;  2,  astragalus ; 
3,  scaphoid  bone ;  4,  long  plantar 
ligament;  5,  inferior  calcaneo-cuboid 
ligament;  6,  inferior  calcaneo-scaph- 
oid ligament ;  7,  plantar  ligaments 
between  the  cuneiform  bones  and 
base  of  the  metatarsus ;  8,  tendon  of 
the  long  peroneal  muscle  passing 
through  a  groove  of  the  cuboid  bone 
above  the  long  plantar  ligament  to 
be  inserted  into  the  first  metatarsal 
bone ;  9,  capsular  ligament  between 
the  latter  and  the  internal  cunei- 
form bone;  10,  plantar  ligament, 
having  the  same  relationship  with 
the  metatarso-phalangeal  and  pha- 
langeal  articulations  that  the  ante- 
rior ligament  has  with  the  corre- 
sponding joints  of  the  fingers;  11, 
lateral  ligaments ;  12,  transverse  liga- 
ment; 13,  lateral  ligaments  of  the 
phalangeal  articulations. 


1  Art.  talo-cal.  scaphoidea  ;  a.  communis. 

3  Superior  cal.-scaph.  lig» 

5  L.  calcaneo-cuboideum  dorsale. 


2  Internal  calcaneo-scaphoid  ligament. 

4  L.  talo-scaphoideum. 

6  Short  calcaneo-cuboid  ligament. 


SPECIAL    ANATOMY   OF    THE    SKELETON.  221 

The  internal  calcaneo-cuboid  ligament,1  a  thick,  strong  band, 
springs  from  the  fossa  at  the  inner  fore  part  of  the  calcaneum,  and 
proceeds  forward  to  be  attached  to  the  inner  side  of  the  cuboid  bone. 

Accessory  to  this  articulation  is  the  long  plantar  ligament,2  a 
strong,  fibrous  band  which  proceeds  from  the  ridge  beneath  the  cal- 
caneum, extending  from  its  posterior  tubercles  to  the  anterior  tubercle, 
and  thence  passing  forward  and  expanding,  it  is  attached  to  the  tuber- 
osity  of  the  cuboid  bone  and  the  bases  of  the  intermediate  three  meta- 
tarsal  bones.  Crossing  over  the  groove  of  the  cuboid  bone,  it  forms 
with  it  a  canal  for  the  passage  of  the  long  peroneal  tendon. 

The  calcaneo-cuboid  articulation  allows  of  slight  rotary  motion. 

Articulations  of  the  five  smaller  metatarsal  bones  with  one 
another  and  with  the  metatarsal  bones. 

The  opposed  articular  surfaces  of  the  scaphoid  and  cuneiform  bones, 
those  between  the  latter  and  between  the  ectocuneiform  and  cuboid 
bone,  have  a  common  synovial  cavity.  This  communicates  between  the 
meso-  and  ectocuneiform  bones  with  the  cavity  between  the  latter  and 
the  second  and  third  metatarsal  bones,  extending  also  between  these 
and  likewise  between  the  third  and  fourth  metatarsal  bones.  A  distinct 
synovial  cavity  is  formed  between  the  cuboid  and  outer  two  metatarsal 
bones,  extending  also  between  the  latter.  A  third  cavity  is  also  formed 
between  the  entocuneiform  and  first  metatarsal  bones.  The  three  ar- 
ticulations are  enclosed  by  ligaments,  which  are  distinguished  accord- 
ing to  their  position  as  dorsal,  plantar,  and  interosseous  ligaments. 
The  dorsal  and  plantar  ligaments  are  short  bands  which  connect 
the  adjacent  bones,  and  generally  accord  with  them  in  number  and  rela- 
tive direction.  Thus,  they  proceed  from  the  scaphoid  to  the  cuneiform 
bones,  from  these  to  the  inner  three  metatarsals,  and  from  the  cuboid 
to  the  outer  two  metatarsals.  Others  pass  transversely  between  the 
cuneiform  bones,  between  the  outer  of  these  and  the  cuboid,  and  be- 
tween the  bases  of  the  metatarsal  bones.  The  interosseous  liga- 
ments consist  of  short  fibres  connecting  the  adjoining  surfaces  in  the 
intervals  of  the  bones.  Of  these  a  strong  one  unites  the  contiguous 
surfaces  of  the  scaphoid  and  cuboid  bones ;  others  in  the  same  manner 
occupy  the  intervals,  and  unite  the  cuneiform  bones  with  each  other 
and  with  the  cuboid  bone ;  a  third  set  consists  of  a  strong  one  con- 
necting the  entocuneiform  and  second  metatarsal,  and  one  passing 
from  each  side  of  the  ectocuneiform  to  the  latter  and  the  third  meta- 
tarsal bone ;  and  a  fourth  set  consists  of  those  between  and  uniting 
the  bases  of  the  metatarsal  bones. 

The  heads  of  the  metatarsal  bones  are  loosely  conjoined  by  the 
transverse  metatarsal  ligament,  a  band  which  extends  across  the 
sole,  and  is  connected  with  the  plantar  portion  of  the  capsular  liga- 
ments of  the  metatarso-phalangeal  articulations. 

1  Interosseous  calcaneo-cuboid  ligament.  2  Long  calcaneo-cuboid  ligament. 


222  SPECIAL    ANATOMY   OF   THE   SKELETON. 

The  metatarso-phalangeal  and  the  phalangeal  articulations  of  the 
toes  have  the  same  construction  as  those  of  the  fingers. 

The  articulation  of  the  astragalus  with  the  calcaneum  allows  a 
limited  rotary  motion.  That  formed  by  these  bones,  together  with  the 
scaphoid  and  cuboid  bone,  permits  the  fore  part  of  the  foot  to  be 
moved  downward  and  inward  or  upward  and  outward,  as  in  the  inver- 
sion and  eversion  of  the  sole.  The  articulations  between  the  smaller 
tarsal  bones  and  the  metatarsal  bones  are  more  or  less  restricted  to 
gliding  motion,  which  is  most  marked  with  the  first  and  last  meta- 
tarsal bones.  The  movements  of  the  toe-joints  are  like  those  of  the 
fingers. 


CHAPTEE    IV. 

THE  CONNECTIVE  TISSUES. 

THE  body  is  largely  composed  of  parts  which,  serve  to  connect,  sup- 
port, and  protect  other  parts,  and  are  chiefly  composed  of  an  exceed- 
ingly tenacious  fibrous  material,  named  from  its  structure  and  function 
the  fibro-connective  tissue.  It  is  the  essential  constituent  of  most  lig- 
aments,- the  tendons,  aponeuroses,  and  fascia?,  the  periosteum  and  peri- 
chondrium,  the  dura  and  sclerotica,  the  outer  tunic  and  sheath  of  blood- 
vessels, the  sheath  of  nerves,  the  submucous  and  subserous  tissues,  the 
areolar  and  parenchymatous  tissues,  the  albuginea,  and  the  dermis. 
All  these,  together  with  the  elastic  ligaments,  are  commonly  distin- 
guished as  connective  tissues. 

FIBRO-CONNECTIVE   TISSUE. 

The  fibro-connective   tissue,1  or  simply  the   fibrous   tissue, 

when  viewed  through  the  microscope  is  seen  to  be  composed  of  narrow 
bundles  of  exceedingly  fine  filaments  or  fibres,  which  are  transparent 
and  homogeneous,  simple  or  unbranched,  running  parallel,  and  ranging 
from  the  -^Vu"  to  the  y^Viy  °f  a  millimetre  in  thickness.  The  fila- 
ments are  held  together  by  a  transparent  homogeneous  cement  or 
matrix  not  distinctly  separable  from  them.  The  bundles  are  of  vari- 
able size,  and  may  be  associated  in  variable  larger  bundles,  which 
may  divide  and  mutually  intersect  one  another.  The  bundles  are  also 
united  by  a  homogeneous  matrix,  and  the  larger  bundles  in  addition 
may  be  connected  by  smaller  ones.  They  may  be  arranged  parallel 
with  one  another,  as  in  tendons,  aponeuroses,.  and  band-like  ligaments, 
or  they  may  intersect  one  another  in  different  directions,  as  in  fasciae, 
the  dermis,  and  other  fibrous  structures.  The  bundles  of  fibres  exhibit 
a  waving  or  undulating  course,  which  is  due  to  slight  contraction,  and 
disappears  with  the  same  degree  of  extension.  This  condition  gives 
rise  to  the  appearance  of  alternate  dark  and  light  striae  across  tendons, 
which  is  obliterated  on  slight  stretching.  The  fibro-connective  tissue, 
on  the  application  of  acetic  acid,  swells,  becomes  more  translucent, 
and  to  a  great  extent  loses  its  fibrous  appearance.  "When  the  ordinary 
connective  tissues  are  boiled  in  water  the  fibro-conn-ective  tissue  is 
almost  entirely  resolved  into  gelatin,  and  hence  is  said  to  be  a  col- 

1  Fibrous  or  fibrillar  connective  tissue ;  white  fibrous  tissue ;  connective  tissue. 

223 


224 


CONNECTIVE   TISSUES. 


lagenous  substance.     These  tissues  are  the  source  of  glue,  and  are  the 
basis  of  jellies  and  soups. 


FIG.  111. 


FIG.  112. 


BUNDLES  OF  FIBRO-CONNECTIVE  TISSUE  FROM 
A  LIGAMENT,  partially  unravelled  into  their 
constituent  fibres. 


FIBRO-CONNECTIVE  TISSUE.  1,  from  a  tendi- 
nous cord  of  the  right  ventricle  of  the  heart ; 
2,  from  a  portion  of  the  dura. 


In  the  various  connective  tissues  above  named,  besides  the  chief 
element  described,  they  contain  more  or  less  elastic  tissue.1  This  is 
obscured  by  the  presence  of  the  predominant  tissue,  but  when  a  speci- 
men prepared  for  the  microscope  is  submitted  to  acetic  acid,  this 
renders  the  elastic  tissue  distinctly  visible.  It  appears  as  well-defined 
fibres  of  variable  thickness,  generally  comparatively  coarse,  and  never 
so  fine  as  the  filaments  of  fibro-connective  tissue.  The  fibres  also  anas- 
tomose in  a  reticular  manner,  and  the  broken  extremities  appear  more 
or  less  curled  and  blunt  at  the  ends.  The  elastic  tissue  occupies  the 
intervals  of  the  fibro-connective-tissue  bundles,  sometimes  embracing 
them  in  nets,  and  occasionally  turning  spirally  around  them. 

.  A  constant  structural  element  of  the  fibro-connective  tissues  is  the 
so-called  connective-tissue  corpuscle.  This  is  ordinarily  a  flat- 
tened cell  or  thin  plate,  often  with  one  or  several  thin  offsets  from  the 
broad  surfaces,  and  dividing  irregularly  at  the  borders  into  branching 
processes.  The  corpuscles  occupy  the  intervals  of  the  connective-tissue 
bundles,  and  conjoin  by  their  branches.  In  sections  of  the  tissue  they 
appear  as  elongated,  spindle-shaped  branching  bodies,  or  in  an  opposite 
direction  as  irregular  stellate  bodies.  On  free  surfaces  of  connective- 
tissue  structures,  as  exemplified  on  tendons  and  aponeuroses,  the  flat- 
tened connective-tissue  corpuscles  do  not  branch,  but  conjoin  by  their 
contiguous  margins  in  the  manner  of  endothelial  cells.  The  corpus- 


1  Yellow  elastic  tissue. 


CONNECTIVE   TISSUES. 


225 


FIG.  113. 


cles  are  composed  for  the  most  part  of  a  clear  protoplasm  with  a 
central  more  granular  mass  and  a  large  oval  nucleus. 

Other  cells  are  observed  in  the  connective  tissues  whose  character 
is  not  very  obvious,  except  certain 
smaller  ones  which  are  endowed 
with  amoeboid  movement  and 
are  evidently  migratory  colorless 
blood-corpuscles. 

Blood-vessels,  lymphatics,  and 
nerves  occur  in  all  the  connective 
tissues,  but  in  very  different  pro- 
portions, being  few  and  small  in 
ligaments,  tendons,  and  fasciae, 
while  they  are  numerous  in  the 
periosteum  and  dura,  and  are  all 
in  greater  abundance  in  the  sub- 
mucous  tissue  and  dermis.  Gen- 
erally, however,  they  simply  pass 
through  and  are  supported  by  the 
connective  tissue,  and  are  des- 
tined to  supply  other  parts,  while  in  their  course  they  furnish  a  few 
small  ones  to  the  fibro-connective-tissue  structure. 


FIBRO-CONNECTIVE  TISSUE  from  beneath  the 
annular  ligament  of  the  wrist,  and  pertaining 
to  the  synovial  sheath  of  the  flexor  tendons. 
Treated  with  acetic  acid.  The  darker  lines,  1, 
2,  3,  exhibit  fibres  of  the  mingled  elastic  tissue. 


AREOLAR    TISSUE. 

The  loosest  condition  of  fibre-connective  tissue  constitutes  the  are- 
olar  tissue,1  which  is  named  from  the  circumstance  that  its  com- 
ponent bundles  intersect  one  another  and  include  a  multitude  of  freely 
communicating  clefts  or  areolse.  Of  this  character  are  the  entire  super- 
ficial fascia  investing  the  body  beneath  the  skin,  together  with  its  at- 
tachment to  the  latter  and  to  the  deep  fascia;  the  subinucous  and 
subserous  tissues ;  the  sheaths  of  blood-vessels  and  their  attachments ; 
similar  envelopes  of  the  lymphatics,  together  with  accumulations  of 
the  same  material  in  various  recesses  and  intervals  of  the  muscles  and 
other  organs ;  the  sheaths  of  nerves  and  the  connecting  material  of 
their  fibres ;  the  connecting  material  of  the  muscles,  of  their  fleshy 
bundles,  and  of  their  sheaths,  together  with  contiguous  parts;  and 
the  parenchyma  of  organs,  such  as  that  which  associates  the  lobules 
and  follicles  of  glands  and  the  lobules  and  air-cells  of  the  lungs.  Thus 
the  areolar  tissue  is  widely  distributed,  and  generally  serves  to  hold 
parts  together,  to  contribute  to  their  strength,  to  convey  and  support 
the  principal  vessels  and  nerves,  and  at  the  same  time  to  permit  of 
limited  movement  among  all  the  parts  concerned. 


1  Connective  tissue ;  cellular  tissue  ;  tela  cellulosa  or  cellularis  ;  reticulated,  fil- 
amentous, laminated,  or  porous  tissue ;  cellular  or  reticular  substance. 

15 


226  CONNECTIVE   TISSUES. 

The  fibro-connective-tissue  bundles  of  the  areolar  tissue  vary  greatly 
in  size,  and  interlace  in  every  direction.  The  density  or  laxity  of 
the  areolar  tissue  mainly  depends  on  the  size  of  its  constituent  bundles 
and  the  closeness  with  which  they  are  associated.  They  are  mingled 
with  variable  proportions  of  fine,  reticular  fibres  of  elastic  tissue,  with 
connective-tissue  corpuscles  and  other  corpuscles.  The  cleft-like  inter- 
spaces are  occupied  by  lymphatic  moisture,  in  which  a  few  lymph- 
corpuscles  move  about.  They  are  readily  inflated  with  air,  in  which 
condition  the  areolar  tissue  appears  white  and  fleecy,  and  composed 
of  delicate,  transparent  vesicles  of  variable  size.  It  is  from  the  free 
communication  of  these  interspaces  that  liquids  so  readily  pervade  the 
body,  as  the  serum  of  dropsy,  the  extravasation  of  blood  from  injuries 
to  the  vessels,  the  pervasion  of  pus  in  abscesses,  and  the  infiltration 
of  urine  in  rupture  of  the  urethra.  The  areolar  tissue  is  the  chief  seat 

FIG.  114.  FTG-  115- 


AREOLAR  TISSUE  FROM  THE  AXILLA,  exhibit-  DIAGRAM  OP  THE  ARRANGEMENT  OF  THB 
ing  its  composition  of  bundles  of  fibro-connec-  FIBRO-CONNECTIVE  TISSUE  IN  THE  EXTERNAL 
tive  tissue,  among  which  are  groups  of  fat-cells.  COAT  OF  BLOOD-VESSELS. 

of  accumulations  of  adipose  tissue  or  fat,  with  the  disappearance  of 
which  it  collapses  or  becomes  more  compact.  From  its  constituent 
material  and  arrangement,  it  is  endowed  with  considerable  tenacity 
and  extensibility,  which  admirably  adapt  it  for  the  union  of  parts 
without  interfering  with  their  movements  or  variable  changes  in  size. 

The  vessels  and  nerves  of  the  various  connective  tissues  are  almost 
entirely  those  which  traverse  and  are  supported  by  these  tissues  in 
their  course  to  other  parts. 

The  fibro-connective  tissue  is  the  most  tenacious  of  all  organic  tis- 
sues, and  is  admirably  adapted  to  the  purposes  of  holding  parts  together 
and  protecting  them,  and  of  communicating  muscular  power  to  parts 
to  be  moved.  Advantage  has  been  taken  of  its  qualities  in  the  arts, 


CONNECTIVE   TISSUES. 


227 


and  thus  the  dermis,  or  connective-tissue  layer  of  the  skin  of  animals, 
forms  that  most  important  material,  leather,  and  the  similar  layer  of 
the  intestines  forms  the  strongest  of  cords,  called  catgut.  Our  early 
ancestors  also  found  tendons  and  raw  hide  the  best  materials  for  bow- 
strings and  for  cords  to  bind  things  together. 

Flexible  at  all  times,  the  connective  tissues  are  more  or  less  ex- 
tensible and  inextensible  according  to  the  arrangement  of  their  con- 
stituent bundles.  The  band-like  ligaments  are  composed  of  compact 
parallel  bundles,  which  are  inextensible,  and  thus  hold  the  bones  firmly 
together  and  prevent  them  from  being  pulled  apart.  Tendons  and 
aponeuroses,  likewise,  are  composed  of  parallel  bundles,  and  under 
ordinary  conditions  are .  perfectly  inextensible,  so  that  they  communi- 
cate the  power  of  their  muscles  to  the  parts  to  be  moved  without  any 
loss  which  would  occur  in  stretching  them.  In  the  connective-tissue 
layers  of  the  hollow  viscera,  in  the  blood-vessels,  in  the  sheaths  of 
muscles,  and  in  capsular  ligaments,  the  diagonal  intersection  of  the 
widely-spread  bundles  of  fibro-connective  tissue,  while  permitting  lim- 
ited extensibility  and  expansion,  preserves  the  integrity  of  the  parts. 


FIG.  116. 


ELASTIC   TISSUE. 

Besides  the  variable  proportions  of  elastic  tissue  which  enter  into 
the  composition  of  the  different  connective  tissues  indicated,  it  enters 
largely  into  the  walls  of  the  blood-  and  lymphatic  vessels,  especially 
the  arteries,  in  the  ligaments  of  'the  larynx, 
the  vocal  cords,  and  in  the  submucous  tracheal 
and  bronchial  tissue,  and  it  almost  wholly 
composes  the  vertebral  elastic  ligaments.  In 
four-footed  mammals  it  forms  the  nuchal  liga- 
ment, which  is  intended  to  sustain  the  head 
and  thus  economize  muscular  power.  In  ani- 
mals in  which  the  head  is  unusually  large  or 
weighted  with  great  antlers,  or  tusks,  as  in  the 
elk  and  elephant,  the  ligament,  composed  of 
compact  elastic  tissue,  is  of  huge  proportions. 
In  man,  in  whom  the  head  is  balanced  on  the 
spine,  the  same  ligament  is  reduced  to  the  con- 
dition of  a  mere  partition  of  fibre-connective 
tissue  between  the  muscles  at  the  sides  of  the 
back  of  the  neck. 

In  the  large  herbivorous  quadrupeds,  a 
thick,  strong  membrane  of  elastic  tissue  aids 
in  the  support  of  the  pendent  abdomen  ;  in 
man  it  is  represented  only  by  the  deeper  layer  of  the  superficial  fascia. 

As  its  name  implies,  the  tissue  is  highly  elastic,  approaching  in  this 
respect  india-rubber.     It  is  buff-yellow  in  color,  and  opaque. 


ELASTIC  TISSUE,  from  the 
elastic  ligaments  of  the  ver- 
tebral arches,  consisting  of 
coarse  anastomosing  fibres ; 
magnified. 


228 


CONNECTIVE   TISSUES. 


In  the  yellow  ligaments  of  the  vertebrae,  in  which  the  elastic  tissue 
is  presented  in  its  purest  condition,  it  is  composed  of  longitudinal  par- 
allel fibres  in  bundles,  collected  into  variably  larger  prismatic  bundles 
united  by  ordinary  fibro-connective  tissue,  which  also  penetrates  among 
the  fibres  of  the  elastic  tissue.  These  fibres  are  comparatively  coarse, 
tolerably  uniform,  about  -j-^Vrr  of  a  millimetre  in  diameter,  prismatic, 
nearly  straight  or  flexuose,  and  mutually  forking  and  intersecting  in 
their  course.  From  the  latter  condition  the  tissue  in  longitudinal  sec- 
tion appears  reticular,  with  the  meshes  as  narrow  lanceolate  fissures. 
The  fibres  are  transparent  and  homogeneous.  When  broken  they  curl 
at  the  extremities  and  end  abruptly,  indicating  a  degree  of  fragility, 
though  they  are  highly  flexible  and  extensible.  In  some  structures  the 
elastic  nets  are  composed  of  fine  fibres  with  wide  intervals.  In  the 


FIG.  117. 


FIG.  118. 


ELASTIC  TISSUE,  from  the  middle  coat  of  the 
pulmonary  artery  of  the  horse ;  highly  magni- 
fied. 


ELASTIC  TISSUE,  from  the  middle  coat  of  the 
carotid  artery  of  the  horse ;  highly  magnified. 


vocal  membrane  and  in  most  areolar  tissues  the  fibres  are  exceedingly 
fine.  In  other  parts  the  fibres  are  larger  and  broader,  and  the  intervals 
proportionately  small,  so  that  the  tissue  may  appear  to  be  a  homogene- 
ous membrane  with  rounded  apertures,  as  in  the  fenestrated  membrane 
of  blood-vessels. 

The  blood-vessels  of  elastic  tissue,  in  its  purest  condition,  as  in  the 
yellow  vertebral  ligaments,  are  comparatively  few.  They  run  in  the 
interstitial  connective  tissue,  and  communicate  with  capillaries  between 
the  smaller  bundles  of  the  elastic  tissue.  Lymphatic  vessels  pursue 
the  same  course. 

ADIPOSE  OK   FAT   TISSUE. 

The  adipose  or  fat  tissue  is  an  important,  though  not  an  essen- 
tial, structural  element  of  the  body ;  nor  does  it  alone  form  any  dis- 
tinct or  separate  organ.  Its  quantity  is  very  variable,  and  is  more 
or  less  related  with  differences  of  age,  sex,  habit,  health,  and  other 
conditions.  Commonly  most  abundant  in  the  infant  and  the  mature 
female,  in  the  emaciation  of  disease  or  through  starvation  it  may  dis- 
appear almost  completely ;  and  sometimes  in  a  condition  of  apparent 


CONNECTIVE   TISSUES. 


229 


FIG.  119. 


health  it  may  accumulate  to  such  a  degree  as  to  be  regarded  as  a  dis- 
ease in  itself.  It  is  usually  associated  with  the  looser  forms  of  fibro- 
connective  tissue  and  the  blood-vessels,  and  accompanies  these  in  their 
distribution  through  other  organs. 

The  adipose  tissue  commonly  forms  a  considerable  and  continuous 
layer l  immediately  beneath  the  skin,  for  the  most  part  occupying  the 
more  superficial  layer  of  the  superficial  fascia,  and  thence  extending 
into  the  meshes  of  the  deeper  part  of  the  dermis.  In  this  posi- 
tion it  is  most  abundant  in  the  infant  and  mature  female,  giving  to 
them  their  characteristic  rounded  symmetry 
of  shape.  Ordinarily  it  accumulates  most 
beneath  the  skin  of  the  breast,  the  abdomen, 
and  the  buttocks.  In  the  palms  of  the 
hands  and  soles  of  the  feet  it  serves  as  an 
elastic  cushion  to  moderate  the  influence 
of  pressure  on  the  important  parts  be- 
neath, and  in  these  positions  it  is  most  per- 
sistent, and  is  even  retained  in  ordinary 
emaciation.  It  also- occupies  the  intervals 
of  muscles,  the  hollows  of  the  temples, 
cheeks,  and  other  similar  places ;  and  it  fills 
the  interspaces  of  the  eyeball  with  its  mus- 
cles and  other  important  organs  of  the  orbit. 
Its  disappearance  in  emaciation  gives  rise  to 
the  sunken  temples,  cheeks,  and  eyes  so 
characteristic  of  many  diseases. 

Adipose  tissue  also  collects  along  the 
course  of  the  blood-vessels  and  nerves,  and 
is  often  conspicuous  along  those  of  the  heart 
and  intestines.  It  often  accumulates  to  a  considerable  degree  between 
the  folds  of  the  peritoneum,  around  the  intestines  and  the  kidneys, 
and  in  a  great  measure  in  these  positions  contributes  to  produce  the 
protuberant  abdomen  of  corpulent  persons.  It  likewise  fills  up  the 
intervals  around  the  articulations,  and  occupies  the  interior  of  some 
of  the  synovial  fringes ;  it  also  forms  the  soft,  yellow  marrow  of  the 
bones. 

The  adipose  tissue  in  the  living  body  is  usually  a  pale  yellow,  soft 
substance,  varying  in  consistence  and  tenacity  in  proportion  to  the 
fibro-connective  tissue  with  which  it  is  associated.  It  is  most  consist- 
ent in  the  subcutaneous  fat,  and  is  softest  in  the  yellow  marrow  of  the 
bones.  In  the  dead  body,  with  the  reduction  of  the  temperature  it 
becomes  solidified  and  harder. 

The  adipose  tissue  is  composed  of  little  vesicles  filled  with  an  oil  or 
liquid  fat,  and  these  vesicles  are  collected  in  little  groups  sustained  by 


ADIPOSE  TISSUE,  WITH  CONNEC- 
TIVE TISSUE,  from  the  superficial 
fascia  of  the  abdomen;  highly 
magnified.  The  groups  of  fat-ves- 
icles are  observed  contained  in 
the  meshes  of  connective  tissue. 


Panniculus  adiposus. 


230  CARTILAGES. 

bundles  of  fibro-connective  tissue  and  blood-vessels.  The  groups  of 
vesicles  are  collected  into  larger  and  larger  masses,  which  present  a 
more  or  less  lobulated  appearance,  and  are  supported  in  the  meshes  of 
a  fibro-connective-tissue  matrix. 

The  fat-vesicles  are  spherical  or  oval  cells,  usually  rendered  more 
or  less  polyhedral  by  mutual  pressure,  and  commonly  range  from  the 
^i-g.  to  the  -j^j-  of  an  inch  in  diameter. 

The  fat-cell  consists  of  a  delicate,  transparent,  homogeneous,  mem- 
branous wall,  distended  with  a  single  clear  globule  of  homogeneous  oil 
or  liquid  fat.  Ordinarily,  nothing  further  is  visible  in  the  structure 
of  the  fat  cell,  but  it  has  been  shown  that  in  each  cell  the  oil-globule 
is  enveloped  by  an  exceedingly  delicate  film  of  protoplasm,  next  the 
wall.  To  one  side  of  the  cell  a  flattened,  elliptical  nucleus  is  embedded 
in  the  protoplasm. 

In  emaciation  from  disease  or  starvation,  the  oil-globule  of  the  fat- 
cell  undergoes  diminution,  and  may  entirely  disappear,  and  be  substi- 
tuted by  a  serous  liquid. 

The  fat-cells  are  derived  from  cells  of  protoplasm,  and  may  be  pro- 
duced by  the  transformation  of  lymphoid  cells,  connective-tissue  cor- 
puscles, and  the  marrow-cells  of  bones. 

The  adipose  tissue  is  richly  supplied  with  blood-vessels,  the  capil- 
laries of  which  form  a  delicate,  reticular  sponge,  enclosing  in  its  meshes 
single  fat-cells  or  groups  of  several  cells.  Serves  pass  through  adipose 
tissue  in  their  course  to  other  parts,  but  appear  not  to  be  distributed  to 
its  structure. 

THE   CAKTILAGES. 

The  cartilages,  or  gristles,  are  of  three  kinds, — those  composed  of 
pure  cartilage ;  and  the  fibro-cartilages  and  elastic  cartilages,  which 
are  composed  of  variable  proportions  of  the  former  tissue  with  fibro- 
connective  or  elastic  tissue. 

CARTILAGE. 

Cartilage,  true  or  hyaline  cartilage,  is  a  dense,  bluish-white,  or 
sometimes  yellowish-white,  pearly  substance,  of  less  hardness  than 
bone.  Apparently  homogeneous  and  opaque,  or  slightly  translucent, 
it  is  elastic  and  highly  flexible,  but  inextensible,  and,  though  of  firm 
consistence,  is  less  tenacious  than  fibro-connective  tissue.  Easily  cut, 
in  thin  slices  it  is  translucent  or  transparent,  more  or  less  opalescent, 
and  to  the  naked  eye  homogeneous.  Like  the  fibro-connective  tissue, 
when  dried  it  is  exceedingly  hard,  yellow,  and  translucent,  but  readily 
imbibes  water,  and  resumes  its  original  condition. 

The  physical  properties  of  cartilage  render  it  well  adapted  to  its 
purposes.  It  enters  mostly  into  the  construction  of  the  skeleton,  and 
in  all  the  more  movable  joints  invests  the  free  surfaces  of  the  bones, 
providing  them  with  an  elastic  covering  which  facilitates  motion  and 
moderates  the  force  of  concussion.  It  also  composes  the  costal  cartilages, 


CARTILAGES. 


231 


FIG.  120. 


CARTILAGE;  section  through  the  thickness  of  the 
oval  cartilage  of  the  nose.  1,  towards  the  exterior ; 
2,  towards  the  interior  surface  ;  highly  magnified. 
It  exhibits  groups  of  cartilage-cells  embedded  in  a 
homogeneous  or  faintly  granular  matrix. 


which,  without  diminishing  the  strength  of  the  framework  of  the  chest, 
contribute  to  its  elasticity  and  security.  It  further  forms  the  principal 
cartilages  of  the  larynx,  except  the  epiglottis,  those  of  the  windpipe 
and  of  the  nose,  to  all  of  which  it  gives  .the  necessary  firmness  to  retain 
the  passages  they  enclose  at  all  times  freely  open  to  currents  of  air. 

The  skeleton  commences  in  the  embryo,  chiefly  in  the  condition  of 
cartilage,  and  in  the  subsequent  growth  of  the  bones  the  osseous  tissue 
is  largely  preceded  by  the  pro- 
duction of  cartilage.  Those  car- 
tilages which  are  converted  into 
bones  are  distinguished  as  tem- 
porary cartilages,  while  those 
which  remain  unchanged  are  the 
permanent  cartilages,  though 
even  some  of  these  in  later  life 
undergo  conversion  into  bone, 
as  exemplified  by  the  cartilages 
of  the  larynx.  The  ensiform 
cartilage  of  the  adult  is  the 
remaining  unossified  portion  of 
the  last  segment  of  the  sternum. 

The  true  cartilages,  except  those  of  the  movable  joints,  which  are 
distinguished  as  articular  cartilages,  are  invested  with  a  membrane, 
the  perichondrium,  which  in  structure  and  function  accords  with  the 
periosteum  of  the  bones. 

When  bones  are  macerated  in  dilute  muriatic  acid  and  the  earthy 
constituents  are  dissolved,  the  articular  cartilages  are  readily  detached, 
and  in  this,  condition,  when  closely  bent,  are  easily  broken,  with  per- 
pendicular edges,  which  show  a  distinctly  striated  condition  in  the 
same  direction,  apparently  indicating  a  fibrous  constitution.  In  patho- 
logical specimens  these  cartilages  are  also  frequently  seen  more  or  less 
resolved  into  a  fibrous  condition. 

Under  the  microscope  thin  sections  of  cartilage  present  a  uniform 
hyaline  matrix,  in  which  are  embedded  scattered  cells,  sometimes  single, 
but  mostly  in  groups  of  two  or  more,  often  up  to  a  dozen,  or  even  a 
greater  number. 

In  the  articular  cartilages  the  matrix  appears  slightly  clouded  and 
obscurely  granular.  In  the  costal  cartilages,  some  portions  more  than 
others,  especially  in  advanced  age,  present  a  more  or  less  finely  fibrillar 
condition  of  the  matrix. 

The  cells  of  cartilage,  called  cartilage-corpuscles,  when  single  are 
spherical  or  oval,  or  nearly  so ;  when  in  pairs  each  is  half  oval  or  ovoid, 
apparently  as  if  resulting  from  the  division  of  an  original  single  oval 
cell.  When  the  groups  consist  of  three  or  more  cells  they  are  usually 
arranged  in  rows  or  columns,  and  the  intermediate  cells  are  more  or 
less  discoid.  If  the  group  consists  <  f  four  or  more  together  they 


232 


CARTILAGES. 


appear  as  corresponding  segments  of  a  spheroid  or  ovoid.  The  shape 
of  the  groups  and  of  the  cells  composing  them  is  evidently  that  which 
is  due  to  multiplication  by  division  of  originally  single,  spherical  or 
oval  cells. 

In  the  articular  cartilages  the  groups  or  columns  of  cells  in  the 
deepest  part  are  arranged  more  or  less  perpendicularly  to  the  surface 
of  bone  beneath.  At  a  higher  level  they  are  irregularly  oblique  in 


FIG.  121. 


FIG.  122 


SECTION  OF  COSTAL  CARTILAGE.  The  upper 
part  is  towards  the  exterior  surface,  where  the 
groups  of  cells  are  arranged  parallel  to  it ;  the 
lower  part  is  towards  the  interior,  where  the 
groups  are  arranged  vertically  to  the  free  sur- 
faces; highly  magnified. 

relation  with  the  former ;  and  ap- 
proaching the  free  surface  of  the 
cartilage  they  become  horizontal 
or  parallel  with  the  latter,  and 
also  flattened,  as  if  influenced  by 
pressure  during  their  production 


VERTICAL  SECTION  OF  ARTICULAR  CARTILAGE 
from  the  carpal  surface  of  the  radius.  1,  2,  3, 
articular  cartilage ;  below  this  is  a  portion  of 
the  bone,  5,  6,  7.  1,  exterior  portion  of  the  car- 
tilage, exhibiting  the  groups  of  cells  lying 
parallel  to  the  slightly  irregular  free  surface ; 
2,  3,  the  cells  arranged  vertically  in  the  deeper 
part  of  the  cartilage;  4,  groups  of  cells  ob- 
scured by  osseous  deposit ;  5,  structure  of  the 
bone,  exhibiting  the  concentric  laminae  and 
lacunae ;  6,  a  vascular  canal ;  7,  a  marrow  areola 
of  the  spongy  substance  of  the  bone.  The 
specimen  is  highly  magnified,  but  the  depth 
of  the  articular  cartilage  is  proportionately  re- 
duced, so  as  to  exhibit  the  relation  of  all  the 
parts  without  making  too  large  a  figure. 

and  growth.  In  the  costal  carti- 
lages the  cells  are  larger,  and  the  groups  in  general  have  a  variably 
radiated  arrangement  from  the  interior,  and  gradually  become  parallel 
with  the  surface  and  flattened  in  the  same  direction  as  they  approach 
the  latter. 

The  cartilage-corpuscle  consists  of  translucent  protoplasm,  faintly 
granular,  defined  by  a  transparent,  homogeneous  wall,  which  is  blended 
with  the  cartilage  matrix,  and  commonly  is  scarcely  to  be  distinguished 
from  it.  It  contains  a  spherical  nucleus,  and  not  unfrequently  one  or 
several  little  oil-globules.  The  nucleus  contains  a  clear  nucleoplasm, 
together  with  one  or  several  nucleoli. 


CARTILAGES. 


233 


By  the  imbibition  of  water  or  other  liquids,  or  by  the  action  of 
electricity,  the  protoplasm  of  the  cartilage-corpuscle  shrinks  from  its 
wall  into  an  irregular  mass,  enclosing  the  nucleus. 

The  articular  cartilages  are  thin  plates  which  invest  the  articular 
surfaces  of  bones,  the  structures  of  the  two  being  continuous.  The 
osseous  structure  extends  into  the  cartilage  in  a  multitude  of  minute 
irregular  points  and  ridges,  and  molecules  of  bone-earth  extend  still 
farther  into  the  cartilage  and  envelop  the  deepest  stratum  of  cartilage- 
corpuscles.  On  articular  eminences  the  cartilages  are  thickest  centrally, 
and  thin  away  at  the  periphery,  and  in  articular  cavities  the  reverse 
condition  exists.  The  free  surface  of  these  cartilages  is  devoid  of  any 
especial  investment,  but  at  the  margin  it  becomes  continuous  with  the 
nbro-cbnnective  tissue  of  the  adjacent  synovial  membrane,  and  many 
of  the  contiguous  cartilage-corpuscles  are  provided  with  branching 
processes,  and  appear  to  be  transitional  in  character  with  the  neigh- 
boring connective-tissue  corpuscles.  The  articular  cartilages  are  de- 
void of  vessels,  but  dilated  capillary  loops  of  the  subjacent  bone  reach 
their  attached  surface,  and  a  zone  of  fine  capillaries  from  the  vessels 
of  the  adjacent  synovial  membrane  surround  their  circumference. 

The  articular  cartilages  retain  their  character  through  life,  and, 
together  with  the  cartilages  of  the  nose,  are  alone  deserving  the  dis- 
tinction of  being  called  permanent  cartilages. 

The  costal  cartilages,  which  are  the  thickest  examples  of  cartilage, 
besides  their  perichondrium  furnished  with  nutrient  blood-vessels  are 
pervaded  by  a  few  narrow  canals,  mostly  longitudinal,  which  give 

PTG.  123. 


SECTION  OF  COSTAL  CARTILAGE,  crossing  the  free  surfaces,  but  taken  from  near  the 
centre.  To  the  left,  which  was  towards  the  exterior  surface,  the  groups  of  corpuscles 
are  embedded  in  a  homogeneous  matrix ;  towards  the  right,  the  matrix  has  assumed 
a  decidedly  fibrous  character.  Specimen  from  an  adult  of  about  forty  years  of  age. 

passage  to  similar  vessels,  but  these  do  not  farther  enter  the  cartilagi- 
nous tissue.  These  cartilages  in  the  advance  of  life  undergo  change, 
becoming  more  rigid  and  hard  from  the  deposit  of  bone-earth  in  the 
matrix.  The  deposit  takes  place  irregularly,  occurring  earlier  and 
most  abundantly  contiguous  to  the  osseous  connections  of  the  carti- 
lages. The  process  of  deposit,  called  calcification,  rarely  extends 
completely  throughout  the  cartilages. 

The  cartilages  of  the  larynx   towards  the  middle  of  life  undergo 


234  CARTILAGES. 

change,  and  gradually  become  more  or  less  completely  ossified.  The 
change  occurs  later  in  the  female. 

When  cartilages  are  fractured  in  life  they  usually  become  reunited 
by  fibre-connective  tissue,  which  often  is  subsequently  converted  into 
bone. 

The  true  cartilages  yield  chondrin  on  long  boiling,  a  material  having 
different  chemical  reactions  from  gelatin. 

FIBRO-CARTILAGE. 

Fibro-cartilage  is  composed  chiefly  of  fibro-connective  tissue,  with 
a  small  and  variable  proportion  of  embedded  cartilage-corpuscles.  Like 
true  cartilage,  it  possesses  great  firmness  and  elasticity  without  exten- 
sibility, but  is  more  flexible  and  tenacious.  It  cuts  with  more  resistance, 
and  presents  a  compact  fibrous  structure.  The  fibro-cartilages  are  as 
follows  : 

1.  The  interarticular  fibro-cartilages.     These  occur  in  the  articu- 
lations of  the  mandible,  clavicle,  wrist,  and  knee.     They  occupy  the 
interval  of  the  articular  cartilages,  and  conform  to  their  opposed  sur- 
faces.    They  are  plates,  thinning  towards  the  centre,  with  the  surfaces 
free  and  smooth,  and  the  peripheral  border  attached  to  the  capsular 
ligament,  whence  the  contiguous  synovial  membrane  is  reflected  on  the 
margin  of  the  free  surfaces.     In  the  joints  of  the  mandible  and  clavicle 
they  are  disks ;  in  the  wrist-joint  the  fibro-cartilage  is  triangular ;  and 
in  the  knee-joint  there  are  two,  named  from  their  shape  the  semilunar 
cartilages. 

These  fibro-cartilages  are  mainly  composed  of  bundles  of  fibro-con- 
nective tissue,  interlacing  and  compactly  felted  together,  without  inter- 
stices such  as  exist  in  ligaments  and  tendons.  On  the  free  surfaces  the 
structure  assumes  more  the  character  of  true  cartilage.  The  cartilage- 
corpuscles  are  comparatively  few,  and  scattered  among  the  fibro-con- 
nective-tissue  bundles,  often  single,  but  more  frequently  in  pairs,  having 
the  appearance  of  being  derived  through  the  division  of  originally  single 
cells.  They  possess  the  same  character  as  those  of  true  cartilage. 

The  interarticular  cartilages  not  only  adapt  but  aid  in  maintaining 
the  apposition  of  the  articular  cartilages,  moderate  pressure  upon  them, 
and  facilitate  the  gliding  movement  of  the  joints. 

2.  The  connecting  fibro-cartilages  unite  the  opposed  articular 
surfaces  of  the  vertebral  centra  and  of  the  pubes,  giving  the  articu- 
lations limited  flexibility.     They  are  the  intervertebral  and  the  inter- 
pubic  disks,  and  are  immediately  continuous  with  thin  plates  of  true 
cartilage  investing  the  bones.     The  intervertebral  disks  mainly  con- 
sist of  numerous  concentric  layers  of  fibro-connective-tissue  bundles, 
the  interior  of  which  gradually  merge  into  a  central  tenacious  pulp. 
With  the  fibro-connective-tissue  bundles  are  associated  scattered  carti- 
lage-corpuscles, which   are  more  abundant  in  the  interior  layers  ap- 
proaching the  eenti-al  pulp.     The  corpuscles,  usually  in  groups  of  two 


FASCIAE. 


235 


or  three  or  more,  exhibit  a  concentric  laminar  structure,  and  many 
are  provided  with  long  branching  processes.  The  central  pulp  consists 
of  a  reticular  cell-structure  in  a  soft  fibrous  matrix,  probably  derived 
from  the  cells  of  the  chorda  dorsalis  of  the  embryo.  It  frequently 
occupies  an  exceedingly  irregular  space,  with  an  interior  lacerated 
villous  surface,  resembling  the  subcutaneous  synovial  bursse,  like  that 
upon  the  patella.  The  disk  of  the  pubic  symphysis  approximates  in 
structure  the  intervertebral  disks. 

3.  The  circumferential  fibre-cartilages  consist  of  bands  which 
extend  the  margin  of  articular  cavities,  serving  to  increase  their  depth, 
as  in  the  glenoid   ligament   surrounding  the  glenoid  cavity  and  the 
cotyloid  ligament  surrounding  the  acetabulum. 

4.  The  investing  fibro- cartilages  consist  of  thin  layers,  lining 
grooves  of  the  bones  which  give  passage  to  tendons. 

5.  The  palpebral  cartilages,  or  tarsi,  serve  to  preserve  the  form 
of  the  eyelids,  and  consist  almost  entirely  of  closely-compacted  bundles 
of  nbro-connective  tissue. 

The  fibro-cartilages  are  devoid  of  vessels  beyond  their  attached 
surfaces.  Like  the  connective  tissues,  they  yield  gelatin  on  boiling, 
indicating  the  great  predominance  of  the  fibro-connective  tissue. 

ELASTIC   CARTILAGE. 

Elastic  cartilage,  in  appearance  more  nearly  resembling  true  car- 
tilage than  the  former,  is  intermediate  in  tenacity  and  flexibility,  and 
is  represented  by  the  auricular  cartilage,  that  of  the  eustachian  tube, 
the  epiglottic  cartilage,  and  the  cornicles  of  the  larynx. 

It  is  composed  of  a  matrix  of  elastic  tissue  embedded  in  a  more 
homogeneous  or  faintly  granular  substance,  mingled  with  numerous 
cartilage-corpuscles.  The  fibres 
of  elastic  tissue  are  closely  felted, 
and  freely  anastomose  with  one 
another.  The  cartilage-corpuscles, 
commonly  in  pairs,  are  scattered 
irregularly  among  the  matrix  of 
elastic  fibrous  tissue,  and  are  each 
enveloped  with  a  clearer  layer  of 
the  homogeneous  substance.  The 
elastic  cartilages  are  invested  with 
a  vascular  perichondrium. 

All  the  cartilages  appear  to  be 
devoid  of  nerves,  as  they  are  of  ves- 
sels. They  are  totally  insensible. 


FIG.  124 


SECTION  OF  ELASTIC  CARTILAGE  FROM  THE 
AURICLE  OF  THE  EAR.  The  cells  are  seen  em- 
bedded in  a  fibrous  matrix.  1,  exterior  sur- 
face, where  the  cells  are  parallel  to  it ;  2,  towards 
the  middle.  Highly  magnified. 


FASCIAE. 

A  fascia  is  a  membrane  of  variable  texture,  more  or  less  compact 
or   loose,    and   composed   of  interwoven   bundles   of  fibro-connective 


236  FASCIAE. 

tissue.  The  fasciae  form  a  covering  or  investment  for  the  muscles  and 
other  organs,  serving  to  protect  and  retain  them  together,  give  them 
attachment,  and  at  the  same  time  support  and  convey  vessels  and 
nerves  to  them. 

The  principal  fasciae,  named  from  their  relative  position  the  super- 
ficial and  the  deep,  succeed  each  other  beneath  the  skin,  and  invest 
the  body  like  additional  integuments. 

The  superficial  fascia  is  a  membrane  of  loose  fibrous  structure, 
situated  immediately  beneath  the  skin,  and  connecting  it  with  the 
deeper  parts.  It  varies  in  thickness,  compactness,  and  distinctness 
in  different  positions.  For  the  most  part  it  consists  of  two  closely- 
united  layers,  of  which  the  more  superficial *  is  of  looser  texture  and 
serves  as  the  matrix  of  the  subcutaneous  fat.  With  the  disappear- 
ance of  the  latter,  as  in  lean  persons,  it  becomes  more  distinctly  mem- 
branous. The  deeper  layer  of  the  superficial  fascia  is  more  compact, 
and  contains  the  principal  superficial  vessels,  especially  veins,  and  the 
trunks  of  the  cutaneous  nerves.  It  is  comparatively  free  from  fat, 
but  also  becomes  more  or  less  pervaded  with  this  material  in  obesity. 
In  certain  positions,  as  the  eyelids,  lips,  anus,  penis,  and  scrotum,  the 
superficial  fascia  is  always  destitute  of  fat;  but  in  the  palms  of  the 
hands  and  soles  of  the  feet  it  is  constantly  present. 

The  deep  fascia  is  usually  a  more  dense  and  strong  layer  of  fibro- 
connective  tissue,  closely  enveloping  the  muscles  and  forming  a  nearly 
continuous  covering  to  the  body  beneath  the  superficial  fascia,  to  which 
it  is  attached.  It  is  also  tightly  attached  to  subcutaneous  processes  and 
borders  of  bones  where  it  is  continuous  with  their  periosteum.  It  varies 
greatly  in  thickness  and  strength  in  different  positions,  and  in  many  as- 
sumes more  or  less  the  character  of  an  aponeurosis,2  affording  partial 
attachment  to  muscles,  or  actually  becoming  continuous  with  the  apo- 
neurosis or  tendons  of  the  latter.  From  the  inner  surface  of  the  deep 
fascia,  laminae  extend  between  the  muscles  and  become  attached  to 
contiguous  bony  borders,  forming  the  so-called  intermuscular  par- 
titions, which  also  afford  attachment  to  muscles.  When  the  latter 
are  not  attached  to  the  fascia  this  is  adherent  by  loose  connective 
tissue,  which  does  not  interfere  with  the  muscular  movements.  In  the 
vicinity  of  some  of  the  joints  the  deep  fascia  is  strengthened  by  trans- 
verse bands  which  arch  over  bony  grooves,  attached  to  their  borders, 
and  convert  them  into  canals  for  the  passage  of  tendons.  Such  bands 
constitute  the  annular  and  vaginal  ligaments. 

1  Panniculus  adiposus.  2  Aponeurosis  of  investment. 


OHAPTEE  Y. 

THE   MUSCULAR   SYSTEM. 

THE  muscles  are  the  chief  organs  of  motion  in  all  the  higher 
forms  of  animal  life,  and  for  this  power  depend  on  a  peculiar  substance 
composed  of  special  fibres,  which  are  the  essential  element  of  structure 
of  the  muscular  tissue.  In  the  living  condition  the  muscle-fibres 
possess  the  quality  of  shrinking  or  contracting,  and  perhaps  also  of 
actively  elongating  or  expanding,  under  a  variety  of  causes  or  stimuli 
which  may  impress  them.  Thus,  the  muscles  contract  under  mechani- 
cal irritation,  chemical  agency,  the  electric  current,  and  extremes  of 
temperature.  Ordinarily,  in  the  living  animal  they  display  their 
motive  power  under  impressions  which  proceed  directly  from  the 
nervous  system.  A  single  muscle-fibre  is  an  independent  motor  power, 
and  may  act  alone  or  in  concert  with  others ;  and  it  is  therefore  to  be 
physiologically  regarded  as  a  muscle,  as  much  as  any  of  the  collec- 
tions of  muscle-fibres  which  are  commonly  distinguished  and  specially 
named  as  muscles. 

All  the  more  obvious  movements  in  the  higher  animals  are  pro- 
duced by  muscles,  as  those  of  locomotion  and  prehension,  and  those 
concerned  in  the  functions  of  the  alimentary  apparatus,  the  circulation 
and  the  respiration,  arid  others.  Many  of  the  muscles,  like  those  of 
locomotion,  prehension,  and  respiration,  are  ordinarily  more  or  less 
under  the  control  of  the  animal  and  act  intentionally,  or  through 
the  will  or  volition,  and  are  hence  called  voluntary  muscles,  though 
they  may  act  under  other  stimuli,  and  in  many  cases  do  so  habitually, 
as  in  those  of  respiration.  Other  muscles  are  beyond  the  control  of 
the  will,  as  those  of  the  circulatory  and  digestive  apparatus,  and  are 
thence  called  the  involuntary  muscles.  The  two  kinds  of  muscles  not 
only  differ  in  the  ordinary  mode  in  which  they  are  excited  to  activity, 
but  also  differ  in  anatomical  characters. 

The  muscular  tissue  is  one  of  the  most  important  characteristics 
of  the  higher  animals  in  contradistinction  to  plants.  The  latter  de- 
rive all  the  material  of  their  composition  directly  from  the  air,  water, 
and  soil,  in  which  they  are  incessantly  enveloped,  and  are  therefore  in 
general  stationary  in  position.  The  animal  derives  its  chief  materials 
directly  or  indirectly  from  the  plant,  and  hence  the  necessity  of  motors 
to  enable  it  to  apply  to  the  latter  as  occasion  requires.  The  muscular 
tissue  is  familiarly  known  as  the  flesh,  or  meat,  of  animals,  and  it  is 

237 


238  THE    MUSCULAR   SYSTEM. 

the  substance  which  on  the  whole  furnishes  the  most  important  food  of 
man,  as  it  contains  in  the  least  bulk  and  in  the  most  assimilable  con- 
dition the  greatest  amount  of  material  of  which  his  body  is  composed. 

The  muscles  vary  greatly  in  size,  and  are  ordinarily  proportioned 
to  the  work  or  movement  to  be  performed,  and  are  so  intimately  re- 
lated with  their  activity  that  they  increase  or  decrease  with  the  latter. 
Thus  exercise  enlarges  the  muscles,  and  inactivity  reduces  them. 

The  smallest  muscles  are  microscopic,  and  may  consist  of  a  single 
muscle-fibre ;  the  larger  ones  consist  of  bundles  of  muscle-fibres,  which 
bundles  may  be  isolated,  arranged  in  layers,  or  collected  into  larger  and 
larger  bundles.  The  various  muscles,  ordinarily  distinguished  as  such, 
vary  greatly  in  size,  form,  and  distinctness,  and  they  more  or  less  con- 
form to  the  position  they  occupy.  Thus,  on  the  limbs  they  appear  dis- 
tinct and  mostly  of  elongated  forms,  on  the  chest  and  abdomen  in  broad 
layers,  and  in  the  walls  of  the  hollow  viscera  and  vessels  as  concentric 
laminae. 

The  voluntary  muscles  are  especially  characterized  by  the  regular 
transverse,  striped  condition  of  their  fibres,  whence  they  are  called 
striped  muscle-fibres,  or  striped  muscles,  while  in  the  involun- 
tary muscles  generally  the  fibres  exhibit  no  such  stripes,  and  are  dis- 
tinguished as  unstriped  muscle-fibres  or  unstriped  muscles. 
The  heart,  though  an  involuntary  muscle,  is  composed  of  striped 
muscle-fibres ;  but  these  are  otherwise  peculiar,  and  will  be  described 
as  the  cardiac  muscular  tissue. 

THE    UNSTKIPED  OK   INVOLUNTAKY   MUSCLES. 

The  unstriped  or  involuntary  muscles1  in  general  form  com- 
ponent layers  of  the  walls  of  the  hollow  viscera,  as  the  stomach  and 
intestines,  the  urinary  bladder,  and  the  uterus ;  and  likewise  in  the 
blood-vessels,  the  air-passages,  and  in  glandular  ducts.  They  also 
enter  into  the  construction  of  the  skin,  the  iris,  and  other  parts  to  be 
described  hereafter. 

Unstriped  muscle-fibres2  constitute  the  simplest  kind  of  mus- 
cular tissue.  Each  fibre  is  a  variably  elongated,  fusiform,  nucleated 
cell,  straight  or  slightly  flexuose,  rounded  prismatic  and  often  flat- 
tened, and  tapering  at  the  ends.  The  fibres  exhibit  a  more  or  less  dis- 
tinctly longitudinal  striated  appearance,  and  are  composed  of  a  corre- 
sponding fibrillar  sarcous  substance,  which  is  enclosed  by  a  delicate  and 
closely-adherent  sheath,  the  sarcolemma,  which  is  homogeneous  and 
elastic.  The  nucleus  of  each  fibre  is  commonly  central  and  elliptical. 

The  unstriped  muscle-fibres  differ  greatly  in  length  and  propor- 
tionate width  in  different  organs  and  parts.  They  are  longest  and 
thickest  in  the  muscular  coat  of  the  bowels,  and  are  shortest  and  pro- 

1  Muscle  of  organic  life. 

y  Smooth  muscles  or  muscle-cells  or  fibres ;  contractile  fibre-cells. 


THE    MUSCULAR   SYSTEM. 


239 


portionately  wider  in  th,e  coats  of  the  blood-vessels,  in  which  they  are 
sometimes  divided  or  irregular  at  the  ends.  They  are  collected  into 
smaller  or  larger  bundles,  and  these  again  in  many  positions  form  con- 


PIG.  125. 

i 


UNSTRIATED  MUSCLE-FIBRES.     1,  from  the  small  intestine ;  2,  from  the  middle  coat  of  an 
artery ;  3,  from  a  vein. 

tinuous  layers.  The  fibres  of  a  bundle  are  imbricated,  and  adhere 
together  by  a  cementing  substance  like  that  which  unites  the  epithelial 
and  endothelial  cells.  The  bundles  of  muscle-fibres  are  sheathed  and 
united  by  ordinary  connective  tissue. 

THE   STKIPED   OR   VOLUNTARY  MUSCLES. 

The  striped  or  voluntary  muscles  generally  form  distinct  fleshy 
masses,  which  are  mostly  attached  to  the  bones  and  other  parts  by 
means  of  fibrous  structures,  named  aponeuroses  and  tendons.  They 
vary  greatly  in  size,  proportions,  and  shape.  Thus,  there  are  long  and 
short  muscles,  broad  and  narrow,  thick  and  thin,  cylindrical,  band-like, 
fusiform,  triangular,  rhomboid,  square,  and  circular  muscles.  The  sar- 
torius  muscle  is  nearly  two  feet  in  length ;  the  stapedius  about  one- 
fourth  of  an  inch.  The  attachments  of  the  muscles  are  the  points 
from  which  and  on  which  they  act ;  the  commonly  more  fixed  point, 
generally  that  nearest  the 
axis  of  the  body,  is  called 
the  origin,  while  the  oppo- 
site point,  or  that  commonly 
moved  by  the  muscle,  is  the 
insertion.  The  terms  are 
relative,  for  the  muscle  may 
act  from  either  extremity ; 
and  only  in  a  few  instances, 
as  in  some  of  those  of  the 
face,  do  they  act  invariably 
from  the  fixed  bony  attach- 
ment upon  the  movable  soft 
parts. 

In   the   construction  of 
the  fleshy  mass  of  the  mus- 
cle, called  its  belly,  the  mus- 
cle-fibres are  collected  into  smaller  and  larger  bundles,  called  primary 
and  secondary  bundles,  or  fascicles.1    These  may  be  collected  into 


FIG.  126. 


TRANSVERSE  SECTION  OF  THE  LOWER  END  OF  THE  ULNO- 
CARPAL  FLEXOR,  magnified,  a,  section  of  tendon  ap- 
pearing as  two  crescents,  composed  of  prismatic  bundles 
of  fibrous  tissue ;  6,  a  secondary  bundle  of  crescentic 
shape,  consisting  of  primary  bundles  of  muscle-fibres ; 
c,  a  flattened  cylindrical  secondary  bundle,  consisting 
of  primary  bundles  of  muscle-fibres ;  d,  secondary  and 
primary  bundles  in  outline;  e,  sheath  of  the  muscle, 
composed  of  fibro-connective  tissue. 


1  Fasciculi ;  lacerti. 


240 


THE    MUSCULAR   SYSTEM. 


FIG.  127. 


still  larger  ones,  producing  coarse-looking  muscles,  as  exemplified  by 
the  great  gluteal  muscle. 

The  muscle-fibres  are  generally  parallel  with  one  another  in  the 
same  fascicle,  and  the  fascicles  pursue  the  same  course  or  are  more  or 
less  convergent.  Commonly,  they  proceed  in  the  same  direction  as 
the  muscle,  straight  or  convergent ;  but  in  many  cases  they  pursue  a 
more  or  less  slanting  course  across  the  general  direction  of  the  muscle. 
In  some  of  the  longest  muscles,  as  the  sartorius  and  gracilis,  the  fleshy 
fascicles  run  parallel  with  one  another  throughout  their  entire  length. 
In  others,  comparatively  short  fascicles  proceed  obliquely  from  opposite 
sides  of  the  tendon  of  origin  and  converge  to  that  of  insertion,  pro- 
ducing an  appearance  like  a  feather,  whence  the  name  of  penniform 
muscle,1  as  exemplified  by  the  femoral  rectus.  In  some  the  fascicles 
proceed  in  -the  same  way  from  one  side  of  a  tendon  to  another,  pro- 
ducing a  semipenniform  muscle,2  as  the  semimembranosus  muscle. 

The  tissue  of  the  voluntary  muscles,  as  well  as  some  others,  is  com- 
posed of  striped  muscle-fibres.3  These  commonly  consist  of  narrow, 

straight  columns,  which  are  variably  pris- 
matic, with  rounded  borders  and  tapering 
extremities.  Exceptionally,  in  the  muscles 
of  the  tongue  and  face,  many  of  them 
branch  at  their  insertion  into  the  mucous 
membrane  and  skin.  In  the  same  muscle, 
generally,  they  approximate  some  uniform- 
ity, though  many  present  considerable  dif- 
ference in  size,  which  is  especially  the  case 
in  different  parts  of  the  body.  In  the 
muscles  of  the  limbs  and  trunk  they  are 
much  larger  than  in  those  of  the  face ;  in 
the  former  ranging  from  jfa  to  -^^  of  an 
inch  in  thickness,  in  the  latter  from  ^-jVfr  to 
•7-^-5-  of  an  inch.  They  are  usually  longest 
in  the  longest  muscles,  but  are  not  propor- 
tioned with  the  size  of  these.  Commonly 
they  do  not  exceed  an  inch  or  two,  and  in 
the  shortest  muscles  accord  with  these  in 
length.  In  the  construction  of  the  fleshy 
belly  of  a  muscle  they  are  collected  in  pris- 
matic fascicles,  and  they  terminate  among 
themselves  by  conical  ends ;  and  when  at- 
tached to  tendons  they  terminate  among  the  connective-tissue  bundles 
composing  these. 

1  M.  penniformis,  bipenniformis,  or  pennatus. 

2  M.  semipenniformis,  penniformis,  or  semipennatus. 

3  Striped  or  striated  muscles. 


STRUCTURE  OF  THE  STRIPED  MUS- 
CLES. 1,  fascicles  composed  of  pris- 
matic, striped  muscle-fibres,  termi- 
nating below  in  tapering  ends ;  2, 
cut  extremities  of  the  fibres ;  3,  in- 
vesting fibro-connective  tissue  of 
diagonally  crossing  filaments;  4, 
commencing  tendinous  bundles. 


THE   MUSCULAR   SYSTEM. 


241 


Under  the  microscope  the  fresh  muscular  tissue  appears  translucent, 
with  a  faint,  yellowish  tinge,  which  in  quantity  gives  the  usual  so-called 
flesh-color  to  the  muscles.  The  fibres  are  regularly  marked  by  trans- 
verse stripes  alternately  wider  and  darker  and  narrower  and  lighter, 
very  uniform  in  the  same  muscle,  but  varying  in  different  muscles. 
With  higher  power  of  the  microscope  the  lighter  stripes  appear  divided 
by  a  fine  line.  In  muscular  tissue  from  a  recently-killed  animal,  the 
fibres  may  be  observed  in  motion,  at  one  moment  becoming  shorter  and 
wider,  and  at  the  next  moment  proportionately  longer  and  narrower, 
while  the  stripes  undergo  corresponding  changes. 

The  striped  muscle-fibre  is  composed  of  a  soft  substance,  the  sar- 
cous  matter,1  enclosed  in  a  hyaline  sheath,  the  sarcolemma.2  To 
the  sarcous  matter,  arranged  in  disks,  are  due  the  characteristic  trans- 
verse stripes  of  the  muscle-fibre.  After  death  it  assumes  a  longitu- 
dinally striated  appearance,  with  a  finely-granular  aspect.  When  the 


Fro.  128. 


FIG.  129. 


TRANSVERSE  SECTION  OF  THE  BRACH- 
IAL  BICEPS,  a,  muscle-fibres  with  in- 
tervals occupied  by  connective  tissue ; 
b,  blood-vessel ;  c,  fat-cell ;  d,  capil- 
laries ;  e,  nuclei  of  the  muscle-fibres. 


TRANSVERSE  SECTION  OF  A  FASCICLE  OF  THE  CRE- 
MASTER,  exhibiting  the  prismatic  form  of  the  muscle- 
fibres  ;  highly  magnified. 


muscular  tissue  is  hardened  by  alcohol  or  other  liquid,  the  sarcous 
matter  may  be  torn  into  filaments,  distinguished  as  the  primitive  mus- 
cle-fibrils.3 These  are  of  extreme  fineness,  and  composed  each  of  a 
single  row  of  particles,  named  the  sarcous  elements,*  the  regular 
arrangement  of  which  gives  rise  to  the  equally  regular  transverse 
stripes  of  the  muscle-fibre.  The  sarcous  elements  are  conjoined  by  a 
more  translucent  cementing  substance,  to  which  are  due  the  lighter, 
narrower  stripes 5  of  the  fibre,  as  well  as  of  the  intervals  of  the  fibrils. 
When  muscular  tissue  has  been  submitted  to  the  action  of  the  gastric 
juice  or  hydrochloric  acid,  the  sarcous  matter  is  disposed  to  break  into 
disks,  apparently  indicating  the  fibrillar  condition  to  be  of  relative  char- 
acter. The  sarcolemma  is  a  delicate,  homogeneous,  elastic  membrane 
intimately  connected  with  the  sarcous  matter,  and  in  the  recent  fibre 


1  Myoline. 

4  Rods ;  caskets. 


2  Myolemma ;  primitive  sheath. 


16 


3  Muscular  fibrillse. 
5  Interstitial  disks. 


242 


THE    MUSCULAR   SYSTEM. 


not  distinguishable  from  it,  but  becomes  distinctly  visible  under  the 
action  of  certain  reagents.  It  is  reputed  to  give  off  delicate  partitions1 
separating  the  sarcous  disks 2  from  one  another,  and  giving  rise  to 
the  fine  line  which  divides  the  lighter  transverse  stripes  of  the  muscle- 
fibre  into  two  parts.3 

Flattened  oval  nuclei  lie  here  and  there  embedded  in  the  surface  of 
the  sarcous  matter  immediately  beneath  the  sarcolemma.  Ordinarily 
they  are  not  seen,  but  are  brought  distinctly  into  view  by  the  applica- 
tion of  acetic  acid,  which  renders  the  muscular  tissue  more  translucent. 
The  nuclei  contain  a  granular  or  finely-reticular  nucleoplasm,  with  one 
or  two  clear  nucleoli.  In  young  persons  the  muscular  nuclei  are  more 
numerous. 

The   transverse   striped   condition  of  the  muscle-fibres  is  a  well- 


Fio.  131. 


FIBRILS  FROM  A  MUSCLE-FIBRE  OF  THE  AXO- 
LOTL,  an  amphibian ;  highly  magnified,  a,  bun- 
dle of  fibrils ;  6,  an  isolated  fibril. 


A  MUSCLE-FIBRE  OF  A  SALAMANDER,  an  am- 
phibian, which  had  been  long  kept  in  weak 
alcohol.  1,  sarcous  matter ;  2,  nuclei ;  3,  sarcous 
matter  split  into  disks :  4,  the  sarcolemma. 


marked  character  of  voluntary  muscles  in  man  and  all  other  vertebrate 
animals.  It  is,  however,  not  restricted  to  the  voluntary  muscles,  for  it 
is  also  a  character  of  the  muscles  of  the  pharynx  and  larynx  and  those 
of  the  ear,  the  muscular  coat  of  the  oesophagus,  and  the  heart. 

The  belly  of  the  striped  muscles  is  enveloped  in  a  loose  sheath  of 
fibro-connective  tissue,  from  which  partitions  extend  between  and  en- 
velop the  component  muscular  fascicles,  constituting  the  perimysium. 
More  delicate  partitions  also  extend  between  and  envelop  the  muscle- 
fibres,  forming  the  endomysium.  Both  serve  to  convey  and  support 


1  Krause's  membranes. 


2  Contractile  disks. 


3  Lateral  disks. 


THE   MUSCULAR   SYSTEM.  243 

the  vessels  and  nerves  of  the  muscles.  They  contain  some  mingled 
elastic  tissue,  which  is  most  abundant  in  the  perimysium  enveloping 
the  fleshy  belly. 

It  has  not  been  satisfactorily  determined  in  what  manner  the 
muscle-fibres  end  in  the  tendons  to  which  they  may  be  attached.  They 
are  generally  regarded  as  terminating  abruptly  in  obliquely  truncated, 
rounded,  or  tapering  extremities  where  the  sarcolemma  and  intervening 
connective  tissue  merge  into  and  among  the  connective-tissue  bundles 
of  the  tendon. 

The  tendons,  or  sinews,1  by  which  the  striped  muscles  are  mostly 
connected  with  the  bones  and  other  parts  from  which  they  have  their 
origin  and  into  which  they  are  inserted,  vary  in  character ;  some  con- 
sisting of  the  shortest  fibro-connective-tissue  attachment  of  the  mus- 
cular belly,  while  others  form  broad,  membranous  expansions,  called 
aponeuroses,2  and  others  form  flattened  cylindrical  cords  of  various 
lengths,  which  are  viewed  as  the  most  characteristic  tendons.  These 
are  dense,  white,  and  shining,  very  flexible,  but  inextensible  and  of  the 
greatest  tenacity.  In  their  attachment  with  the  muscular  belly  they 
usually  commence  in  the  interior  or  upon  the  exterior  surface  as  an 
aponeurotic  expansion,  in  which  the  fleshy  fascicles  terminate. 

The  tendons  and  aponeuroses  of  muscles  are  composed  of  prismatic 
fibro-connective-tissue  bundles,  which  run  in  the  same  direction  as  the 
former  throughout,  but  do  not  continue  separate,  as  they  frequently 
intersect  one  another  by  a  mutual  interchange  of  bundles.  The  tendon- 
bundles  consist  of  smaller  ones,  collected  into  larger  ones,  and  are  all 
united  together  by  lower  connective  tissue,  which  also  forms  a  compact 
sheath  for  the  tendon  continuous  with  that  of  the  muscular  belly.  The 
sheath  of  the  tendon,  and  its  extensions  between  the  tendon-bundles, 
accommodate  the  vessels  and  nerves  of  the  tendon. 

The  names  of  muscles  are  commonly  derived  from  some  prominent 
character,  as  office,  shape,  position,  attachment,  course,  and  number  of 
heads  or  points  of  origin. 

To  preserve  the  position  of  narrow  tendons  in  their  course,  they 
frequently  traverse  grooves  on  the  bones,  converted  into  canals  by 
means  of  ligaments.  To  facilitate  the  movement  of  the  tendons  in 
such  canals,  they  are  lined  by  synovial  membrane,  which  is  also  reflected 
upon  and  invests  the  tendons.  Likewise,  for  the  same  purpose,  when 
muscles  pass  over  prominences  usually  a  synovial  bursa  is  introduced 
between  them. 

THE   CAKDIAC    MTJSCULAK  TISSUE. 

The  heart  is  composed  of  muscular  tissue,  which  is  of  much  more 
compact  character  than  that  of  the  voluntary  muscles.  The  muscle- 
fibres,  instead  of  being  collected  into  primary  and  secondary  fascicles 

1  Leaders  ;  thews  ;  tendo  ;  tenon.  2  Expansio  nervosa. 


244  THE   MUSCULAE  SYSTEM. 

associated  and  enveloped  by  connective  tissue,  are  more  uniformly  con- 
joined,  and  are   generally  arranged   in 
FlG-  132-  concentric  layers,   which  surround   the 

cavities  of  the  heart,  and  in  part  project 
into  the  interior  in  numerous,  variably- 
sized,  smooth  columns. 

The  muscle-fibres  are  transversely 
striped  like  those  of  the  voluntary  mus- 
cles, but  otherwise  present  important 
differences.  They  are  less  translucent, 
less  distinct,  and  much  narrower ;  being 

from  a  fourth  to  a  third  the  diameter  of 

STRIATED  MUSCULAR  TISSUE  OF  THE      ,,  „  ,,  ,  „, 

HEART,  highly  magnified.  tnO8e  of  tn®  voluntary  muscles.     They 

are  irregularly  prismatic  and  mutually 

conformable,  with  the  intervals  occupied  by  connective  tissue  traversed 
by  the  capillary  blood-vessels  and  nerves.  They  seem  to  be  destitute  of 
a  distinct  sarcolemma,  and  consist  alone  of  sarcous  matter,  which  is 
longitudinally  striated,  as  well  as  transversely  striped.  The  fibres  are 
transversely  segmented ;  each  segment  being  a  short  columnar  muscle- 
cell,  two  or  three  times  longer  than  broad,  and  containing  a  central 
nucleus.  The  muscle-cells  are  united  with  one  another  at  the  sides  by 
narrower,  oblique  branches  or  offsets,  and  thus  the  muscle-fibres  are 
brought  into  intimate  relationship  by  anastomosis,  and  exhibit  a  con- 
dition in  the  cardiac  muscular  tissue  not  found  elsewhere. 

Vessels  and  nerves  of  the  muscles.  The  muscles  are  highly 
vascular,  in  accordance  with  the  activity  of  these  organs.  The  arteries, 
always  accompanied  by  veins,  a  single  one  for  each,  enter  the  muscles 
at  various  points  between  the  larger  fascicles,  and  usually  on  the  inner 
side.  Branching  and  penetrating  between  the  fascicles,  the  finer  vessels 
enter  the  primitive  fascicles,  and  terminate  in  capillaries  running  be- 
tween the  muscle-fibres,  in  general  parallel  with  the  latter,  and  fre- 
quently joined  by  transverse  vessels  crossing  the  fibres.  In  their  course 
the  vessels  are  supported  by  the  connective-tissue  sheaths  and  par- 
titions, which  are  also  furnished  with  capillaries  supplied  from  the  same 
source. 

Lymphatic  vessels  appear  not  to  exist  in  the  interior  of  muscles, 
though  they  are  abundant  in  the  connective-tissue  sheath. 

The  nerves  of  the  voluntary  muscles  are  of  considerable  size,  and 
generally  enter  them  in  company  with  the  vessels.  Passing  between 
the  fascicles  they  divide,  and  frequently  make  an  interchange  of  bun- 
dles of  nerve-fibres,  producing  a  plexus.  A  number  of  such  plexuses 
in  a  muscle  give  off  narrower  bundles  of  nerve-fibres  and  form  finer 
plexuses,  from  which  single  nerve-fibres  penetrate  between  the  muscle- 
fibres  and  divide  into  branches  distributed  to  the  latter. 

Tendons  and  aponeuroses  are  but  slightly  vascular.  The  chief  vessels 
and  capillaries  traverse  the  connective  tissue  between  the  fibrous  bundles, 


THE   MUSCULAR   SYSTEM. 


245 


generally  parallel  with  these  and  joined  by  transverse  vessels,  as  in  the 
capillaries  of  the  muscular  tissue,  but  much  fewer  and  smaller.  Lym- 
phatics are  abundant  in  the  connective-tissue  sheath  of  tendons,  and 
also  penetrate  the  intervals  of  the  tendon-bundles.  Nerves  are  few  in 
the  tendons,  and  traverse  the  intervals  of  the  fibrous  bundles. 

Termination  of  the  nerves  of  the  muscles.  The  nerves  of  the 
unstriped  or  involuntary  muscles  consist,  for  the  most  part,  of  non- 
medullated  fibres,  which  proceed  from  the  sympathetic  system,  and  con- 
tain but  few  medullated  fibres.  Frequently  branching  in  their  course, 

FIG.  133. 


FIG.  134. 


d 


PLEXUS  OF  NON-MEDULLATED  NEKVE-FIBKES, 
distributed  to  the  muscular  coat  of  a  small 
artery,  in  the  frog.  After  Arnold. 


A  MOTORIAL  END-PLATE,  in  a  muscle-fibre,  a, 
of  a  lizard;  6,  a  medullated  nerve-fibre  di- 
viding into  two  branches,  c ;  d,  the  axial  fibre 
ramifying  in  the  motorial  end-plate. 


they  end  in  intricate  plexuses  among  the  fascicles,  or  between  the  layers 
of  muscle-fibres.  From  the  plexuses  proceed  numerous  fibres,  which 
fork,  and  are  resolved  into  fine  fibrils  running  between  the  muscle- 
fibres.  In  the  mesenteric  plexus  of  the  muscular  coat  of  the  bowels, 
at  the  anastomosis  of  the  nerve-fibres,  little  groups  of  ganglion  cells 
occur.  The  exact  mode  of  termination  of  the  nerve-fibres  in  their 
relation  with  the  unstriped  muscle-fibres  has  not  been  satisfactorily 
ascertained. 

In  the  striped  voluntary  muscles  the  nerves  are  chiefly  composed 
of  medullated  fibres,  of  which  the  chief  funicles  run  parallel  with  and 
between  the  fleshy  fascicles.  Among  these  the  funicles  frequently 
branch,  anastomose,  and  form  plexuses,  from  which  single  nerve-fibres 
proceed,  in  their  course  fork  at  the  nodes,  and  after  dividing  several 
times  in  the  same  manner  give  a  branch  to  each  muscle-fibre.  As  the 
branch  enters  the  latter  its  neurilemma  ceases  by  becoming  continuous 
with  the  sarcolemma,  beneath  which  the  nerve-fibre  ends  in  a  peculiar 


246  THE    MUSCULAR   SYSTEM. 

structure,  named  the  motorial  end-plate.1  This  consists  of  an  ellip- 
tical, granular  disk  situated  immediately  beneath  the  sarcolemma,  and 
resting  on  the  sarcous  substance.  Scattered  through  the  disk  are  a 
number  of  oval  nuclei.  The  nerve-fibre  after  entering  the  muscle-fibre 
forks  into  two  or  more  widely-divergent  branches,  which  after  a  short 
course  lose  their  medullary  sheath,  while  the  axial  fibre  ramifies  in  the 
motorial  disk.  The  further  relationship  of  the  latter  with  the  sarcous 
substance  has  not  been  satisfactorily  determined. 

In  the  cardiac  muscular  tissue  the  nerves,  chiefly  consisting  of 
non-medullated  nerve-fibres,  terminate  in  gangliated  plexuses  similar  to 
those  in  the  muscular  walls  of  the  bowels.  The  terminal  nerve-fibrils 
from  the  plexuses  end  in  the  muscle-cells,  but  in  a  manner  not  posi- 
tively determined. 

MUSCLES   AND  FASCIA   OF   THE   CKANIAL   VAULT. 

The  superficial  fascia  of  the  vault  of  the  cranium  is  a  thin  but 
compact,  inextensible  layer  of  connective  tissue  intimately  blended  with 
the  skin  above,  and  closely  adherent  to  the  epicranial  aponeurosis  and 
muscles  beneath.  Next  the  skin  it  includes  a  dense  layer  of  adipose 
tissue,  in  which  are  embedded  the  roots  of  the  hairs  of  the  scalp  en- 
closed in  their  follicles. 

The  superficial  muscles  of  the  cranial  vault  are  the  frontal  muscle 
of  the  forehead,  the  occipital  and  post-auricular  muscles  of  the  occiput, 
and  the  supra-auricular  and  pre-auricular  muscles  of  the  temple.  The 
frontal  and  occipital  muscles,  united  by  the  intervening  epicranial 
aponeurosis,  are  usually  described  together  with  it  as  the  occipito- 
frontal  muscle.2 

The  frontal  muscle 3  is  a  thin,  pale,  fleshy  lamina,  which  occupies 
the  side  of  the  forehead,  joining  its  fellow  in  the  median  line  below  ; 
but  divergent  and  narrowing  in  a  curved  line  outwardly  above,  where 
it  reaches  the  posterior  border  of  the  frontal  bone.  It  is  connected  by 
its  upper  margin  with  the  epicranial  aponeurosis,  whence  the  fleshy 
fibres  descend,  for  the  most  part  to  end  by  intersecting  the  palpebral 
orbicular  and  superciliary  muscles  within  the  eyebrow,  and  by  a  slip 
which  intersects  the  nasal  pyramidal  muscle  on  the  glabella. 

The  occipital  muscle,4  less  than  half  the  length  of  the  former, 
but  rather  wider  and  redder,  arises  tendinously  from  the  outer  two- 
thirds  or  less  of  the  superior  curved  line  of  the  occipital  bone  and  the 
ridge  of  the  temporal  mastoid  continuous  with  it,  and  ascends  to  ter- 
minate in  a  convex  line  in  the  epicranial  aponeurosis. 

The  epicranial  aponeurosis5  is  common  to  both  sides  of  the 

1  Terminal  plate  ;  neural  eminence. 

2  Musculus  occipito-frontalis  ;  m.  epicranius  ;  m.  cranii  cutaneus. 

3  M.  frontalis ;  m.  epicranius  frontalis. 

*  M.  occipitalis  ;  m.  epicranius  occipitalis. 

6  A.  epicrania ;  occipito-frontal  aponeurosis  ;  galea  aponeurotica. 


THE    MUSCULAR   SYSTEM. 


247 


cranial  vault,  extends  forward  in  the  angular  interval  of  the  frontal 
muscles,  and  backward  between  the  occipital  muscles,  where  it  is 
attached  to  the  occipital  protuberance  and  adjacent  portions  of  the 
superior  curved  line.  Between  the  frontal  and  occipital  muscles  it  is 
most  distinctly  aponeurotic,  especially  the  occipital  portion,  and  is 
chiefly  composed  of  longitudinal  fibres,  of  which  those  from  the  mus- 
cles in  front  intersect  those  from  behind  somewhat  obliquely.  In  the 
temple  the  aponeurosis  is  thinner  and  of  looser  texture,  is  connected 
with  the  auricular  mus- 
cles, and  is  attached  be-  FlG-  135- 
low  to  the  zygoma.  At 
the  fore  part  it  exhibits 
a  thin,  and  mostly  indis- 
tinct, stratum1  of  pale 
fleshy  fibres,  which  pro- 
ceed obliquely  from  the 
vicinity  of  the  ear  towards 
the  frontal  and  palpebral 
orbicular  muscles. 

The  frontal  and  occip- 
ital muscles  and  the  inter- 
vening epicranial  aponeu- 
rosis adhere  closely  and 
tightly  to  the  superficial 
fascia  and  skin  above,  and 
loosely  by  thin  extensible 
connective  tissue  to  the 
periosteum  beneath.  The 
skin  of  the  cranial  vault, 
together  with  the  subja- 
cent superficial  fascia  and 
the  epicranial  aponeurosis 
with  its  muscles  beneath, 
constitutes  the  scalp, 
which  is  readily  detached 
from  the  skull,  while  its 
different  layers  are  sepa- 
rated with  difficulty.  By 
the  alternate  action  of  the 
frontal  and  occipital  mus- 
cles the  scalp  is  moved 
forward  and  backward, 


MUSCLES  OF  THE  HEAD  AND  NECK.  1,  2,  occipito-frontal 
muscle ;  1,  its  frontal  belly ;  2,  its  occipital  belly ;  3,  nasal 
pyramidal  muscle ;  4,  supra-  and  5,  post-auricular  muscles ; 
6,  palpebral  orbicular  muscle;  7,  naso-labial  elevator;  8. 
supra-labial  elevator ;  9,  nasal  compressor ;  10, 11,  zygomatic 
muscles;  12,  masseter;  13,  buccinator;  14.  oral-angle  de- 
pressor; 15,  oral  sphincter  muscle ;  16,  oral-angle  elevator  ; 
17, 18,  infra-labial  depressor ;  19,  sterno-mastoid  muscle ;  20, 
trapezius ;  21,  posterior  belly  of  the  digastric  and  the  stylo- 
hyoid  muscle ;  22,  anterior  belly  of  the  former ;  23,  loop  of 
fibrous  tissue  attaching  the  tendon  of  the  digastric  muscle 
to  the  hyoid  bone ;  24,  omo-hyoid  muscle ;  25,  sterno-hyoid ; 
26,  sterno-thyroid,  seen  to  the  outer  side  and  behind  the 
anterior  part  of  the  omo-hyoid;  27,  mylo-hyoid;  28, 
splenius;  29,  scapular  elevator;  30,  31,  middle  and  anterior 
scalenus  muscles ;  32,  clavicle. 


though   in   most   persons 

this  action  in  great  measure  appears  to  be  confined  to  the  frontal  muscles, 


1  M.  epicranius  temporalis  ;  superficial  temporal  muscle. 


248  THE   MUSCULAR  SYSTEM. 

which  elevate  the  eyebrows  and  throw  the  skin  of  the  forehead  into 
transverse  wrinkles.  The  frontal  and  occipital  muscles  are  supplied  by 
the  facial  nerve. 

In  bald  persons  the  frontal  muscles  frequently  appear  prominent 
and  distinctly  outlined  through  the  skin  of  the  forehead. 

THE   AUKICULAK   MUSCLES. 

The  supra-auricular  muscle l  is  a  broad,  thin,  pale,  fan-shaped 
lamina  occupying  the  upper  part  of  the  temple.  It  arises  from  the 
epicranial  aponeurosis  at  the  upper  border  of  the  latter,  descends,  and 
converges  to  a  thin  tendon,  which  is  inserted  at  the  inner  part  of  the 
auricle  into  the  fore  part  of  the  helix  and  the  prominence  of  the  anti- 
helix. 

The  pre-auricular  muscle 2  is  a  little,  pale,  fleshy  slip,  often  indis- 
tinct, and  scarcely  separated  from  the  former.  It  arises  from  the  epi- 
cranial aponeurosis  above  the  zygoma,  and  is  inserted  into  the  lower 
fore  part  of  the  helix. 

The  post-auricular  muscle8  usually  consists  of  two  well-marked 
bands,  of  redder  hue  than  the  former,  situated  inwardly  back  of  the 
ear.  They  arise,  one  above  the  other,  from  the  mastoid  portion  of 
the  temporal  bone  near  the  origin  of  the  occipital  muscle,  and  proceed 
forward  and  outward  to  be  inserted  into  the  concha  of  the  auricle. 

The  auricular  muscles  are  mostly  inactive,  and  may  be  regarded  as 
rudiments  of  similar  important  organs  in  the  rabbit,  the  cat,  and  the 
donkey. 

The  muscles  of  the  tympanum  are  described  with  the  ear. 

MUSCLES   OF   THE    PACE. 

The  superficial  fascia  of  the  face  is  less  distinct  than  that  of  the 
cranial  vault,  is  of  looser  texture,  contains  more  or  less  fat,  and  is 
blended  with  adjacent  structures.  It  invests  the  superficial  muscles  of 
the  face,  extends  over  the  cheek  and  parotid  gland,  and,  involving  the 
platysma  muscle,  is  continuous  with  the  corresponding  fascia  of  the 
neck.  In  the  eyelids  and  free  border  of  the  lips  it  blends  with  the 
skin,  and  in  these  positions  is  always  free  from  fat.  In  the  hollow  of 
the  cheek  it  usually  contains  a  considerable  accumulation  of  soft  fat, 
extending  outward  and  backward  in  the  interval  between  the  bucci- 
nator muscle  and  the  ramus  of  the  lower  jaw. 

MUSCLES   OF   THE   EYELIDS   AND  EYEBKOWS. 

The  palpebral  orbicular  muscle  *  forms  a  broad,  thin,  fleshy  zone 
in  front  of  the  orbit  immediately  beneath  the  skin.  It  consists  of  two 

1  M.  auricularis  superior  ;  m.  attollens  aurem,  auriculam,  or  auriculae. 

2  M.  aur.  ant. ;  m.  attrahens  aurem,  etc. 

3  M.  aur.  post.  ;  m.  retrahens  aurem,  etc. 

*  M.  orbicularis  palpebrarum  or  oculi ;  sphincter  palp,  or  oculi ;  m.  orb.  latus. 


THE   MUSCULAR   SYSTEM.  249 

portions,  which,  though  continuous  in  other  respects,  both  anatomically 
and  physiologically  exhibit  striking  differences.  The  central  or  palpe- 
bral  portion x  enters  into  the  construction  of  the  eyelids,  and  is  thinner 
and  paler  than  the  rest  of  the  muscle,  and  adheres  to  the  adjacent  thin 
skin  always  completely  devoid  of  interposed  fat  so  common  elsewhere. 
It  arises  from  the  upper  and  lower  margin  of  the  internal  palpebral 
ligament,  and  thence  spreads  outwardly  in  the  upper  and  the  lower  eye- 
lid, the  fibres  intersecting  one  another  externally  and  forming  a  series 
of  concentric  loops  attached  to  the  external  palpebral  ligament.  The 
peripheral  or  orbital  portion  of  the  muscle  extends  beneath  the  eye- 
brow, on  the  cheek  below,  and  on  the  fore  part  of  the  temple.  It  is 
thicker  and  redder  than  the  palpebral  portion,  and  is  separated  from 
the  skin  in  the  usual  manner  by  the  superficial  fascia  with  fat.  It 
arises  narrowly  from  the  inner  extremity  of  the  internal  palpebral  liga- 
ment, the  inner  part  of  the  supraorbital  ridge,  the  length  of  the  nasal 
process,  and  the  infraorbital  margin  of  the  maxilla ;  and  thence  ex- 
tends around  the  orbit,  forming  a  zone  of  fibres  arranged  in  concentric 
circles.  The  upper  border  is  intersected  by  the  frontal  and  supercil- 
iary muscles ;  the  outer  border  is  attached  to  the  temporal  portion  of 
the  epicranial  aponeurosis,  and  the  lower  border  to  the  fascia  of  the 
cheek. 

The  internal  palpebral  ligament 2  is  seen  in  life  as  a  whitish  spot 
at  the  inner  corner  of  the  opening  of  the  eyelids,  and  is  rendered  more 
prominent  by  stretching  the  latter  outwardly.  It  is  a  transverse  fibrous 
cord  immediately  beneath  the  skin,  attaching  the  eyelids  to  the  nasal 
process  of  the  maxilla  in  front  of  the  lachrymal  sac,  and  to  the  lach- 
rymal crest  behind  the  sac.  It  forks  outwardly,  and  terminates  in  the 
palpebral  tarsi.  The  external  palpebral  ligament  is  a  thickened 
portion  of  the  fibrous  membrane,  which  attaches  the  tarsi  to  the  sur- 
rounding margin  of  the  orbit. 

The  palpebral  tensor3  is  a  little  fleshy  slip  situated  at  the  inner 
part  of  the  orbit  behind  the  internal  palpebral  ligament,  and  is  contin- 
uous with  the  orbicular  muscle.  It  arises  from  the  crest  and  adjacent 
orbital  surface  of  the  lachrymal  bone,  crosses  the  lachrymal  sac  for- 
ward and  outward,  and  divides  into  two  portions,  which  cover  the 
lachrymal  canals,  and  near  the  puncta  are  inserted  into  the  palpebral 
tarsi. 

The  palpebral  elevator*  of  the  upper  eyelid  is  a  long,  thin,  fan- 
like  muscle,  which  occupies  the  upper  part  of  the  orbit.  It  arises 
by  its  narrow  extremity  tendinously  from  beneath  the  small  wing  of 
the  sphenoid  bone  in  front  of  the  optic  foramen,  proceeds  forward 
beneath  the  roof  of  the  orbit,  and  thence  emerges  in  a  broad,  thin  apo- 
neurosis, which  descends  to  be  inserted  into  the  upper  border  of  the 

1  M.  ciliaris  or  palpebralis.  '*  Tendo  oculi. 

3  M.  tensor  tarsi ;  muscle  of  Homer.  *  M.  levator  palpebrae  superioris. 


250  THE    MUSCULAR   SYSTEM. 

tarsus  of  the  upper  eyelid  immediately  behind  and  connected  with  the 
supra-palpebral  ligament. 

The  superciliary  muscle 1  is  a  fleshy  slip  lying  on  the  inner  part 
of  the  superciliary  ridge  of  the  frontal  bone  under  the  palpebral  orbic- 
ular muscle.  It  arises  from  the  inner  end  of  the  ridge,  and  ascends 
obliquely  outward  to  the  conjoined  border  of  the  palpebral  orbicular 
and  frontal  muscles  which  it  intersects,  and  is  inserted  into  the  skin  of 
the  eyebrow. 

The  palpebral  orbicular  muscle  entirely  displays  its  action  in  the 
voluntary  and  forcible  closure  of  the  eyelids.  Ordinarily  the  palpebral 
portion  alone  incessantly  acts  in  closing  the  eyelids  momentarily,  es- 
pecially the  upper  one,  in  winking.  The  palpebral  tensor  retains  the 
lachrymal  puncta  in  contact  with  the  eyeball,  so  as  to  facilitate  the 
absorption  of  the  tears.  The  palpebral  elevator  raises  the  upper  eye- 
lid, and  draws  it  backward  beneath  the  fore  part  of  the  orbit.  The 
superciliary  muscles  of  the  two  sides  draw  the  eyebrows  downward 
and  towards  each  other,  and  produce  vertical  wrinkles  on  the  glabella, 
as  in  frowning. 

MUSCLES  OF   THE   NOSE. 

These  consist  of  the  pyramidal,  compressor,  dilator,  depressor,  and 
naso-labial  elevator  muscles. 

The  nasal  pyramidal  muscle "  is  a  little  fleshy  slip  at  the  side  of 
the  root  of  the  nose,  in  contact  with  its  fellow  or  separated  by  a  narrow 
interval  widening  below.  It  starts  from  the  aponeurosis  of  the  com- 
pressor muscle  on  the  bridge  of  the  nose,  and  from  the  adjacent  part 
of  the  nasal  bone,  and  thence  ascends  to  the  glabella,  where  it  inter- 
sects a  slip  of  the  frontal  muscle,  than  which  it  is  redder  in  hue. 

The  nasal  compressor3  is  a  thin,  pale,  fleshy,  triangular  muscle, 
occupying  the  side  of  the  nose  above  the  wing.  It  is  of  variable 
development  and  distinctness,  and  arises  narrowly  from  the  maxilla 
at  the  side  of  the  nasal  orifice,  ascends  forward,  expands  on  the  side 
of  the  nose,  and  terminates  in  a  thin  aponeurosis,  which  is  contin- 
uous with  that  of  the  opposite  side  across  the  bridge  of  the  nose. 
The  aponeurosis  is  tightly  connected  with  the  adjacent  skin,  but  loosely 
with  the  subjacent  bridge  of  the  nose,  so  that  the  former  together 
readily  move  from  side  to  side  on  the  latter.  Above,  the  aponeurosis 
is  connected  with  the  pyramidal  muscle,  and  below  with  the  upper 
border  of  the  wing  and  the  tip  of  the  nose. 

The  nasal  dilator,4  variably  produced  and  mostly  indistinct,  con- 

1  M.  superciliaris ;  m.  corrugator  supercilii. 

2  M.  pyramidalis  nasi ;  m.  dorsalis  narium  ;  m.  procerus  nasi. 

3  M.  compressor  nasi  or  nari  ;    m.  c.  narium  major ;  m.  triangularis  nasi ;  m. 
transversus  nasi  ;  m.  attrahens  nasi ;  m.  constrictor  alas  nasi. 

4  M.  dilatator  naris  ;  m.  dil.  naris  posterior ;  m.  levator  proprius  alse  nasi  pos- 
terior. 


THE   MUSCULAK  SYSTEM.  25 1 

sists  of  a  layer  of  pale  fleshy  fibres  involved  in  the  connective  and 
adipose  tissue  and  adjacent  skin  of  the  wing  of  the  nose.  The  fibres 
spring  from  the  groove  at  the  back  of  the  wing,  and  curve  forward 
and  downward  to  end  in  the  skin  at  the  margin  of  the  nostril. 
Another  and  less  distinct  layer  has  been  described  as  the  anterior 
dilator,1  occupying  the  side  of  the  end  of  the  nose  between  the  skin 
and  the  oval  cartilage.  Its  fibres  curve  from  the  margin  of  the  nostril 
upward  and  forward  to  end  in  the  skin  at  the  tip  of  the  nose. 

The  naso-labial  elevator  2  lies  beneath  the  skin  along  the  side 
of  the  nose  at  the  inner  part  of  the  orbit,  extending  to  the  upper  lip. 
It  arises  narrowly  from  the  nasal  process  of  the  maxilla,  between 
the  nasal  pyramidal  and  the  palpebral  orbicular  muscle,  descends  and 
crosses  the  outer  part  of  the  compressor  and  the  inner  part  of  the 
supra-labial  elevator,  and  is  inserted  into  the  posterior  border  of  the 
nasal  wing,  and  in  union  with  the  latter  muscle  into  the  skin  of  the 
upper  lip,  at  the  upper  part  of  the  oral  sphincter. 

The  nasal  depressor3  is  a  thin,  fleshy  layer,  which  lies  under 
the  upper  lip  next  the  lining  mucous  membrane.  It  arises  from  the 
incisive  fossa  to  the  canine  alveolus  of  the  maxilla,  and  ascends  and 
curves  forward  to  be  inserted  into  the  lower  border  of  the  nasal  septum 
and  the  posterior  border  of  the  nostril,  extending  outwardly  behind  the 
nasal  wing.  In  the  latter  position  it  is  continuous  with  the  origin  of 
the  nasal  compressor,  and  is  intersected  by  the  insertion  of  the  naso- 
labial  elevator,  which  together  with  the  oral  sphincter  covers  it. 

MUSCLES   OF   THE   MOUTH,  LIPS,   AND    CHEEK. 

The  oral  sphincter  *  is  an  elliptical  muscle  surrounding  the  orifice 
of  the  mouth,  and  forming  the  fleshy  basis  of  the  lips.  It  is  inter- 
sected at  the  corners,  or  angles,  of  the  mouth  by  a  number  of  other 
muscles,  chiefly  the  buccinators,  of  which  the  fibres  that  arise  from  the 
maxilla  proceed  to  the  lower  lip,  while  those  from  the  mandible  pass 
to  the  upper  lip.  At  the  free  border  of  the  oral  orifice  the  sphincter 
consists  of  a  rounded  fasciculus5  of  fibres,  forming  an  uninterrupted 
ring,  which  is  covered  by  the  thin  skin  where  it  merges  into  the  lining 
mucous  membrane  of  the  lips.  The  exterior  and  deeper  portion6  of 

1  M.  dil.  naris  anterior ;  m.  lev.  prop,  alse  nasi  anterior. 

2  M.  levator  labii  superioris  alseque  nasi  ;  common  elevator  of  the  lip  and  nose ; 
elevator  of  the  upper  lip  and  .wing  of  the  nose;  superficial  common  elevator  of  the 
wing  of  the  nose  and  of  the  upper  lip  ;   m.  pyramidalis ;  m.  pyr.  narium ;   caput 
angulare  of  the  m.  quadratus  labii  superioris. 

3  M.  depressor  alse  nasi ;  m.  depressor  labii  superioris  alasque  nasi ;  m.  dep.  labii 
sup.  ;  m.  myrtiformis ;  m.  nasalis ;  m.  lateralis  nasi ;  m.  dilatator  narium ;  m.  dil. 
pinnae  ;  m.  fixator  labii  sup.  ;  labio-nasal  depressor. 

4  Sphincter  oris ;    m.  orbicularis  oris ;   m.  constrictor  labiorum  ;    m.  c.  prolabii 
superioris  et  inferioris  ;  oral  orbicular  muscle. 

5  Pars  marginalis,  or  labialis.  6  Facial  part. 


252  THE    MUSCULAR  SYSTEM. 

the  sphincter  is  covered  externally  by  fibres  of  other  muscles  con- 
verging to  the  mouth,  and  by  the  skin  with  an  intervening  layer  of 
connective  and  adipose  tissue,  and  internally  is  covered  by  the  lining 
mucous  membrane  and  labial  glands.  At  the  oral  angle  it  decussates 
with  the  buccinator  behind  the  other  converging  muscles,  which  con- 
sist of  the  elevator  and  depressor  of  the  oral  angle  and  the  zygomatic 
muscle.  In  the  upper  lip  it1  arises  from  the  inferior  border  of  the 
nasal  septum,  where  it  is  closely  connected  with  the  nasal  depressor, 
and  thence  turns  backward,  downward,  and  outward  to  the  oral 
angle,  producing  in  the  divergence  of  the  lateral  portions  the  con- 
spicuous median  groove  of  the  upper  lip.  The  muscle  is  also  rein- 
forced on  each  side  by  a  pair  of  narrow  slips,2  of  which  one  arises  from 
the  incisive  fossa  of  the  maxilla,  and  the  other  from  the  mandible 
below  the  canine  tooth,  and  both  proceed  outwardly  to  the  oral  angle. 

The  supra-labial  elevator3  is  a  quadrate  muscle  situated  below 
the  orbit,  partially  covered  by  the  palpebral  orbicular  muscle,  and 
partially  subcutaneous.  It  arises  immediately  below  the  infraorbital 
margin  from  the  maxilla  and  malar  bone,  and  descends  inwardly,  and 
is  joined  by  the  naso-labial  elevator  to  be  inserted,  in  union  with  it, 
into  the  skin  of  the  upper  lip  and  the  adjacent  portion  of  the  oral 
sphincter. 

The  oral  angle  elevator 4  is  a  triangular  muscle  lying  beneath  the 
preceding.  It  arises  obliquely  across  the  upper  part  of  the  canine 
fossa  of  the  maxilla,  below  the  infraorbital  foramen,  and  descends  out- 
wardly to  the  oral  angle,  where  it  decussates  with  the  other  more  super- 
ficial muscles  converging  to  the  same  point.  Its  inner  border  is  con- 
tiguous to,  and  sometimes  continuous  with,  the  upper  border  of  the  oral 
sphincter. 

The  zygomatic  muscle  5  is  a  fleshy  band  embedded  in  the  sub- 
cutaneous connective  and  adipose  tissue  of  the  cheek.  It  arises  tendi- 
nously  from  the  outer  surface  of  the  malar  zygomatic  process,  and 
descends  obliquely  forward  and  inward  to  the  oral  angle,  where  it 
decussates  with  the  preceding  and  other  converging  muscles. 

The  lesser  zygomatic  muscle 6  is  a  variable  and  inconstant  fas- 
cicle, occupying  a  similar  position  of  the  cheek  in  advance  of  the  former 
muscle.  It  arises  in  front  of  this  from  the  malar  bone,  or  partially  from 

1  M.  nasalis  labii  superioris ;    depressor  septi  mobilis  narium  ;   depressor  apicis 
narium  ;  m.  naso-labialis.  • 

2  Musculi  incisivi ;  m.  accessorii  orbicularis. 

3  M.  levator  labii  superioris  proprius  or  major ;  superior  labial  elevator  ;  elevator 
of  the  upper  lip ;  m.  incisorius  ;  caput  infraorbitale  of  the  m.  quadratus  labii  supe- 
rioris. 

4  M.  levator  anguli  oris ;  elevator  of  the  angle  of  the  mouth ;  m.  caninus  ;  m. 
levator  labiorum  communis. 

6  M.  zygomaticus  major  ;  greater  zygomatic  muscle. 

6  M.  zygomaticus  minor ;  caput  zygomaticum  of  the  m.  quadratus  labii  superioris. 


THE   MUSCULAR  SYSTEM.  253 

this  and  the  adjacent  border  of  the  palpebral  orbicular  muscle,  and  de- 
scends obliquely  inward  and  joins  the  outer  border  of  the  supralabial 
elevator,  to  be  inserted  with  it  into  the  skin  of  the  upper  lip  and  oral 
sphincter. 

The  infra-labial  elevator l  is  a  small  fleshy  layer  situated  under 
the  mucous  membrane  lining  the  lower  lip.  It  arises  from  the  incisive 
fossa  of  the  mandible,  descends  and  widens  and  terminates  in  the  lower 
border  of  the  oral  sphincter  and  adjacent  portion  of  the  skin  of  the 
chin. 

The  infra-labial  depressor2  is  a  rhombic  plane  of  fleshy  fibres  at 
the  side  of  the  chin,  for  the  most  part  subcutaneous,  and  mingled  with 
connective  tissue  and  fat,  in  which  are  embedded  the  roots  of  the  hairs 
of  the  beard.  It  arises  from  the  outer  side  of  the  base  of  the  mandible, 
between  the  mental  protuberance  and  the  mental  foramen,  and  ascends 
inwardly,  to  be  inserted  into  the  skin  of  the  lower  lip,  decussating  with 
the  subjacent  portion  of  the  oral  sphincter  and  with  its  fellow  of  the 
opposite  side. 

The  oral  angle  depressor3  is  a  subcutaneous  triangular  muscle 
occupying  the  side  of  the  chin  behind  the  former,  and  partially  cover- 
ing it.  It  arises  from  the  outer  part  of  the  base  of  the  mandible,  at 
the  side  of  the  chin,  and  partially  is  continuous  from  behind  with  the 
platysma  muscle,  whence  it  ascends  and  converges  to  the  oral  angle, 
where  it  decussates  with  the  oral  angle  elevator  and  other  muscles  con- 
verging to  the  same  point. 

The  buccinator4  occupies  the  deep  part  of  the  cheek  next  the 
lining  membrane  of  the  mouth.  It  is  a  broad,  quadrilateral  muscle, 
extended  between  the  outside  of  the  jaws,  from  the  corner  of  the  mouth 
backward,  within  the  ramus  of  the  mandible  to  the  pharynx.  It  arises 
from  the  base  of  the  molar  portion  of  the  alveolar  processes  of  both 
jaws,  and  behind  from  the  pterygo-maxillary  ligament,  and  thence 
proceeds  forward  to  the  angle  of  the  mouth,  where  it  joins  the  oral 
sphincter,  within  the  position  of  the  other  muscles  which  converge  to 
the  same  point.  From  their  origin,  the  muscular  fibres,  for  the  most 
part,  are  convergent  towards  the  oral  angle,  where  they  decussate,  those 
from  above  passing  into  the  lower  lip,  and  those  from  below  into  the 
upper  lip,  while  others  above  and  below  pass  into  each  corresponding 
lip  without  decussation.  Externally  the  buccinator  is  closely  invested 
with  a  thin  layer  of  the  deep  fascia,  covered  by  the  superficial  fascia 
with  an  accumulation  of  soft,  adipose  tissue,  which  separates  the  mus- 
cle in  front  from  the  skin  and  platysma  muscle,  and  behind  from  the 

1  M.  levator  labii  inferioris ;  elevator  of  the  lower  lip  ;  m.  levator  menti ;  m. 
mentalis;  m.  incisivus  inferius. 

2  M.  depressor  labii  inferioris  ;  depressor  of  the  lower  lip  ;  m.  quadratis  menti. 

1  M.  depressor  anguli  oris  ;  depressor  of  the  angle  of  the  mouth  ;  m.  triangu- 
laris  menti ;  m.  depressor  labiorum  communis  ;  m.  pyramidalis  menti. 
4  Muscle  of  the  cheek ;  trumpeter  muscle. 


254  THE    MUSCULAR   SYSTEM. 

ramus  of  the  mandible.  Opposite  the  second  upper  molar  tooth  it  is 
perforated  by  the  parotid  duct,  around  which  the  contiguous  fibres 
decussate. 

The  pterygo-maxillary  ligament  is  a  narrow  tendinous  inter- 
section between  the  buccinator  and  the  superior  constrictor  of  the 
pharynx,  extended  between  the  lower  extremity  of  the  sphenoidal 
entopterygoid  process  and  the  posterior  extremity  of  the  mylo-hyoid 
ridge  of  the  mandible. 

THE    MUSCLES   OF   MASTICATION. 

These  consist  of  the  temporal,  masseter,  external  pterygoid,  and 
internal  pterygoid  muscles. 

The  temporal  muscle,1  the  largest  of  the  muscles  of  mastication, 
is  fan-shaped,  and  occupies  the  entire  extent  of  the  temporal  fossa,  en- 
closed by  the  temporal  fascia.  It  arises  from  the  surface  of-  the  tem- 
poral fossa,  extending  to  the  infratemporal  crest,  and  from  the  upper 
inner  moiety  of  the  temporal  fascia,  whence  the  fleshy  fascicles  descend 
and  converge  to  an  interior  aponeurosis,  which  narrows  into  a  thick,  flat 
tendon,  passing  through  the  zygomatic  fossa  to  be  inserted  into  the 
apex,  front  border,  and  inner  surface  of  the  coronoid  process  of  the 
mandible.  Its  lower  fore  part  is  contiguous  to  the  masseter  muscle, 
and  usually  intimately  connected  with  it.  Internally  the  insertion  is 
separated  from  the  buccinator  and  pterygoid  muscles  by  an  accumu- 
lation of  areolar  and  adipose  tissue  extending  backward  from  the 
cheek. 

The  temporal  fascia 2  is  a  bluish-white,  shining  aponeurosis,  cover- 
ing the  temporal  muscle  and  outwardly  closing  the  temporal  fossa,  to 
the  circumference  of  which  it  is  attached.  Its  upper  part  gives  origin 
to  the  outer  fleshy  fascicles  of  the  temporal  muscle,  but  is  separated 
below  from  the  latter  by  a  variable  quantity  of  loose  areolar  tissue 
and  fat.  Approaching  the  zygoma,  it  divides  into  two  layers,  which 
are  attached  to  the  inner  and  outer  surface  of  the  former,  and  include 
between  them  a  layer  of  connective  tissue  and  fat.  Its  external  sur- 
face is  invested  by  the  temporal  portion  of  the  epicranial  aponeurosis, 
between  which  and  the  superficial  fascia  are  the  supra-auricular  and 
pre-auricular  muscles. 

The  masseter3  occupies  the  back  part  of  the  cheek  below  the 
zygoma  on  the  outer  side  of  the  ramus  of  the  lower  jaw.  It  is  a 
thick  quadrilateral  muscle,  consisting  of  two  portions.  The  super- 
ficial, larger,  quadrate  portion  arises  tendinously  from  the  anterior 
two-thirds  of  the  lower  border  of  the  zygoma,  descends  with  an  in- 
clination backward,  and  is  inserted  into  the  outer  surface  of  the  lower 
half  and  angle  of  the  ramus  of  the  mandible.  The  deeper,  triangular 

1  M.  temporalis ;  m.  crotaphites.  2  Fascia  temporalis. 

3  M.  massetericus  ;  m.  manducatorius ;  in.  mandibularis  externus. 


THE   MUSCULAR   SYSTEM. 


255 


portion,  partially  visible  behind  the  former,  arises  from  the  posterior 
third  of  the  lower  border  and  the  whole  of  the  internal  surface  of  the 
zygoma,  descends  and  joins  the  other  portion,  and  is  inserted  into  the 
upper  half  of  the  outer  surface  of  the  ramus  of  the  mandible. 

The  masseter  muscle  is  partially  subcutaneous,  but  is  overlapped 
behind  by  the  parotid  gland,  crossed  above  by  the  parotid  duct,  and 
covered  below  by  the  platysma  muscle.  It  is  separated  in  front  from 
the  buccinator  by  an  accumulation  of  areolar  and  adipose  tissue  occu- 
pying a  hollow  outside  the  latter,  and  extending  backward  within  the 
position  of  the  ramus  of  the  lower  jaw. 

FIG.  136. 


VIEW  OF  THE  TEMPORAL  MUSCLE.    The  temporal  fascia  and  zygoma  removed. 

The  external  pterygoid  muscle 1  is  a  pyramidal  fleshy  mass,  occu- 
pying the  upper  part  of  the  zygomatic  fossa.  It  arises  from  the  under 
surface  of  the  great  wing  and  the  outer  surface  of  the  ectopterygoid 
process  of  the  sphenoid  bone,  converges  backward  and  outward,  and  is 
inserted  into  the  front  of  the  neck  of  the  lower  jaw  and  the  capsular 
ligament  and  fibre-cartilage  of  the  articulation.  At  its  origin  it  is  di- 
vided by  a  fissure,  which  receives  the  internal  maxillary  vessels  in  their 
usual  course  on  the  outer  side  of  the  lower  portion  of  the  muscle.  In- 
ternally it  is  in  contact  with  the  internal  pterygoid  muscle,  the  spheno- 
maxillary  ligament,  and  the  inferior  dental  vessels  and  nerve ;  externally 
with  the  insertion  of  the  temporal  muscle  into  the  coronoid  process  of 
the  mandible. 

The  internal  pterygoid  muscle 2  is  quadrilateral,  and  is  situated 
on  the  inner  side  of  the  ramus  of  the  lower  jaw,  nearly  in  like  manner 

1  M.  pterygoideus  externus,  or  minor.         2  M.  pterygoideus  internus,  or  major. 


256 


THE   MUSCULAR   SYSTEM. 


FIG.  137. 


with  the  masseter  on  the  outside.  It  arises  in  the  pterygoid  fossa, 
tendinously  and  fleshy,  from  the  inner  surface  of  the  ectopterygoid 
process  and  the  pyramidal  process  of  the  palate  bone,  descends  back- 
ward and  outward,  and  is  inserted  into  the  lower  back  part  of  the 

inner  surface  of  the  ramus  and 
angle  of  the  lower  jaw.  Between 
it  and  the  ramus  are  the  spheno- 
maxillary  ligament  and  the  inferior 
dental  nerve  and  vessels  ;  internally 
it  is  in  contact  with  the  palatal  ten- 
sor and  the  superior  constrictor  of 
the  pharynx. 

The  muscles  of  mastication  are 
supplied  by  the  motor  division  of 
the  trigeminal  nerve,  the  temporal 
muscle  receiving  two  or  three 
branches,  and  the  other  muscles 
each  usually  one.  The  muscles  are 
elevators  of  the  lower  jaw,  and  in 
the  ordinary  state  of  rest  retain 
the  lower  teeth  in  contact  with  the 
upper  teeth.  In  biting,  the  lower 
jaw  is  mainly  lifted  by  the  tem- 
poral and  masseter  muscles.  In 
masticating,  the  lower  jaw  is  drawn 
forward  by  the  pterygoid  and  mas- 
seter muscles,  is  moved  from  side  to 
side  by  the  alternate  action  of  the 
former  on  opposite  sides,  and  is  drawn  backward  by  the  temporal 
muscles. 

MUSCLES   AND   FASCIAE   OF   THE    NECK. 

The  platysma l  is  a  thin,  broad,  pale  muscle,  situated  immediately 
beneath  the  skin  at  the  side  of  the  neck,  extending  from  the  chest  and 
shoulder  to  the  face.  It  consists  of  a  stratum  of  fleshy  fibres,  lying  be- 
tween the  superficial  and  the  deep  fascia ;  arising  from  the  latter  over 
the  pectoral,  deltoid,  and  latissimus  muscles ;  ascending  obliquely  in- 
ward over  the  clavicle  and  acromion  and  the  side  of  the  neck  to  the 
lower  jaw  and  angle  of  the  mouth.  The  anterior  portion  of  the  muscle 
is  inserted  into  the  base  of  the  mandible  at  the  side  of  the  chin,  extend- 
ing from  the  symphysis  along  the  line  of  origin  of  the  infralabial  and 
oral  angle  depressors.  Behind  this  position  the  muscle  passes  over  the 
base  and  angle  of  the  jaw,  and  proceeds  forward  on  the  masseter  and 
buccinator  muscles  to  end  in  the  oral  angle  and  posterior  portion  of  its 
depressor.  The  anterior  fibres  beneath  the  chin  decussate  with  those 


VIEW  OF  THE  INTERIOR  PART  OF  THE    LEFT 

SIDE  OF  THE  FACE.  1,  condyle  of  the  lower 
jaw;  2,  angle  of  the  jaw;  3,  base;  4,  sym- 
physis; 5,  submaxillary  fossa;  6,  attachment 
of  the  mylo-hyoid  muscle  to  the  correspond- 
ing ridge ;  7,  origin  of  the  genio-hyoid  mus- 
cles; 8,  origin  of  the  genio-glossal  muscles; 
9,  masseter  muscle ;  10,  internal  pterygoid 
muscle;  11,  external  pterygoid  muscle. 


1  Platysma  myoides ;  m.  subcutaneus  colli  or  cervicis. 


THE    MUSCULAR   SYSTEM.  257 

of  the  opposite  muscle  and  become  fixed  in  front  of  the  symphysis 
and  mental  protuberance  of  the  mandible.  Commonly,  a  few  more  or 
less  detached  fibres  at  the  upper  border  of  the  muscle  proceed  nearly 
transversely  across  the  cheek  to  the  oral  angle.  These  have  been 
regarded  as  distinct  under  the  name  of  the  risorius  or  laughing 
muscle.  It  is  variable  and  sometimes  absent. 

The  platysma  is  separated  from  the  parts  beneath  by  the  deep  cer- 
vical fascia.  It  covers  the  acromio-clavicular  attachment  of  the  tra- 
pezius  and  the  greater  extent  of  the  sterno-mastoid  muscle,  crossing 
the  direction  of  their  fibres.  It  also  covers  the  supra-hyoid  and  part 
of  the  infra-hyoid  muscles,  the  submaxillary  gland,  and  the  triangular 
space  which  includes  the  termination  of  the  carotid  artery  and  its  divis- 
ions. On  the  face  it  covers  the  muscles  and  parotid  gland,  extending 
from  the  angle  of  the  jaw  to  the  oral  angle.  It  is  supplied  by  the 
facial  and  superficial  cervical  nerves. 

The  platysma  probably  plays  a  part  in  preventing  undue  pressure 
through  contraction  of  the  skin  of  the  neck  on  the  parts  beneath.  It 
may  aid  in  depressing  the  mandible  and  in  opening  the  mouth.  The 
portion  named  the  risorius,  by  drawing  the  corner  of  the  mouth  out- 
ward, produces  the  appearance  of  smiling.  In  advanced  age,  after 
loss  of  the  teeth  and  alveolar  borders  of  the  jaws,  and  the  consequent 
elevation  of  the  mandible,  the  anterior  borders  of  the  platysma  muscles 
produce  conspicuous  folds  of  the  skin  at  the  fore  part  of  the  neck.  The 
muscle  represents  the  more  extensive  subcutaneous  stratum,  named  the 
panniculus  carnosus,  present  in  many  mammals,  and  producing  move- 
ments of  the  skin  such  as  are  observed  in  a  horse  when  it  shakes  the 
flies  from  its  sides. 

The  deep  cervical  fascia  is  the  connective-tissue  membrane 
which  invests  all  the  deeper  parts  of  the  neck  subjacent  to  the  super- 
ficial fascia  and  platysma,  variably  produced  and  distinct  in  different 
positions.  It  is  more  or  less  firmly  fixed  to  the  contiguous  hard  parts, 
and  sheathes  all  the  softer  parts,  varying  in  thickness,  texture,  and 
strength  among  these.  At  the  back  of  the  neck  it  is  superficially  at- 
tached to  the  occipital  protuberance,  nuchal  ligament,  and  spinous  pro- 
cesses below ;  thence  it  affords  a  thin  investment  to  the  trapezius  muscle, 
from  the  outer  border  of  which  it  extends  across  the  posterior  cervical 
triangle  attached  below  to  the  clavicle.  Sheathing  the  sterno-mastoid 
muscle,  attached  to  the  mastoid  process,  the  clavicle  and  sternum,  it 
proceeds  across  the  anterior  cervical  triangle  to  the  median  line  of 
the  neck,  where  it  becomes  continuous  with  the  fascia  of  the  other 
side,  and  above  is  fixed  to  the  base  of  the  mandible.  Beneath  the 
sterno-mastoid  muscle  it  forms  a  loose  sheath  to  the  great  cervical 
blood-vessels  and  accompanying  nerves,  and  is  continuous  inwardly 
with  the  more  compact  membrane  which  invests  the  pharynx  and 
oesophagus,  the  trachea  and  larynx,  and  the  muscles  in  front  of  the 
latter;  and  outwardly  with  the  equally  compact  layer  which  invests 

17 


258  THE    MUSCULAR   SYSTEM. 

the  splenius  and  scalenus  muscles,  the  brachial  plexus  of  nerves  and 
subclavian  vessels,  and  is  fixed  to  the  first  rib.  It  encloses  the  sub- 
maxillary  and  parotid  glands,  invests  the  digastric,  stylo-hyoid,  and 
mylo-hyoid  muscles,  is  fixed  to  the  hyoid  bone,  mandible,  and  zygoma, 
and  is  continuous  with  the  fascia  of  the  masseter  and  pterygoid  mus- 
cles. It  is  reinforced  by  a  thin  aponeurotic  band,  named  the  stylo- 
maxillary  ligament,  which  descends  from  the  styloid  process  of  the 
temporal  bone  to  the  inner  part  of  the  angle  of  the  mandible,  and  is 
thence  extended  as  a  thinner  expansion  between  the  parotid  and  sub- 
maxillary  glands  to  the  contiguous  part  of  the  sheath  of  the  great 
cervical  vessels.  A  distinct  portion  of  the  fascia  encloses  the  posterior 
belly  of  the  omo-hyoid  muscle  and  its  intermediate  tendon,  which  is 
attached  by  the  same  means  to  the  contiguous  part  of  the  sheath  of 
the  great  cervical  vessels,  is  thence  extended  and  fixed  to  the  inner 
side  of  the  clavicle,  and  serves  to  retain  the  muscle  in  its  position.  In 
the  posterior  cervical  triangle,  along  the  course  of  the  great  vessels, 
the  fascia  forms  a  loose  envelope  to  the  cervical  lymphatic  glands, 
mingled  with  more  or  less  fat,  and  continuous  below  with  the  areolar 
connective  tissue  of  the  axilla.  Similar  portions  of  connective  tissue, 
with  fat  and  lymphatic  glands,  occupy  the  vicinity  of  the  salivary 
glands  and  the  fossae  at  the  bottom  of  the  neck. 

The  sterno-mastoid  muscle l  is  the  largest  and  most  conspicu- 
ous of  the  muscles  of  the  neck,  and  extends  obliquely  from  the  fore 
part  of  the  chest  to  the  head,  back  of  the  ear.  It  consists  of  a  flat- 
tened, cylindroid  belly,  expanding  at  the  extremities,  and  arising  by 
separate  heads  from  the  sternum  and  clavicle.  The  sternal  head,2 
narrow  and  rounded,  arises  by  a  flattened  tendon  from  the  upper  front 
part  of  the  sternum  close  to  its  fellow,  and  thence  ascends  obliquely 
backward  and  outward  at  the  side  of  the  neck.  The  clavicular  head,3 
of  variable  width,  arises  partially  tendinous  and  fleshy  from  the  upper 
border,  usually  of  the  inner  third  of  the  clavicle,  whence  it  ascends 
nearly  vertically  and  unites  with  the  former  head.  The  common  belly, 
continuing  in  the  direction  of  the  latter,4  is  inserted  teridinously  into 
the  temporal  mastoid  process,  extending  from  its  apex  upward  and 
backward  and  along  the  outer  half  of  the  superior  curved  line  of  the 
occipital  bone.  The  angular  interval  of  the  two  heads,  situated  above 
the  sterno-clavicular  articulation,  is  variable  in  size,  and  is  closed  by 
the  apposition  of  the  two  layers  of  the  fascia  ensheathing  the  muscle. 
The  clavicular  head  is  also  variable  in  extent,  sometimes  being  as 
narrow  as  the  sternal  head,  and  sometimes  widening  outwardly  nearly 
to  the  insertion  of  the  trapezius.  Occasionally  it  remains  distinct,  and 

1  M.   sterno-cleido-mastoideus ;  sterno-cleido-mastoid  ra.  ;  m.   mastoideus  colli ; 
m.  nutator  capitis. 

2  Caput  sternale ;  m.  sterno-mastoideus  ;  m.  nutator  capitis  int.  or  ant. 

3  C.  claviculare  ;  m.  cleido-mastoideus  ;  m.  nutator  capitis  ext.  or  post. 


THE   MUSCULAR   SYSTEM. 


259 


FIG.  138. 


ascends  behind  the  sternal  head  to  be  inserted  into  the  apex  of  the 
mastoid  process. 

The  sterno-mastoid  muscle  is  covered  the  greater  part  of  its  extent 
along  the  middle  by  the  platysma,  and  is  also  crossed  by  the  external 
jugular  vein,  the  superficial 
cervical,  and  the  great  au- 
ricular nerve.  Its  lower 
portion  rests  on  the  stern  o- 
hyoid  and  sterno-thyroid 
muscles,  and  crosses  the 
omo-hyoid ;  and  above  it  is 
in  contact  with  the  sca- 
leni,  scapular  elevator, 
splenius,  and  digastric  mus- 
cles. About  the  middle  of 
the  neck  it  crosses  the 
great  cervical  blood-ves- 
sels contained  within  their 
sheath.  The  accessory 
nerve  pierces  its  upper 
third  within,  and  is  its 
main  source  of  supply; 
other  nerves  being  derived 
from  the  cervical  plexus. 

In  action  the  sterno- 
mastoid  muscle  may  flex 
the  head  towards  the  shoul- 
der of  the  same  side,  or  it  may  turn  the  head  with  the  face  di- 
rected towards  the  opposite  side.  Ordinarily,  both  muscles  maintain 
the  erect  position  of  the  head  with  the  face  directed  forward,  and 
in  greater  action  bend  the  head  backward  with  the  face  directed  up- 
ward. Most  authorities  assert  that  the  two  muscles  acting  together 
bow  the  head  forward,  but  this  appears  to  be  an  error  in  the  view 
that  their  insertion  is  posterior  to  the  articulation  of  the  skull  with 
the  vertebral  column. 

The  course  of  the  sterno-mastoid  divides  the  quadrilateral  space  at 
the  side  of  the  neck  into  two  triangles,  which  are  important  in  their 
surgical  relations.  The  anterior  cervical  triangle  is  defined  in  front  by 
the  median  line  of  the  neck,  behind  by  the  anterior  border  of  the 
sterno-mastoid,  and  above  by  the  base  of  the  lower  jaw.  The  posterior 
cervical  triangle  is  defined  in  front  by  the  posterior  border  of  the 
sterno-mastoid,  behind  by  the  anterior  border  of  the  trapezius,  and 
below  by  the  clavicle. 


FRONT  VIEW  OF  THE  MUSCLES  OF  THE  NECK.  1,  posterior, 
and  2,  anterior  belly  of  the  digastric  ;  3,  its  intermediate 
tendon  attached  to  the  hyoid  bone  and  passing  through 
the  insertion  of  the  stylo-hyoid  muscle,  4 ;  5,  mylo-hyoid ; 
6,  genio-hyoid ;  7,  stylo-glossal ;  8,  hyo-glossal ;  9,  styloid 
process;  10,  stylo-pharyngeal ;  11,  sterno-mastoid;  12,  its 
sternal  origin ;  13,  its  clavicular  origin ;  14,  sterno-hyoid ; 
15,  sterno-thyroid ;  16,  thyro-hyoid ;  17,  18,  omo-hyoid ; 
19,  trapezius ;  20,  anterior  scalenus ;  21,  middle  scalenus 
muscle. 


260  THE   MUSCULAR   SYSTEM. 

SUPRA-   AND  INFKA-HYOID  MUSCLES. 

Of  these,  the  digastric,  stylo-hyoid,  mylo-hyoid,  and  genio-hyoid 
muscles  are  situated  above  the  hyoid  bone,  with  which  they  are  con- 
nected, while  the  sterno-hyoid,  sterno-thyroid,  thyro-hyoid,  and  orao- 
hyoid  are  situated  below  it. 

The  digastric  muscle l  is  situated  behind  and  beneath  the  lower 
jaw,  curving  from  within  the  position  of  the  mastoid  process  to  the 
chin ;  and  it  consists  of  two  conical  bellies,  united  by  an  intermediate 
cylindrical  tendon.  The  anterior,  shorter  belly  arises  from  a  rough 
impression  within  the  base  of  the  mandible,  close  to  the  symphysis, 
and  descends  backward  and  outward  to  the  intermediate  tendon.  The 
posterior  belly,  longer  and  narrower  than  the  former,  arises  from  the 
digastric  fossa  of  the  temporal  bone,  and  descends  forward  and  inward 
to  the  intermediate  tendon.  This  usually  passes  through  a  perforation 
of  the  stylo-hyoid  muscle,  and  in  advance  is  connected  with  the  side 
of  the  hyoid  bone  by  an  aponeurotic  band,  which  serves  to  maintain 
the  curved  course  of  the  digastric.  An  extension  of  the  band  forms  a 
thin  membrane,  connecting  the  anterior  belly  of  the  muscle  with  that 
of  the  opposite  side,  between  the  chin  and  hyoid  bone.  The  anterior 
belly  is  in  contact  above  with  the  mylo-hyoid  muscle,  and  below  and 
outwardly  with  the  submaxillary  gland.  The  posterior  belly  out- 
wardly crosses  the  course  of  the  external  and  internal  carotid  arteries, 
the  internal  jugular  vein,  and  the  accompanying  nerves.  It  is  for  the 
most  part  covered  by  the  mastoid  process,  the  sterno-mastoid  and 
splenius  muscles,  and  the  parotid  gland. 

The  stylo-hyoid  muscle2  is  a  slender  fleshy  fascicle,  situated 
above  the  posterior  belly  of  the  digastric.  It  arises  by  a  narrow 
tendon  from  behind  the  outer  part  of  the  styloid  process,  near  its  base, 
and  descends  in  company  with  the  digastric  muscle  to  be  inserted  into 
the  hyoid  bone  at  the  junction  of  the  body  and  greater  cornu.  Usually 
it  is  perforated  near  its  insertion  by  the  digastric  tendon,  but  not  un- 
frequently  is  inserted  to  the  outside  of  the  latter  without  being  per- 
forated. The  muscle  is  sometimes  feebly  produced,  and  occasionally  is 
absent.  Its  relations  are  the  same  as  those  of  the  contiguous  belly  of 
the  digastric  muscle. 

The  mylo-hyoid  muscle3  is  a  flat,  triangular,  fleshy  layer,  situated 
within  the  position  of  the  lower  jaw,  and  forming  with  its  fellow  a 
muscular  floor  or  diaphragm  to  the  cavity  of  the  mouth.  It  arises, 
partially  fleshy  and  tendinous,  from  the  mylo-hyoid  ridge  of  the 
mandible,  extending  from  the  symphysis  to  the  last  molar  tooth, 
whence  the  fibres  proceed  obliquely  inward  and  downward ;  the  pos- 
terior, longer,  to  be  inserted  into  the  body  of  the  hyoid  bone ;  the 

1  M.  digastricus ;  m.  biventer  mandibulae,  or  maxillae  inferioris. 

2  M.  stylo-hyoideus.  3  M.  mylo-hyoideus ;  m.  transversus  mandibulae. 


THE    MUSCULAR   SYSTEM.  261 

others  becoming  successively  shorter  and  ending  in  a  median  fibrous 
raphe  extending  from  the  hyoid  bone  to  the  symphysis  of  the  chin. 
The  upper  surface  of  the  muscle  is  in  contact  with  the  genio-hyoid, 
hyo-glossal,  and  stylo-glossal  muscles,  the  lingual  gland,  and  the  hypo- 
gastric  and  lingual  nerves.  The  lower  surface  is  in  contact  with  the 
anterior  belly  of  the  digastric  muscle,  and  with  the  submaxillary  gland. 
The  posterior  border  is  free,  and  has  the  duct  of  the  latter  gland  turn- 
ing over  it.  The  inner  part  of  the  muscle  is  sometimes  more  or  less 
deficient. 

Between  the  mylo-hyoid  muscle  above,  with  the  mandible  out- 
wardly, and  the  digastric  muscle  with  the  stylo-hyoid  muscle  below, 
there  is  a  triangular  recess,  which  lodges  the  submaxillary  gland. 

The  genio-hyoid  muscle 1  is  a  fleshy  band  situated  beneath  the 
tongue,  in  contact  with  its  fellow  immediately  above  the  inner  part  of 
the  mylo-hyoid  muscle.  It  arises  tendinously  from  the  lower  division 
of  the  mental  tubercle,  and  descends  backward  to  be  inserted  tendi- 
nous and  fleshy  into  the  front  of  the  body  of  the  hyoid  bone.  It  is 
in  contact  above  with  the  genio-glossal  muscle. 

The  sterno-hyoid  muscle 2  is  a  thin,  fleshy  band,  situated  imme- 
diately beneath  the  skin  along  the  side  of  the  trachea  and  larynx.  It 
arises,  partially  tendinous  and  fleshy,  behind  the  sternal  extremity  of 
the  clavicle  and  the  contiguous  portion  of  the  sternum,  and  ascends 
inwardly  to  be  inserted  into  the  lower  border  of  the  hyoid  bone.  The 
muscles  of  the  two  sides  are  widely  separated  at  their  origin,  but 
approach  near  together  as  they  ascend  at  the  sides  of  the  trachea,  and 
diverge  slightly  at  the  sides  of  the  larynx,  allowing  the  beak  of  the 
latter  to  project  between  them. 

The  sterno-thyroid  muscle 3  lies  behind  the  preceding,  than  which 
it  is  considerably  wider  and  extends  more  outwardly.  It  arises,  par- 
tially tendinous  and  fleshy,  from  behind  the  first  costal  cartilage  and 
the  middle  of  the  presternum,  extending  variably  more  or  less  outward 
to  the  end  of  the  former,  or  inward  to  the  median  line  of  the  latter, 
and  ascends  at  the  side  of  the  trachea  to  be  inserted  into  the  oblique 
ridge  at  the  side  of  the  thyroid  cartilage.  Behind,  the  muscle  is  in  con- 
tact with  the  innominate  vein,  the  common  carotid  artery,  the  trachea, 
and  the  thyroid  gland. 

The  thyro-hyoid  muscle,4  situated  at  the  side  of  the  larynx, 
appears  like  a  continuation  of  the  preceding  muscle.  It  arises  from 
the  oblique  ridge  of  the  thyroid  cartilage,  and  ascends  to  be  inserted 
into  the  lower  border  of  the  body  and  greater  cornu  of  the  hyoid  bone. 
It  rests  against  the  thyroid  cartilage  and  thyro-hyoid  membrane,  and 
is  covered  by  the  sterno-hyoid  and  omo-hyoid  muscles. 

1  M.  genio-hyoideus. 

2  M.  sterno-hyoideus  ;  m.  sterno-cleido-hyoideus  ;  m.  cleido-hyoideus. 

3  M.  sterno-thyroideus.  *  M.  thyro-hyoideus. 


262  THE   MUSCULAR  SYSTEM. 

The  omo-hyoid  muscle  l  is  a  long,  narrow  band,  extending  from 
the  shoulder  across  the  neck,  beneath  the  sterno-mastoid  muscle,  up  to 
thehyoid  bone.  It  consists  of  two  fleshy  bellies  with  an  intermediate 
flat  tendon,  which  crosses  the  carotid  artery  and  jugular  vein  and  ad- 
heres closely  to  their  sheath.  The  posterior  belly  arises  from  the  upper 
border  of  the  scapula  at  the  coracoid  foramen,  and  thence  proceeds 
nearly  horizontally  forward  from  beneath  the  trapezius  and  behind  the 
sterno-mastoid  muscle,  where  it  joins  the  intermediate  tendon.  From 
this  the  anterior  belly  turns  upward  and  forward  at  an  obtuse  angle, 
and  ascends  at  the  outer  border  of  the  sterno-hyoid  muscle  to  be  in- 
serted immediately  to  its  outer  side  into  the  inferior  border  of  the 
hyoid  bone.  The  deep  cervical  fascia  investing  the  posterior  belly  of 
the  muscle,  with  a  firmer  extension  of  the  same  on  the  tendon,  is 
attached  below  to  the  first  costal  cartilage  and  inner  surface  of  the 
clavicle,  and  serves  to  maintain  the  angular  course  of  the  muscle. 

In  its  course  the  omo-hyoid  muscle  crosses  the  scalenus  muscles,  the 
axillary  plexus,  and  the  great  cervical  blood-vessels,  and  at  its  upper 
part  lies  on  the  sterno-thyroid  and  thyro-hyoid  muscles.  It  is  subject 
to  frequent  variation.  The  posterior  belly  arises  variably  from  any 
part  of  the  superior  border  of  the  scapula,  including  the  coracoid  fora- 
men ;  the  intermediate  tendon  varies  in  length,  is  sometimes  partial, 
and  occasionally  absent ;  and  the  anterior  belly  is  often  more  or  less 
blended  with  the  sterno-hyoid  muscle. 

Most  of  the  infra-hyoid  muscles  receive  their  motor  nerves  chiefly 
from  the  descending  cervical  branch  of  the  hypoglossal  nerve;  the 
thyro-hyoid  muscle  rebeiving  a  direct  branch  of  the  latter. 

The  infra-hyoid  muscles  are  depressors  of  the  hyoid  bone  and  larynx 
and  other  parts  adherent  to  them.  They  act  in  swallowing,  succeed- 
ing the  action  of  the  supra-hyoid  and  other  muscles  in  lifting  the  same 
parts.  The  omo-hyoid  muscles  in  some  degree  serve  to  maintain  the 
median  position  of  the  parts  in  front  of  the  neck,  the  larynx  and 
pharynx,  and  the  trachea  and  oesophagus,  which  together  are  very 
movable  on  the  cervical  vertebrse. 

MUSCLES  OP  THE   TONGUE. 

See  The  Alimentary  Apparatus. 

MUSCLES   OF   THE   PALATE. 
See  The  Alimentary  Apparatus. 

MUSCLES   OF   THE   PHAKYNX. 

See  The  Alimentary  Apparatus. 

MUSCLES  OF   THE   PEEINEUM. 

See  The  Perineum. 

1  M.  omo-hyoideus ;  m.  coraco-hyoideus ;  m.  costo-hyoideus ;  m.  scapulo- 
hyoideus. 


THE   MUSCULAR   SYSTEM. 


263 


FIG.  139. 


LATEKAL   CERVICAL   MUSCLES. 

The  scaleni  muscles  form  a  group  at  the  lower  part  of  the  side  of 
the  neck,  extending  to  the  upper  two  ribs,  behind  the  sterno-mastoid 
muscle  and  the  clavicle. 

The  anterior  scalenus,1  situated  in  front  of  the  others,  arises 
tendinously  by  four  narrow  heads  from  the  ends  of  the  costal  processes 
of  the  third  to.  the  sixth  cervical  vertebra,  inclusively.  The  heads 
unite  in  a  fleshy  belly,  which  descends  outwardly,  and  is  inserted  ten- 
dinously into  the  first  rib,  in  advance  of  the  impression  for  the  sub- 
clavian  artery.  Its  lower  part  is  immediately  behind  the  clavicle, 
and  in  front  of  the  insertion  is  crossed  by  the  subclavian  vein,  and 
above  by  the  omo-hyoid  muscle.  The  phrenic  nerve  descends  in  front 
of  it ;  and  behind,  it  is  in 
relation  with  the  brachial 
plexus  of  nerves,  the  sub- 
clavian artery,  and  the 
apex  of  the  pleura. 

The  middle  scale- 
nus,2 the  largest  of  the 
series,  is  situated  behind 
the  preceding.  It  arises 
tendinously  by  six  nar- 
row heads  from  the  ends 
of  the  transverse  pro- 
cesses of  all  the  cervi- 
cal vertebra  except  the 
atlas.  The  heads  unite 
in  a  fleshy  belly,  which 
descends  outwardly,  and 
is  inserted  into  the  first 
rib  from  its  tubercle  to  12 
the  impression  for  the 
subclavian  artery. 

The  brachial  plexus  of 
nerves  and  the  subclavian 
artery  pass  outwardly  be- 
tween the  anterior  and 
middle  scalenus  muscles. 

The  posterior  scalenus,3  the  smallest  of  the  series,  is  situated 
behind  the  lower  part.  It  arises  tendinously  by  two  or  three  narrow 
heads  from  the  transverse  processes  of  the  corresponding  lower  cer- 

1  M.  scalenus  anticus  ;  m.  s.  prior,  or  primus  ;  anterior  scalene  muscle. 

2  M.  scalenus  medius  ;  m.  s.  secundus ;  middle  scalene  muscle. 

3  M.  scalenus  posticus  ;  m.  s.  tertius  ;  posterior  scalene  muscle. 


DEEP  MUSCLES  OF  THE  FRONT  OF  THE  NECK.  1,  basilar 
process ;  2,  mastoid  process ;  3,  greater  pre-rectus  muscle ; 
4,  small  pre-rectus ;  5,  lateral  pre-rectus ;  6,  long  cervical 
muscle ;  7,  atlantal  muscle ;  8,  posterior  scalenus ;  9,  an- 
terior scalenus ;  10,  middle  scalenus ;  11, 12,  first  and  second 
ribs;  13,  position  at  which  the  subclavian  artery  and 
brachial  plexus  of  nerves  pass  over  the  first  rib,  between 
the  anterior  and  middle  scalenus  muscles ;  14,  third  thoracic 
vertebra ;  15,  atlas ;  16, 17,  intertransverse  muscles. 


264  THE   MUSCULAR   SYSTEM. 

vical  vertebrae,  and  descends  to  be  inserted  into  the  second  rib  external 
to  its  angle. 

The  scaleni  muscles  are  variable  in  the  number  of  heads  and  in 
other  respects.  Sometimes  a  slip  of  the  anterior  scalenus  joins  the 
middle  scalenus,  descending  behind  the  subclavian  artery.  The  pos- 
terior scalenus  is  also  at  times  continuous  with  the  middle  scalenus, 
and  occasionally  it  is  altogether  absent. 

The  scaleni  acting  from  the  vertebrae  are  elevators  of  the  upper 
ribs,  and  thus  assist  in  the  movement  of  inspiration.  Acting  from  the 
ribs,  they  act  as  flexors  of  the  neck,  and  bend  the  head  forward.  They 
are  supplied  by  the  adjacent  cervical  nerves. 

PKEYEKTEBKAL  MUSCLES  OF  THE  NECK. 

The  prevertebral  muscles  consist  of  the  greater,  small,  and  lateral 
pre-recti  muscles,  and  the  atlantal  and  long  cervical  muscles,  situated 
in  front  of  the  cervical  and  upper  thoracic  vertebrae. 

The  greater  pre-rectus 1  is  situated  in  front  of  the  cervical  ver- 
tebrae, ascending  to  the  head.  It  arises  tendinously  by  four  narrow 
heads  from  the  ends  of  the  costal  processes  of  the  third  to  the  sixth 
cervical  vertebra,  inclusively,  opposite  the  same  points  of  origin  of 
the  anterior  scalenus.  The  heads  ascend  inwardly,  and  unite  in  a  flatr 
fleshy  belly,  which  lies  at  the  side  of  the  centra  of  the  vertebrae,  and 
is  inserted  into  the  occipital  basilar  process.  The  front  surface  of  the 
muscle  is  in  contact  with  the  pharynx,  and  supports  the  sympathetic 
nerve  and  the  great  vessels  of  the  neck,  enclosed  in  their  sheath  to- 
gether with  the  vagus  nerve. 

The  small  pre-rectus 2  is  situated  behind  the  upper  extremity  of 
the  former  muscle.  It  is  a  short,  fleshy  layer,  which  arises  in  front 
of  the  side  of  the  atlas,  and  is  inserted  into  the  basilar  process  behind 
the  greater  pre-rectus.  Behind  it  is  the  occipito-atlantal  articulation. 

The  lateral  pre-rectus3  is  a  short  muscle  situated  outwardly  from 
the  former.  It  arises  in  front  of  the  costal  process  of  the  atlas,  and 
ascends  to  be  inserted  into  the  occipital  jugular  process.  Behind  it  is 
the  vertebral  artery,  and  in  front  the  internal  jugular  vein. 

The  atlantal  muscle 4  arises  by  three  narrow  heads  tendinously 
from  the  costal  processes  of  the  third,  fourth,  and  fifth  cervical  verte- 
brae, ascends  obliquely  inward,  and  is  inserted  into  the  anterior  tubercle 
of  the  atlas. 


1  M.  rectus  capitis  anticus  major ;   m.   longus  capitis ;    great  anterior  straight 
muscle  of  the  head ;  larger  anterior  straight  muscle ;  m.  r.  c.  interims  major ;  in. 
trachelo-hasilaris  major. 

2  M.  rec.  cap.  ant.  minor ;  m.  r.  c.  internus  minor ;    smaller  anterior  straight 
muscle ;  m.  trachelo-basilaris  major.  3  M.  rectus  capitis  lateralis. 

4  M.  longus  atlantis  :  superior  oblique  portion  of  the  in.  longus  colli ;  m.  obliquus 
colli  superior. 


THE   MUSCULAR   SYSTEM.  265 

The  long  cervical  muscle1  arises,  tendinously  and  fleshy,  from 
the  sides  of  the  centra  of  the  lower  two  cervical  and  the  upper  two  or 
three  thoracic  vertebrae,  and  divides  into  two  portions,  of  which  the 
inner  ascends  to  be  inserted  into  the  sides  of  the  centra  of  the  second, 
third,  and  fourth  cervical  vertebrae,  and  the  outer,  smaller  portion  as- 
cends to  be  inserted  tendinously  into  the  costal  processes  of  the  fifth 
and  sixth  cervical  vertebrae.  This  and  the  preceding  muscle  are  com- 
monly described  as  one,  under  the  name  of  the  longus  colli. 

In  front  of  the  prevertebral  muscles  are  the  pharynx  and  oesophagus, 
the  sympathetic  nerve,  and  the  great  vessels  of  the  neck  contained 
within  their  sheath. 

The  prevertebral  fascia  is  a  thin  connective-tissue  membrane, 
investing  the  front  of  the  cervical  vertebrae  and  the  prevertebral 
muscles,  attached  to  the  basilar  process  above,  and  extending  to  the 
third  thoracic  vertebra  below.  On  each  side  it  is  continuous  with  the 
deep  cervical  fascia  investing  the  splenius  and  scalenus  muscles,  and 
with  the  sheaths  of  the  cervical  and  subclavian  blood-vessels,  and  of 
the  brachial  plexus  of  nerves.  It  is  remarkably  free  from  fat,  and  has 
attached  to  it  the  pharynx  and  oesophagus  by  means  of  loose  connec- 
tive tissue,  which  allows  the  ready  gliding  movement  of  these  parts 
in  deglutition  and  other  functions. 

The  prevertebral  muscles  generally  are  flexors  of  the  head  and 
neck.  They  are  supplied  by  branches  from  the  adjacent  cervical  nerves. 

POSTVERTEBEAL   MUSCLES  OF   THE   NECK. 

The  greater  post-rectus 2  arises  tendinously  from  the  end  of  the 
spinous  process  of  the  axis,  ascends  outwardly,  gradually  expanding, 
and  is  inserted  into  and  below  the  outer  part  of  the  inferior  curved 
line  of  the  occipital  bone. 

The  small  post-rectus3  arises  tendinously  from  the  median  tuber- 
cle of  the  atlas,  ascends  and  expands,  and  is  inserted  into  and  below 
the  inner  part  of  the  same  line  as  the  preceding  muscle. 

The  supra-oblique  muscle  *  arises  tendinously  from  the  end  of 
the  transverse  process  of  the  atlas,  and  ascends  backward  to  be  inserted 
outwardly  between  the  curved  lines  of  the  occipital  bone. 

The  infra-oblique  muscle,5  larger  than  any  of  the  preceding, 
arises  tendinously  from  the  end  of  the  spinous  process  of  the  axis, 
and  ascends  outwardly  to  be  inserted  into  the  end  of  the  transverse 
process  of  the  atlas. 

1  M.  longus  colli ;  inferior  oblique  and  vertical  portions  of  the  longus  colli. 

2  M.  rectus  capitus  posticus  major,  superficialis,    or   inferior ;    longer  straight 
muscle ;  m.  axoido-occipitalis. 

3  M.  r.  c.  p.  minor  or  profundus  ;  smaller  straight  muscle  ;  m.  atlo-occipitalis. 

4  M.  obliquus  capitis  superior  or  minor;  superior  oblique  m. 

5  M.  o.  c.  inferior  or  major  ;  inferior  oblique  m. ;  m.  axo-atloideus. 


266  THE    MUSCULAR   SYSTEM. 


•    MUSCLES   OP  THE   THORAX. 

The  muscles  of  the  thoracic  wall,  independent  of  those  especially 
concerned  in  the  movements  of  the  upper  limbs,  are  the  intercostals, 
subcostals,  sterno-costal  muscle,  and  costal  elevators. 

The  intercostal  muscles l  occupy  the  corresponding  spaces  of  the 
ribs  in  pairs,  and  are  composed  of  short,  oblique  fleshy  fascicles  extended 
between  the  contiguous  borders  of  the  ribs,  alternating  in  direction  in 
each  pair  of  muscles.  The  eleven  intercostal  spaces  of  each  side  of  the 
thorax  are  consequently  occupied  by  twenty-two  intercostal  muscles. 

The  external  intercostal  muscle  2  starts  behind  in  the  position  of 
the  tubercle  of  the  ribs,  and  extends  to  the  anterior  extremity  of  the 
latter.  Its  fleshy  fascicles,  mingled  with  tendinous  fibres,  descend  from 
the  margin  of  the  rib  above  obliquely  forward  to  the  contiguous  border 
of  the  rib  below.  In  advance  of  the  position  at  which  the  muscle 
ceases,  the  remainder  of  the  intercostal  space  is  occupied  by  a  thin 
aponeurosis,  the  fibres  of  which  pursue  the  same  course  as  those  of  the 
muscle.  In  the  upper  three  or  four  intercostal  spaces  the  muscle  does 
not  reach  the  fore  end  of  the  ribs,  and  in  the  last  two  it  extends  between 
the  costal  cartilages. 

The  internal  intercostal  muscle,3  thinner  than  the  former,  and 
with  its  fascicles  pursuing  an  opposite  direction,  arises  from  the  inner 
surface  of  the  rib  above,  within  the  position  of  the  subcostal  groove, 
and  is  inserted  into  the  inner  portion  of  the  upper  border  of  the  rib 
below.  It  starts  in  front  with  the  commencement  of  the  intercostal 
space,  and  extends  behind  to  about  the  angle  of  the  ribs,  whence  a  thin 
aponeurosis  continues  to  the  termination  of  the  space  and  becomes  con- 
tinuous with  the  anterior  costo-transverse  ligament.  In  the  lower  two 
spaces  the  muscles  are  continuous  with  the  internal  oblique  muscle  of 
the  abdomen.  Between  the  intercostal  muscles  are  the  corresponding 
vessels  and  nerve.  Internally  they  are  lined  by  the  pleura ;  externally 
they  are  attached  to  adjacent  muscles,  the  pectorals,  abdominal  oblique, 
serrati,  rhomboid,  and  latissimus,  by  loose,  extensible  connective  tissue. 

The  subcostal  muscles  *  are  dependencies  of  the  internal  inter- 
costals, and  consist  of  small  and  variable  fascicles  extended  between 
the  inner  surfaces  of  two  or  three  adjacent  ribs  in  the  vicinity  of  the 
angle,  and  covered  by  the  pleura.  They  are  very  inconstant,  and 
when  present  are  best  produced  on  the  lower  ribs. 

The  sterno-costal  muscle  5  is  placed  within  the  thorax  behind 
the  costal  cartilages.  Thin  and  variable  in  extent,  it  arises  by  a  short 
aponeurosis  from  the  inner  surface  laterally  of  the  lower  part  of 
the  mesosternum  and  ensiform  process,  and  spreads  outwardly  and 

1  M.  intercostales.  2  M.  intercostalis  externus. 

3  M.  intercostalis  interims.  4  M.  subcostales ;  m.  infracostales. 

6  M.  triangularis  sterni ;  m.  sterno-costalis. 


THE    MUSCULAR   SYSTEM. 


267 


upward  into  four  or  five  slips,  which  are  inserted  into  the  outer  part  of 
the  costal  cartilages  from  the  sixth  to  the  third  or  second  inclusive. 
Its  lower  part,  nearly  horizontal,  is  continuous  with  the  series  of  slips 
pertaining  to  the  origin  of  the  abdominal  transversalis  muscle.  The 
pleura  covers  its  inner  surface,  and  the  mammary  vessels  lie  between 
it  and  the  costal  cartilages. 

The  costal  elevators l  are  little  fan-shaped  muscles,  each  of  which 
arises  from  the  end  of  the  vertebral  transverse  process  above  a  rib, 
and  descends  and  expands  to  be  inserted  into  the  back  of  the  next  rib 
below,  between  the  tubercle  and  angle.  The  lower  ones  are  commonly 
prolonged  by  additional  slips  to  the  second  rib  below.  They  lie  against 
the  external  intercostal  muscles,  and  are  covered  by  the  longissimus  and 
ilio-costalis  muscles.  Above  they  lie  in  series  with  the  middle  and  poste- 
rior scalenus  muscles,  and  below  with  the  lumbar  intertransverse  muscles. 

The  action  of  the  intercostal  and  other  muscles  above  described  is 
a  matter  of  dispute.  It  is  probable  that  they  may  act  in  concert  in 
respiration  in  raising  the  ribs  and  expanding  the  chest,  and  in  depress- 
ing the  ribs  and  contracting  the  chest,  as  predetermined  by  the  alternate 
action  of  other  muscles. 


FIG.  140. 


THE   DIAPHKAGM. 

The  diaphragm,2  a  most 
important,  extensive,  and 
beautiful  muscle,  makes  a 
complete  partition  between 
the  cavities  of  the  thorax  and 
abdomen,  and  appears  as  a 
dome-like  roof  of  the  latter, 
projecting  high  up  into  the 
former.  It  rises  higher  on  the 
right  side,  where  it  ordinarily 
reaches  a  level  with  the  junc- 
tion of  the  fifth  costal  carti- 
lage and  sternum,  while  on 
the  left  side  it  reaches  a  level 
with  a  corresponding  junc- 
tion of  the  sixth  cartilage.  It 
consists  of  a  peripheral  mus- 
cular layer  attached  around 
the  inferior  border  of  the 
thorax,  and  ascending  to  a 
central  tendinous  layer. 

The  central  tendon 3  occupies  the  highest  part  of  the  diaphragm, 

1  M.  levatores  costarum ;  m.  supracostales. 

2  Diaphragma  ;  midriff;  musculus  phrenicus. 

3  Centrum  tendineum  ;  c.  phrenicum  ;  cordiform  tendon  ;  trefoil  tendon. 


INFERIOR  VIEW  OF  THE  DIAPHRAGM.  1,  2,  3,  the  three 
lobes  of  the  central  tendon,  surrounded  by  the  fleshy 
fascicles  derived  from  the  inferior  margin  of  the 
thorax,  the  crura,  4,  5,  and  the  arcuate  ligaments,  6,  7; 
8,  aortic  opening;  9,  oasophageal  opening;  10,  caval 
opening ;  11,  psoas  muscle ;  12,  quadrate  lumbar  muscle. 


268  THE   MUSCULAR   SYSTEM. 

and  appears  as  a  broad,  glistening  aponeurosis.  It  has  nearly  the 
form  in  outline  of  the  entire  diaphragm,  or  of  the  lower  opening 
of  the  thorax,  but,  being  somewhat  indented  at  the  fore  part  on  each 
side,  it  is  trilobed.  The  lateral  portions,  or  lobes,1  diverge  backward 
and  downward  on  each  side  of  the  vertebral  column,  and  include 
a  deep  notch  behind,  in  front  of  the  latter;  while  the  intermediate 
lobe  is  anterior  and  directed  forward  towards  the  sternum.  The 
lobes  are  oval ;  the  right  one  being  the  largest  and  the  left  the 
smallest.  The  tendon  is  composed  of  bands  which  run  in  different 
directions,  straight  and  curved,  and  intersect  one  another,  and  then 
radiate  in  arching  fibres  to  the  surrounding  muscular  layer.  The 
latter  may  be  conveniently  described  as  consisting  of  a  vertebral  and 
a  costo-sternal  portion,  which  are,  however,  continuous,  and  together 
enclose  the  central  tendon. 

The  vertebral  portion 2  of  the  diaphragm  in  greater  part  forms  a 
pair  of  fleshy  bellies  named  the  crura,  or  pillars.3  These  occupy  the 
sides  of  the  lumbar  vertebrae,  from  which  they  arise  by  tendons  closely 
connected  with  the  anterior  vertebral  ligament.  The  right  crus,  vari- 
ably longer  and  larger  than  the  other,  usually  arises  from  the  centra 
and  intervening  ligaments  of  the  second,  third,  and  fourth  lumbar 
vertebrae;  and  the  left  crus,  from  the  corresponding  points  of  the 
second  and  third  vertebrae.  The  tendons  of  origin  are  close  together 
at  their  commencement,  whence  they  pass  from  behind  the  aorta, 
slightly  divergent,  ascend  at  its  sides,  and  for  the  most  part  gradually 
merge  into  the  fleshy  fascicles  of  the  crura,  while  a  small  portion 
continues  to  ascend  at  their  inner  margin,  and  forms  a  narrow  arch 
across  the  front  of  the  aorta,  over  the  position  of  the  last  thoracic 
vertebra.  By  this  arrangement  the  crura  leave  between  them  an 
opening  for  the  passage  of  the  aorta.  The  fleshy  fascicles  of  the 
crura  ascend,  diverge,  arch  forward,  and  spread  laterally  to  terminate 
in  the  posterior  notch  of  the  central  tendon  of  the  diaphragm.  In 
their  course,  the  innermost  fascicles  of  the  crura  decussate  in  front  of 
the  aortic  opening,  and  thence  diverging,  leave  between  them  another 
opening  for  the  passage  of  the  oesophagus.  The  decussating  fascicle 
from  the  right  crus  is  variably  larger  than  that  of  the  left  crus,  and 
commonly  ascends  in  front  of  it. 

External  to  the  crura  of  the  diaphragm  are  two  narrow,  arching 
fibrous  bands,  the  arcuate  ligaments,4  from  the  upper  part  of  which 
a  fleshy  layer  ascends  to  the  posterior  border  of  the  central  tendon, 
continuous  inwardly  with  the  crura  and  outwardly  with  the  costo- 
sternal  portion  of  the  diaphragm. 

The  internal  arcuate  ligament 5  arches  outwardly  from  the  side 
of  the  first  lumbar  centrum,  or  occasionally  from  the  second,  to  the 

1  Alse.  *  Portio  vertebralis  ;  p.  lumbalis  ;  lesser  or  lower  muscle. 

3  Capita ;  appendices.  *  Ligamenta  arcuata. 

8  L.  arcuatum  internum  ;  arcus  interims. 


THE   MUSCULAR   SYSTEM.  269 

end  of  the  transverse  process  of  the  latter.  The  external  arcuate 
ligament 1  in  like  manner  arches  from  the  end  of  the  same  transverse 
process  outwardly  to  the  lower  border  of  the  last  rib.  The  arcuate 
ligaments  below  are  continuous  with  the  psoas  and  lumbar  fasciae. 

The  costo-sternal  portion 2  of  the  diaphragm  arises  by  fleshy 
slips  from  the  inner  surface  of  the  lower  six  costal  cartilages,  alter- 
nating with  intervening  slips  of  the  abdominal  transversalis  muscle, 
and  from  the  inside  of  the  ensiform  process  of  the  sternum.  From 
this  origin  it  ascends  in  a  continuous  vaulted  layer,  and  terminates 
along  the  anterior  and  lateral  borders  of  the  central  tendon.  The 
slips  to  the  lateral  lobes  of  the  tendon  are  longest,  and  those  to  the 
middle  lobe  decrease  in  advance.  Those  proceeding  from  the  sternum 
are  shortest,  and  usually  are  somewhat  separated  from  the  rest  by  a 
narrow  interval  on  each  side,  which  is  occupied  by  connective  tissue,  and 
closed  by  the  apposition  of  the  pleura  above  and  the  peritoneum  below. 

The  aortic  opening3  of  the  diaphragm  is  a  long,  elliptical  aper- 
ture, opening  into  the  abdomen  obliquely  in  front  of  the  upper  three 
lumbar  and  last  thoracic  vertebrae.  It  is  bounded  behind  by  the  centra 
of  these  vertebrae  and  by  the  anterior  vertebral  ligament,  at  the  sides  by 
the  tendinous  origin  of  the  crura  of  the  diaphragm,  and  at  its  upper 
extremity  by  the  fibrous  arch  uniting  the  crura  across  the  position  of 
the  last  thoracic  vertebra.  Besides  the  aorta,  it  also  gives  passage  to 
the  thoracic  duct,  the  azygos  vein,  and  occasionally  the  left  sympathetic 
nerve. 

The  oesophageal  opening  *  is  likewise  an  oblique,  elliptical  aper- 
ture, and  is  situated  above,  in  advance,  and  a  little  to  the  left  of  the 
position  of  the  aortic  opening.  It  is  formed  by  the  separation  of  the 
fleshy  fascicles,  which  diverge  from  the  crura  of  the  opposite  sides,  and 
again  converge,  after  passing  the  opening,  to  end  in  the  central  tendon ; 
at  the  bottom  of  the  posterior  notch  of  which,  the  opening  is  situated. 
It  transmits  the  oesophagus  with  the  vagus  nerves. 

The  caval  opening,5  for  the  passage  of  the  inferior  cava,  occupies  a 
higher  position  than  the  preceding  openings,  in  the  central  tendon  at 
the  junction  behind  of  the  right  and  middle  lobes,  a  little  in  advance 
and  to  the  right  of  the  position  of  the  ossophageal  opening.  It  is 
quadrate,  due  to  the  direction  of  the  tendinous  bands  which  surround 
it ;  and  it  is  closely  attached  to  the  wall  of  the  inferior  cava. 

Besides  the  foregoing,  the  right  crus  transmits  the  corresponding 
sympathetic  and  splanchnic  nerves ;  and  the  left  crus  the  left  splanchnic 
nerves  and  the  hemiazygos  vein. 

The  diaphragm  is  deeply  vaulted,  being  convex  above  and  concave 


1  L.  a.  externum  ;  arcus  externus. 

2  Portio  costo-sternalis  ;  greater  or  inferior  muscle. 

3  Foramen  aorticum  ;  hiatus  aorticus. 

*  Foramen  oesophageum  ;  hiatus  oesophageus.         5  F.  quadratum  ;  f.  venae  cavae. 


270  THE   MUSCULAR   SYSTEM. 

below.  On  the  right  side  it  rises  nearly  an  inch  higher  than  on  the 
left.  In  forced  expiration  it  ascends  on  the  right  to  a  level  in  front 
with  the  fourth  costal  cartilage ;  at  the  side  with  the  fifth,  sixth,  and 
seventh  ribs ;  and  behind  with  the  eighth  rib.  On  the  left  it  usually 
ascends  the  breadth  of  one  or  two  ribs  lower.  In  forced  inspiration  it 
descends  from  one  to  two  inches,  and  its  slope  nearly  accords  with  a 
line  from  the  ensiform  process  to  the  tenth  rib.  At  its  circumference 
the  diaphragm  is  highest  behind  the  sternum ;  but  centrally,  where  the 
heart  rests  upon  it,  it  is  on  a  slightly  lower  level  than  on  each  side. 

The  diaphragm  by  its  upper  surface  is  tightly  adherent  to  the 
pericardium,  and  on  each  side  is  invested  with  the  pleura ;  and  beneath 
it  is  covered  by  the  peritoneum.  On  its  right  side,  above,  rests  the 
right  lung,  and  beneath  it  is  in  contact  with  the  liver ;  on  its  left  side 
rest  the  heart  and  the  left  lung,  and  it  is  in  contact  beneath  with  the 
greater  extremity  of  the  stomach,  the  spleen,  and  the  left  kidney. 

The  diaphragm  is  supplied  by  the  phrenic  nerves  and  the  phrenic 
plexus  of  the  sympathetic.  It  is  the  chief  muscle  of  respiration.  In 
its  movements  the  central  tendon  appears  to  maintain  a  nearly  fixed 
position,  on  account  of  its  firm  attachment  to  the  pericardium  and 
mediastinal  folds,  and  the  connection  of  these  with  the  summit  of  the 
chest.  With  contraction  of  the  muscular  portion  of  the  diaphragm  the 
capacity  of  the  chest  proportionately  increases,  and  produces  inspira- 
tion of  air  into  the  lungs,  while  the  abdominal  viscera  are  pressed 
downward,  and  the  abdomen  is  rendered  protuberant.  In  relaxation 
of  the  diaphragm  the  abdominal  muscles  below  contract,  press  the 
viscera  upward,  reduce  the  capacity  of  the  chest,  and  cause  expiration. 
In  all  expulsive  actions  of  the  lungs  and  bowels,  the  contraction  of  the 
diaphragm  promotes  the  effects,  as  exemplified  in  coughing  and  vomit- 
ing, in  the  discharge  of  the  urine  and  faeces,  and  in  childbirth. 

MUSCLES   AND   FASCIAE   OF   THE   ABDOMEN. 

The  muscles  of  the  exterior  wall  of  the  abdomen  consist  of  six  on 
each  side,  occupying  the  interval  between  the  vertebral  column  and  the 
median  line  in  front  of  the  abdomen,  and  extending  from  the  thorax  to 
the  pelvis.  Three  of  them,  named  from  the  principal  direction  of 
their  fleshy  fibres  the  external  oblique,  internal  oblique,  and  trans- 
versalis  muscles,  are  of  great  comparative  breadth,  each  for  the  most 
part  occupying  the  extent  of  the  space  above  indicated.  Their  fleshy 
bellies  at  the  sides  of  the  abdomen  terminate  in  front  in  aponeuroses, 
which  unite  in  the  median  line  to  form  the  linea  alba,  extending  from 
the  end  of  the  sternum  to  the  symphysis  of  the  pubes.  The  other 
three  muscles  on  each  side  are  longitudinal  and  comparatively  narrow, 
two  of  them,  the  rectus  and  pyramidalis  muscles,  being  situated  in 
front,  ensheathed  by  the  aponeuroses  of  the  broad  muscles,  and  the 
third  one,  the  quadrate  lumbar  muscle,  situated  at  the  side  of  the  loins 
behind. 


THE    MUSCULAR   SYSTEM.  271 

The  superficial  fascia  of  the  abdomen l  is  part  of  that  which 
everywhere  invests  the  body,  and  is  of  the  same  general  character, 
consisting  of  two  layers,  of  which  the  subcutaneous  layer  is  thicker, 
of  looser  texture,  and  is  the  position  of  the  usual  variable  accumula- 
tion of  subcutaneous  fat.  The  deeper,  thinner,  and  more  distinctly 
membranous  layer,  comparatively  free  from  fat,  is  strongest  in  front 
of  the  abdomen,  and  adheres  to  the  subjacent  aponeuroses  by  loose  con- 
nective tissue.  It  adheres  most  tightly  to  the  linea  alba,  around  the 
umbilicus,  to  the  pubic  symphysis,  and  in  the  inguinal  region,  after 
passing  over  Poupart's  ligament,  to  the  fascia  lata  immediately  beneath. 
Around  the  external  abdominal  ring  it  is  loosely  attached,  and  in  this 
position  the  subcutaneous  layer  becomes  free  from  fat,  and  the  two 
unite  in  a  single  membrane,  which  descends  upon  the  spermatic  cord, 
undergoes  a  change  of  structure  through  the  association  of  unstriped 
muscular  fibres,  and  thus  forms  the  dartos  tunic  of  the  scrotum. 
From  the  groin  and  front  of  the  pubis  the  deeper  layer  of  the  super- 
ficial fascia  becomes  continuous  with  that  of  the  penis.  From  the 
connection  of  the  fascia  to  the  lower  end  of  the  linea  alba  and  the 
pubic  symphysis,  considerable  bundles  of  connective  and  elastic  tissue 
descend  and  form  the  suspensory  ligament  of  the  penis. 

In  large  herbivorous  quadrupeds  the  deeper  layer2  of  the  superficial 
fascia  of  the  abdomen  is  a  thick  membrane,  composed  of  yellow  elastic 
tissue,  admirably  adapted  to  sustain  the  weight  of  the  abdominal 
contents. 

Subjacent  to  the  superficial  fascia  a  thin  connective-tissue  layer 
invests  the  fleshy  belly  of  the  external  oblique  muscle,  continuous  in 
front  with  the  outer  border  of  its  aponeurosis.  It  corresponds  with 
the  deep  fascia  in  other  parts  of  the  body. 

The  external  oblique  muscle 3  is  the  largest  and  most  superficial 
of  the  broad  muscles  of  the  abdomen.  It  is  an  irregularly  quadri- 
lateral layer,  with  its  fleshy  belly  occupying  the  side  and  its  aponeu- 
rosis the  front  of  the  abdomen.  It  arises  by  eight  angular  points  from 
the  outer  surface  and  lower  borders  of  the  inferior  eight  ribs,  in  an 
oblique  line  extending  downward  and  backward.  The  upper  points 
are  near  the  anterior  ends  of  the  ribs,  while  those  succeeding  are 
farther  back,  and  the  lowest  one  is  attached  to  the  end  of  the  last 
costal  cartilage.  The  upper  five  points  successively  enlarge  and  in- 
clude between  them  similar  points  of  the  great  serratus  muscle,  while 
the  lower  three  points  diminish  and  include  similar  points  of  the  latis- 
simus  muscle.  The  fleshy  fascicles  descend  from  their  origin  obliquely 
forward,  and  for  the  most  part  terminate  in  the  aponeurosis;  those 
behind,  from  the  lower  ribs,  descending  less  obliquely  to  be  inserted 
into  the  outer  lip  of  the  iliac  crest.  The  aponeurosis  unites  with  its 

1  Fascia  superficialis  abdominis.  2  Tunica  abdominalis. 

3  Descending  oblique  muscle;  m.  obliquus  abdominis  externus  or  descendens ; 
great  oblique  muscle. 


272 


THE    MUSCULAR   SYSTEM. 


fellow  in  the  median  line  of  the  abdomen,  extending  from  the  ensiform 
process  of  the  sternum  to  the  symphysis  of  the  pubes,  and  contributes 
to  form  the  linea  alba.  From  this  position,  for  the  greater  part  of  its 
length,  it  spreads  outwardly  for  three  or  four  inches,  and  at  the  lower 
part  widens  to  the  anterior  superior  iliac  spine,  whence  it  narrows  to 

FIG.  141. 


MUSCLES  OF  THE  FRONT  OF  THE  THORAX  AND  ABDOMEN.  1,  greater  pectoral  muscle;  2,  deltoid 
muscle ;  3,  latissimus ;  4,  great  serratus ;  5,  subclavius  muscle ;  6,  small  pectoral  muscle ;  7,  coraco- 
brachial  muscle ;  8,  brachial  biceps ;  9,  coracoid  process  of  the  scapula ;  10,  origin  of  the  great 
serratus  muscle ;  11,  intercostal  muscles ;  12,  external  oblique  muscle  of  the  abdomen ;  13,  its 
aponeurosis ;  14,  lower  border  of  the  latter,  named  Poupart's  ligament ;  15,  external  abdominal 
ring,  the  lower  extremity  of  the  inguinal  canal ;  16,  abdominal  rectus  muscle ;  17,  pyramidal 
muscle;  18,  internal  oblique  muscle;  19,  conjoined  tendon  of  the  internal  oblique  and  trans- 
versalis  muscles ;  20,  position  of  the  inguinal  canal  below  the  arching  edges  of  the  preceding  two 
muscles. 

the  pubis.  Its  fibres  pursue  the  same  course  as  the  fleshy  fascicles 
of  the  muscle,  cross  at  the  linea  alba,  and  interlace  with  those  of  the 
opposite  aponeurosis.  A  denser  portion  of  the  aponeurosis,  starting 
about  an  inch  above  the  anterior  superior  iliac  spine  and  partially  from 
this,  in  its  descent  separates  from  the  rest  of  the  aponeurosis  above 
and  converges  into  a  narrower  band,  named  Poupart's  ligament,1 


1  Lig.  Pouparti,  Fallopise,  or  Vesalii ;  1.  iliopubicum  ;  crural  arch;  arcus  cruralis. 


THE    MUSCULAE   SYSTEM.  273 

which  is  inserted  into  the  pubic  spine,  and  is  thence  extended  out- 
wardly along  the  pectineal  line  for  about  three-fourths  of  an  inch. 
This  extension  of  the  insertion  is  named  Gimbernat's  ligament,1 
and  terminates  outwardly  in  a  concave  free  margin,  forming  the  inner 
boundary  of  the  femoral  ring,  which  will  be  subsequently  described. 
The  interval,  produced  by  the  separation  of  Poupart's  ligament  from  the 
upper  portion  of  the  external  oblique  aponeurosis,  widens  in  its  approach 
to  the  pubis,  and  at  the  upper  part  is  occupied  by  a  thin  connective- 
tissue  membrane.  The  lower  part  of  the  interval  forms  the  external 
abdominal  ring,2  the  inferior  or  outer  end  of  the  inguinal  canal, 
which  transmits  the  spermatic  cord  in  the  male  and  the  round  ligament 
of  the  uterus  in  the  female.  The  ring  is  situated  immediately  above  the 
body  of  the  pubis,  and  is  obliquely  oval,  with  the  long  diameter  con- 
forming to  the  direction  of  the  separation  of  the  aponeurosis  producing 
it.  In  the  male  it  is  about  an  inch  long  and  half  as  wide,  and  in  the 
female  is  much  smaller.  The  sides  of  the  ring  are  distinguished  as  its 
columns,3  the  external  column 4  being  formed  by  Poupart's  ligament, 
and  the  internal  column 5  by  that  portion  of  the  external  oblique 
aponeurosis  which  is  inserted  into  the  pubic  symphysis.  Some  ten- 
dinous fibres  curving  from  the  groin  to  the  linea  alba  are  named 
the  intercolumnar  fibres,6  and  serve  to  maintain  the  conjunc- 
tion above  of  the  two  portions  of  the  aponeurosis  which  form  the 
columns  of  the  ring.  A  delicate  connective-tissue  membrane,  the 
spermatic  fascia/  springs  from  the  margin  of  the  external  abdominal 
ring,  and  is  thence  prolonged  downward  as  an  investment  to  the  sper- 
matic cord.  Poupart's  ligament  in  its  course  curves  downward  in  the 
line  of  the  groin,  and  is  connected  below  with  the  deep  femoral  fascia  of 
the  thigh.  Prom  its  insertion  and  that  of  Gimbernat's  ligament  behind, 
a  portion  of  the  fibres  form  the  triangular  ligament,8  a  variable  apo- 
neurotic  expansion,  which  curves  inwardly  beneath  the  spermatic  cord 
.and  behind  the  position  of  the  external  abdominal  ring,  and  becomes 
closely  united  with  the  fore  part  of  the  sheath  of  the  rectus  muscle. 

The  internal  oblique  muscle 9  lies  within  the  position  of  the  pre- 
ceding muscle,  in  contact  with  it,  and  is  smaller  and  thinner.  It  arises 
fleshy  from  the  lumbar  fascia  in  the  angle  between  the  crest  of  the  ilium 
and  the  outer  border  of  the  dorsal  extensor  muscle,  tendinously  from 
the  middle  lip  of  the  anterior  two-thirds  of  the  iliac  crest,  and  fleshy 
from  the  outer  half  of  Poupart's  ligament.  Prom  this  origin  the  fleshy 

1  L.  Gimbernati.  2  Annulus  abdominalis  externus ;  a.  inguinalis  ext. 

3  Pillars  ;  crura.  *  Inferior  column  or  pillar ;  crus  inferius. 

6  Superior  column  or  pillar;  crus  superius. 

6  Fibrae  intercolumnares  ;  f.  collaterals. 

T  External  spermatic  fascia ;  intercolumnar  fascia. 

8  Lig.  triangulare  or  inguinale  internum  ;  1.  Gimbernati  reflexum  ;  ligament  ol 
Colles. 

9  M.  obliquus  internus  or  ascendens ;  m.  o.  abdominis  int.  or  asc.  ;  petit  oblique, 

18 


274 


THE   MUSCULAR   SYSTEM. 


FIG.  142. 


fibres  mostly  ascend  obliquely  forward  and  inward,  but  gradually 
become  less  inclined  below ;  those  from  the  anterior  superior  iliac  spine 
proceeding  horizontally  forward,  and  those  from  Poupart's  ligament 
arching  forward  and  downward.  The  upper  more  posterior  fascicles 
are  inserted  into  the  inferior  margins  of  the  lower  three  or  four  costal 
cartilages  in  the  same  plane  as  the  internal  intercostal  muscles,  while 
the  others  terminate  in  an  aponeurosis  which  extends  from  the  lower 
margin  of  the  thorax  to  the  pubis  and  unites  with  its  fellow  in  the 
linea  alba.  Along  the  upper  three-fourths  of  the  outer  edge  of  the 

rectus  muscle  the  aponeurosis  di- 
vides into  two  laminae,  of  which 
one  proceeds  in  front  and  the  other 
behind  the  rectus  to  the  linea  alba, 
and  thus  enclose  the  muscle  in  a. 
sheath.  The  anterior  lamina  of 
the  aponeurosis,  a  short  distance 
from  its  commencement  above, 
gradually  widens  below,  and  blends 
with  the  external  oblique  aponeu- 
rosis as  it  proceeds  to  the  linea 
alba.  Below  the  point  of  division 
the  aponeurosis  remains  in  great 
part  free  from  that  of  the  exter- 
nal oblique  muscle,  and  behind 
joins  that  of  the  transversalis  mus- 
cle to  form  the  conjoined  ten- 
don, which  extends  to  the  linea 
alba,  and  below  is  inserted  into  the 
crest  and  pectineal  line  of  the 
pubis. 

The    transversalis     muscle1 
VIEW  OF  THE  LEFT  SIDE  OF  THE  ABDOMEN,  i,    gucceeds   the  former,  and   is   next 

portion  of  the  latissimus  muscle ;  2,  origin  of  .  . 

the  great  serratus;  3,  origin  of  the  external  the    abdominal    Cavity.        it     arises 

oblique  ;  4,  external  intercostals ;  5,  internal  fleshy  from  the  inner  surface  of  the 

in tercostals ;  6,  transversalis  muscle  ;  7.  its  apo-  ,  .  „ 

neurotic  origin;  8,  its  aponeurosis  in  front;  lower  SIX  COStal  Cartilages,  alternat- 

9,  lower  part  of  the  internal  oblique  muscle;  ing  with    Contiguous   points  of  Ori- 

10,  abdominal  rectus  of  the  right  side ;  11,  po-        .          /?    ,,          •,.      -,  f  ,-, 
sition  of  the  inguinal  canal  between   the     gm    of    the  Diaphragm;    from    the 
arched  border  of  the  internal  oblique  and     lumbar   fascia    ill   a   line  descending 


transversalis  muscles  and  Poupart's  ligament: 
the  figure  rests  on  the  transversalis  fascia ;  12, 
the  vaginal  tensor  muscle. 


from  near  the  end  of  the  last  rib 
to  the  iliac  crest;  from  the  inner 
lip  of  the  crest  in  advance ;  and 

from  the  outer  third  of  Poupart's  ligament.  Prom  this  extensive 
origin  the  muscular  fascicles,  for  the  most  part,  proceed  horizontally 
forward  and  inward,  while  the  lowest  arch  inward  and  downward, 


1  M.  transversalis  abdominis. 


THE   MUSCULAR   SYSTEM.  275 

and  all  terminate  in  a  broad  aponeurosis,  which  extends  to  the  linea 
alba  from  the  sternum  to  the  pubis.  The  aponeurosis  widens  out- 
wardly below  its  middle,  and  to  a  greater  extent  than  do  the  aponeuroses 
in  front,  but  narrows  above  to  a  greater  degree,  so  that  at  the  upper 
extremity  the  fleshy  fibres  of  the  muscle  approach  the  linea  alba  nearer 
than  in  any  other  position  of  the  broad  muscles.  The  upper  three- 
fourths  of  the  aponeurosis  after  a  short  course  unite  with  the  posterior 
lamina  of  the  internal  oblique  aponeurosis,  though  to  a  gradually  lessen- 
ing extent  above,  and  the  united  aponeuroses  proceed  behind  the  rectus 
muscle  to  the  linea  alba.  About  midway  between  the  umbilicus  and 
pubis  the  united  aponeuroses  thin  away  and  terminate  in  a  more  or 
less  defined  crescentic  border,1  which  is  continuous  with  the  subjacent 
transversalis  fascia.  The  lower  fourth  of  the  transversalis  aponeurosis 
proceeds  in  front  of  the  rectus,  and  unites  with  that  of  the  internal 
oblique  muscle  to  form  the  conjoined  tendon,  which  extends  to  the 
linea  alba,  and  is  also  inserted  into  the  crest  and  pectineal  line  of  the 
pubis  immediately  behind  the  insertion  of  Poupart's  and  Gimbernat's 
ligaments.  The  lowest  fleshy  fascicles  of  the  internal  oblique  and  trans- 
versalis muscles  are  more  or  less  blended,  and  usually  thinner,  paler, 
and  less  regular  than  elsewhere,  and  they  arch  from  Poupart's  liga- 
ment over  the  spermatic  cord  to  end  in  the  conjoined  tendon.  Ap- 
proaching the  pubis,  the  outer  border  of  the  latter  is  less  compact,  and 
is  continuous  with  the  adjacent  transversalis  fascia. 

The  rectus  muscle 2  extends  along  the  front  of  the  abdomen, 
enclosed  in  a  sheath  formed  by  the  aponeuroses  of  the  broad  muscles, 
and  separated  from  its  fellow  by  the  linea  alba.  It  arises  from  the 
crest  and  symphysis  of  the  pubes  by  a  flat  tendon,  from  which  the 
fleshy  belly  gradually  widens  to  near  the  position  of  the  umbilicus, 
and  then  proceeds  of  more  uniform  width  to  the  front  of  the  thorax, 
where  it  becomes  wider  and  thinner,  and  is  inserted  tendinously  into 
the  fifth,  sixth,  and  seventh  costal  cartilages,  and  sometimes  into  the 
ensiform  process  of  the  sternum.  In  its  course  the  muscular  belly 
is  interrupted  commonly  by  three  short  tendinous  intersections,3 
which  are  transverse,  variably  bent,  angular  or  zigzag,  and  sometimes 
interrupted.  Usually  one  is  situated  below  the  end  of  the  ensiform 
process,  another  on  a  level  with  the  umbilicus,  and  the  third  in  an 
intermediate  position.  Sometimes  there  is  another,  mostly  incomplete, 
below  the  umbilicus.  They  are  chiefly  confined  to  the  superficial  part 
of  the  muscle,  and  are  intimately  connected  with  the  fore  part  of  its 
sheath.  As  observed  through  the  aponeuroses  in  front  of  the  muscle, 
they  are  known  as  the  linese  transversse. 

The  pyramidal  muscle  *  is  a  triangular  fleshy  slip,  situated  in  front 

1  Linea  or  plica  semilunaris. 

2  M.  rectus  abdominis  ;  straight  muscle  of  the  abdomen. 

8  Inscriptions  tendinese.  4  M.  pyramidalis  abdominis. 


276  THE    MUSCULAR   SYSTEM. 

of  the  origin  of  the  abdominal  rectus,  and  included  within  the  same 
aponeuroses.  It  arises  from  the  body  and  symphysis  of  the  pubes, 
and  ascends  for  two  or  three  inches  to  be  inserted  into  the  linea  alba. 
It  is  variable  in  size,  and  is  frequently  absent  on  one  or  both  sides. 

The  cremaster  is  a  thin  plane  of  fleshy  fibres,  invested  with 
connective  tissue,  sheathing  the  fore  part  of  the  spermatic  cord,  and 
extending  from  the  inguinal  canal  to  the  testicle.  The  muscle  is 
attached  to  Poupart's  ligament  outwardly  below  the  origin  of  the 
lowest  fibres  of  the  internal  oblique  muscle,  and  inwardly  is  attached 
to  the  pectineal  line  of  the  pubis.  The  fibres  of  the  cremaster  form 
on  the  spermatic  cord  a  series  of  loops,  the  lowest  of  which  reach 
and  expand  upon  the  testicle.  In  the  female  usually  a  few  small 
corresponding  fibres  accompany  the  round  ligament. 

The  linea  alba,  as  expressed  by  the  name,  is  a  conspicuous  white 
fibrous  structure  in  the  median  line  of  the  abdomen,  extending  from 
the  ensiform  process  of  the  sternum  to  the  symphysis  of  the  pubes. 
It  is  produced  by  the  intersection  of  the  fibrous  bundles  of  the  aponeu- 
roses of  the  broad  muscles,  passing  from  side  to  side  of  the  abdomen. 
It  gradually  widens  from  its  commencement,  and  approaching  the 
umbilicus  reaches  three-fourths  of  an  inch  or  more,  but  below  the 
latter  rapidly  decreases,  and  becomes  a  narrow  partition,  separating 
the  recti  muscles.  The  umbilicus  is  a  cicatrix  in  the  linea  alba 
remaining  from  the  original  connection  of  the  umbilical  cord. 

Along  the  outer  limit  of  the  rectus,  the  bellies  of  the  muscles  on 
each  side  glimmering  through  the  aponeuroses  give  rise  to  the  appear- 
ance of  another,  though  less  conspicuous,  white  line,  which  follows 
the  curvature  below  of  the  rectus  muscle,  and  is  called  the  linea  semi- 
lunaris.  The  tendinous  intersections  of  the  rectus,  in  like  manner 
seen  through  the  aponeuroses,  give  rise  to  the  lineae  transversse, 
extending  between  the  linea  alba  and  linea  semilunaris.  The  sur- 
faces corresponding  with  the  fleshy  bellies  of  the  muscles,  as  defined 
by  the  different  lines  indicated,  are  variably  prominent,  proportioned  to 
the  development  of  the  muscles  generally,  and  in  powerfully  muscular 
men  become  more  or  less  evident  even  on  the  exterior  of  the  body. 

The  quadrate  lumbar  muscle 1  is  situated  at  the  back  of  the 
abdominal  cavity,  ascending  obliquely  from  the  crest  of  the  ilium  to 
the  last  rib,  at  the  side  of  the  lumbar  vertebrae.  It  is  a  flat,  rectan- 
gular muscle,  a  little  wider  below,  and  is  enclosed  in  a  sheath  formed 
by  the  anterior  two  layers  of  the  lumbar  fascia.  It  arises  partially 
tendinous  and  fleshy  from  the  ilio-lumbar  ligament  and  adjacent  por- 
tion behind  of  the  iliac  crest,  and  ascends  to  be  inserted  tendinously 
into  the  lower  border  of  the  last  rib  for  half  its  length,  and  into  the 
ends  of  the  transverse  processes  of  the  upper  three  or  four  lumbar 
vertebras.  Commonly,  in  addition  slips  arise  tendinously  from  the 

1  M.  quadratus  lumborum ;  m.  scalenus  lumborum  ;  m.  ilio-lumbalis. 


THE    MUSCULAR   SYSTEM. 


277 


FIG.  143. 


upper  border  of  the  transverse  processes  of  the  lower  two  or  three 
lumbar  vertebrae,  and  join  the  muscle  in  front,  to  be  inserted  with  it 
into  the  last  rib. 

The  transversalis  fascia 1  is  part  of  the  general  connective- 
tissue  investment  of  the  abdominal  cavity  attaching  the  peritoneal 
lining  to  the  muscular  walls  of  the  latter.  It  is  very  thin  the  greater 
part  of  its  extent,  and  above  is  continuous  with  the  connective-tissue 
layer  attaching  the  peritoneum  to  the  diaphragm.  Behind,  it  is  con- 
tinuous with  the  anterior 
layer  of  the  lumbar  fascia, 
and  below  is  attached  along 
the  crest  of  the  ilium,  and 
is  thence  continuous  with 
the  iliac  fascia  investing  the 
iliac  muscle.  It  is  thickest  at 
the  lower  front  part  of  the 
abdomen,  where  it  comes 
into  contact  with  the  pos- 
terior surface  of  the  rectus 
muscle,  and  is  continuous 
above  with  the  termination 
behind  of  the  aponeurotic 
sheath  of  the  latter.  In 
this  position  the  epigastric 
vessels  ascend  through  the 
fascia  to  the  rectus  muscle. 
In  the  inguinal  region  it  is 
strongest,  somewhat  apo- 
neurotic, and  is  attached  to 
Poupart's  ligament,  the  tri- 
angular ligament,  and  the 
conjoined  tendon. 

The  inguinal  canal 2 
occupies  the  inguinal  region 
or  groin,  and,  though  not  a 
distinct  canal  as  the  name 
would  seem  to  indicate,  is 
the  passage  which  transmits 
the  spermatic  cord,  or  round 


VIEW  OF  THE  INGUINAL  CANAL.  1,  portion  of  the  exter- 
nal oblique  muscle ;  2,  its  aponeurosis ;  3,  portion  of  the 
latter  raised  up,  exposing  the  inguinal  canal ;  4,  linea 
alba;  5,  internal  column,  and  6,  external  column;  7, 
intercolumnar  fibres;  8,  external  abdominal  ring;  9, 
anterior  superior  iliac  spine ;  10.  arching  border  of  the 
internal  oblique  and  transversalis  muscles;  11,  con- 
joined tendon  of  the  latter  muscles ;  12,  fibres  of  the 
cremaster  muscle  descending  on  the  spermatic  cord; 
13,  rests  on  the  transversalis  fascia;  to  its  right  are 
the  epigastric  vessels  crossing  the  course  of  the  in- 
guinal canal;  14,  iliac  portion  of  the  fascia  lata;  15, 
pubic  portion;  16.  falciform  process;  17,  saphenous 
opening;  18,  saphenous  vein  joining  the  femoral  vein 
through  the  saphenous  opening ;  19,  the  femoral  artery 
and  vein  exposed  by  raising  the  portion  of  fascia  which 
forms  the  falciform  process ;  20,  suspensory  ligament  of 
the  penis. 


ligament,  through  the  ab- 
dominal wall.  It  is  situated  above  and  parallel  with  Poupart's  ligament, 
and  is  about  an  inch  and  a  half  long.  It  commences  at  the  internal 
abdominal  ring,  situated  about  midway  in  the  groin,  and  terminates 
below  at  the  external  abdominal  ring.  It  is  bounded  in  front  by 


transversalis. 


*  Canalis  inguinalis. 


278  THE   MUSCULAR   SYSTEM. 

the  external  oblique  aponeurosis;  behind  by  the  transversalis  fascia, 
the  triangular  ligament,  and  the  conjoined  tendon  of  the  internal  ob- 
lique and  transversalis  muscles ;  above  by  the  lower  arching  border  of 
the  latter  muscles ;  and  beneath  by  Poupart's  ligament  and  its  attach- 
ment to  the  transversalis  fascia. 

The  internal  abdominal  ring1  is  that  point  in  the  transversalis 
fascia,  about  midway  in  the  groin,  at  which  the  chief  constituents  of 
the  spermatic  cord  converge,  and  thence  emerge  from  the  abdomen 
through  the  inguinal  canal.  Though  not  a  distinct  opening  in  the 
transversalis  fascia,  it  is  conveniently  regarded  as  such ;  and  from  it 
the  transversalis  fascia  is  prolonged  on  the  cord  as  a  thin  investment 
distinguished  as  the  infundibuliform  fascia.2  The  inner  margin 
of  the  ring  is  usually  better  defined  by  a  slight  thickening  of  the 
transversalis  fascia  in  this  position.  The  peritoneum  covering  the 
ring  commonly  exhibits  a  variably  slight  depression,  from  the  out- 
side of  which  a  filament  may  sometimes  be  observed  extending  upon 
the  cord.  The  depression  and  filament  are  the  remains  of  the  foetal 
communication  between  the  peritoneum  and  the  vaginal  tunic  of  the 
testicle. 

The  lumbar  fascia  is  the  name  commonly  applied  to  three  mem- 
branous layers,  which  ensheathe  the  dorsal  extensor  and  quadrate  lum- 
bar muscles  and  afford  origin  to  the  transversalis,  internal  oblique,  and 
latissimus  muscles.  The  anterior  layer  is  the  thinnest,  and  lies  in 
front  of  the  quadrate  lumbar  muscle  next  the  abdominal  cavity.  It  is 
attached  inwardly  to  the  fore  part  of  the  transverse  processes  of  the 
lumbar  vertebrae,  above  to  the  external  arcuate  ligament  of  the  dia- 
phragm, below  to  the  front  of  the  ilio-lumbar  ligament  and  iliac  crest, 
and  outwardly  joins  the  posterior  layer  of  the  lumbar  fascia.  The 
middle  layer,  thicker  than  the  former  and  somewhat  aponeurotic,  lies 
behind  the  quadrate  lumbar  muscle,  and  together  with  the  anterior 
layer  ensheathes  the  muscle.  It  is  attached  inwardly  to  the  ends  of 
the  transverse  processes  of  the  lumbar  vertebrae,  above  to  the  last  rib, 
below  to  the  ilio-lumbar  ligament  and  iliac  crest,  and  outwardly  joins 
the  posterior  layer  of  the  lumbar  fascia.  The  posterior  layer  is 
subcutaneous,  and  is  a  strong  aponeurosis  which  gives  origin  to  the 
latissimus  muscle,  and  is  attached  to  the  ends  of  the  spinous  pro- 
cesses of  the  lumbar  vertebra?  and  sacrum  and  to  the  back  part  of  the 
crest  of  the  ilium.  Behind,  it  closely  embraces  the  dorsal  extensor 
muscle,  and  joined  outwardly  by  the  middle  layer  of  the  fascia,  includes 
the  latter  in  a  sheath.  Proceeding  farther  it  is  joined  by  the  anterior 
layer  of  the  fascia,  and  on  a  line  descending  from  the  end  of  the  last 
rib  to  the  iliac  crest  gives  partial  origin  to  the  transversalis  and  inter- 
nal oblique  muscles.  Considerable  connective-tissue  layers  occupy  the 

1  Annulus  abdominalis  interims ;  upper  or  posterior  abdominal  ring  ;  apertura 
interna  canalis  inguinalis.  2  Processus  vaginalis. 


THE    MUSCULAR   SYSTEM.  279 

intervals  of  the  broad  muscles  of  the  abdomen,  continuous  behind  with 
the  lumbar  fascia,  and  in  the  inguinal  region  with  the  transversalis 
fascia. 

PSOAS  MUSCLE.    ' 

See  Muscles  of  the  Lower  Limb. 

The  abdominal  muscles  are  supplied  by  the  inferior  intercostal,  the 
ilio-hypogastric,  and  the  ilio-inguinal  nerves.  Together  they  compress 
the  abdominal  viscera,  and  assist  in  expiration,  in  the  expulsion  of  the 
contents  of  the  stomach,  intestines,  and  urinary  bladder,  and  also  in 
the  birth  of  the  child. 

FASCIAE  OF   THE   PELVIS. 

The  pelvic  fascia J  is  a  thin  membrane  lining  the  cavity  of  the 
pelvis.  It  is  continuous  with  the  iliac  and  transversalis  fasciae,  and  is 
attached  to  the  brim  of  the  pelvis  and  the  surface  immediately  below, 
extending  along  the  origin  of  the  internal  obturator  muscle.  From  the 
latter  it  continues  back  over  the  pyriformis  muscle  and  sacral  plexus  of 
nerves,  behind  the  internal  iliac  vessels,  to  be  attached  to  the  front  of  the 
sacrum.  It  passes  beneath  the  obturator  vessels  in  their  course  from 
the  pelvis,  and  is  attached  forward  to  the  lower  part  of  the  pubic  sym- 
physis.  Descending  on  the  inner  surface  of  the  internal  obturator  mus- 
cle, it  forms  a  thickened,  curved,  tendinous  line,  which  extends  from 
the  pubic  symphysis  to  the  spine  of  the  ischium,  gives  attachment  to 
the  anal  elevator  muscle,  and  divides  into  two  layers,  the  obturator 
and  recto-vesical  fasciae.  Internally  it  is  covered  by  the  peritoneum. 

The  obturator  fascia2  is  a  continuation  of  the  pelvic  fascia,  de- 
scending on  the  lower  part  of  the  internal  obturator  muscle,  and  is  at- 
tached to  the  pubic  arch,  the  ischial  tuberosity,  and  the  great  sciatic 
ligament.  By  a  strong  process,  extended  across  the  pubic  arch  within, 
it  is  continuous  with  that  of  the  opposite  side ; — the  process  consti- 
tuting the  posterior  layer  of  the  triangular  ligament  of  the  pubes.3 
From  its  upper  border  extends  the  anal  fascia,4  a  thin  layer  which 
invests  the  outer  surface  of  the  anal  elevator  and  sphincter  muscles. 

The  obturator  fascia  encloses  the  pudic  vessels  and  nerve  in  their 
course.  The  interval  of  the  obturator  fascia  and  anal  elevator  is  a  con- 
siderable space,  widening  below,  and  named,  from  its  position  between 
the  ischium  and  rectum,  the  ischio-rectal  fossa,  which  is  occupied 
by  areolar  tissue,  with  more  or  less  fat.  The  disappearance  of  this  fat 
in  emaciation  produces  the  sinking  of  the  perineum  around  the  anus. 

The  recto-vesical  fascia,5  the  inner  division  of  the  pelvic  fascia, 
descends  on  the  inner  surface  of  the  anal  elevator  muscle  to  the  side 

1  F.  pelvica.  2  F.  obturatoria. 

3  Posterior  or  superior  layer  of  the  deep  perineal  fascia. 

4  Ischio-rectal  fascia. 

6  Visceral  layer  of  the  pelvic  fascia. 


280  THE   MUSCULAR  SYSTEM. 

of  the  prostate,  the  bladder,  and  the  rectum.  The  fascia  divides  at 
the  side  of  the  prostate  into  two  layers,  which  closely  invest  it, 
together  with  the  prostatic  plexus  of  veins,  and  unite  with  the  layers 
of  the  opposite  side.  An  extension  of  the  inferior  or  posterior  layer 
extends  backward  and  invests  the  seminal  vesicles,  the  vasa  deferentia, 
and  the  fundus  of  the  bladder,  including  the  vesical  plexus  of  veins. 
Extensions  of  the  recto-vesical  fascia  upward  invest  the  bladder  and 
rectum,  being  thickest  where  these  organs  are  not  covered  by  the  peri- 
toneum. The  fasciae  of  the  two  sides  unite  between  the  bladder  and 
rectum,  and  a  thin  investment  is  prolonged  below  on  the  latter  to 
the  anus  within  the  insertion  of  the  anal  elevator  muscle.  A  narrow 
process  of  the  fascia  proceeding  from  the  pubis  below  the  symphysis 
to  the  upper  part  of  the  prostate  and  neck  of  the  bladder  is  named 
the  anterior  vesical  ligament.1  Between  the  ligaments  of  the  two 
sides  the  fascia  is  thin,  and  depressed  in  a  hollow.  The  extension  of 
the  attachment  of  the  fascia  from  the  side  of  the  prostate  to  the  side  of 
the  fundus  of  the  bladder  constitutes  the  lateral  vesical  ligament.2 

THE   FASCIAE   AND   MUSCLES   OF   THE   BACK  OF   THE   TKUNK. 

The  superficial  fascia  of  the  back  of  the  trunk  forms  a  consider- 
able connective-tissue  layer,  with  a  continuous  subcutaneous  stratum  of 
adipose  tissue,  which  varies  with  the  condition  of  the  body.  The  deep 
fascia  is  a  thin,  compact,  connective-tissue  membrane,  investing  the 
superficial  muscles,  and  continuous  with  similar  thinner  intervening 
septa.  It  adheres  tightly  in  the  median  line  to  the  occipital  protuber- 
ance, the  nuchal  ligament,  and  the  spinous  processes  of  the  vertebral 
column,  outwardly  above  to  the  superior  curved  line  of  the  occipital 
bone  extending  to  the  mastoid  process,  below  to  the  crest  of  the  ilium, 
and  also  along  the  spine  and  acromion  of  the  scapula  to  the  clavicle. 
At  the  outer  border  of  the  trapezius  and  latissimus  muscles  it  is  con- 
tinuous with  the  deep  cervical  fascia,  and  with  that  of  the  axilla  and 
of  the  abdomen. 

The  muscles  of  the  back  of  the  trunk  consist  of  a  more  superficial 
set,  mostly  broad,  and  extending  outwardly  from  the  spinous  processes 
of  the  vertebral  column  to  be  connected  with  the  upper  limb,  and  a 
deeper, -more  numerous  set,  mostly  longitudinal,  and  occupying  the 
grooved  area  on  each  side  of  the  vertebral  column ;  in  the  thoracic 
region  reaching  outward  to  the  angles  of  the  ribs.  In  the  superficial 
set  they  form  two  layers,  of  which  the  first  contains  the  trapezius  and 
latissimus  muscles,  and  the  second  contains  the  scapular  elevator  and 
rhomboid  muscles.  In  the  deeper  set  they  form  three  layers,  as  follows : 
1,  the  feplenius,  supraserratus,  and  infraserratus  muscles ;  2,  the  dorsal 
extensor,  longissimus,  ilio-costalis,  spinalis,  ascending  cervical,  cervical 

1  Anterior  true  ligament  of  the  bladder ;  pubo-prostatic  ligament. 

2  Lateral  true  ligament  of  the  bladder. 


THE    MUSCULAR   SYSTEM.  281 

transversalis,  trachelo-mastoid,  and  complexus  muscles;  3,  the  semi- 
spinalis,  multifidus,  spinal  rotator,  interspinal,  intertransvei'se,  greater 
post-rectus,  small  post-rectus,  supraoblique  and  infraoblique  muscles. 

SUPERFICIAL   MUSCLES   OF  THE  BACK. 

The  trapezius1  is  a  large  triangular  muscle  lying  immediately 
beneath  the  skin  at  the  back  of  the  neck  and  thorax,  extending  out- 
wardly to  the  shoulder.  It  is  a  broad,  thick,  fleshy  layer,  arising  by  a 
narrow,  thin  aponeurosis  from  the  occipital  protuberance  and  inner 
third  of  the  superior  curved  line,  from  the  nuchal  ligament,  and  from 
the  ends  of  the  spinous  process  of  the  last  cervical  and  all  the  thoracic 
vertebrae  with  their  supraspinous  ligament.  From  this  extensive  origin 
the  fleshy  fascicles  converge  outwardly  and  are  inserted  tendinously ; 
the  uppermost  fascicles  descending  and  turning  forward  in  the  neck  to 
be  inserted  into  the  posterior  border  of  the  outer  third  of  the  clavicle ; 
the  succeeding  fascicles  gradually  becoming  more  horizontal,  and  pro- 
ceeding outward  to  be  inserted  into  the  inner  margin  of  the  acromion 
and  into  the  upper  lip  of  the  posterior  border  of  the  spine  of  the  scap- 
ula ;  while  the  inferior  fascicles  ascend  and  end  in  a  flat,  firm  tendon, 
which  glides  on  the  triangular  surface  at  the  commencement  of  the  scap- 
ular spine,  and  is  then  inserted  into  the  latter.  The  aponeurosis  of  origin 
extends  the  width  of  its  attachment  to  the  occipital  bone,  and  in  this 
position  is  of  looser  texture,  lacks  the  usual  tendinous  appearance,  and 
is  tightly  attached  to  the  adjacent  skin.  Narrowing  along  the  nuchal 
ligament,  it  widens  at  the  bottom  of  the  neck,  forming  with  that  of 
the  other  side  an  elliptical  patch,  between  the  position  of  the  shoulders 
extending  from  the  sixth  cervical  to  the  third  thoracic  vertebra. 
Thence  it  narrows  along  the  thorax,  but  slightly  widens  again  towards 
the  lower  end.  It  is '  chiefly  composed  of  transverse  tendinous  fibres, 
which  are  in  part  continuous  between  the  two  muscles  at  their  attach- 
ment to  the  nuchal  ligament  and  in  the  intervals  below  of  the  spinous 
processes. 

The  trapezius  is  variable  in  its  origin,  especially  in  the  number  of  its 
attachments  to  the  thoracic  vertebrae ;  and  its  occipital  attachment  may 
be  reduced  or  may  even  be  entirely  wanting.  It  covers  the  sple.nius, 
complexus,  scapular  elevator,  rhomboid,  and  supraspinatus  muscles,  and 
portions  of  the  infraspinatus  and  latissimus  muscles. 

The  trapezius  is  supplied  by  the  accessorius  nerve,  which,  after 
being  joined  by  branches  from  the  third  and  fourth  cervical  nerves, 
enters  the  muscle  beneath  its  outer  border,  near  the  clavicle ;  and  it 
also  directly  receives  branches  from  the  latter  nerves. 

In  the  complete  action  of  the  trapezius  the  shoulder,  and  with  it 
the  upper  limb,  is  drawn  directly  backward.  Different  portions  acting 

1  M.  trapezius  ;  m.  cueullaris. 


282 


THE    MUSCULAR   SYSTEM. 


alone  or  in  concert  with  other  muscles  may  elevate  or  depress  the 
shoulder,  and  at  the  same  time  draw  it  backward. 

The  latissimus,1  as  expressed  by  the  name,  is  one  of  the  broadest 
of  muscles.     It  lies  immediately  beneath  the  skin,  and  occupies  the 


FIG.  114. 


MUSCLES  OF  THE  BACK.  1,  2,  trapezius  ;  3,  the  acromion;  4,  latissimus;  5,  deltoid  muscle;  6, 
infraspinatus,  and  to  its  outer  side  the  teres  muscles ;  7,  external  oblique  muscle  of  the  abdo- 
men ;  8,  middle  gluteus ;  9,  great  gluteus  muscle ;  10,  scapular  elevator ;  11, 12,  rhomboid  muscles ; 
13,  14,  splenius;  15,  aponeurosis  extending  from  the  supra-  to  the  infraserratus  muscle,  16;  17, 
supraspinatus :  18,  infraspinatus  muscle ;  19,  lesser  teres,  and  20,  greater  teres  muscle ;  21,  brachial 
triceps ;  22,  great  serratus  muscle ;  23,  internal  oblique  muscle  of  the  abdomen. 

back  from  about  the  middle  of  the  thorax  down  to  the  hip,  and  extends 
outward  and  upward  along  the  side  of  the  former  and  back  of  the 
axilla  to  the  arm.  It  arises  by  a  broad,  thin  aponeurosis  from  the 
supraspinous  ligament  and  ends  of  the  spinous  processes  usually  of  the 
lower  five  or  six  thoracic  vertebra?,  of  the  lumbar  vertebrae,  and  of  the 
sacrum,  and  from  the  outer  lip  of  the  crest  of  the  ilium  behind  the  inser- 
tion of  the  external  oblique  muscle  of  the  abdomen ;  and  is  reinforced  by 


1  M.  latissimus  dorsi ;  m.  anitersor  or  aniscalptor. 


THE   MUSCULAE   SYSTEM.  283 

fleshy  slips  from  the  lower  three  ribs,  alternating  with  similar  slips  of 
the  latter  muscle.  From  this  extended  origin  the  fleshy  fascicles  gen- 
erally converge  outwardly  in  a  narrower  and  proportionately  thick 
band-like  portion,  ascending  behind  the  axilla  and  terminating  in  a 
thin,  flat  tendon,  which  is  inserted  into  the  inner  ridge  of  the  bi- 
cipital  groove  of  the  humerus.  The  uppermost  fascicles  from  their 
origin  first  incline  downward,  the  next  proceed  horizontally,  and  the 
greater  number  which  follow  become  successively  longer  and  more 
ascending  to  the  outermost  ones  from  the  crest  of  the  ilium,  which 
are  nearly  vertical  in  their  course.  The  slips  from  the  ribs  in  succession 
join  the  outer  portion  of  the  muscle  in  front.  As  the  muscle  is  about  to 
ascend  behind  the  axilla  its  upper  border  passes  over  the  inferior  angle 
of  the  scapula,  from  which  it  frequently  receives  an  accessory  slip. 
The  muscle  then  winds  outward,  forward,  and  upward  round  the  lower 
part  of  the  greater  teres  muscle,  and  in  front  of  this  ascends  to  its  in- 
sertion. The  aponeurosis  of  origin  is  narrowest  and  thinnest  above, 
and  becomes  stronger  and  widens  outwardly  to  the  iliac  crest  below, 
and  then  narrows  again  in  the  sacro-iliac  interval.  It  corresponds  with 
the  posterior  layer  of  the  lumbar  fascia,  and  tightly  embraces  the 
dorsal  extensor  muscle  in  the  loin,  where  it  is  continuous  outwardly  in 
front  with  the  middle  layer  of  the  lumbar  fascia.  The  tendon  of  inser- 
tion, scarcely  an  inch  and  a  half  wide,  is  adherent  below  to  that  of  the 
teres  muscle,  but  is  free  from  this  again,  and  has  a  synovial  bursa 
interposed  previous  to  its  insertion  into  the  bicipital  ridge,  along  which 
it  extends  a  little  higher  than  the  insertion  of  the  teres  tendon. 

The  latissimus  is  subcutaneous  throughout,  except  at  its  origin 
from  the  thoracic  vertebra,  where  it  is  covered  by  the  trapezius,  and 
at  its  insertion,  where  it  is  covered  in  front  by  the  axillary  vessels  and 
nerves.  It  rests  above  on  the  greater  teres  muscle,  and  below  it  covers 
the  infraserratus  muscle,  the  vertebral  aponeurosis,  the  ribs,  and  the 
intercostal  muscles. 

Between  the  adjacent  borders  of  the  latissimus  and  trapezius  and 
the  base  of  the  scapula  is  a  triangular  interval,  which  is  enlarged  by 
raising  the  upper  limb,  and  is  occupied  by  part  of  the  greater  rhomboid 
muscle  and  portions  of  two  ribs  with  the  intervening  intercostal  muscle. 
The  position  is  a  favorable  one  for  auscultation. 

The  latissimus  muscle  is  supplied  by  the  long  subscapular  nerve  of 
the  brachial  plexus.  It  draws  the  upper  limb  doAvnward  and  back- 
ward, and  by  rotating  the  arm  inward  directs  the  palm  of  the  hand 
backward. 

The  small  rhomboid  muscle l  is  a  narrow,  fleshy  fascicle  situated 
at  the  lower  part  of  the  neck,  under  the  trapezius.  It  arises  by  a 
short  aponeurosis  from  the  lower  extremity  of  the  nuchal  ligament 
and  the  ends  of  the  spinous  processes  of  the  last  cervical  and  first 

1  M.  rhomboideus  minor,  or  superior  ;  lesser  rhomboid  m. 


284  THE    MUSCULAR   SYSTEM. 

thoracic  vertebrae,  and  proceeds  outward  and  downward,  to  be  inserted 
tendinously  into  the  base  of  the  scapula,  opposite  the  commencement 
of  its  spine. 

The  greater  rhomboid  muscle l  is  a  broad,  fleshy  layer  situated 
under  the  trapezius,  immediately  below  the  former,  from  which  it  is 
separated  by  a  fissure  occupied  with  connective  tissue.  It  arises  by  a 
thin  aponeurosis  from  the  supraspinous  ligament  and  spinous  processes 
of  the  upper  four  or  five  thoracic  vertebrae,  and  proceeds  outward  and 
downward,  to  be  inserted  into  the  base  of  the  scapula  below  the  com- 
mencement of  its  spine.  The  greater  part  of  the  insertion  is  into  a 
narrow  tendinous  arch  of  variable  extent,  but  usually  reaching  from 
the  position  of  the  scapular  spine  to  the  inferior  angle,  the  interval 
between  the  arch  and  base  of  the  scapula  being  occupied  by  a  thin 
connective-tissue  layer. 

Internally  the  rhomboid  muscles  cover  the  supraserratus  muscle, 
and  are  partially  in  contact  with  the  dorsal  extensor  muscle,  the  ribs, 
and  the  intercostal  muscles.  They  are  supplied  by  branches  from  the 
fifth  cervical  nerve.  In  action  they  draw  the  scapula  backward  and 
upward. 

The  supraserratus 2  is  a  thin,  flat  quadrilateral  muscle  situated  on 
the  upper  part  of  the  thorax,  under  the  rhomboid  muscles.  It  arises 
by  a  thin  aponeurosis,  intimately  united  with  that  of  the  latter,  from 
the  spinous  processes  of  the  last  cervical  and  upper  two  or  three  tho- 
racic vertebras,  and  descends  outwardly,  to  be  inserted  by  fleshy  angu- 
lar slips  into  the  upper  border  of  the  second,  third,  fourth,  and  fifth 
ribs  a  little  beyond  their  angle.  Internally  it  is  in  contact  with  the 
splenius,  dorsal  extensor,  and  intercostal  muscles  and  the  ribs. 

The  infraserratus,3  larger  than  the  former,  is  situated  at  the  lower 
part  of  the  thorax,  under  the  latissimus.  It  arises  by  a  thin  aponeu- 
rosis, in  common  with  that  of  the  latter,  from  the  supraspinous  liga- 
ment and  spinous  processes  of  the  lower  two  thoracic  and  upper  two 
or  three  lumbar  vertebrae,  ascends  obliquely  outward,  and  is  inserted 
by  wide,  fleshy,  angular  slips  into  the  four  lower  ribs  a  little  beyond 
their  angle.  Internally  the  muscle  is  in  contact  with  the  dorsal 
extensor  muscle. 

The  supra-  and  infraserratus  muscles  are  supplied  by  the  contigu- 
ous intercostal  nerves.  From  the  direction  of  these  muscles  they  are 
antagonistic,  the  one  aiding  in  the  elevation,  the  other  in  the  depression, 
of  the  ribs ;  in  respiration. 

The  scapular  elevator  *  is  situated  at  the  side  of  the  neck,  be- 
neath the  trapezius  and  sterno-mastoid  muscles,  covered  in  the  interval 

1  M.  rhomboideus  major,  or  inferior. 

2  M.  serratus  superior  posticus  ;  posterior  superior  serrate  m. 
8  M.  serratus  inferior  posticus  ;  posterior  inferior  serrate  m. 

4  M.  levator  scapulae ;  m.  levator  anguli  scapulae  ;  m.  patientite  ;  elevator  muscle 
of  the  scapular  angle. 


THE   MUSCULAR   SYSTEM.  285 

of  these  by  the  skin.  It  is  a  thick  muscle,  which  arises  tendinously 
by  four  narrow  heads  from  the  transverse  processes  of  as  many  of  the 
upper  cervical  vertebrae,  and  descends  obliquely  backward  to  be  in- 
serted into  the  base  of  the  scapula  between  the  superior  angle  and 
commencement  of  its  spine.  It  descends  along  the  outer  border  of 
the  splenius  and  greater  rhomboid  muscles,  in  contact  in  front  and  be- 
neath with  the  middle  scalenus,  cervical  transversalis,  cervical  ascending, 
and  supraserratus  muscles,  and  behind  with  the  splenius  and  trapezius 
muscles.  The  scapular  elevator  is  supplied  by  branches  from  the  third 
and  fourth  cervical  nerves,  and  sometimes  from  the  fifth. 

The  vertebral  fascia  is  a  delicate  aponeurotic  layer  enclosing  the 
dorsal  extensor  and  other  muscles  which  occupy  the  vertebral  groove  in 
the  thoracic  region.  It  is  attached  inwardly  to  the  spinous  processes 
of  the  thoracic  vertebrae,  and  outwardly  to  the  angles  of  the  ribs,  is  con- 
tinuous below  with  the  aponeurosis  of  the  infraserratus  and  latissimus 
muscles,  and  extends  above  beneath  the  supraserratus  muscle  to  blend 
with  the  deep  cervical  fascia. 

DEEP  MUSCLES  OF  THE  BACK. 

The  dorsal  extensor1  extends  along  the  side  of  the  spine  from 
the  back  of  the  pelvis  to  the  neck,  occupying  the  vertebral  groove,  and 
reaching  outwardly  to  the  angles  of  the  ribs.  From  its  division,  ac- 
cessories, and  numerous  attachments,  it  is  very  complex  in  character. 
Starting  in  a  pointed  manner  behind  the  pelvis,  it  forms  a  thick,  fleshy 
mass  in  the  loin,  and  thence  ascends  and  tapers  away  on  the  chest,  but 
is  continued  by  accessory  slips  to  the  neck  and  head.  It  arises  mainly 
by  a  strong,  longitudinally  fasciculated  aponeurosis,  which  covers  the 
back  of  the  muscle,  and  is  attached  to  the  spinous  processes 'of  the 
sacrum,  lumbar,  and  lower  two  or  three  thoracic  vertebrae,  to  the  inner 
posterior  part  of  the  crest  of  the  ilium,  and  to  the  lateral  border  below 
and  end  of  the  sacrum.  From  the  anterior  face  of  the  aponeurosis  nu- 
merous fleshy  fascicles,  together  with  others  from  the  contiguous  rough 
inner  surface  of  the  ilium,  ascend  and  form  in  the  loin  the  prominently 
convex  mass  which  is  sheathed  by  the  lumbar  fascia.  Approaching 
the  thorax  the  muscle  divides  into  two  portions,  the  longissimus  and 
ilio-costalis,  lying  close  together  and  continuing  upward. 

The  longissimus,2  the  larger  and  longer  portion  of  the  dorsal  ex- 
tensor, lies  to^the  inner  side,  and  is  inserted  by  fleshy  fascicles  into  the 
back  of  the  transverse  processes  and  the  anapophyses  of  the  lumbar  ver- 
tebrae, and  the  adjacent  middle  layer  of  the  lumbar  fascia  in  front  of  the 
muscle,  and  by  long,  thin  tendons,  which  proceed  upward  to  be  inserted 
into  the  ends  of  the  transverse  processes  of  the  thoracic  vertebrae,  and 

.  l  M.  erector  spinae ;  m.  extensor  dorsi  communis. ;  m.  extensor  trunci;  m.  sacro- 
spinalis ;  m.  opistothenar. 
2  M.  longissimus  dorsi. 


286 


THE    MUSCULAR    SYSTEM. 


FIG.  145. 


by  accompanying  fleshy  slips  inserted  into  the  ribs  between  the  tuber- 
cle and  angle,  except  two,  three,  or  more  of  the  upper  ones. 

The  ilio-costalis,1  or  smaller  and  outer  portion  of  the  dorsal  exten- 
sor, ascends  obliquely  outward,  and  is  resolved  into  a  half-dozen  fleshy 

slips,  which  are  inserted  by  as  many 
tendons  in  succession  into  the  angles 
of  the  lower  six  ribs. 

The  ilio-costalis  accessory 2  con- 
sists of  half  a  dozen  fleshy  slips,  which 
arise  by  flat  tendons  from  the  ribs  be- 
neath and  internal  to  the  insertion  of 
the  ilio-costalis  tendons,  and  ascend  in 
series  with  the  latter  to  be  inserted  by 
narrow  tendons  into  the  angles  of  the 
upper  six  ribs. 

The  longissimus  rests  on  the  mul- 
tifidus  and  semispinalis  muscles,  the 
transverse  processes  of  the  lumbar 
vertebrae,  the  middle  layer  of  the  lum- 
bar fascia,  the  ends  of  the  transverse 
processes  of  the  thoracic  vertebra?,  and 
the  ribs.  The  ilio-costalis  lies  against 
the  outer  side  of  the  former,  covering 
its  lateral  insertions,  and  also  rests  on 
the  middle  layer  of  the  lumbar  fascia 
and  ribs.  The  ilio-costalis  accessory 
lies  on  the  ribs,  and  appears  as  a  con- 
tinuation of  the  ilio-costalis  tnuscle. 

The  spinalis3  is  a  slender  acces- 
sory portion  of  the  longissimus,  lying 
between  it  and  the  ends  of  the  adjacent 
spinous  processes.  Closely  connected 
with  the  aponeurosis  of  the  dorsal  ex- 
tensor, it  usually  arises  by  three  or  four 
tendinous  slips  from  the  spinous  pro- 
cesses of  the  contiguous  lumbar  and 
thoracic  vertebras,  uniting  in  a  small 
fleshy  belly,  and  terminating  in  from 
four  to  nine  tendinous  slips,  which 
ascend  and  are  inserted  into  as  many 
of  the  spinous  processes  of  the  tho- 
racic vertebra?  above.  It  lies  on  the 
semispinalis  muscle  beneath,  and  is  also  closely  connected  with  it. 


DEEP  MUSCLES  OF  THE  BACK.    1,  2,  3, 

4,  5,  6,  the  dorsal  extensor  muscle.     1, 
origin  from  the  ilium,  sacrum,  lumbar 
and  lower  thoracic  vertebrae ;  2,  insertion 
into   the   ribs,    named    the    ilio-costalis 
muscle;  3,  insertion,  named  the  longissi- 
mus ;  4,  offset,  named  the  spinalis  muscle ; 

5,  6,  prolongations  to  the  neck,  named 
the  cervical  ascending  and  transversalis 
muscles;  7,  trachelo-mastoid  muscle;  8, 
complexus;     9,     cervical     transversalis 
muscle;  10,  11,  semispinalis  muscle;  12, 
13,  small  and  greater  post-recti;   14,  15, 
supra-    and    infraoblique    muscles ;    16, 
multifldus ;  17,  costal  elevators ;  18,  inter- 
transverse  muscles ;  19,  quadrate  lumbar 
muscle. 


1  IVt.  ilio-costalis,  sacro-lumbalis,  s.  lumbaris,  or  lumbo-costalis. 

2  M.  accessorius  ad  ilio-costalem  or  ad  sacro-lumbalem.          3  M.  spinalis  dorsi. 


THE    MUSCULAR   SYSTEM.  287 

The  cervical  transversalis,1  usually  united  with  the  longissimus, 
appears  as  its  continuation  into  the  neck.  With  a  flat,  fleshy  belly,  lying 
between  the  longissimus  to  the  outer  side  below  and  the  splenius  to 
the  inner  side  above,  it  commonly  arises  by  as  many  narrow  tendons 
from  the  ends  of  the  transverse  processes  of  the  upper  four  to  six 
thoracic  .vertebrae,  and  ascends  to  be  inserted  by  similar  tendons  into 
the  transverse  processes  of  the  intermediate  five  cervical  vertebrae. 

The  cervical  ascending  muscle,2  situated  to  the  outer  side  of 
the  former,  consists  of  four  or  five  fleshy  slips  arranged  in  continuous 
series  with  those  of  the  ilio-costalis  accessory  muscle,  of  which  it  may 
be  regarded  as  an  extension  into  the  neck.  It  arises  by  tendons  from 
the  angles  of  the  upper  four  or  five  ribs  internal  to  the  insertion  of  the 
ilio-costalis  accessory  tendons,  and  ascends  to  be  inserted  by  slender 
tendons  into  the  transverse  processes  of  the  lower  three  or  four  cervical 
vertebrae,  usually  excepting  the  last  one. 

The  trachelo-mastoid  muscle,3  regarded  as  an  accessory  of  the 
longissimus  to  the  head,  lies  to  the  inner  side  and  above  the  cervical 
transversalis.  It  is  a  thin,  flat  muscle  at  the  side  of  the  neck,  lying 
between  the  splenius  and  complexus.  Very  variable  in  the  extent  of 
its  origin,  it  commonly  arises  by  four  or  more  tendons  connected  with 
those  of  the  cervical  transversalis,  from  the  ends  of  the  transverse 
processes  of  the  upper  three  or  four  thoracic  vertebrae,  except  the 
first  and  second,  and  from  the  articular  processes  of  the  lower  three 
or  four  cervical  vertebrae.  Ascending  outwardly,  it  is  inserted  into 
the  posterior  border  of  the  mastoid  process  beneath  the  splenius  and 
sterno-mastoid  muscles. 

The  splenius 4  is  a  broad  muscle  extending  from  the  upper  part  of 
the  thorax,  around  the  back  and  side  of  the  neck,  beneath  the  trapezius. 
It  arises  tendinously  from  the  lower  half  of  the  nuchal  ligament  and 
from  the  spinous  processes  of  the  last  cervical  and  upper  six  thoracic 
vertebrae.  Ascending  obliquely  outward  it  divides  into  two  portions, 
the  capito-  and  cervico-splenius.  The  capito-splenius,5  wider  and 
thicker  than  the  other  portion,  continues  to  the  head,  and  is  inserted 
into  the  lower  part  of  the  mastoid  process,  and  thence  backward  into 
the  outer  part  of  the  superior  curved  line  of  the  occipital  bone  beneath 
the  sterno-mastoid  insertion.  The  cervico-splenius 6  winding  forward 
is  inserted  into  the  costal  processes  of  the  upper  two  to  four  cervical 
vertebrae. 

The  splenius  rests  against  the  spinalis,  longissimus,  semispinalis, 
complexus,  cervical  transversalis,  and  trachelo-mastoid  muscles.  Below 
it  is  covered  by  the  rhomboid  and  supraserratus  muscles,  and  above  by 
the  trapezius  and  sterno-mastoid.  At  the  upper  back  part  of  the  neck 


1  M.  transversalis  cervicis.  2  M.  cervicalis  adscendens  or  descendens. 

3  M.  trachelo-mastoideus  ;  in.  complexus  parvus. 

4  M.  splenius.  5  M.  splenius  capitis.  6  M.  splenius  colli  or  cervicis. 


288  THE    MUSCULAR   SYSTEM. 

it  is  separated  from  its  fellow  by  a  large  triangular  space,  in  which  the 
complexus  is  visible. 

The  complexus,1  a  broad,  thick  muscle,  situated  partly  beneath 
the  former  at  the  back  of  the  neck,  arises  by  tendinous  slips  from  the 
transverse  processes,  usually  of  the  last  cervical  to  the  sixth  thoracic 
vertebra,  and  from  the  articular  processes  and  their  capsular  ligaments 
of  the  next  three  or  four  cervical  vertebrae  above.  Ascending  the  neck 
the  muscle  becomes  narrower,  and  is  inserted  into  the  inner  impressed 
surface  between  the  curved  lines  of  the  occipital  bone.  The  upper 
part  of  the  muscle  is  crossed  by  an  irregular  and  incomplete  tendinous 
intersection.  An  inner  portion  of  the  muscle  next  the  nuchal  ligament 
is  interrupted  by  a  narrow  tendinous  band,  giving  it  the  appearance 
of  a  distinct  muscle,  which  is  often  described  as  such,  with  the  name 
of  the  biventer.2  It  is  sometimes  connected  by  a  slip  with  the  spiuous 
processes  of  the  last  cervical  and  first  thoracic  vertebrae. 

The  complexus  covers  the  cervical  semispinalis  and  the  post-recti 
and  oblique  muscles  and  the  deep  cervical  artery.  It  is  covered  by 
the  trapezius,  trachelo-mastoid,  cervical  trans versalis,  and  splenius  mus- 
cles. 

The  semispinalis  3  occupies  the  vertebral  groove  in  the  neck  and 
thorax  beneath  the  complexus  and  longissimus.  It  consists  of  a  fleshy 
layer  of  oblique  fascicles  with  tendinous  attachments,  extending  from 
transverse  and  articular  processes  to  the  neighboring  spinous  processes, 
usually  across  four  or  five  to  six  vertebrae.  It  consists  of  two  portions, 
variably  distinct  and  very  variable  in  the  number  of  their  attachments. 
The  cervical  semispinalis,4  the  upper,  thicker  portion,  arises  tendi- 
nous and  fleshy  from  the  transverse  processes  commonly  of  the  upper 
four  thoracic  vertebrae  and  the  articular  processes  of  the  lower  three 
or  four  cervical  vertebrae,  and  ascends  inwardly  to  be  inserted  into  the 
spinous  processes  of  the  latter  from  the  fifth  to  the  second,  the  fascicle 
attached  to  the  axis  being  the  largest.  The  thoracic  semispinalis,5 
a  thinner  stratum  than  the  former,  arises  by  narrow  tendinous  slips 
from  the  transverse  processes  of  the  thoracic  vertebrae,  commonly 
from  the  fifth  or  sixth  to  the  tenth,  and  ascends  inwardly  to  be  in- 
serted by  half  a  dozen  tendons  into  the  spinous  processes  of  the  lower 
two  cervical  and  the  upper  four  to  six  thoracic  vertebrae. 

The  semispinalis  rests  on  the  multifidus  muscle,  covered  by  the 
complexus,  splenius,  longissimus,  and  spinalis  muscles.  Lying  on  the 
cervical  semispinalis  are  the  deep  cervical  artery  and  the  posterior 
cervical  plexus  of  nerves. 

The  multifidus6  occupies  the  bottom  of  the  vertebral  groove  at 


1  M.  complexus ;  m.  c.  magnus  ;  m.  trachelo-occipitalis  ;  m.  semispinalis  capitis. 

2  M.  biventer  cervicis  ;  m.  digastricus  cervicalis. 

3  M.  semispinalis.  4  M.  semispinalis  cervicis. 
5  M.  semispinalis  dorsi.                                        °  M.  multifidus  spinae. 


THE   MUSCULAR   SYSTEM.  289 

the  side  of  the  spine  from  the  sacrum  to  the  axis,  beneath  the  dorsal 
extensor  and  semispinalis  muscles.  More  largely  produced  towards 
the  lower  part  of  the  spine,  it  is  thinnest  in  the  thoracic  region.  It 
consists  of  numerous  comparatively  short,  fleshy  fascicles,  which  arise 
from  the  back  of  the  sacrum,  the  posterior  extremity  of  the  iliac  crest, 
and  the  posterior  sacro-iliac  ligament,  from  the  articular  and  accessory 
processes  of  the  lumbar  vertebrae,  from  the  transverse  processes  of  the 
thoracic  vertebras,  and  from  the  articular  processes  of  the  lower  four 
cervical  vertebras.  Ascending  obliquely  across  the  vertebral  groove, 
they  are  inserted  into  the  lamina?  and  the  sides  of  the  spinous  processes 
of  from  one  to  three  of  the  vertebrae  above.  The  deepest  and  shortest 
fascicles  extend  between  the  adjacent  vertebra?,  others  pass  to  the 
second  above,  and  the  superficial  and  longest  reach  to  the  third  or 
fourth. 

The  spinal  rotators L  are  a  series  of  eleven  little  muscles  on  the 
sides  of  the  thoracic  vertebra?  beneath  the  multifidus.  Each  arises 
from  the  upper  border  of  a  transverse  process,  and  proceeds  obliquely 
inward  to  be  inserted  into  the  lower  border  of  the  lamina  of  the  verte- 
bral arch  above  extending  to  the  base  of  the  spinous  process.  The 
first  of  the  series  occupies  the  space  between  the  upper  two  thoracic 
vertebra?,  and  the  last  the  space  between  the  lower  two. 

The  interspinous  muscles 2  occupy  the  intervals  of  the  spinous 
processes  in  pairs,  pertaining  to  the  two  sides  of  the  body,  and  consist 
of  short,  fleshy  fascicles  extended  between  the  processes.  In  the  neck, 
from  the  axis  downward,  they  are  short,  narrow  fascicles  between  the 
ends  of  the  spinous  processes.  In  the  thorax  they  for  the  most  part 
do  not  appear,  except  a  few  fleshy  fibres  in  one  or  two  of  the  upper 
and  lower  spaces ;  and  in  the  loins  there  are  four  pairs,  consisting  of 
thin  lamina?  separated  by  the  interspinous  ligament. 

The  intertransverse  muscles 3  occupy  the  intervals  of  the  trans- 
verse processes,  are  best  developed  in  the  neck,  and  least  in  the  thorax. 
In  the  neck  they  are  little  columnar  bundles,  a  pair  for  each  interval 
of  the  vertebra? ;  one 4  between  the  transverse  and  the  other 5  between 
the  costal  processes.  The  vertebral  artery  ascends,  and  the  anterior 
cervical  nerves  pass  outwardly,  between  them.  In  the  thorax  they 
appear  as  small,  fleshy  fascicles 6  in  the  lower  three  or  four  spaces,  and 
are  undeveloped  in  the  upper  spaces.  In  the  loins  there  are  four  pairs, 
of  which  one 7  forms  a  thin  lamina  extended  between  the  transverse 
processes,  and  the  other8  is  a  narrow  fascicle  extended  between  the 
metapophyses  and  anapophyses. 


1  M.  rotatores  dorsi.  2  M.  interspinales. 

3  M.  intertransversales  or  intertransversarii. 

4  M.  intertransversalis  cervicis.  5  M.  int.  cervicis  posticus. 

6  M.  intertransversales  dorsi.  7  M.  intertransversalis  lumborum. 

8  M.  interarticularis  lumborum  ;  m.  interaccessorius  ;  m.  interobliquus. 

19 


290  THE   MUSCULAR  SYSTEM. 

The  coccygeal  extensor l  is  a  small,  fleshy  fascicle,  occasionally 
found  extending  from  behind  the  lower  extremity  of  the  sacrum  to 
the  coccyx,  apparently  a  rudiment  of  the  extensor  of  the  caudal 
vertebrae,  or  of  the  tail,  in  lower  animals. 

All  the  deeper  muscles  of  the  back  above  described  which  act  on 
the  vertebral  column  and  the  head  are  supplied  by  the  posterior 
branches  of  the  spinal  nerves.  They  extend  the  vertebral  column  and 
the  head,  but  do  not  necessarily  act  together.  Acting  on  one  side 
alone  they  produce  lateral  bending  of  the  spine. 

FASCIAE   AND   MUSCLES   OF   THE   UPPEK   LIMB. 

The  superficial  fascia  of  the  upper  limb  is  of  loose  texture,  and 
invests  it  throughout.  Its  more  superficial  layer  is  more  or  less  per- 
vaded with  adipose  tissue,  and  between  it  and  the  deeper  layer  are 
contained  the  superficial  veins  and  lymphatics,  and  the  cutaneous 
nerves.  In  the  hand  it  is  intimately  connected  with  the  skin,  and 
not  separable  from  it. 

The  deep  fascia  of  the  upper  limb  extends  from  that  of  the  front 
and  back  of  the  chest.  Attached  to  the  sternum,  along  the  clavicle, 
the  acromion,  the  spine  and  the  base  of  the  scapula,  it  invests  the 
muscles  of  the  shoulder  and  unites  them  closely  together.  It  forms 
a  thin  and  closely-adherent  investment  to  the  pectoral,  deltoid,  trape- 
zius,  and  latissimus  muscles.  Behind  the  deltoid  it  becomes  stronger, 
and  thence  extending  over  the  infraspinatus  and  lesser  teres  muscles, 
assumes  an  aponeurotic  appearance.  In  the  armpit  it  forms  a  layer, 
the  axillary  fascia,  which  is  extended  across  the  axilla  in  a  concave 
manner,  attached  in  front  to  the  fascia  investing  the  axillary  border 
formed  by  the  pectoral  muscles,  behind  to  that  of  the  border  formed 
by  the  latissimus  and  greater  teres  muscles,  and  below  to  that  of  the 
serratus  muscle.  In  the  arm  the  deep  fascia  is  loosely  attached  to  the 
muscles  it  invests.  In  front,  on  the  flexor  muscles,  it  is  thin  ;  behind, 
investing  the  brachial  triceps,  it  is  thicker,  and  becomes  stronger  ap- 
proaching the  elbow.  It  is  chiefly  composed  of  transverse  fibres,  inter- 
sected by  longitudinal  and  some  oblique  fibres.  It  forms  on  each  side 
the  intermuscular  septum,  attached  along  the  supracondyloid  ridges. 
The  external  intermuscular  septum  extends  from  the  correspond- 
ing epicondyle  to  the  insertion  of  the  deltoid  tendon,  from  which  it 
receives  some  fibres.  The  internal  intermuscular  septum,  stronger 
than  the  former,  extends  from  the  corresponding  epicondyle  to  the 
insertion  of  the  coraco-brachial  muscle.  At  the  elbow  the  deep  fascia 
is  attached  to  all  the  contiguous  bony  processes,  and  is  continuous 
with  their  periosteum  and  the  adjacent  ligaments,  and  further 
receives  fibres  from  the  tendons  of  the  brachial  biceps  and  triceps 
muscles. 

1  M.  extensor  coccygis  ;  m.  sacro-coccygeus  posticus. 


THE   MUSCULAR   SYSTEM. 


291 


MUSCLES   OF   THE   BKEAST   AND  SHOULDER. 

The  greater  pectoral  muscle 1  is  a  large,  thick,  triangular,  fleshy 
layer  situated  immediately  beneath  the  skin  at  the  side  of  the  breast, 
extending  outwardly  to  the  shoulder.  It  arises  from  the  inner  half  of 
the  front  of  the  clavicle,  the  front  of  the  sternum,  and  of  the  costal 
cartilages  articulating  with  the  latter,  and  by  a  slip  from  the  sheath  of 

FIG.  146. 


MUSCLES  OF  THE  FEONT  OF  THE  TKUNK  ;  on  the  left  side  are  seen  the  superficial  muscles,  on 
the  right  the  deeper  ones.  1,  greater  pectoral  muscle ;  2,  deltoid ;  3,  latissimus ;  4,  great  serratus ; 
5,  "subclavian ;  6,  small  pectoral ;  7,  coraco-brachial ;  8,  hrachial  biceps ;  9,  coracoid  process ;  10, 
great  serratus  muscle ;  11,  intercostals ;  12,  external  oblique ;  13,  its  aponeurosis ;  14,  Poupart's 
ligament ;  15,  external  abdominal  ring ;  the  figure  rests  upon  the  falciform  process  of  the  fascia 
lata  bounding  the  saphenous  opening  externally ;  16.  abdominal  rectus  muscle  of  the  right  side, 
exposed  by  removing  the  front  of  its  sheath,  which  remains  on  the  left  .side ;  17,  pyramidal 
muscle ;  18,  internal  oblique ;  19,  conjoined  tendon  of  the  internal  oblique  and  transversalis  mus- 
cles ;  20,  position  of  the  inguinal  canal  below  the  arching  edges  of  the  muscles  just  named. 

the  abdominal  rectus.  From  its  broad  origin,  the  muscle  converges 
outwardly,  and  approaching  its  insertion  becomes  twisted,  so  that  the 
lower  fleshy  fascicles  pass  behind  the  upper  ones,  and  together  end  in 
a  broad  tendon,  which  is  doubled  on  itself,  and  is  thus  inserted  into 


1  M.  pectoralis  major. 


292  THE    MUSCULAR   SYSTEM. 

the  outer  ridge  of  the  bicipital  groove  of  the  humerus.  In  the  ordi- 
nary position  of  the  upper  limb  at  rest,  suspended  at  the  side  of  the 
body,  the  fascicles  of  the  upper  portion  of  the  muscle  descend  obliquely 
outward  and  end  in  the  fore  part  of  the  tendon  of  insertion,  while 
the  middle  ones  pursue  a  more  horizontal  course,  and  with  the  lower 
ascending  ones  pass  behind  the  former  and  end  in  the  back  part  of 
the  tendon  of  insertion.  When  the  limb  is  raised,  the  upper  fascicles 
of  the  muscle  proceed  horizontally  outward,  and  the  others  become 
successively  more  obliquely  ascending. 

The  origin  of  the  muscle  from  the  clavicle  and  costal  cartilages  is 
mainly  fleshy ;  that  from  the  sternum  and  sheath  of  the  abdominal 
rectus  aponeurotic.  The  tendinous  fibres  from  the  sternum  are  inter- 
sected by  those  of  the  opposite  muscle.  The  clavicular  origin  is  usually 
more  or  less  separated  from  the  rest  of  the  muscle  by  a  fissure  occupied 
by  the  investing  fascia.  In  the  origin  from  the  costal  cartilages,  the 
first,  or  the  seventh  of  these,  or  both,  may  be  excluded,  and  sometimes 
also  the  slip  from  the  sheath  of  the  abdominal  rectus  is  wanting. 

The  anterior  portion  of  the  tendon  of  insertion  is  the  thicker,  and 
gives  offsets  below  to  the  insertion  of  the  deltoid  muscle  and  the 
brachial  fascia ;  the  posterior  portion  extends  higher  on  the  humerus, 
and  from  its  upper  border  gives  off  a  thin  expansion,  which  covers  the 
bicipital  groove  and  is  attached  to  the  capsular  ligament  of  the  shoulder- 
joint.  The  twist  in  the  muscle  occasions  a  doubling  upon  itself  at  the 
outer  part,  producing  the  thick  anterior  rounded  border  of  the  armpit. 

The  pectoral  muscle  is  subcutaneous,  but  is  covered  at  its  upper  part 
by  the  platysma  muscle,  and  at  the  lower  fore  part  by  the  mammary 
gland.  Internally  it  is  in  contact  with  the  ribs  and  costal  cartilages, 
the  subclavian,  small  pectoral,  serratus,  and  intercostal  muscles.  It 
forms  the  anterior  wall  of  the  axilla,  and  covers  the  axillary  vessels 
and  nerves.  Its  upper  outer  border  is  in  contact  with  the  deltoid 
muscle,  separated  by  a  narrow  interval  occupied  by  the  cephalic  vein. 

The  small  pectoral  muscle l  is  situated  immediately  under  the 
former.  It  is  triangular,  and  arises  by  thin  aponeurotic  slips  from 
the  external  surface  of  the  third,  fourth,  and  fifth  ribs,  near  their 
cartilages,  ascends  outwardly  and  converges  to  a  flat  tendon,  which  is 
inserted  into  the  front  border  of  the  coracoid  process  of  the  scapula. 
Its  anterior  surface  is  in  contact  with  the  greater  pectoral  muscle ;  its 
posterior  surface  with  the  ribs,  intercostal  and  serratus  muscles,  and  is 
next  the  axillary  space  with  its  chief  vessels  and  nerves. 

The  subclavian  muscle 2  is  a  narrow  one  situated  below  the  clavi- 
cle, under  the  greater  pectoral  muscle.  It  arises  by  a  short  tendon  from 
the  first  costal  cartilage,  contiguous  to  the  costo-clavicular  ligament, 
and  proceeds  upward  and  outward  to  be  inserted  into  the  shallow- 

1  M.  pectoralis  minor  ;  lesser  pectoral  muscle  ;  in.  coraco-pectoralis  ;  m.  serratus 
anterior;  m.  s.  a.  minor.  2  M.  subclavius. 


THE   MUSCULAK   SYSTEM.  293 

grooved  under  surface  of  the  clavicle,  extending  to  the  coraco-clavic- 
ular  ligament. 

The  muscle  crosses  above  the  axillary  vessels  and  nerves  as  these 
proceed  over  the  first  rib.  It  is  closely  invested  with  a  strong,  thin, 
aponeurotic  membrane,  the  costo-coracoid  fascia,1  extending  from 
the  costal  cartilage  to  the  root  of  the  coracoid  process  of  the  scapula, 
and  attached  in  front  and  behind  the  muscle  to  the  clavicle. 

The  great  serratus  2  is  a  broad,  quadrilateral  muscle,  occupying  the 
side  of  the  chest  at  the  inner  part  of  the  axilla.  It  arises  from  the 
outer  surface  of  the  eight  upper  ribs,  by  fleshy  slips  commencing  at 
their  fore  part  in  a  series  of  angular  points,  of  which  the  lower  five 
alternate  with  similar  points  of  the  external  oblique  muscle  of  the 
abdomen.  The  muscle,  from  its  broad  origin,  proceeds  backward,  con- 
verges, and  becomes  proportionately  thicker,  and  is  inserted  along  the 
front  border  of  the  base  of  the  scapula.  The  first  two  slips  appear  as 
a  separate  portion  of  the  muscle,  and  proceed  from  the  upper  two  ribs 
directly  backward  to  be  attached  to  the  flat  surface  in  front  of  the 
superior  angle  of  the  scapula.  The  third  slip  from  the  second  rib 
expands  behind  and  becomes  thinner,  and  with  the  next  slip  is  at- 
tached along  the  greater  part  of  the  base  of  the  scapula.  The  remain- 
ing slips  together  present  a  fan-like  appearance,  and  converge  to  be 
attached  to  the  flat  surface  in  front  of  the  inferior  angle  of  the 
scapula. 

Sometimes  the  serratus  is  reinforced  by  a  slip  from  the  ninth  rib, 
and  rarely,  also,  from  the  tenth  rib.  Occasionally  the  first  slip  has  no 
attachment  to  the  first  rib.  Sometimes  the  muscle  is  more  or  less 
divided  into  two  or  three  distinct  portions,  and  rarely  it  is  defective 
from  the  absence  of  one  or  more  slips. 

By  its  internal  surface  the  serratus  is  in  contact  with  the  ribs  and 
intercostal  muscles,  and  with  part  of  the  supraserratus  muscle.  Its 
external  surface  forms  the  inner  wall  of  the  axilla,  is  in  contact  behind 
with  the  subscapular  and  latissimus  muscles,  in  front  is  covered  above 
by  the  pectoral  muscles,  and  below  is  subcutaneous.  It  is  supplied  by 
the  posterior  thoracic  nerve. 

MUSCLES   OF  THE    BACK   AND  SHOULDER. 

The  trapezius,  latissimus,  rhomboid,  and  scapular  elevator,  all  appro- 
priate muscles  of  the  upper  limb,  are  described  with  those  of  the  back 

of  the  trunk. 

MUSCLES   OF   THE    SHOULDER 

The  supra-  and  infraspinatus  muscles,  occupying  the  back  of  the 
scapula,  are  enclosed  by  like-named  fasciae  attached  to  the  margins  of 
the  corresponding  fossae.  The  fasciae  are  strongest  internally  where 

1  Lig.  costo-coracoideum  ;  1.  bicorne ;  clavicular  fascia  ;  bifid  ligament. 

2  M.  serratus  magnus ;  m.  serratus  anticus ;   m.  ser.  ant.  major ;  great  serrated 
muscle. 


294 


THE   MUSCULAR   SYSTEM. 


they  give  partial  origin  to  the  muscles,  and  become  thinner  and  of 
looser  texture  towards  the  shoulder-joint.  The  infraspinatus  fascia  is 
especially  strong  and  aponeurotic  at  its  lower  part,  where  it  is  imme- 
diately subjacent  to  the  skin  and  superficial  fascia  of  the  back. 

The  supraspinatus  muscle,1  occupying  the  supraspinous  fossa, 
arises  from  about  two-thirds  of  its  surface  next  the  base  of  the  scap- 
ula and  from  the  contiguous  portion  of  the  investing  fascia.  The  fas- 
cicles converge  to  a  tendon  which  proceeds  outward  beneath  the  acro- 

mion,  over  the  shoulder- 

FIG-  147-  joint,  closely  adherent  to 

the  capsular  ligament 
and  the  tendon  of  the  in- 
fraspinatus muscle,  and  is 
inserted  into  the  upper 
division  of  the  greater  tu- 
berosity  of  the  humerus. 
It  is  covered  by  the  tra- 
pezius  muscle  and  the 
acromion. 

The  infraspinatus 2 
is  a  thick,  triangular  mus- 
cle, occupying  the  greater 
part  of  the  infraspinous 
fossa.  Its  fascicles  arise 
from  about  two-thirds  of 

the  surface  of  the  latter  next  the  base,  and  from  the  contiguous  por- 
tion of  the  investing  fascia,  and  converge  outward  and  upward  to  a 
tendon,  which  proceeding  from  within  the  fleshy  belly  covers  the 
back  of  the  shoulder-joint,  adherent  to  the  capsular  ligament,  and  is 
inserted  into  the  middle  division  of  the  greater  tuberosity  of  the 
humerus.  Partially  subcutaneous,  it  is  covered  by  the  deltoid  and 
trapezius  above  and  by  the  latissimus  at  the  lower  scapular  angle. 
A  small  bursa  is  sometimes  placed  between  its  tendon  and  the  capsular 
ligament  of  the  shoulder-joint. 

The  supra-  and  infraspinatus  muscles  are  supplied  by  the  supra- 
scapular  nerve  of  the  brachial  plexus. 

The  lesser  teres  muscle 3  lies  along  the  outer  border  of  the  infra- 
spinatus muscle,  with  which  it  is  closely  connected.  It  arises  from  the 
grooved  surface  behind  the  axillary  border  of  the  scapula  and  from 
the  adjacent  tendinous  septa  between  it,  the  infraspinatus,  and  the 
greater  teres  muscles,  and  ascends  outwardly  to  a  tendon  which  crosses 
the  back  of  the  shoulder-joint  below  the  infraspinatus  muscle,  and  is 


MUSCLES  ON  THE  BACK  OF  THE  SCAPULA.  1,  supraspinatus 
muscle  ;  2,  infraspinatus  muscle ;  3,  lesser  teres  muscle ;  4, 
greater  teres  muscle. 


1  M.  supraspinatus ;  m.  suprascapularis  ;  m.  superscapularis  superior. 

2  M.  infraspinatus  ;  m.  superscapularis  inferior. 

3  M.  teres  minor;  lesser  terete  muscle. 


THE    MUSCULAR   SYSTEM. 


295 


FIG.  148. 


inserted  into  the  lower  division  of  the  greater  tuberosity  of  the  humerus ; 
and  by  a  few  fleshy  fibres  is  extended  to  the  bone  a  short  distance 
below.  It  is  covered  above  by  the  deltoid  muscle,  is  partially  subcu- 
taneous below  and  behind,  and  in  front  is  in  contact  with  the  long  head 
of  the  brachial  triceps  muscle. 

The  greater  teres 1  lies  externally  to  the  preceding,  and  contrib- 
utes with  the  latissimus  to  form  the  posterior  border  of  the  axilla. 
It  arises  from  the  dorsal  surface  of  the  expanded  inferior  angle  of  the 
scapula  and  from  the  tendinous  septum  between  it  and  the  lesser  teres 
and  infraspinatus  muscles,  and  ascends  outwardly  to  end  in  a  broad, 
flat  tendon,  which  is  inserted  into  the  posterior  bicipital  ridge  of  the 
humerus,  in  front  of  the  tendon  of  the  latissimus.  Partially  adhering 
to  the  latter,  the  two  tendons  are  separated  close  to  their  insertion  by 
an  intervening  bursa.  In  its  ascent  it  diverges  from  the  lesser  teres, 
and  is  separated  from  it 
by  the  long  head  of  the 
triceps.  Its  posterior  sur- 
face, partially  subcutane- 
ous, is  covered  below  by 
the  latissimus,  which 
twists  obliquely  around  its 
outer  border  to  its  front. 

The  subscapular 
muscle 2  occupies  the  cor- 
responding  fossa,  and 
forms  the  posterior  wall 
of  the  axilla ;  and  is  in- 
vested with  a  thin  fascia, 
which  separates  it  from 
other  structures  of  the  armpit  and  from  the  great  serratus  muscle.  It 
arises  by  large  fleshy  fascicles  and  tendinous  fibres  from  the  basal  two- 
thirds  of  the  surface  of  the  subscapular  fossa,  and  converges  outward 
and  upward  to  a  broad  tendon,  which  passes  in  front  of  the  shoulder- 
joint  closely  adherent  to  the  capsular  ligament,  and  is  inserted  into  the 
small  tuberosity  of  the  humerus,  extending  a  little  way  down  the  bone. 
Between  its  posterior  surface  and  upper  border  outwardly  and  the 
neck  and  coracoid  process  of  the  scapula  a  bursa  is  interposed,  usually 
communicating  with  the  cavity  of  the  shoulder-joint.  Near  its  insertion 
it  is  crossed  in  front  by  the  conjoined  heads  of  the  coraco-brachialis  and 
brachial  biceps  muscles,  usually  having  a  bursa  intervening. 

The  subscapular  and  greater  teres  muscles  are  supplied  by  the  sub- 
scapular  nerves ;  the  lesser  teres  by  the  circumflex  nerve. 

The  subscapular  muscle  rotates  the  humerus  inward ;    the  supra- 


MUSCLES  ON  THE  FRONT  OF  THE  SCAPULA.     1,  subscapular 

muscle;    2,  greater  teres  muscle;   3,  upper  part  of  the 
brachial  triceps ;  4,  supraspinatus  muscle. 


1  M.  teres  major ;  greater  terete  muscle  ;  m.  scapulo-humeralis. 

2  M.  subscapularis. 


296 


THE    MUSCULAR   SYSTEM. 


FIG.  149. 


and  infraspinatus  and  the  lesser  teres  muscles  outward.  The  tendons 
of  insertion  of  all  together  strongly  reinforce  the  capsular  ligament  of 
the  shoulder-joint.  The  greater  teres  muscle  draws  the  humerus  down- 
ward and  inward. 

The  deltoid  muscle,1  large,  powerful,  and  of  triangular  shape, 

forms  the  rounded  prominence  of  the 
shoulder.  It  arises  tendinously  from 
the  outer  third  below  of  the  clavicle, 
the  outer  border  of  the  acromion,  and 
the  inferior  margin  of  the  spine  of  the 
scapula.  Composed  of  coarse  bundles 
of  fascicles  with  a  penniform  arrange- 
ment intersected  with  tendinous  bands, 
the  bundles  converge  to  a  tendon  which 
partially  faces  the  muscle  beneath,  and 
is  inserted  into  the  angular  roughness 
outwardly  near  the  middle  of  the  hu- 
merus. The  external  surface  of  the  del- 
toid muscle  is  subcutaneous,  and  its  an- 
terior border  is  contiguous  to  the  greater 
pectoral  muscle,  with  the  cephalic  vein 
lying  along  the  interval.  Between  the 
muscle  and  the  tendons  embracing  the 
shoulder-joint  inserted  into  the  tuberos- 
ities  of  the  humerus  there  is  a  large 
bursa,  which  extends  backward  beneath  the  acromion.  The  deltoid 
muscle  covers  the  coracoid  process  and  the  coraco-acromial  ligament, 
the  origins  of  the  biceps,  coraco-brachialis,  and  long  and  outer  heads 
of  the  triceps,  and  the  insertions  of  the  supra-  and  infraspinatus,  lesser 
teres,  and  subscapular  muscles. 

The  deltoid  muscle  is  supplied  by  the  circumflex  nerve.  It  raises 
the  upper  limb  from  the  body,  and  with  other  muscles  may  assist  in 
drawing  it  forward  or  backward. 

MUSCLES  OF   THE  AKM. 

The  brachial  biceps 2  occupies  the  fore  part  of  the  arm,  where  it 
forms  a  conspicuous  prominence  when  the  forearm  is  flexed.  It  is  a 
long  fusiform  muscle  arising  by  two  heads,  distinguished  as  long  and 
short,  though  the  difference  in  this  respect  is  trifling.  The  longer 
head  arises  by  a  slender  tendon  from  the  top  of  the  glenoid  cavity  of 
the  scapula,  where  it  is  continuous  with  the  glenoid  ligament.  The 
tendon  passes  outwardly  within  the  capsule  of  the  shoulder-joint, 

1  M.  deltoideus  or  deltiformis  ;  m.  supra-acromio-humeralis  ;  m.  attollens  humeri. 

2  M.  biceps  flexor  cubiti ;  m.  biceps  brachii ;   m.   flexor  radii ;  scapulo-radial 
muscle. 


THE  DELTOID  MUSCLE.  1,  its  inser- 
tion ;  2,  its  origin  from  the  clavicle;  3, 
origin  from  the  spine  and  acromion 
of  the  scapula. 


THE   MUSCULAR   SYSTEM. 


297 


where  it  is  sheathed  by  the  lining  synovial  membrane ;  thence  emerging 
from  the  joint  between  the  tuberosities  of  the  humerus,  it  descends  in 
the  bicipital  groove,  and  terminates  in  a  fleshy  belly.  This  descends  the 
arm,  and  is  joined  by  the  shorter  head  of  the  muscle,  which  arises  in 
union  with  the  coraco-brachialis  muscle  by  a  short,  flat  tendon  from  the 
coracoid  process  of  the  scapula.  The  common  belly,  convex  in  front 
and  flat  behind,  tapers  below  and  ends  above  the  elbow  in  a  thick 
tendon,  which  passes  over  the  elbow-joint  backward,  in  the  pit  between 
the  long  supinator  and  terete  pronator,  and  winds  outward  upon  the 
tuberosity  of  the  radius  to  be  inserted  into  its  back  part.  Between  the 
fore  part  of  the  tuberosity  and  the  tendon 
a  bursa  is  introduced.  With  the  rotation  of 
the  radius  inward  the  tendon  becomes  more 
wound  upon  the  tuberosity,  and  when  the 
bone  is  rotated  outward  the  tendon  be- 
comes unwound.  Opposite  the  elbow  the 
tendon  gives  off  an  aponeurotic  process, 
which  proceeds  downward  and  inward,  and 
merges  in  the  deep  fascia  of  the  forearm 
over  the  origin  of  the  muscles  from  the 
inner  epicondyle. 

The  greater  part  of  the  biceps  is  sub- 
cutaneous, its  upper  extremity  being  cov- 
ered by  the  greater  pectoral  and  deltoid 
muscles.  It  rests  successively  on  the 
shoulder-joint,  the  subscapular,  greater 
teres,  latissimus,  and  brachialis  muscles ; 
with  its  inner  border  related  to  the  coraco- 
brachialis  muscle,  the  brachial  vessels,  and 
the  median  nerve,  and  its  outer  border  to 
the  deltoid  and  long  supinator  muscles. 
The  aponeurotic  offset  from  the  tendon  of 
insertion  crosses  the  brachial  vessels  and 
the  median  nerve. 

The  biceps  frequently  exhibits  varia- 
tion from  the  usual  arrangement.  It  some- 
times has  a  third  head  arising  from  the 
humerus,  related  with  the  brachialis  or 
coraco-brachialis  muscle,  and  joining  the  coracoid  portion  of  the  biceps 
and  its  aponeurotic  oifset  from  the  tendon  of  insertion. 

The  coraco-brachialis  muscle l  is  situated  at  the  upper  part  of 
the  arm  to  the  inner  side  and  behind  the  biceps.  It  arises  partially 
tendinous  and  fleshy  in  conjunction  with  the  tendon  of  the  shorter 
head  of  the  biceps  from  the  end  of  the  coracoid  process  of  the  scapula. 


MUSCLES  OF  THE  FORE  PART  OP 
THE  ARM.  1,  coracoid  process  of  the 
scapula;  2,  coraco-clavicular  liga- 
ment ;  3,  coraco-acromial  ligament ; 
4,  subscapular  muscle ;  5,  greater 
teres  muscle;  6,  coraco-brachialis 
muscle ;  7,  brachial  biceps ;  8,  its  in- 
sertion into  the  tuberosity  of  the 
radius;  9,  brachialis  muscle;  10, 
brachial  triceps. 


1  M.  coraco-brachialis  ;  m.  coraco-humeralis. 


298  THE   MUSCULAR   SYSTEM. 

Descending,  it  is  inserted  tendinously,  and  to  a  small  degree  fleshy, 
into  a  narrow,  roughened  impression  near  the  middle  of  the  humerus, 
between  the  origin  of  the  brachialis  and  the  triceps  muscle.  It  is  com- 
monly pierced  by  the  musculo-cutaneous  nerve,  and  its  inner  border  is 
in  contact  with  the  brachial  vessels.  It  is  occasionally  divided  into  two 
muscles,  as  in  apes.  Not  unfrequently  some  of  its  fibres  join  those  of 
the  brachialis  muscle. 

The  brachialis *  is  situated  at  the  lower  fore  part  of  the  arm  be- 
neath the  biceps  muscle.  It  arises  from  the  front  surface  of  the  hu- 
merus, commencing  in  a  pair  of  angular  points  embracing  the  deltoid 
insertion,  reaching  to  near  the  elbow,  to  the  inner  intermuscular  septum, 
and  to  the  origin  of  the  long  supinator  and  longer  carpo-radial  extensor 
outwardly.  The  fleshy  fascicles,  descending  somewhat  convergent, 
pass  in  front  of  the  elbow-joint  closely  adherent  to  the  capsular  liga- 
ment, and  are  inserted  by  a  short,  thick  tendon  into  the  fore  part  of 
the  coronoid  process  of  the  ulna.  The  muscle  lies  immediately  behind 
the  biceps,  projecting  on  both  sides.  It  supports  the  brachial  vessels 
and  the  median  nerve ;  and  the  musculo-spiral  nerve  lies  on  its  outer 
side  covered  by  the  long  supinator  muscle. 

The  biceps,  coraco-brachialis,  and  brachialis  muscles  are  supplied 
by  the  musculo-cutaneous  nerve,  but  the  last,  also,  usually  receives  a 
branch  from  the  musculo-spiral  nerve. 

If  the  palm  of  the  hand  is  turned  downward,  the  first  action  of  the 
biceps  by  rotating  the  radius  outward  is  to  turn  the  palm  upward ;  a 
continuance  of  the  action  flexes  the  forearm  on  the  arm,  and  a  further 
action  is  to  raise  the  limb  at  the  shoulder.  The  coraco-brachialis  mus- 
cle, with  the  shorter  head  of  the  biceps,  draws  the  arm  inward  and 
upward.  The  action  of  the  brachialis  muscle  is  simply  flexion  of  the 
forearm  on  the  arm. 

The  brachial  triceps 2  occupies  the  back  of  the  arm,  extending 
the  whole  length  of  the  posterior  surface  of  the  humerus.  Its  upper 
tapering  part  is  divided  into  three  portions  or  heads,  whence  its  name ; 
and  its  lower  demi-cylindrical  part  is  faced  behind  for  more  than  half 
its  length  by  an  aponeurosis,  which  is  joined  by  another  within  the  mus- 
cle, and  forms  with  it  the  tendon  of  insertion.  The  middle  or  long 
head 3  arises  tendinous  from  the  roughened  impression  of  the  neck  of 
the  scapula  below  the  glenoid  cavity,  descends  in  close  connection  with 
the  capsule  of  the  shoulder-joint,  and  at  the  inner  back  part  of  the  hu- 
merus between  the  other  two  heads  of  the  muscle,  to  end  in  the  upper 
extremity  of  the  tendon  of  insertion  extending  a  short  distance  along 
its  inner  border.  The  external  head,4  little  shorter  than  the  former, 

1  M.  brachialis  ;  m.   brachialis  anticus  or  internus  ;   m.  brachiseus  interims  ;   m. 
humero-cubitalis. 

2  M.  triceps  extensor  cubiti ;  m.  triceps  brachii ;  m.^brachialis  externus  or  pos- 
terior. 

3  M.  anconseus  longus.  4  M.  anconaeus  externus ;  m.  vastus  externus. 


THE    MUSCULAR   SYSTEM. 


299 


FIG.  151. 


arises  tendinous  and  fleshy  from  the  outer  back  part  of  the  humerus, 
commencing  pointedly  below  the  greater  tuberosity  and  extending  to  the 
musculo-spiral  groove  near  the  middle  of  the  bone,  whence  the  fibres 
descend  obliquely  to  terminate  along  the  outer  part  of  the  tendon  of 
insertion.  The  internal  or  short  head1  arises,  for  the  most  part, 
fleshy  from  the  surface  of  the  humerus  below  the  musculo-spiral  groove, 
commencing  pointedly  below  the  insertion  of  the  tendon  of  the  greater 
teres  muscle,  and  on  each  side  from  the  intermuscular  septum,  reach- 
ing to  near  the  elbow,  and  it  descends  obliquely  to  terminate  in  the 
tendon  of  insertion,  with  a  few  fibres  reach- 
ing the  olecranon.  The  tendon  of  insertion 
of  the  triceps,  composed  of  the  posterior  apo- 
neurotic  facing  joined  by  the  layer  from 
within  the  muscle,  converges  to  be  inserted 
into  the  back  portion  of  the  upper  surface 
of  the  olecranon  extending  along  its  outer 
border,  where  it  is  continuous  with  the  fascia 
covering  the  anconeus  muscle.  In  advance 
of  the  insertion  into  the  olecranon,  a  small 
bursa  intervenes  between  the  tendon  and  the 
elbow-joint.  The  musculo-spiral  groove  of  the 
humerus  separates  the  external  and  internal 
heads  of  the  triceps,  and  with  them  forms 
a  canal  traversed  by  the  superior  profunda 
blood-vessels  and  the  musculo-spiral  nerve. 

A  short  distance  above  the  elbow,  on  each 
side,  there  is  usually  a  fleshy  fascicle,  an  off- 
set from  the  triceps,  distinguished  as  the  sub- 
anconeus.2  It  arises  from  the  back  of  the 
humerus,  and  descends  to  be  inserted  into  the 
capsular  ligament  of  the  elbow-joint. 

The  anconeus  3  is  situated  at  the  outer 
back  part  of  the  elbow,  and  appears  to  be  a 
continuation  of  the  triceps,  with  which  it  is 
sometimes  continuous.  Small  and  triangular, 
it  arises  tendinous  from  the  back  of  the  outer 
epicondyle  of  the  humerus,  and  its  fleshy  fascicles  diverge  backward  and 
downward  to  be  inserted  into  the  outer  side  of  the  olecranon  and  the 
depressed  surface  of  the  ulna  extending  several  inches  downward.  Sub- 
cutaneously  it  is  invested  with  a  strong  fascia,  which  is  continuous 
with  the  insertion  of  the  tendon  of  the  triceps.  Its  deep  surface  is  con- 
tiguous to  the  elbow-joint,  the  radial  orbicular  ligament,  and  the  short 
supinator  muscle. 

1  M.  anconaeus  interims  or  brevis  ;  m.  vastus  interims. 

2  M.  subanconseus.  3  M.  anconaeus  ;  m.  anc.  parvus  or  quartus. 


VIEW    OF  THE    BRACHIAL    TRI- 
CEPS ON  THE  BACK  OF  THE  RIGHT 

ARM.  1,  external  head;  2,  long 
head ;  3,  short  head ;  4,  insertion 
of  the  muscle  into  the  olecranon 
of  the  ulna;  5,  radius;  6,  capsular 
ligament  of  the  shoulder-joint. 


300  THE    MUSCULAR   SYSTEM. 

The  triceps  and  anconeus  are  supplied  by  the  musculo-spiral  nerve. 
Together  they  are  the  extensors  of  the  forearm  on  the  arm.  The  long 
head  of  the  triceps  will  also  draw  the  upper  limb  downward  towards  the 
scapula. 

FASCIAE   AND   MUSCLES   OF   THE   FOREAKM  AND   HAND. 
FASCIA   OF    THE   FOREARM. 

The  superficial  fascia  of  the  forearm,  continuous  with  that  of  the 
arm,  is  a  well-marked,  loose  connective-tissue  layer,  which  involves  the 
subcutaneous  fat  and  the  superficial  veins,  and  connects  the  skin  with 
the  deep  fascia  and  subcutaneous  bony  surfaces.  The  extension  of  the 
same  fascia  in  the  palm  of  the  hand  is  of  firmer  texture,  and  more 
closely  connects  the  skin  and  subjacent  fat  to  the  deep  fascia,  allowing 
much  less  freedom  of  movement  of  the  skin. 

The  deep  fascia  of  the  forearm,1  likewise  continuous  with  that  of 
the  arm,  is  a  shining  bluish-white  aponeurosis  firmly  attached  to  the 
subcutaneous  processes  and  borders  of  the  bones  of  the  forearm  and 
investing  the  muscles.  It  is  composed  of  transverse  and  oblique  fibres, 
intersected  by  longitudinal  fibres.  It  is  stronger  on  the  back  than  on 
the  front  of  the  forearm,  and  is  thickest  approaching  the  wrist.  From 
its  inner  surface  partitions  extend  between  the  muscles,  so  that  each  is 
separately  enclosed  in  a  sheath.  In  the  upper  part  of  the  forearm  the 
intermuscular  septa  appear  superficially  as  more  distinct  white  lines 
defining  the  muscles,  and  their  opposed  surfaces,  together  with  the 
inner  surface  of  the  investing  fascia,  give  origin  to  many  of  the  fleshy 
fascicles  of  the  muscles.  Approaching  the  wrist  in  front  and  behind 
the  deep  fascia  becomes  denser,  and  is  continuous  with  the  annular 
ligaments. 

The  anterior  annular  ligament 2  is  a  strong,  wide,  fibrous  band, 
which  is  extended  transversely  across  the  carpus,  converting  its  deep 
concavity  into  the  carpal  canal  for  the  passage  of  the  flexor  tendons 
of  the  fingers.  It  is  attached  on  the  one  side  to  the  pisiform  bone  and 
the  unciform  process  of  the  unciform  bone,  and  on  the  other  side  to 
the  tuberosity  of  the  scaphoid  bone  and  the  fore  part  of  the  trapezium. 
Above,  it  is  continuous  with  the  deep  fascia  of  the  forearm,  and  partially 
receives  the  insertion  of  the  tendons  of  the  long  palmar  and  ulno-carpal 
flexor  muscles.  Below,  it  is  continuous  with  the  palmar  fascia,  and 
gives  partial  origin  to  the  small  muscles  of  the  thumb  and  little  finger. 
Beneath  it  proceed  the  tendons  of  the  superficial  and  deep  digital  and 
long  pollical  flexors  and  the  median  nerve,  all  together  enveloped  in 
one  large  and  much-folded  synovial  sheath,  which  extends  a  short  dis- 
tance above  and  below  the  ligament  into  the  forearm  and  the  palm  of 
the  hand.  Two  prolongations  of  the  sheath  extend  upon  the  tendons 
of  the  long  pollical  flexor  and  of  the  little  finger  to  their  insertion. 

1  F.  antebrachialis. 

2  L.  annulare  or  transversum  anterius  ;  1.  commune  or  carpi  volare. 


THE    MUSCULAR   SYSTEM.  301 

At  the  outer  attachment  of  the  annular  ligament  with  the  scaphoid 
bone  and  the  trapezium  it  converts  the  groove  of  the  latter  into  a 
distinct  canal,  lined  by  a  synovial  sheath,  for  the  passage  of  the 
tendon  of  the  radio-carpal  flexor. 

The  posterior  annular  ligament 1  appears  as  a  reinforcement  of 
the  deep  fascia  of  the  forearm  through  fibrous  bundles  which  extend 
in  a  broad  band  obliquely  across  from  the  outer  side  of  the  radius  to  the 
inner  side  of  the  ulna  and  carpus.  Below,  it  is  continuous  with  the 
deep  fascia  on  the  back  of  the  hand.  In  its  course  across  the  wrist  it 
is  attached  to  the  ridges  at  the  back  of  the  radius  and  ulna,  and  con- 
verts the  intervening  grooves  into  canals  for  the  passage  of  the  exten- 
sor tendons.  It  forms  six  distinct  passage-ways,  each  lined  by  a  sepa- 
rate synovial  sheath.  These  are  from  without  inwardly,  as  follows: 
1,  on  the  outer  side  of  the  radial  styloid  process  for  the  tendons  of  the 
first  and  second  pollical  extensors ;  2,  behind  the  styloid  process  for  the 
tendons  of  the  radio-carpal  extensors ;  3,  inward  to  the  latter  behind 
the  radius  for  the  third  pollical  extensor;  4,  next  inward  for  the 
tendons  of  the  common  digital  and  indical  extensors ;  5,  between  the 
radius  and  ulna  for  the  minimal  extensor ;  6,  in  the  groove  behind  the 
ulna  for  the  ulno-carpal  extensor.  The  synovial  sheaths  accompany 
the  tendons  to  their  destination. 

FASCIAE  OF  THE  HAND. 

The  dorsal  fascia2  of  the  hand  is  a  delicate  aponeurotic  mem- 
brane, chiefly  composed  of  transverse  fibres,  continuous  above  with  the 
posterior  annular  ligament,  and  extending  over  the  extensor  tendons 
to  the  fingers,  where  it  blends  with  the  expanded  tendons. 

The  palmar  fascia 3  consists  of  three  portions,  of  which  the  lateral 
are  thin  connective-tissue  layers  investing  the  muscles  of  the  ball  of  the 
thumb  and  those  of  the  little  finger.  The  middle  portion,  to  which  the 
name  is  especially  applied,  is  a  strong,  triangular  aponeurosis,  extended 
across  the  hollow  of  the  hand  between  the  annular  ligament  and  the 
roots  of  the  fingers.  It  is  chiefly  composed  of  longitudinal  bundles  of 
fibres,  which  radiate  mainly  from  the  tendon  of  the  long  palmar  muscle 
and  partly  from  the  front  of  the  annular  ligament.  As  it  expands  it  be- 
comes thinner,  and  approaching  the  fingers  divides  into  four  processes, 
each  of  which  divides  into  two  others,  which  are  attached  to  the  sides 
of  the  first  phalanx  and  the  contiguous  ligaments  of  the  articulation. 
Between  the  primary  processes  the  digital  vessels  and  nerves  and  the 
tendons  of  the  lumbrical  muscles  issue,  and  in  the  intervals  of  the 
secondary  processes  the  flexor  tendons  pass  to  the  fingers.  At  the 
division  of  the  palmar  fascia  it  is  intersected  by  transverse  bundles  of 
fibres,  forming  the  superficial  transverse  ligament.  On  each  side 

1  L.  annulare  or  transversum  posterius  ;  1.  commune  or  carpi  dorsale. 

2  F.  dorsalis  maims.  s  p  palmaris  ;  aponeurosis  palmaris. 


302  THE    MUSCULAR   SYSTEM. 

it  is  connected  by  a  thin  septum  with  the  interosseous  fascia,  a  thin 
membrane  investing  the  interosseous  muscles  and  fixed  to  the  inter- 
vening metacarpal  bones.  Superficially  the  palmar  fascia  is  connected 
by  numerous  short  bands  to  the  subjacent  skin.  It  covers  the  super- 
ficial palmar  arch  and  digital  vessels,  the  digital  nerves,  and  the  flexor 
tendons  with  the  lumbrical  muscles. 

MUSCLES  OF  THE  FRONT  AND  INNER  PAET  OF  THE  FOREARM. 

Eight  muscles  occupy  the  inner  front  part  of  the  forearm,  five  of 
which  are  superficial  and  the  others  more  deeply  situated.  The  former 
consist  of  the  terete  pronator,  the  radio-carpal  flexor,  the  long  palmar 
muscle,  the  ulno-carpal  flexor,  and  the  superficial  digital  flexor.  These- 
are  all  intimately  connected  at  their  origin  from  the  inner  epicondyle 
of  the  humerus,  to  which  they  are  attached  by  a  common  tendon. 
The  deeper  muscles  are  the  deep  digital  flexor,  the  long  pollical  flexor, 
and  the  quadrate  pronator. 

The  terete  pronator l  crosses  obliquely  the  upper  part  of  the  front 
of  the  forearm  from  the  inner  side  of  the  elbow.  It  arises  tendinous 
and  fleshy  by  two  heads,  of  which  the  larger  comes  from  the  fore  part  of 
the  inner  epicondyle  of  the  humerus,  the  contiguous  deep  fascia,  and  the 
intermuscular  septum  between  it  and  the  radio-carpal  flexor  ;  and  the 
smaller  head,  a  thin  fascicle,  comes  from  the  inner  side  of  the  coronoid 
process  of  the  ulna  and  joins  the  former.  The  common  belly  proceeds 
outward  and  downward  and  ends  in  a  flat  tendon,  which  turns  over 
the  radius  and  is  inserted  into  the  rough  impression  about  the  middle 
of  its  outer  surface.  The  muscle  is,  for  the  most  part,  subcutaneous, 
but  is  covered  at  its  insertion  by  the  long  supinator.  and  is  crossed  by 
the  radial  vessels  and  nerve.  It  forms  the  inner  boundary  of  the  an- 
gular depression  in  front  of  the  elbow,  in  which  are  the  brachial  vessels, 
the  median  nerve,  and  biceps  tendon.  The  ulnar  vessels  pass  beneath 
it,  and  the  median  nerve  passes  between  its  two  heads.  It  overlies  the 
brachialis  muscle  and  the  radial  origin  of  the  superficial  digital  flexor. 
The  coronoid  head  of  the  muscle  is  especially  liable  to  variation,  and 
is  sometimes  absent. 

The  quadrate  pronator  2  is  situated  at  the  lower  part  of  the  fore- 
arm beneath  the  flexors,  and  extends  across  the  front  of  the  bones  and 
interosseous  membrane  just  above  the  wrist.  A  flat  muscle,  it  arises 
from  the  anterior  surface  of  the  ulna  at  its  lower  part,  and  passes 
almost  directly  outward  and  a  little  downward  to  be  inserted  into  the 
fore  part  of  the  radius,  reaching  its  outer  border.  Its  fascicles  are 
partially  transverse  and  oblique,  and  some  of  them  arise  from  an  apo- 
neurotic  fascia  which  invests  the  muscle.  Lying  immediately  on  it 
are  the  long  pollical,  deep  digital,  and  ulno-carpal  flexors,  and  the  radial 
blood-vessels. 

1  M.  pronator  teres  ;  m.  pr.  radii  teres ;  round  pronator  m. ;  m.  epitrochlo-radialis. 

2  M.  pronator  quadratus  ;  m.  cubito-radialis. 


THE    MUSCULAR   SYSTEM. 


303 


The  quadrate  pronator  is  sometimes  more  or  less  distinctly  divided 
into  two  muscles,  and  sometimes  it  extends  more  upward  or  down- 
ward. 

The  pronator  muscles,  whose  action  is  indicated  by  the  name,  are 
supplied  by  the  median  nerve. 

The  long  palmar  muscle1  is  subcutaneous,  and  lies  between  the 
radio-carpal  and  ulno-carpal  flexors,  resting  on  the  superficial  digital 
flexor.  It  arises  from  the  inner  epicondyle  of  the  humerus  by  the 


FIG.  152. 


SUPERFICIAL  MUSCLES  OF  THE  FRONT  OF  THE 
FOREARM.  1,  lower  part  of  the  brachial  biceps; 
2,  brachialis ;  3,  lower  part  of  the  brachial  tri- 
ceps ;  4,  terete  pronator;  5,  radio-carpal  flexor; 
6,  long  palmar  muscle;  7,  superficial  digital 
flexor ;  8,  ulno-carpal  flexor ;  9,  palmar  fascia ; 
10,  short  palmar  muscle ;  11,  pollical  abductor ; 
12,  short  pollical  flexor ;  13,  long  supinator ;  14, 
pollical  extensors.  The  crossing  and  trans- 
verse bands  on  the  fingers  are  the  vaginal  liga- 
ments enclosing  the  flexor  tendons. 


FIG.  153. 


DEEP  MUSCLES  OF  THE  FRONT  OF  THE  FORE- 
ARM. 1,  internal  lateral  ligament  of  the  elbow- 
joint;  2,  capsular  ligament  of  the  same;  3, 
orbicular  ligament  enclosing  the  head  of  the 
radius ;  4,  deep  digital  flexor ;  5,  long  pollical 
flexor ;  6,  quadrate  pronator ;  7,  pollical  ad- 
ductor ;  8,  9,  interosseous  muscles. 


common  tendon  and  from  the  ad- 
joining intermuscular  septa,  from 
which  the  small  fusiform  belly  de- 
scends and  terminates  in  a  long,  slender  tendon,  reaching  the  wrist; 
partially  inserted  into  the  fore  part  of  the  annular  ligament,  and  par- 


M.  palmaris  longus  ;  m.  epitrochlo-palmaris  ;  m.  palmaris  minimus. 


304  THE   MUSCULAR   SYSTEM. 

tially  ending  in  reinforcing  the  median  palmar  fascia.  The  tendon 
sometimes  gives  an  offset  which  affords  attachment  to  the  small  mus- 
cles of  the  thumb.  The  median  nerve  lies  to  the  inner  side  of  the 
tendon,  near  the  wrist.  The  muscle  is  frequently  absent,  and  when 
present  is  subject  to  variations  of  form  and  attachment. 

The  radio-carpal  flexor1  is  a  fusiform  muscle  lying  subcutane- 
ously  between  the  former  and  the  terete  pronator,  resting  on  the  super- 
ficial digital  flexor.  It  arises  from  the  inner  epicondyle  of  the  humerus 
by  the  common  tendon,  and  from  the  contiguous  investing  fascia  and 
intermuscular  septa,  and  descends  to  about  the  middle  of  the  forearm, 
where  it  ends  in  a  flat  tendon.  Eeaching  the  wrist,  the  tendon  pro- 
ceeds through  a  passage,  formed  by  the  outer  part  of  the  annular  liga- 
ment and  the  groove  of  the  trapezium,  lined  by  a  synovial  sheath, 
and  is  inserted  into  the  base  of  the  second  metacarpal  bone.  The 
radial  blood-vessels  are  placed  to  the  outer  side  of  its  tendon.  Some- 
times it  is  partially  inserted  into  the  annular  ligament,  and  sometimes 
into  the  third  metacarpal  bone. 

The  ulno-carpal  flexor2  lies  subcutaneously  along  the  ulnar  side 
of  the  forearm.  It  arises  by  two  heads  closely  connected  by  a  tendi- 
nous arch  at  the  inner  side  of  the  elbow,  beneath  which  the  ulnar  nerve 
descends.  The  shorter  head  arises  from  the  inner  epicondyle  of  the 
humerus  by  the  common  tendon  of  this  and  the  preceding  muscles ; 
the  other  arises  by  an  aponeurosis  from  the  inner  border  of  the  ole- 
cranon  and  the  posterior  border  of  the  ulna  for  two- thirds  its  length. 
The  fleshy  fascicles  descend  and  terminate  in  a  tendon  which  occupies 
the  anterior  border  of  the  lower  half  of  the  muscle,  and  is  inserted  into 
the  pisiform  bone,  with  offsets  extending  to  the  fifth  metacarpal  and 
unciform  bones  and  the  annular  ligament.  The  muscle  rests  on  the 
deep  digital  flexor,  with  the  ulnar  nerve  descending  between  them  • 
and  with  the  ulnar  vessels  descending  beneath  its  lower  half. 

The  long  palmar  and  the  radio-carpal  flexor  muscles  are  supplied 
by  the  median  nerve ;  the  ulno-carpal  flexor  by  the  ulnar  nerve.  All 
are  flexors  of  the  hand  at  the  wrist ;  the  long  palmar  muscle  also 
renders  the  palmar  fascia  tense. 

The  superficial  digital  flexor3  is  the  largest  muscle  of  the  super- 
ficial group,  and  lies  beneath  the  others.  It  arises  with  them  from  the 
inner  epicondyle  of  the  humerus  by  the  common  tendon,  from  the  adja- 
cent intermuscular  septa,  the  internal  lateral  ligament  of  the  elbow-joint, 
the  inner  side  of  the  coronoid  process  of  the  ulna,  and  from  the  ob- 
lique line  of  the  radius  extending  from  its  tuberosity  to  the  insertion  of 
the  terete  pronator.  The  fleshy  fascicles  descend  and  form  a  wide  and 

1  M.  flexor  carpi-radialis  ;  m.  radialis  interritis  or  anterior;  m.  palmaris  magnus. 

2  M.  flexor  carpi-ulnaris ;  m.  ulnaris  interims ;  ni.  cubito-carpien ;  m.  cubitalis 
internus. 

3  M.  flexor  sublimis  digitorum ;  m.  flexor  perforatus ;  superficial  flexor  muscle 
of  the  fingers. 


THE   MUSCULAR   SYSTEM. 


305 


thick  flattened  belly,  which  about  the  middle  of  the  forearm  divides 
into  four  parts,  terminating  in  tendons.  These  proceed  to  the  wrist,  pass 
beneath  the  annular  ligament  in  pairs,  one  in  front  of  the  other,  and 
•diverge  in  the  palm  of  the  hand,  the  front  pair  to  the  middle  and  ring 
fingers,  the  back  pair  to  the  index  and  little  fingers,  all  being  finally 
inserted  into  the  middle  of  the  second  phalanges.  In  front  of  the  first 
phalanges  the  tendons  are  split  to  give  passage  to  the  accompanying 
tendons  of  the  deep  digital  flexor,  around  which  the  divided  tendons 
are  closely  folded  and  again  united  behind,  when  they  are  once  more 
separated  to  be  inserted  in  the  lateral  borders  of  the  second  pha- 
langes. 

The  superficial  digital  flexor  rests  on  the  deep  digital  and  long  pol- 
lical  flexors,  and  covers  the  median  nerve  and  ulnar  blood-vessels.  In 
the  palm  of  the  hand  its  tendons  are  covered  by  the  median  palmar 
fascia,  crossed  by  the  superficial  palmar  arch  of  vessels,  and  lie  in  front 
of  the  accompanying  tendons  of  the  deep  digital  flexor.  The  radial 
origin  is  sometimes  wanting,  which  is  also  the  case  with  the  tendon  to 
the  little  finger,  ordinarily  the  smallest.  The  muscle  is  occasionally 
subdivided  so  that  each  tendon  of  insertion  has  a  distinct  belly. 

FIG.  154. 


METACAEPAL  BONE  AND  PHALANGES  OF  THE  FINGERS,  WITH  THEIR  TENDONS  AND  LIGAMENTS. 
In  the  upper  figure  the  flexor  tendons  are  retained  in  position  by  the  vaginal  ligaments,  com- 
posed of  transverse  and  obliquely  crossing  bands ;  in  the  lower  figure  the  flexor  tendons  are 
freed  from  the  vaginal  ligaments.  1,  metacarpal  bone;  2,  tendon  of  the  superficial  digital 
flexor;  3,  tendon  of  the  deep  digital  flexor, passing  through  a  cleft  (*)  of  the  former;  4,  tendon 
of  the  common  digital  extensor ;  5,  a  lumbrical  muscle,  inserted  into  the  extensor  tendon ;  6,  an 
interosseous  muscle,  also  inserted  into  the  latter. 

The  deep  digital  flexor,1  another  large,  thick  muscle,  lies  beneath 
the  former  and  the  ulno-carpal  flexor,  at  the  inner  fore  part  of  the 
forearm.  It  arises  from  the  ulnar  attachment  of  the  aponeurosis 
of  the  ulno-carpal  flexor,  from  the  inner  and  anterior  surface  of  the 
ulna,  commencing  on  each  side  of  the  insertion  of  the  brachialis  and 
reaching  to  within  a  short  distance  of  the  quadrate  pronator,  and 

1  M.  flexor  profundus  digitorum;  m.  flexor  perforans  ;  deep  flexor  muscle  of  the 
fingers. 

20 


306  THE    MUSCULAR   SYSTEM. 

from  the  contiguous  half  of  the  interosseous  membrane.  The  descend- 
ing fleshy  fascicles  form  a  belly,  dividing  about  the  middle  of  the  fore- 
arm into  three  or  sometimes  four  parts,  from  which  proceed  four  flat 
tendons  facing  the  front  of  the  muscle.  The  first  tendon,  intended  for 
the  index  finger,  is  distinct  from  the  others,  which  are  more  or  less 
divided,  or  fasciculate,  and  interjoin  to  the  wrist.  Here  the  tendons 
pass  in  company  with  and  behind  those  of  the  superficial  digital  flexor 
beneath  the  annular  ligament  into  the  palm  of  the  hand,  and  thence 
diverge  to  the  fingers,  where  they  pass  through  the  slits  of  the  super- 
ficial tendons  and  proceed  to  be  inserted  into  the  bases  of  the  last 
phalanges. 

The  deep  digital  flexor  is  covered  by  the  ulno-carpal  and  superficial 
digital  flexors,  with  the  ulnar  vessels  and  nerve  intervening,  lies  be- 
tween the  ulno-carpal  and  long  pollical  flexors,  and  rests  on  the  radius, 
interosseous  membrane,  and  quadrate  pronator.  In  the  palm  of  the 
hand  its  tendons  rest  on  the  pollical  adductor  and  the  interosseous 
muscles,  with  the  deep  palmar  arch  of  vessels  intervening. 

The  long  pollical  flexor l  lies  at  the  radial  side  of  the  former  mus- 
cle. It  arises  from  the  anterior  surface  of  the  radius,  commencing  below 
the  tuberosity  and  oblique  line  and  reaching  nearly  to  the  quadrate  pro- 
nator, from  the  adjacent  part  of  the  interosseous  membrane,  and  com- 
monly by  a  slip  from  the  coronoid  process.  The  fascicles  descend 
obliquely  and  terminate  in  a  flat  tendon,  which  passes  beneath  the 
outer  part  of  the  annular  ligament,  thence  between  the  two  heads  of 
the  short  pollical  flexor  and  sesamoid  bones,  and  proceeds  to  be  in- 
serted into  the  base  of  the  last  phalanx  of  the  thumb. 

The  muscle  lies  on  the  radius  and  interosseous  membrane  above 
and  the  quadrate  pronator  below ;  on  it  rest  the  radial  vessels ;  and  it 
is  covered  by  the  superficial  digital  and  radio-carpal  flexors  and  the 
long  supinator  muscle. 

The  superficial  digital  and  long  pollical  flexors  are  supplied  by  the 
median  nerve,  the  deep  digital  flexor  by  the  latter  and  the  ulnar  nerve. 
The  action  of  these  muscles  is  indicated  by  the  name,  and  produces 
the  closed  fist,  and  further  continued  flexes  the  hand. 

The  tendons  of  the  superficial  and  deep  digital  and  long  pollical 
flexors  and  the  median  nerve  pass  together  through  the  carpal  canal, 
which  is  formed  by  the  deep  concavity  of  the  carpus  bridged  across  by 
the  anterior  annular  ligament.  In  the  flexion  and  extension  of  the 
hand  the  tendons  move  freely  up  and  down  in  the  canal,  and  glide  upon 
one  another.  They  are  enveloped  in  a  complex  folded  synovial  sheath, 
which  invests  each  tendon  and  the  nerve  and  lines  the  canal,  reach- 
ing above  to  the  radio-carpal  articulation  and  below  to  the  carpo- 
metacarpal  articulations. 

In  front  of  the  digits  the  flexor  tendons  are  closely  confined  in 

1  M.  flexor  longus  pollicis  ;  long  flexor  muscle  of  the  thumb. 


THE   MUSCULAR   SYSTEM.  307 

canals,  which  maintain  their  position,  but  permit  ready  upward  and 
downward  motion  in  the  flexion  and  extension  of  the  fingers  and 
thumb.  These  digital  canals  are  formed  by  vaginal  ligaments,1 
which  are  strong  fibrous  bands  arching  over  the  tendons  and  firmly 
fixed  to  the  roughened  lateral  borders  of  the  phalanges.  Opposite  the 
joints  thinner  membranes2  strengthened  by  obliquely  decussating 
bands3  occupy  the  intervals  of  the  former  ligaments  and  complete 
the  canals.  The  latter  are  lined  by  a  synovial  sheath,  which  is  re- 
flected on  and  invests  each  tendon.  The  sheath  forms  little  folds4 
between  the  tendons  and  the  phalanges ;  some  of  them  consisting  of 
slender  bands5  extended  between  the  tendons  and  the  front  of  the 
phalanges,  and  others6  short  and  broad,  between  the  insertion  of  the 
tendons  and  the  phalanges  immediately  above. 

The  synovial  sheaths  of  the  tendon  of  the  long  pollical  flexor  and 
those  of  the  little  finger  are  prolonged  from  the  carpal  canal  into  their 
respective  digital  canals. 

MUSCLES  OF  THE  OUTER  AND  BACK  PART  OP  THE  FOREARM. 

Twelve  muscles  form  the  mass  at  the  outer  and  back  part  of  the 
forearm,  and  consist  of  extensors  and  supinators  arranged  in  two 
layers.  The  superficial  layer  is  composed  of  the  anconeus,  already 
described,  the  long  supinator,  two  radio-carpal,  the  ulno-carpal,  the 
digital,  and  the  minimal  extensors ;  the  deep  layer  is  composed  of  the 
short  supinator,  three  pollical  extensors,  and  the  indical  extensor. 

The  long  supinator7  lies  superficially  along  the  outer  part  of  the 
forearm.  It  arises  from  the  outer  part  of  the  external  supracondylar 
ridge  of  the  humerus  and  the  intermuscular  septum  between  it  and 
the  triceps.  Its  fascicles  descend  and  form  a  thin  belly,  ending  about 
the  middle  of  the  forearm  in  a  flat  tendon,  which  proceeds  to  be  in- 
serted into  the  base  of  the  styloid  process  of  the  radius.  It  lies  on 
the  longer  radio-carpal  extensor,  the  short  supinator,  the  terete  pro- 
nator,  and  the  superficial  digital  flexor,  and  covers  the  radial  vessels 
and  nerve.  In  the  arm  it  is  in  contact  internally  with  the  brachialis 
muscle,  having  the  musculo-spiral  nerve  interposed ;  and  at  the  elbow 
forms  the  outer  boundary  of  the  angular  depression  in  front.  Near 
the  wrist  it  is  crossed  outwardly  by  the  tendons  of  the  first  and  second 
pollical  extensors. 

The  short  supinator8  lies  beneath  the  long  supinator  and  super- 
ficial extensors  folded  around  the  upper  outer  part  of  the  radius.  It' 
arises  tendinously  from  the  back  of  the  outer  epicondyle  of  the  hu- 
merus, from  the  external  lateral  and  orbicular  ligaments  of  the  elbow, 

1  Ligamenta  vaginalia  or  transversa.         2  L.  vaginalia.  3  L.  cruciata. 

*  Vincula  accessoria  tendinum.  5  Ligamenta  longa.        6  L.  brevia. 

7  M.  supinator  longus  ;  m.  brachio-radialis ;  m.  supinator  radii  longus. 

8  M.  supinator  brevis  ;  m.  supinator  radii  brevis. 


308 


THE    MUSCULAR   SYSTEM. 


from  the  depression  of  the  ulna  below  the  radial  articulation  extending 
a  short  distance  down  the  outer  border  of  the  bone,  and  from  the 
investing  aponetirosis,  which  also  springs  from  the  tendon  of  origin 
of  the  muscle.  The  fleshy  fascicles  descend  from  the  back  of  the  elbow 
obliquely  outward,  winding  around  the  radius,  into  the  outer  part  of 
which  they  are  inserted,  extending  from  the  fore  part  of  the  neck  and 
behind  and  below  the  tuberosity  to  the  insertion  of  the  terete  pronator. 

FIG.  155. 


MUSCLES  OP  THE  BACK  OF  THE  FOREARM.  1, 
brachial  biceps ;  2,  brachialis ;  3,  brachial  tri- 
ceps ;  4,  long  supinator ;  5,  longer  radio-carpal 
extensor;  6,  shorter  radio-carpal  extensor;  7, 
insertion  of  the  tendons  of  the  last  two  mus- 
cles ;  8,  common  digital  extensor ;  9,  minimal 
extensor;  10,  ulno-carpal  extensor;  11,  anco- 
neus ;  12,  ulno-carpal  flexor ;  13,  first  and  second 
pollical  extensors;  14,  third  pollical  extensor; 
15,  posterior  annular  ligament. 


DEEP  MUSCLES  ON  THE  BACK  OF  THE  FOREARM. 
1,  humerus ;  2,  olecranon ;  3,  ulna ;  4,  anconeus ; 
5,  short  supinator;  6,  first  pollical  extensor;  7, 
second  pollical  extensor;  8,  third  pollical  ex- 
tensor ;  9,  indical  extensor ;  10,  the  dorsal  inter- 
osseous  muscles  between  the  metacarpal  bones. 


The  muscle  covers  the  outer  back 
part  of  the  elbow-joint,  as  well  as 
the  upper  part  of  the  radius ;  and 
it  is  pierced  by  the  posterior  interosseous  nerve. 

The  longer  radio-carpal  extensor/  subcutaneous  behind  and  par- 
tially covered  by  the  long  supinator,  arises  below  it  from  the  external 


1  M.  extensor  carpi-radialis  longior ;  m.  ext.  radialis  longus  ; 
ternus  longus. 


m.  ext.  radialis  ex- 


THE   MUSCULAR   SYSTEM.  309 

supracondylar  ridge  of  the  humerus  and  the  intermuscular  septum.  The 
fleshy  belly  descends  to  about  the  middle  of  the  forearm,  where  it  ends 
in  a  flat  tendon,  which  runs  along  the  outer  border  of  the  radius  and 
through  a  canal  behind  the  styloid  process,  and  thence  across  the 
carpus  to  be  inserted  into  the  outer  part  of  the  base  of  the  second 
metacarpal  bone. 

The  shorter  radio-carpal  extensor,1  partially  covered  by  and 
thicker  than  the  former,  arises  tendinously  in  common  with  the  suc- 
ceeding extensors  from  the  outer  epicondyle  of  the  humerus,  from  the 
adjacent  intermuscular  septa,  and  from  the  investing  fascia.  Its  fleshy 
belly  descends  and  ends  in  a  tendon,  which  accompanies  that  of  the 
longer  muscle,  closely  adherent,  but  diverges  from  it,  after  passing 
through  the  canal  behind  the  styloid  process  of  the  radius,  and  crosses 
the  carpus  to  be  inserted  into  the  outer  side  of  the  base  of  the  third 
metacarpal  bone. 

Passing  side  by  side  through  the  canal  behind  the  styloid  process 
of  the  radius,  the  tendons  of  the  radio-carpal  extensors  are  invested 
with  a  synovial  sheath.  Approaching  the  wrist  they  are  crossed 
outwardly  by  the  three  pollical  extensors.  The  longer  radio-carpal 
extensor  partly  covers  the  elbow-joint,  the  shorter  muscle,  and  the 
wrist-joint ;  the  shorter  radio-carpal  extensor  partly  covers  in  succes- 
sion the  short  supinator,  the  terete  pronator,  the  radius,  and  the  wrist- 
joint. 

The  ulno-carpal  extensor2  lies  subcutaneously  at  the  inner  side 
of  all  the  other  extensors.  It  arises  in  common  with  these  from  the 
outer  epicondyle  of  the  humerus,  from  the  posterior  border  of  the  ulna 
several  inches  below  the  anconeus,  and  from  the  investing  fascia.  De- 
scending, it  ends  in  a  tendon  which  runs  through  the  canal  behind  the 
styloid  process  of  the  ulna,  and  thence  crosses  the  carpus  to  be  inserted 
inwardly  into  the  base  of  the  last  metacarpal  bone.  Internally  the 
muscle  lies  on  the  ulna  in  contact  with  the  deep  extensors. 

The  longer  radio-carpal  extensor  is  supplied  from  the  trunk  of  the 
musculo-spiral  nerve,  the  shorter  radio-carpal,  and  the  ulno-carpal  ex- 
tensors by  its  posterior  interosseous  divisions.  They  are  extensors  of 
the  hand  on  the  forearm.  One  or  other  of  the  radio-carpal  extensors 
is  sometimes  divided  and  partially  inserted  into  the  succeeding  meta- 
carpal bone.  Sometimes  the  ulno-carpal  extensor  gives  an  offset  to 
the  extensor  tendons  of  the  little  finger,  and  not  unfrequently  one  to 
the  minimal  adductor  muscle. 

The  digital  extensor3  lies  subcutaneously  at  the  back  of  the  fore- 
arm, between  the  radio-carpal  and  the  ulno-carpal  extensors.  It  arises 

1  M.  extensor  carpi-radialis  brevior ;  m.  ext.  radialis  brevis  ;  m.  radialis  externus 
brevis. 

2  M.  extensor  carpi-ulnaris ;  m.  ulnaris  externus  ;  m.  cubitalis  externus. 

3  M.  extensor  digitorum  communis. 


310  THE    MUSCULAR   SYSTEM. 

from  the  outer  epicondyle  of  the  humerus  in  common  with  the  other 
extensors,  from  the  investing  deep  fascia,  and  from  the  adjacent  inter- 
muscular  septa.  Below  the  middle  of  the  forearm  its  belly  terminates 
in  three  tendons,  which  descend  together  and  pass  under  the  annular 
ligament  back  of  the  radius,  and  thence  diverge  on  the  wrist  and  back 
of  the  hand ;  the  third  tendon  dividing,  so  that  four  tendons  proceed 
to  the  digits,  extending  to  the  last  phalanges.  On  the  back  of  the 
hand  the  tendons  become  more  flattened,  the  intermediate  pair  lying 
on  the  corresponding  metacarpal  bones,  while  the  first  one  crosses 
obliquely  the  second  interosseous  space,  and  the  fourth  one  usually  lies 
close  to  the  third,  and  rather  abruptly  diverges  across  the  lower  part 
of  the  last  interosseous  space  to  the  little  finger.  On  the  back  of  the 
hand  the  tendons  are  connected  by  a  thin  intervening  aponeurosis, 
which  at  several  points  is  strengthened  by  oblique  bands.  The 
stixmgest  of  these  extends  from  the  third  tendon  obliquely  downward 
across  the  lower  part  of  the  intervening  space  to  the  second  tendon, 
and  another  extends  in  a  nearly  similar  position  from  the  fourth  to  the 
third  tendon.  A  thinner  band  may  also  extend  transversely  or  nearly 
so  from  the  first  to  the  second  tendon,  but  is  often  scarcely  produced. 
At  the  metacarpo-phalangeal  articulations  the  tendons  become  narrower 
and  thicker,  and  furnish  thin  lateral  oifsets  to  the  contiguous  capsular 
ligaments,  reinforcing  them  in  this  position  and  serving  as  posterior 
ligaments  to  the  joints.  From  these  the  tendons  spread  over  the  first 
phalanges,  and  are  joined  at  the  sides  by  broad,  triangular  expansions 
from  the  insertion  of  the  adjacent  interosseous  and  lumbrical  muscles. 
The  median  thicker  portion  of  each  tendon  is  inserted  into  the  base 
of  the  second  phalanx,  and  serves  as  a  posterior  ligament  to  the  con- 
tiguous phalangeal  articulation.  The  lateral  portions  of  the  tendon 
then  converge  upon  the  back  of  the  second  phalanx,  and  are  inserted 
together  into  the  base  of  the  terminal  phalanx,  and  serve  as  a  posterior 
ligament  to  the  second  phalangeal  articulation. 

To  the  thumb  there  are  three  extensor  muscles,  which  lie  beneath 
the  superficial  layer  of  extensors  in  the  forearm,  crossing  obliquely 
downward  from  the  ulnar  to  the  radial  side. 

The  first  pollical  extensor,1  the  external  and  largest,  arises  from 
the  posterior  surface  of  the  ulna  and  radius  and  the  intervening 
interosseous  membrane  below  the  insertion  of  the  short  supinator. 
Descending  obliquely  outward,  it  terminates  in  a  tendon  which  passes 
through  a  canal  on  the  outer  side  of  the  styloid  process  of  the  radius 
and  then  over  the  wrist  to  be  inserted  into  the  base  of  the  metacarpal 
bone  of  the  thumb.  The  tendon  is  not  unfrequently  divided,  and  is 
partly  inserted  into  the  trapezium  ;  or  it  may  afford  an  attachment  to 
the  small  muscles  of  the  thumb. 

1  M.  extensor  metacarpi  pollicis  ;  metacarpal  extensor  of  the  thumb  ;  m.  abductor 
longus  pollicis. 


THE   MUSCULAR   SYSTEM.  311 

The  second  pollical  extensor,1  the  smallest  of  the  series,  lies  to 
the  inner  side  of  the  preceding.  It  arises  from  the  posterior  surface 
of  the  radius  and  contiguous  portion  of  the  interosseous  membrane 
below  the  preceding  muscle,  which  it  accompanies.  Terminating  in  a 
tendon,  this  passes  through  the  same  groove  as  the  former  muscle, 
crosses  the  wrist,  and  proceeds  along  the  back  of  the  first  metacarpal 
bone  to  be  inserted  into  the  base  of  the  first  phalanx  of  the  thumb. 

The  third  pollical  extensor2  lies  to  the  inner  side  of  the  pre- 
ceding, and  partly  covers  it.  It  arises  from  the  ulna  and  interosseous 
membrane  just  below  the  first  extensor,  and  pursues  the  same  course, 
but  diverges  from  it.  Terminating  in  a  tendon,  this  passes  alone 
through  a  different  canal  from  that  of  the  former  muscles  at  the  back 

O 

of  the  radius ;  thence  crosses  the  carpus,  and  joins  the  tendon  of  the 
second  extensor,  but  continues  along  the  first  phalanx  to  be  inserted 
into  the  base  of  the  terminal  phalanx  of  the  thumb. 

The  first  and  second  pollical  extensors  are  covered  by  the  digital 
and  minimal  extensors,  and  are  crossed  by  the  posterior  interosseous 
vessels  and  nerve.  Together  they  proceed  outward  and  downward 
across  the  tendons  of  the  radio-carpal  extensors  and  long  supinator, 
and  at  the  wrist  the  radial  vessels.  The  third  pollical  extensor  crosses 
the  tendons  of  the  radio-carpal  extensors,  separated  from  the  other  pol- 
lical extensors  by  a  triangular  space,  which  in  the  extreme  extension 
of  the  thumb  appears  as  a  superficial  depression  at  the  outer  back  part 
of  the  wrist,  and  which  at  bottom  contains  the  radial  blood-vessels. 

The  second  pollical  extensor  is  sometimes  absent,  or  appears  fused 
with  the  first  or  with  the  third  one. 

The  indical  extensor,3  a  narrow  muscle  placed  to  the  inner  side 
of  the  last  described,  arises  below  and  partly  beneath  it  from  the  ulna 
and  contiguous  interosseous  membrane.  Descending,  it  terminates  in 
a  tendon  which  accompanies  the  tendons  of  the  digital  extensor  through 
the  canal  at  the  back  of  the  radius,  and  thence  proceeds  along  the  ulnar 
side  of  the  first  tendon  of  the  latter  to  the  index  finger,  where  it 
becomes  part  of  the  common  tendon. 

The  minimal  extensor,4  another  slender  muscle,  is  placed  along 
the  inner  side  of  the  digital  extensor,  with  which  it  is  commonly  closely 
connected.  Arising  in  common  with  the  latter  muscle  and  from  the 
adjacent  intermuscular  septa,  it  ends  in  a  tendon,  which  passes  through 
a  canal  behind  the  lower  radio-ulnar  articulation,  and  thence  crosses 
the  wrist  to  the  back  of  the  hand,  and  proceeds  to  the  little  finger. 
The  tendon  is  usually  divided  into  two  parts,  of  which  one  is  joined 

1  M.  extensor  prirni  internodii  pollicis  ;  first  phalangeal  extensor  of  the  thumb  ; 
short  extensor  of  the  thumb  ;  extensor  brevis  pollicis  or  minor. 

2  M.  extensor  secundi  internodii  pollicis;  second  phalangeal  extensor;  long  ex- 
tensor of  the  thumb ;  extensor  pollicis  longus  or  major. 

3  M.  extensor  indicis  ;  m.  indicatorius  ;  indicator  muscle. 

*  M.  extensor  minimi  digiti ;  proper  extensor  muscle  of  the  little  finger. 


312 


THE    MUSCULAE   SYSTEM. 


FIG.  157. 


at  the  metacarpo-phalangeal  articulation  by  an  offset  from  the  fourth 
tendon  of  the  digital  extensor,  and  both  are  subsequently  joined  by  the 
latter  to  form  the  common  tendon  of  the  little  finger.  Sometimes  the 
muscle  has  an  additional  tendon  terminating  in  that  of  the  adjoining 
finger,  and  rarely  it  is  absent. 

The  extensors  of  the  thumb  and  fingers  are  supplied  by  the  pos- 
terior interosseous  branch  of  the  musculo-spiral  nerve. 

The  arrangement  of  the  extensor  tendons  on  the  back  of  the  thumb 
is  similar  to  that  on  the  fingers.  On  the  back  of  the  metacarpo- 
phalangeal  articulation  the  capsular  ligament  is  reinforced  by  offsets 
from  the  extensor  tendons.  On  the  first  phalanx  the  tendons  of  the 
extensors  are  joined  at  the  sides  by  triangular  expansions  derived  from 
the  insertion  of  the  small  muscles  of  the  thumb. 

MUSCLES   OF   THE   HAND. 

The  hand,  besides  containing  the  tendons  of  the  muscles  of  the 

forearm  in  their  course  to  the  fingers, 
has  also  many  small  muscles,  which 
for  the  most  part  occupy  the  palm. 
They  consist  of  the  short  palmar  and 
lumbrical  muscles,  those  of  the  thumb 
and  of  the  little  finger,  and  the  inter- 
osseous  muscles. 

The  short  palmar  muscle '  con- 
sists of  a  thin  subcutaneous  layer  of 
fleshy  fascicles  at  the  inner  part  of 
the  palm  resting  on  the  muscles  of 
the  little  finger.  It  arises  from  the 
inner  margin  of  the  median  palmar 
fascia  and  the  annular  ligament,  and 
passes  directly  inward  to  be  inserted 
into  the  skin  along  the  inner  border 
of  the  palm.  The  ulnar  vessels  pass 
beneath  the  muscle.  It  is  supplied  by 
the  ulnar  nerve. 

The  lumbrical  muscles 2  are  four 
worm-like  fascicles,  which  lie  in  the 
intervals  of  the  flexor  tendons  in  the 
hollow  of  the  palm.  They  arise  from 
the  tendons  of  the  deep  digital  flexor, 
commencing  beneath  the  annular  lig- 
ament, thence  extend  downward  and 
proceed  to  the  radial  side  of  the  meta- 
carpo-phalangeal articulations,  where 
they  end  in  tendons  expanding  in  triangular  aponeuroses,  which  termi- 

1  M.  palmaris  brevis  ;  m.  p.  cutaneus.  2  M.  lumbricales ;  m.  fidicinales. 


MUSCLES  OF  THE  PALMAR  SURFACE  OF 
THE  HAND.  1,  anterior  annular  ligament ; 
2,  origin  and  insertion  of  the  pollical  ab- 
ductor; 3,  pollical  opponent;  4,  5,  two 
bellies  of  the  short  pollical  flexor;  6,  pol- 
lical adductor;  7,  lumbrical  muscles:  8, 
tendons  of  the  deep  digital  flexor  passing 
through  the  slits  of  the  superficial  ten- 
dons; 9,  tendon  of  the  long  pollical  flexor, 
passing  from  between  the  bellies  of  the 
short  flexor;  10,  minimal  abductor;  11, 
minimal  flexor;  12,  pisiform  bone;  13, 
first  interosseous  muscle. 


THE   MUSCULAR   SYSTEM.  313 

nate  by  joining  and  reinforcing  the  extensor  tendons  on  the  back  of 
the  first  phalanges  of  the  fingers.  The  outer  two  muscles  arise  from 
the  radial  side  of  the  corresponding  two  tendons ;  the  inner  two  from 
the  contiguous  sides  of  the  corresponding  three  tendons. 

The  number  of  these  muscles  is  occasionally  diminished  or  increased, 
and  sometimes  their  insertion  is  variable.  They  are  supplied  by  the 
median  and  ulnar  nerves. 

MUSCLES    OP    THE    THUMB. 

Four  muscles  occupy  the  ball  of  the  thumb,1 — the  pollical  abduc- 
tor, opponent,  short  flexor,  and  adductor. 

The  pollical  abductor2  is  a  flat  muscle,  the  most  superficial  of 
the  group.  It  arises  from  the  ridge  of  the  trapezium  and  the  annular 
ligament,  and  passes  downward  and  outward  to  be  inserted  by  a  flat 
tendon  into  the  outer  part  of  the  base  of  the  first  phalanx  of  the 
thumb. 

The  pollical  opponent,3  larger  than  the  former  and  lying  par- 
tially beneath  it,  arises  from  the  same  parts,  from  which  its  fascicles 
diverge  outward  and  downward  to  be  inserted  into  the  outer  border 
and  contiguous  palmar  surface  of  the  metacarpal  bone  its  whole 
length. 

The  short  pollical  flexor,4  the  largest  muscle  of  the  group,  is  placed 
to  the  inner  side  of  the  former  partially  covered  by  the  abductor.  It 
consists  of  two  portions,  separated  by  an  interval  traversed  by  the 
tendon  of  the  long  flexor.  The  anterior  more  superficial  portion  arises 
from  the  annular  ligament  and  trapezium,  the  deeper  portion  from  the 
trapezoid,  magnum,  and  adjacent  part  of  the  second  and  third  meta- 
carpal bones.  The  two  portions  unite  behind  the  long  flexor  tendon, 
and  descend  to  be  inserted  into  the  outer  and  inner  part  of  the  base 
of  the  first  phalanx,  involving  the  contiguous  sesamoid  bones;  the 
outer  portion  joining  with  the  abductor,  the  inner  with  the  adductor. 

The  pollical  adductor,6  a  triangular  muscle,  is  the  most  deeply 
seated  of  the  group.  It  arises  from  the  ridge  in  front  of  the  middle 
metacarpal  bone,  and  proceeds  outward  to  be  inserted  tendinously,  in 
conjunction  with  the  inner  portion  of  the  short  flexor,  into  the  base 
of  the  first  phalanx  of  the  thumb.  It  covers  the  outer  two  interos- 
seous  spaces  invested  behind  by  an  aponeurosis ;  its  anterior  surface 
is  in  contact  with  the  short  pollical  flexor,  the  tendons  of  the  deep 
digital  flexor,  and  the  lumbrical  muscles. 

The  pollical  abductor,  opponens,  and  anterior  portion  of  the  short 
flexor  are  supplied  by  the  median  nerve ;  the  deeper  portion  of  the 
latter  muscle  and  the  adductor  are  supplied  by  the  ulnar  nerve. 

1  Thenar  eminence.  2  M .  abductor  pollicis. 

8  M.  opponens  pollicis.  4  M.  flexor  brevis  pollicis. 

5  M.  adductor  pollicis. 


314  THE   MUSCULAR   SYSTEM. 

MUSCLES   OP   THE    LITTLE    FINGER. 

The  prominence  *  at  the  inner  part  of  the  palm  is  formed  by  the 
short  muscles  of  the  little  finger,  consisting  of  the  minimal  abductor, 
flexor,  and  adductor. 

The  minimal  abductor,2  the  most  superficial  of  the  group,  arises 
from  the  pisiform  bone  and  the  tendon  of  insertion  of  the  ulno-carpal 
flexor,  and  descends  to  be  inserted  tendinously  into  the  ulnar  side  of 
the  base  of  the  first  phalanx  of  the  little  finger,  and  by  a  slip  into  the 
adjacent  extensor  tendon.  Sometimes  a  second  head  springs  from  the 
annular  ligament  or  some  other  contiguous  point. 

The  minimal  flexor,3  placed  at  the  radial  side  of  the  former,  arises 
from  the  hook  of  the  unciform  bone  and  from  the  annular  ligament, 
and  descends  to  be  inserted  in  common  with  the  abductor  into  the  first 
phalanx.  At  its  origin  a  narrow  angular  interval,  between  it  and  the 
abductor,  gives  passage  to  the  ulnar  communicating  vessels  and  accom- 
panying nerve.  Often  the  muscle  is  but  feebly  produced,  and  occa- 
sionally it  is  absent,  in  which  case  the  abductor  is  larger  than  usual. 

The  minimal  adductor  *  lies  beneath  the  preceding  muscles,  arises 
from  the  same  points  as  the  flexor,  and  is  inserted  along  the  ulnar 
border  of  the  last  metacarpal  bone. 

All  the  muscles  of  the  above  group  are  supplied  by  the  ulnar  nerve. 

Interosseous  muscles.5  These  occupy  the  intervals  of  the  meta- 
carpal bones ;  four  on  the  dorsal  aspect  of  the  hand,  and  three  on  the 
palmar  aspect. 

The  dorsal  interosseous  muscles  6  are  double-headed  and  pen- 
niform,  and  arise  from  adjacent  sides  of  the  metacarpals,  between 
which  they  are  placed,  but  especially  from  the  side  of  that  of  the 
finger  into  which  each  muscle  is  inserted.  Each  terminates  in  a 
tendon,  which  is  inserted  into  the  side  of  the  base  of  the  first  pha- 
lanx and  into  the  contiguous  extensor  tendon  on  the  back  of  the 
finger.  The  first  dorsal  interosseous  muscle 7  is  the  largest ;  its  outer 
head  from  the  proximal  half  of  the  first  metacarpal  and  its  inner  head 
from  the  length  of  the  second ;  and  is  inserted  into  the  radial  side  of 
the  index  finger.  The  angular  interval  between  its  two  heads,  wider 
than  in  the  other  muscles,  gives  passage  to  the  radial  vessels  between 
the  back  and  palm  of  the  hand.  The  second  and  third  muscles  are 
inserted  on  the  two  sides  of  the  middle  finger,  and  the  fourth  one  on 
the  ulnar  side  of  the  ring-finger. 

The  palmar  interosseous  muscles8  arise  from  one  side  of  the 

1  Hypothenar  eminence.  2  M.  abductor  minimi  digiti. 

3  M.  flexor  brevis  minimi  digiti. 

4  M.   adductor  minimi  digiti ;  m.  adductor  ossis  metacarpi  minimi  digiti ;  m. 
opponens  digiti  minimi. 

5  M.  interossei.  6  M.  interossei  extern!  or  bicipites. 
7  M.  abductor  indicis.  8  M.  interossei  interni. 


THE   MUSCULAR   SYSTEM.  315 

palmar  aspect  of  their  respective  metacarpal  bones,  and  are  inserted 
on  the  same  side  into  the  first  phalanges  and  extensor  tendons  in  the 
manner  of  the  dorsal  muscles.  The  first  palmar  interosseous.  muscle 
pertains  to  the  ulnar  side  of  the  index  finger,  and  the  others  to  the 
radial  side  of  the  ring  and  little  fingers. 

Viewing  the  axis  of  the  middle  finger  as  a  line  of  departure  and 
approach,  the  dorsal  interosseous  muscles  act  as  abductors  to  the 
fingers,  while  the  palmar  interosseous  muscles  act  as  adductors.  To- 
gether with  the  corresponding  muscles  of  the  thumb  and  little  finger, 
each  digit  has  its  abductor  and  adductor,  as  well  as  its  flexor  and 
extensor. 

The  interosseous  muscles  are  supplied  by  the  deep  palmar  branch 
of  the  ulnar  nerve. 

FASCIAE   AND  MUSCLES   OF  THE   LOWER   LIMB. 

The  superficial  fascia  of  the  lower  limb  is  like  that  elsewhere, 
and  in  general  consists  of  two  layers  vai'iably  distinct  in  different  posi- 
tions ;  the  deeper  more  compact  and  membranous  in  appearance,  the 
subcutaneous  of  looser  texture  and  including  the  usual  adipose  tissue 
occupying  this  layer.  Over  the  gluteal  region  its  two  layers  are 
less  distinct ;  but  the  fascia  is  thick,  and  includes  the  largest  accumula- 
tion of  adipose  tissue  contributing  to  the  prominence  of  the  buttock. 
In  the  sole  of  the  foot  it  is  also  thick  and  mixed  with  adipose  tissue, 
which  here  serves  as  a  cushion  to  alleviate  the  effect  of  pressure  on 
the  important  parts  above.  It  is  continuous  with  the  superficial  fascia 
of  the  abdomen  and  loins.  Between  its  layers  it  contains  the  superficial 
veins,  and  in  the  groin  the  lymphatic  glands.  Its  deeper  layer  adheres 
to  Poupart's  ligament,  and  internally  is  continuous  with  t£ie  dartos 
tunic  of  the  scrotum  and  with  the  superficial  perineal  fascia.  Below 
Poupart's  ligament,  it  covers  the  saphenous  opening  of  the  deep  fas- 
cia, in  which  position  it  is  traversed  by  many  small  blood-vessels  and 
lymphatics,  which  pass  out  and  in  through  the  opening,  whence  the 
name  of  cribriform  fascia  given  to  this  portion  of  the  superficial 
fascia.  Subcutaneous  bursa3  are  found  in  it  over  the  patella,  the  heel, 
and  the  phalangeal  articulations. 

The  deep  fascia  of  the  thigh,1  named  the  femoral  fascia,  or 
more  commonly  the  fascia  lata,  is  a  bluish-white  aponeurotic  mem- 
brane, chiefly  composed  of  longitudinal  fibres  intersected  by  transverse 
and  oblique  fibres.  It  forms  a  continuous  sheath  to  the  thigh,  varying 
in  thickness  in  different  positions ;  is  for  the  most  part  movably  at- 
tached to  the  muscles  beneath  by  loose  connective  tissue ;  and  by 
means  of  partitions  extending  from  its  inner  surface  furnishes  each 
muscle  with  a  separate  sheath.  The  fascia  is  tightly  attached  above 
to  the  crest  of  the  ilium,  the  back  of  the  sacrum  and  coccyx,  to  Pou- 

1  Fascia  femoris. 


316 


THE   MUSCULAR   SYSTEM. 


FIG.  158. 


part's  ligament,  the  body  and  arch  of  the  pubis,  the  tuberosity  of  the 
ischium,  and  the  great  sciatic  ligament.  Below,  it  is  attached  to  all 
the  bony  prominences  about  the  knee-joint,  the  condyles  of  the  femur, 
the  heads  of  the  tibia  and  fibula,  and  the  patella.  The  thickest  portion 
starts  from  the  fore  part  of  the  crest  of  the  ilium  in  a  broad  band, 
named  the  ilio-tibial  band,1  which  descends  along  the  outer  part  of 
the  thigh  to  be  attached  to  the  head  of  the  tibia.  From  over  the  great 
trochanter  it  is  reinfoi'ced  by  the  upper  portion  of  the  tendon  of  inser- 
tion of  the  great  gluteal  muscle,  and  lower  receives  the  insertion  of  a 

special  muscle,  the  fascial 
tensor.  The  thinnest  por- 
tion of  the  fascia  is  at  the 
inner  and  upper  part  of  the 
thigh,  where  it  invests  the 
adductor  muscles.  Ap- 
proaching the  knee,  it  is  of 
intermediate  thickness,  re- 
ceives here  reinforcements 
from  the  neighboring  ten- 
dons, and  contributes  to 
form  the  capsule  of  the  joint. 
Behind  the  knee  it  passes 
between  the  flexor  muscles 
on  each  side  over  the  pop- 
liteal space,  and  is  thence 
continuous  below  with  the 
deep  fascia  of  the  leg.  Cov- 
ering the  great  gluteal  mus- 
cle, it  is  thin  and  closely 
adheres  to  the  latter,  but 
is  thick  in  advance,  where 
it  covers  the  middle  gluteal 
muscle  and  gives  partial 
origin  to  it.  Of  the  parti- 
tions extending  between  the 
muscles,  the  chief  are  the 
external  and  internal  in- 
termuscular  septa,2  at- 
tached along  the  linea  as- 
pera  and  thence  along  the 
supracondylar  ridges.  The 
external  thicker  septum  separates  the  external  vastus  in  front  from  the 
short  head  of  the  femoral  biceps  behind,  and  gives  partial  origin  to 
these  muscles.  The  internal  septum  separates  the  internal  vastus  from 


VIEW  OF  THE  FEMORAL  FASCIA.  1,  external  oblique 
muscle;  2,  its  aponeurosis ;  3,  portion  of  the  latter  raised 
up,  exposing  the  inguinal  canal;  4,  linea  alba:  5,  inter- 
nal column;  6,  external  column  formed  by  Poupart's 
ligament;  7,  intercolumnar  fibres;  8,  external  abdomi- 
nal ring,  the  termination  of  the  inguinal  canal;  9,  an- 
terior superior  spine  of  the  ilium ;  10,  arching  lower 
border  of  the  internal  oblique  and  transversalis  mus- 
cles; 11,  conjoined  tendon  of  the  latter;  12,  fibres  of 
the  cremaster  descending  on  the  spermatic  cord  from 
below  the  muscles  just  named ;  13,  rests  on  the  trans- 
versalis fascia ;  to  its  right  are  the  epigastric  vessels 
crossing  the  course  of  the  inguinal  canal ;  14,  iliac  por- 
tion of  the  femoral  fascia ;  15,  pubic  portion ;  16,  fal- 
ciform process;  17,  saphenous  opening;  18,  saphenous 
vein  joining  the  femoral  vein  through  the  saphenous 
opening;  19,  the  femoral  artery  and  vein  exposed  by 
raising  the  iliac  portion  of  fascia  which  forms  the  falci- 
form process ;  20,  suspensory  ligament  of  the  penis. 


1  Fascia  lata. 


Ligamenla  intermuscularia. 


THE   MUSCULAR   SYSTEM.  31 7 

the  adductors,  with  the  aponeurotic  attachment  of  which  it  becomes 
blended. 

In  front  of  the  thigh  below  Poupart's  ligament  is  the  saphenous 
opening,1  an  aperture  in  the  femoral  fascia,  through  which  the  internal 
saphenous  vein  enters  to  join  the  femoral  vein.  The  opening  is  ex- 
ternally defined  by  a  semicircular  edge  of  the  fascia  which  extends 
outwardly  in  front  of  the  femoral  vessels  and  over  the  sartorius  muscle 
towards  the  ilium,  whence  it  is  named  the  iliac  portion,'2  and  is 
attached  along  Poupart's  ligament.  From  the  inner  part  of  the  open- 
ing the  femoral  fascia,  here  named  the  pubic  portion,3  extends  out- 
wardly behind  the  femoral  vessels  attached  to  the  pectineal  line  of  the 
pubis,  and  becomes  continuous  with  the  ilio-psoas  fascia.  The  semi- 
circular edge  of  the  iliac  portion  of  the  femoral  fascia,  named  the 
falciform  process,4  at  its  upper  extremity 5  is  continuous  with  Gim- 
bernat's  ligament,  and  at  its  lower  extremity  with  the  pubic  portion 
of  the  fascia,  between  the  conjunction  of  the  internal  saphenous  and 
femoral  vein.  The  lower  extremity,  is  most  sharply  defined,  and  the 
middle  portion  least,  where  it  is  continuous  with  the  cribriform  fascia, 
which  occupies  the  saphenous  opening. 

The  ilio-psoas  fascia6  invests  the  femoral  flexor,  consisting  of  the 
iliac  and  psoas  muscles,  which  occupy  the  back  part  of  the  abdominal 
cavity.  Attached  along  the  iliac  crest  and  Poupart's  ligament,  it  is 
here  continuous  with  the  transversalis  fascia,  than  which  it  is  stronger. 
Its  most  compact  and  strongest  part  extends  below  from  the  iliac  crest 
inwardly  to  the  brim  of  the  pelvis,  where  it  is  tightly  fixed,  and  in  this 
position  receives  the  expanded  insertion  of  the  tendon  of  the  small 
psoas  muscle  when  it  exists.  A  thinner  portion  of  the  fascia  extends 
upward  on  the  psoas,  attached  inwardly  to  the  lumbar  vertebrae  and 
sacrum,  outwardly  continuous  with  the  anterior  layer  of  the  lumbar 
fascia,  and  above  with  the  internal  arcuate  ligament  of  the  diaphragm. 
In  the  groin  the  ilio-psoas  fascia,  connected  outwardly  with  the  trans- 
versalis fascia  and  Poupart's  ligament,  is  prolonged  beneath  the  latter, 
on  the  muscle  it  invests,  into  the  thigh  behind  the  femoral  blood-vessels. 
In  this  position  it  is  continuous  inwardly  with  the  pubic  portion  of 
the  femoral  fascia,  and  outwardly  with  the  iliac  portion  of  the  latter, 
and  is  further  connected  with  an  intermuscular  septum  extending 
between  the  psoas  and  pectineus  to  the  ilio-pubic  eminence  and  the 
capsule  of  the  hip-joint.  The  peritoneum  covers  the  ilio-psoas  fas- 
cia, but  is  separated  from  the  iliac  portion  by  a  considerable  quantity 
of  loose  areolar  tissue  usually  associated  with  more  or  less  fat.  The 
external  iliac  vessels  lie  upon  the  ilio-psoas  fascia,  but  the  lumbar 
plexus  of  nerves  lies  behind  it. 

1  Fovea  ovalis.  *  Sartorial  fascia.  3  Pectineal  fascia. 

4  Processus  falciformis.  5  Hay's  ligament ;  femoral  ligament. 

6  F.  iliaca  or  lumbo-iliaca. 


318 


THE  MUSCULAR   SYSTEM. 


FIG.  159. 


MUSCLES   OF   THE   FRONT   AND  OUTER   PART  OF   THE   THIGH. 

The  fascial  tensor l  is  a  short,  flat  muscle  at  the  outer  part  of  the 
thigh,  enclosed  in  a  sheath  of  the  femoral  fascia.  It  arises  tendinous 
from  the  outer  border  of  the  anterior  superior  spine  and  contiguous 
portion  of  the  crest  of  the  ilium,  between  the  origin  of  the  sartorius 
and  middle  gluteal  muscles,  and  descends  about  one-fourth  way  on  the 
outer  side  of  the  thigh,  where  it  ends  in  the  femoral  fascia,  which  it  re- 
inforces, and  in  conjunction  with  it  is  extended  as  the  ilio-tibial  band  to 

the  head  of  the  tibia.  It  diverges  from  the 
origin  of  the  sartorius,  with  the  femoral  rec- 
tus  lying  between,  and  rests  on  the  latter,  the 
middle  gluteal,  and  external  vastus  muscles. 
The  sartorius,2  the  longest  muscle  of 
the  body,  is  ribbon-like  and  remarkable  for 
the  great  length  of  its  fleshy  fascicles,  which 
extend  parallel  throughout.  It  is  subcuta- 
neous the  entire  length,  and  pursues  a  half- 
spiral  course  from  the  hip  to  the  knee,  cross- 
ing in  front  of  the  thigh  from  the  outer  to 
the  inner  side.  It  arises  tendinous  from 
the  anterior  superior  iliac  spine  and  the 
contiguous  margin  of  the  notch  below,  and 
thence  descends  obliquely  across  the  front 
of  the  thigh  to  the  inner  side.  Continu- 
ing to  the  knee  behind  the  inner  condyle 
of  the  femur,  it  terminates  in  a  tendon 
which  curves  forward  and  expands  in  an 
aponeurosis  inserted  into  the  upper  part 
of  the  inner  surface  of  the  tibia  near  the 
tubercle.  An  offset  from  the  tendon  above 
reinforces  the  capsule  of  the  knee-joint,  and 
another  below  reinforces  the  fascia  of  the 
l3g.  In  its  course  in  succession  it  lies  on 
the  iliac  muscle,  the  rectus,  the  femoral  ves- 
sels, the  pectineus,  the  long  and  great  ad- 
ductors, the  internal  vastus,  the  gracilis,  and 
the  inner  side  of  the  knee-joint.  The  tendon 
of  insertion  covers  those  of  the  gracilis  and 
semitendinosus,  but  is  separated  from  them 
by  a  prolongation  of  the  bursa  which  is  in- 
terposed between  the  same  tendons  and  the 
internal  lateral  ligament  of  the  knee. 
At  the  upper  part  of  the  thigh  the  muscle  forms  the  outer  boundary 


MtJSCLES    OF    THE    FRONT    AND 
OUTER    PART    OF   THE   THIGH.       1, 

crest  of  the  ilium ;  2,  anterior 
superior  iliac  spine;  3,  middle 
gluteal  muscle ;  4,  fascial  tensor ; 
5,  sartorius ;  6,  femoral  rectus ; 
7,  external  vastus ;  8,  internal 
vastus ;  9,  insertion  of  the  quadri- 
ceps into  the  patella;  10,  iliac 
muscle ;  11,  psoas  muscle ;  12,  pec- 
tineus; 13,  long  adductor;  14, 
great  adductor ;  15,  gracilis. 


1  M.  tensor  vaginae  femoris  ;  m.  t.  fasciae  latae;  m.  fascialis.  2  M.  ilio-pretibialis. 


THE    MUSCULAE   SYSTEM.  319 

of  the  space  named  Scarpa's  triangle,  which  is  traversed  through 
the  middle  by  the  femoral  vessels. 

The  fleshy  mass  forming  the  front  and  outer  part  of  the  thigh  is 
mainly  composed  of  the  quadriceps  muscle,1  named  from  its  con- 
sisting of  four  portions  or  heads  terminating  in  a  common  tendon,  in 
which  is  embedded  the  patella,  and  is  thence  extended  to  be  inserted 
into  the  tubercle  of  the  tibia.  Of  the  four  portions  of  the  quadri- 
ceps, the  femoral  rectus  appears  as  a  distinct  muscle  isolated  from  the 
rest  except  at  its  insertion,  while  the  others,  named  the  external  vas- 
tus,  internal  vastus,  and  crureus,  are  closely  connected  and  envelop  the 
femur  from  the  trochanters  to  the  condyles,  leaving  little  more  than 
the  linea  aspera  projecting  behind  for  the  attachment  of  other  muscles. 

The  femoral  rectus 2  lies  in  an  intermediate  position  in  front  of 
the  other  portions  of  the  quadriceps.  It  is  fusiform,  and  arises  by  two 
short,  stout  tendons,  of  which  one  springs  from  the  anterior  inferior 
spine  of  the  ilium,  while  the  other  curves  forward  from  the  impression 
above  and  behind  the  acetabulum.  Below  the  upper  margin  of  the  latter 
the  tendons  unite  in  one,  which  descends  and  expands  in  an  aponeu- 
rosis  in  front  of  the  muscle,  whose  fascicles  pennately  arranged  ter- 
minate in  a  posterior  aponeurosis,  which  narrows  into  a  flattened  cylin- 
drical tendon  proceeding  to  be  inserted  into  the  base  of  the  patella. 

The  external  vastus,3  the  largest  portion  of  the  quadriceps,  occu- 
pies the  outer  part  of  the  thigh,  and  is  for  the  most  part  subcutaneous 
and  covered  by  the  thickest  portion  of  the  femoral  fascia.  It  arises 
by  a  broad  aponeurosis,  which  faces  the  greater  part  of  the  muscle 
externally,  and  springs  from  the  upper  part  of  the  anterior  intertro- 
chanteric  ridge  of  the  femur,  from  the  front  and  outer  part  of  the 
base  of  the  great  trochanter,  from  behind  the  rough  insertion  of  the 
great  gluteal  muscle,  and  from  the  outer  lip  of  the  linea  aspera.  The 
large  mass  of  fleshy  fascicles  from  this  aponeurosis,  with  additional 
ones  from  the  surface  of  the  femur  immediately  beneath  the  attach- 
ment of  the  latter,  from  the  tendon  of  insertion  of  the  great  gluteal 
muscle,  and  from  the  external  intermuscular  septum  adjoining  the  short 
head  of  the  biceps,  descend  obliquely  forward  and  end  in  the  aponeu- 
rosis of  insertion.  This  occupies  the  deep  surface  and  anterior  border 
of  the  lower  half  of  the  muscle ;  and  it  descends  and  converges  into  a 
thicker,  flat  tendon,  which  partially  passes  behind  that  of  the  rectus, 
blends  with  it  and  other  portions  of  the  common  tendon  of  the  quad- 
riceps, and  is  inserted  into  the  outer  part  of  the  base  of  the  patella.  A 
few  superficial  fascicles  join  the  outer  border  of  the  tendon  of  the  rec- 
tus, and  the  deeper  portion  of  the  muscle  is  to  a  greater  or  less  extent 
connected  with  the  crureus. 

The  internal  vastus  and  crureus  are  so  intimately  connected  that 

1  M.  quadriceps  extensor  cruris.  2  M.  rectus  femoris. 

3  M.  vastus  externus;  m.  extensor  cruris  externus. 


320  THE   MUSCULAR   SYSTEM.  » 

they  may  be  regarded  as  one  of  the  chief  divisions  of  the  quadriceps. 
The  former  occupies  the  inner  side  of  the  thigh,  for  the  most  part  sub- 
cutaneous and  covered  by  the  deep  fascia ;  the  latter,  the  front  and 
outer  part  of  the  femur,  covered  by  the  rectus  and  external  vastus. 
They  are  partially  separated  by  a  narrow  interval  extending  in  a  line 
from  near  the  small  trochanter  to  the  inner  side  of  the  patella. 

The  internal  vastus l  arises  by  an  aponeurosis,  facing  it  internally, 
attached  to  the  femur  in  a  line  directed  from  near  the  small  trochanter 
to  the  linea  aspera,  and  along  the  inner  lip  of  the  latter  and  its  inner 
branch  directed  to  the  internal  epicondyle,  and  by  numerous  fleshy 
fascicles  from  the  femur  beneath  the  origin  of  the  aponeurosis  and  from 
the  tendons  of  insertion  of  the  long  and  great  adductors.  The  fascicles 
in  general  descend  forward  and  outward  and  terminate  in  an  aponeu- 
rosis, which  is  common  to  it  and  the  crureus,  and  descends  and  con- 
verges to  be  inserted  into  the  inner  side  of  the  patella,  partly  passing 
under  the  rectus  tendon  and  blending  with  it.  The  fleshy  fascicles 
descend  lower  than  in  the  external  vastus,  so  as  to  give  a  more  fleshy 
covering  to  the  inner  side  of  the  knee. 

The  crureus 2  arises  fleshy  from  the  upper  two-thirds  of  the  front 
surface  of  the  femur,  commencing  below  the  intertrochanteric  ridge, 
and  extending  on  the  outer  surface  beneath  the  origin  of  the  external 
vastus  and  from  the  external  intermuscular  septum  adjoining  the  short 
head  of  the  biceps.  The  fleshy  fascicles  descend,  those  externally  and 
below  being  directed  more  forward,  and  all  terminate  in  a  superficial 
aponeurosis,  which  is  common  to  the  crureus  and  internal  vastus,  and 
converges  and  descends  beneath  the  tendon  of  the  rectus  to  form  the 
deeper  portion  of  the  common  tendon  inserted  into  the  base  of  the  patella. 

The  inner  surface  of  the  femur  beneath  the  internal  vastus,  except 
along  its  line  of  origin,  and  the  lower  third  of  the  front  surface 
beneath  the  crureus,  except  at  the  origin  of  the  subcrureus,  are  free 
from  muscular  attachment. 

The  subcrureus3  is  a  fleshy  band  arising  from  the  lower  fore  part 
01  the  femur  beneath  the  crureus,  usually  more  to  the  outer  side.  It 
descends  and  terminates  on  the  synovial  pouch,  which  is  prolonged 
from  the  knee-joint  upward  beneath  the  tendon  of  the  quadriceps.  It 
is  of  variable  size,  and  appears  like  a  detached  fascicle  of  the  crureus ; 
from  which  it  is  sometimes  not  distinct.  Occasionally  it  is  double,  and 
consists  of  two  lateral  portions. 

The  common  tendon  of  the  quadriceps  is  inserted  into  the  base 
of  the  patella,  extending  upon  its  sides.  The  more  superficial  fibres 
descend  upon  the  anterior  surface  of  the  bone  closely  adherent  to  it, 
and  join  the  ligament  of  the  patella,  which  is  to  be  regarded  as  the 
final  insertion  of  the  quadriceps  into  the  tubercle  of  the  tibia.  A 

1  M.  vastus  interims  ;  m.  extensor  cruris  internus. 

2  M.  crureus  or  cruralis.          3  M.  subcrureus  or  subcruralis  ;  m.  articularis  genu. 


THE   MUSCULAR   SYSTEM.  321 

thin  expansion  from,  the  tendon  on  each  side  joins  the  femoral  fascia, 
and  with  this  is  closely  connected  with  the  capsular  ligament  of  the 
knee-joint,  and  is  attached  to  the  head  of  the  tibia. 

The  fascial  tensor  is  supplied  by  the  superior  gluteal  nerve ;  the 
sartorius  and  quadriceps  by  the  crural  nerve.  The  quadriceps  is  the 
extensor  of  the  leg  upon  the  thigh ;  the  rectus  may  assist  in  the  flexion 
of  the  lower  limb.  The  fascial  tensor,  besides  the  action  indicated  by 
the  name,  may  assist  in  the  rotation  inwardly  of  the  lower  limb.  The 
sartorius  may  assist  in  the  latter  movement,  or  may  assist  in  the  flexion 
of  the  thigh  on  the  body  and  of  the  leg  on  the  thigh.  It  has  been 
considered  to  be  the  chief  agent  in  producing  the  position  assumed  by 
the  tailor  when  sitting  at  work,  whence  the  name. 

MUSCLES  ON  THE  INKEK  FOKE  PAKT  OF  THE  THIGH. 

The  inner  side  of  the  thigh  is  occupied  by  three  adductors,  together 
with  the  pectineus  and  gracilis  muscles.  They  form  the  basis  of  the 
triangular  space  which  is  traversed  by  the  femoral  blood-vessels. 

The  gracilis l  lies  superficially  along  the  inner  side  of  the  thigh, 
and  is  a  long  ribbon-like  muscle,  which  arises  by  an  aponeurosis  from 
the  pubis  along  the  anterior  border  of  the  lower  part  of  the  symphysis 
and  the  descending  ramus.  Descending,  it  tapers  below  and  ends  in  a 
narrow  tendon,  which  passes  to  the  inner  side  of  the  knee,  turns  for- 
ward, and  expands  to  be  inserted  into  the  tibia  near  its  tubercle  and 
beneath  the  insertion  of  the  tendon  of  the  sartorius.  Covered  by  the 
femoral  fascia,  the  muscle  rests  against  the  short  and  great  adductors. 
Its  tendon  crosses  the  internal  lateral  ligament  of  the  knee,  with  a 
synovial  bursa  interposed. 

The  femoral  flexor,  or  ilio-psoas  muscle,2  in  greater  part,  is 
situated  within  the  abdomen,  and  consists  of  two  portions,  usually  de- 
scribed as  the  psoas  and  iliac  muscles,  the  former  occupying  the  side 
of  the  loin,  the  latter  the  iliac  fossa  of  the  hip,  uniting  and  emerging 
from  beneath  the  femoral  arch  to  be  inserted  into  the  femur. 

The  psoas  muscle3  is  the  large  fusiform  belly  situated  at  the  side 
of  the  lumbar  vertebrae,  from  which  it  arises  by  five  slips  attached  to 
the  contiguous  prominent  borders  of  the  centra  and  intervertebral 
disks  and  to  intervening  thin  tendinous  arches,  which  span  the  con- 
strictions of  the  centra  and  give  passage  to  the  lumbar  vessels  and 
communicating  branches  of  the  sympathetic  with  the  lumbar  nerves. 
The  first  attachment  starts  from  the  contiguous  borders  of  the  last 
thoracic  and  first  lumbar  vertebra? ;  the  last  attachment  from  the  cor- 
responding borders  of  the  lower  two  lumbar  vertebrae.  The  muscle 
descends,  crosses  the  brim  of  the  pelvis,  and  converges  to  a  tendon, 

1  M.  gracilis ;  m.  rectus  interims ;  m.  sub-pubio-pretibialis 

2  M.  ilio-psoas  ;  m.  flexor  femoris. 

3  M.  psoas  magnus  or  major;  m.  lumbaris  or  m.  1.  interims. 

21 


322  THE    MUSCULAR   SYSTEM. 

which  commences  within  the  fleshy  belly  and  appears  at  its  outer  side, 
where  it  receives  the  fascicles  of  the  iliac  muscle,  then  emerges  beneath 
the  femoral  arch,  and  proceeds  to  be  inserted  into  the  small  trochanter 
of  the  femur. 

The  iliac  muscle l  is  fan-shaped,  and  arises  chiefly  from  the  inner 
margin  of  the  iliac  crest  with  the  adjacent  two-thirds  of  the  surface 
of  the  iliac  fossa  reaching  to  the  anterior  iliac  spines,  and  by  a  few 
fascicles  from  the  ilio-lumbar  ligament  and  contiguous  portion  of  the 
ala  of  the  sacrum.  The  fleshy  fascicles  descend  and  converge,  for  the 
most  part  to  terminate  with  the  psoas  tendon  of  insertion  into  the 
small  trochanter,  some  of  the  outermost  fascicles  descending  to  be 
inserted  into  the  oblique  line  extending  from  the  latter  to  the  linea 
aspera. 

The  psoas  commences  under  the  external  arcuate  ligament  of  the 
diaphragm,  and  rests  against  the  lumbar  vertebrae,  the  quadrate  lum- 
bar muscle,  the  inner  portion  of  the  iliac  muscle,  and  the  brim  of  the 
pelvis.  The  iliac  muscle  rests  on  the  ilium,  the  origin  of  the  femoral 
rectus,  and  the  hip-joint,  from  the  capsule  of  which  it  usually  derives  a 
few  fibres.  The  common  tendon  passes  along  the  groove  between  the 
anterior  inferior  iliac  spine  and  the  ilio-pubic  eminence ;  and  between  it 
and  the  capsule  of  the  hip-joint  is  a  large  synovial  bursa,  which  some- 
times communicates  with  the  cavity  of  the  joint.  The  external  iliac 
vessels  rest  against  the  inner  border  of  the  psoas  along  the  brim  of  the 
pelvis,  but  lie  in  front  of  the  muscle  as  they  become  the  femoral  vessels. 
The  lumbar  plexus  of  nerves  is  embedded  in  the  psoas,  and  its  branches 
emerge  at  different  points  of  the  muscle  ;  the  ilio-inguinal  and  external 
cutaneous  nerves  cross  over  the  iliac,  and  the  crural  nerve  descends 
in  a  groove  between  the  latter  and  the  psoas  muscle. 

The  ilio-psoas  muscle  is  the  flexor  of  the  hip-joint,  or  it  bends  the 
lower  limb  on  the  body  or  the  body  on  the  thigh.  It  also  rotates  the 
limb  outwardly,  and  thus  widens  the  basis  of  support  of  the  body, 
which  it  further  contributes  to  maintain  in  the  erect  position.  The 
psoas  is  supplied  by  small  branches  from  the  lumbar  plexus,  the  iliac 
muscle  by  branches  of  the  crural  nerve. 

More  frequently  than  otherwise,  on  one  or  both  sides  of  the  body, 
there  exists  a  muscle,  named  the  small  psoas.2  It  commonly  arises 
from  the  contiguous  prominent  margins  of  the  centra  of  the  last  tho- 
racic and  first  lumbar  vertebrae  and  intervening  disk,  proceeds  out- 
wardly, and  after  a  short  distance  terminates  in  a  long,  flat  tendon, 
which  descends  in  front  and  on  the  inner  side  of  the  psoas  to  the 
brim  of  the  pelvis,  to  which  it  is  fixed,  expanding  in  the  corresponding 
attachment  of  the  ilio-psoas  fascia. 

The  pectineus  muscle,3  flat  and  quadrate,  is  situated  at  the  upper 

1  M.  iliacus,  orm.  i.  interims.  2  M   psoas  parvus  or  minor. 

3  M.  pectineus  or  pectinalis. 


THE   MUSCULAR   SYSTEM.  323 

inner  part  of  the  thigh.  It  arises  from  the  pubis  attached  to  the  line 
extending  from  the  pubic  spine  to  the  ilio-pubic  eminence,  and  descends 
outward  and  backward  to  be  inserted  tendinously  into  the  femur  be- 
hind the  small  trochanter  and  into  the  contiguous  portion  of  the  line, 
directed  to  the  linea  aspera.  It  is  placed  between  the  psoas  outwardly 
and  the  long  adductor  inwardly,  and  rests  on  the  external  obturator 
and  small  adductor  muscles.  In  front  it  is  covered  with  the  femoral 
fascia,  and  has  the  femoral  vessels  lying  upon  it. 

The  long  adductor,1  a  flat,  triangular  muscle,  lies  in  the  same 
plane  to  the  inner  side  of  the  former.  It  arises  tendinous  from  the 
front  of  the  body  of  the  pubis  near  the  angle,  descends  backward  and 
outward,  expanding  in  its  course,  and  is  inserted  by  a  wide,  thin  tendon 
into  the  middle  third  of  the  linea  aspera,  where  it  is  united  with  the 
aponeurosis  of  origin  of  the  internal  vastus  and  the  insertion  of  the 
great  adductor.  It  rests  behind  against  the  small  and  great  adductors, 
and  is  covered  in  front  by  the  femoral  fascia,  the  sartorius,  and  the 
gracilis.  The  femoral  vessels  rest  upon  it,  and  the  femoral  profunda 
vessels  pass  behind  it. 

The  short  adductor,2  concealed  by  the  pectineus  and  long  adductor, 
arises  partially  tendinous  and  fleshy  from  the  front  of  the  body  and 
descending  ramus  of  the  pubis  beneath  the  former,  descends  obliquely 
backward  and  outward,  and  is  inserted  by  a  wide,  thin  tendon  into 
the  upper  part  of  the  linea  aspera  immediately  behind  the  attachment 
of  the  pectineus  above  and  the  long  adductor  below.  It  rests  on  the 
external  obturator  and  great  adductor  muscles,  and  has  the  femoral 
profunda  vessels  crossing  it  in  front. 

The  great  adductor 3  is  a  large,  triangular  muscle  forming  a  par- 
tition between  the  other  muscles  on  the  front  and  back  of  the  thigh. 
It  arises  partially  tendinous  and  fleshy  from  the  descending  ramus  of 
the  pubis  beneath  the  former  muscle,  and  from  the  ramus  and  outer 
and  lower  fore  part  of  the  tuberosity  of  the  ischium.  From  this  origin 
the  coarse,  fleshy  fascicles  diverge  outward  and  downward,  successively 
increasing  in  length  ;  the  upper,  shortest,  passing  almost  horizontally 
outward,  the  lowest,  longest,  descending  almost  vertically,  and  they 
terminate  in  a  broad  aponeurosis,  which  is  inserted  into  the  great  part 
of  the  length  of  the  femur,  commencing  within  the  insertion  of  the 
great  gluteal,  and  below  that  of  the  quadrate  femoral  muscle  extending 
along  the  linea  aspera  and  the  supracondylar  ridge  to  the  inner  epi- 
condyle.  The  longest  fascicles  from  the  ischial  tuberosity  form  the 
inner  limit  of  the  muscle,  and  terminate  in  a  thickened,  tendon-like 
border  to  the  aponeurosis  of  insertion,  descending  to  be  fixed  to  the 
inner  epicondyle  of  the  femur.  The  aponeurosis  along  the  course  of 

1  M.  adductor  longus  ;  caput  longum  tricipitis. 

2  M.  adductor  brevis  ;  caput  breve  tricipitis. 

3  M.  adductor  magnus  ;  caput  magnum  tricipitis. 


324  THE    MUSCULAR   SYSTEM. 

its  attachment  to  the  linea  aspera  is  interrupted  by  three  or  four  aper- 
tures, with  arching  fibres  springing  from  the  bone,  for  the  passage  pf 
the  perforating  vessels.  Another  and  larger  aperture  at  the  lower 
third  of  the  aponeurosis  is  the  inferior  extremity  of  a  passage,  called 
Hunter's  canal,  for  the  transmission  of  the  femoral  vessels  between  the 
fore  and  back  part  of  the  thigh. 

The  great  adductor  is  in  contact  behind  with  the  great  gluteal  and 
the  flexor  muscles,  internally  with  the  gracilis,  and  in  front  with  the 
short  and  long  adductors  and  the  internal  vastus.  The  femoral  pro- 
funda  vessels  descend  in  front  of  its  insertion  into  the  linea  aspera, 
and  the  sciatic  nerve  descends  behind  the  muscle. 

Hunter's  canal  is  situated  about  the  middle  of  the  thigh  beneath 
the  sartorius  muscle.  It  is  several  inches  in  length,  and  descends  with 
a  slight  inclination  backward  and  outward  close  to  the  femur.  Its 
posterior  wall  is  formed  by  the  aponeurosis  of  the  great  adductor  in- 
serted into  the  linea  aspera,  its  outer  wall  by  the  connection  of  the 
internal  vastus  with  the  latter,  and  its  anterior  wall  by  an  aponeurosis 
of  transverse  fibres  springing  from  the  internal  vastus  and  extended 
inwardly  in  front  of  the  femoral  vessels  to  the  aponeuroses  of  the  long 
and  great  adductors. 

All  the  muscles  of  the  group  above  described  are  supplied  by  the 
obturator  nerve.  The  pectineus  also  receives  a  branch  from  the  crural 
nerve,  while  that  from  the  former  is  inconstant.  The  great  adductor 
also  receives  a  branch  from  the  great  sciatic  nerve.  All  the  muscles 
are  adductors,  but  assist  in  other  actions :  thus,  the  pectineus  and  long 
and  short  adductors  assist  in  flexion  of  the  thigh,  the  inner  portion  of 
the  great  adductor  assists  in  its  extension,  and  the  gracilis  assists  in 
flexion  of  the  leg. 

MUSCLES    OF  THE   BUTTOCK. 

The  thick,  rounded  prominence  of  the  buttock  is  composed  of  the 
three  gluteal  muscles.  Covered  by  them  are  the  rotators  of  the  thigh, 
consisting  of  the  internal  obturator  and  pyriform  muscles  arising  from 
within  the  pelvis,  and  the  external  obturator,  geminus,  and  quadrate 
femoral  muscles  arising  from  its  exterior. 

The  great  gluteal  muscle,1  the  most  superficial  and  the  largest 
of  those  of  the  buttock,  is  a  thick,  quadrate,  and  coarsely-fasciculated 
mass.  It  arises  partly  tendinous  and  fleshy  from  a  small  surface  at 
the  outer  part  of  the  posterior  extremity  of  the  crest  of  the  ilium  and 
the  superior  curved  line  below,  from  the  side  behind  of  the  lower  ex- 
tremity of  the  sacrum  and  of  the  coccyx,  from  the  great  sacro-sciatic 
ligament,  and  from  the  lumbar  fascia  investing  the  dorsal  extensor  in 
the  interval  of  the  sacrum  and  ilium.  From  this  origin  the  fascicles 
proceed  obliquely  outward  and  downward,  and  terminate  in  a  thick 

1  M.  gluteus  magnus  or  maximus. 


THE   MUSCULAR   SYSTEM. 


325 


FIG.  160. 


aponeurosis,  the  upper  part  of  which  passes  over  the  great  trochanter 
and  merges  in  the  femoral  fascia  at  the  outer  side  of  the  thigh,  while 
the  lower  portion  converges  to  be  inserted  into  the  roughened  line 
behind  the  femur,  extending  from  the  base  of  the  great  trochanter 
to  the  linea  aspera.  The  muscle,  in  great  part,  rests  on  the  middle 
gluteal,  and  its  lower  portion  forming  the  fold  of  the  buttock  covers 
the  small  rotators,  the  ischial  tuberosity,  the  origin  of  the  femoral 
flexors,  and  the  great  trochanter.  It  also  covers  the  sciatic,  pudic,  and 
gluteal  vessels  and  nerves  as  these  emerge  from  the  pelvis.  Between 
the  fascial  termination  and  the  great  trochanter  a  large  multilocular 
synovial  bursa  is  interposed,  or  sometimes  several  smaller  ones,  and 
another  intervenes  between  it  and 
the  upper  part  of  the  external 
vastus  muscle. 

The  middle  gluteal  muscle,1 
broad,  thick,  and  fan-shaped,  is 
partly  situated  beneath  the  former, 
but  in  greater  part  in  advance,  and 
covered  by  a  thick  portion  of  the 
femoral  fascia.  It  arises  from  the 
outer  margin  of  the  iliac  crest  and 
from  the  sickle-shaped  surface  be- 
low and  between  the  superior  and 
middle  curved  lines,  and  from  the 
investing  fascia  in  front.  The 
fleshy  fascicles  in  descending  ter- 
minate in  a  strong,  flattened  ten- 
don, which  is  inserted  into  an  ob- 
lique impression  along  the  outer 
back  border  of  the  great  trochan- 
ter. A  small  synovial  bursa  inter- 
venes between  the  tendon  and  the 
upper  part  of  the  latter.  The  mus- 
cle covers  the  small  gluteal,  and  at 
its  anterior  border  is  usually  more 
or  less  united  with  it,  and  in  this 
position  is  overlapped  by  the  fas- 
cial tensor.  The  posterior  border 
is  in  contact  with  the  pyriform 

muscle.     The  deep  branches  of  the  gluteal  vessels  and  the  superior 
gluteal  nerve  run  beneath  it. 

The  small  gluteal  muscle 2  is  fan-shaped  and  situated  beneath  the 
preceding  muscle.  It  arises  from  the  dorsum  of  the  ilium  between  the 
middle  and  inferior  curved  lines,  including  the  upper  border  of  the 


MUSCLES  OF  THE  BUTTOCK.  1,  ilium;  2,  sa- 
crum ;  3,  posterior  sacro-iliac  ligament ;  4,  tu- 
berosity of  the  ischium ;  5,  great  sacro-sciatic 
ligament;  6,  small  sacro-sciatic  ligament;  7, 
great  trochanter ;  8,  small  gluteal  muscle ;  9, 
pyriform  muscle ;  10,  12,  geminus  muscle,  in- 
cluding between  its  two  bellies  the  termination, 
11,  of  the  internal  obturator  muscle  ;  13,  quad- 
rate femoral  muscle ;  14,  upper  part  of  the  great 
adductor ;  15,  external  vastus  muscle ;  16,  fem- 
oral biceps;  17,  gracilis;  18,  semitendinosus 
muscle. 


1  M.  gluteus  medius. 


2  M.  gluteus  minimus  or  tertius. 


326  THE    MUSCULAR   SYSTEM. 

great  sciatic  foramen,  whence  it  converges  and  descends  to  terminate  in 
a  superficial  aponeurosis  narrowing  to  a  strong  tendon,  which  is  in- 
serted into  an  impression  at  the  fore  part  of  the  base  of  the  great  tro- 
chanter.  The  muscle  covers  the  lower* part  of  the  ilium  and  the  upper 
part  of  the  hip-joint,  from  the  capsule  of  which  its  tendon  receives  a 
strong  fibrous  offset.  The  deep  gluteal  vessels  and  superior  gluteal 
nerve  cross  its  surface. 

The  pyriform  muscle l  is  situated  partly  within  the  back  of  the 
pelvis  and  partly  without  at  the  back  of  the  hip-joint.  Flat  and  trian- 
gular, it  arises  in  front  of  the  sacrum  from  the  intermediate  three  seg- 
ments outside  the  position  of  the  sacral  foramina,  slightly  from  the 
iliac  margin  of  the  great  sciatic  foramen,  and  the  front  surface  of  the 
great  sacro-sciatic  ligament.  Converging  and  passing  outward  through 
the  great  sciatic  foramen,  it  ends  in  a  rounded  tendon  which  is  inserted 
into  the  upper  fore  part  of  the  great  trochanter,  more  or  less  conjoined 
with  the  adjacent  tendons  of  the  internal  obturator  and  geminus 
muscles.  Within  the  pelvis  the  muscle  looks  towards  the  rectum, 
with  the  sacral  plexus  of  nerves  and  the  internal  iliac  vessels  lying 
against  it.  Outside  the  pelvis  it  lies  on  the  ilium  and  over  the  hip- 
joint,  from  which  it  is  separated  by  the  tendon  of  the  small  gluteal, 
and  is  here  covered  by  the  great  gluteal  muscle.  At  the  upper  border 
of  the  muscle  the  gluteal  vessels  and  superior  gluteal  nerve  emerge 
from  the  pelvis,  and  at  the  lower  border  the  sciatic  and  internal  pudic 
vessels  and  nerves. 

The  internal  obturator  muscle2  is  mainly  situated  within  the 
pelvis  at  the  front  and  side,  and  partly  outside  behind  the  hip-joint. 
It  arises  within  the  pelvis,  in  front  and  above  the  obturator  foramen, 
from  the  contiguous  surface  of  the  ramus  of  the  ischium  and  the 
pubis,  behind  the  foramen  from  the  upper  part  of  the  plane  of  the 
ischium  and  adjacent  surface  of  the  ilium  extending  to  the  great 
sciatic  foramen,  and  from  the  inner  surface  of  the  obturator  mem- 
brane except  its  lower  portion.  The  fleshy  fascicles  converge  down- 
ward and  backward,  and  the  muscle  emerges  from  the  pelvis  through 
the  small  sciatic  foramen,  and  ends  in  a  narrow,  flat  tendon,  which  is 
joined  by  the  geminus  muscle,  and  with  it  is  inserted  into  the  fore 
part  of  the  upper  border  of  the  great  trochanter.  The  tendon  com- 
mences within  the  muscle  in  four  or  five  slips  uniting  in  a  folded  apo- 
neurosis, which  plays  on  the  groove  at  the  fore  part  of  the  small  sci- 
atic foramen.  The  groove  is  invested  with  fibro-cartilage  and  furnished 
with  a  synovial  bursa,  which  is  reflected  on  the  folded  aponeurosis. 
Within  the  pelvis  the  muscle  is  covered  by  the  obturator  portion  of 
the  pelvic  fascia,  which  separates  it  from  the  anal  elevator,  and  its 
lower  part  is  crossed  by  the  pudic  vessels  and  nerve.  Outside  the 

1  M.  pyriformis  or  pyramidalis  ;  m.  iliacus  externus. 

2  M.  obturator  interims. 


THE   MUSCULAR   SYSTEM.  327 

pelvis  its  tendon  lies  on  the  capsular  ligament  of  the  hip-joint,  usually 
with  a  synovial  bursa  interposed  ;  is  crossed  by  the  sciatic  vessels  and 
nerves,  and  is  covered  by  the  great  gluteal  muscle. 

The  geminus  muscle l  is  situated  at  the  back  of  the  hip-joint, 
embracing  the  terminal  portion  of  the  internal  obturator  muscle.  It 
consists  of  a  pair  of  small  fleshy  bellies  conjoined  by  an  aponeurosis 
under  the  tendon  of  the  latter,  and  inserted  conjointly  with  it  into  the 
great  trochanter.  The  upper  belly,2  placed  above  the  internal  obtu- 
rator, arises  from  the  back  of  the  spine  of  the  ischium,  and  proceeds 
outward  to  blend  with  the  upper  part  of  the  obturator  tendon  and  be 
inserted  with  it.  The  lower  belly,3  larger  than  the  former  and  placed 
below  the  obturator,  arises  from  the  upper  back  part  of  the  tuberosity 
of  the  ischium,  and  in  the  same  manner  proceeds  outwardly  to  join  the 
lower  part  of  the  obturator  tendon  and  be  inserted  with  it.  The  two 
bellies  may  be  separated,  and  sometimes  the  upper  one  is  very  small  or 
is  absent. 

The  geminus  muscle  is  placed  between  the  pyriform  above  and 
the  femoral  quadrate  muscle  below,  in  contact  in  front  with  the  cap- 
sular ligament  of  the  hip-joint,  and  crossed  behind  by  the  same  vessels 
and  nerves  as  the  internal  obturator,  where  it  is  also  covered  by  the 
great  gluteal  muscle. 

The  external  obturator  muscle*  is  situated  at  the  fore  part  of 
the  pelvis  extending  outward  behind  the  hip-joint,  and  is  concealed 
in  front  by  the  heads  of  the  muscles  at  the  inner  part  of  the  thigh. 
It  arises  from  the  outer  surface  of  the  conjoined  rami  of  the  ischium 
and  pubis,  from  the  body  of  the  latter  contiguous  to  the  obturator 
foramen,  and  from  the  outer  surface  of  the  anterior  half  of  the  obtu- 
rator membrane.  The  fleshy  fascicles  converge  and  proceed  outward 
between  the  acetabulum  and  tuberosity  of  the  ischium,  and  terminate 
in  a  tendon  which  passes  behind  the  hip-joint  and  the  neck  of  the 
femur  to  be  inserted  into  the  fossa  at  the  base  of  the  great  trochanter. 
The  muscle  is  in  contact  with  the  ilio-psoas,  pectineus,  and  great  ad- 
ductor muscles,  and  approaching  its  insertion  is  covered  behind  by  the 
femoral  quadrate  muscle. 

The  femoral  quadrate  muscle5  is  situated  at  the  back  of  the 
hip-joint,  covered  by  the  lower  border  of  the  great  gluteal  muscle.  It 
arises  along  the  outer  border  of  the  tuberosity  of  the  ischium,  and 
proceeds  horizontally  outward  to  be  inserted  into  a  line  of  the  femur 
descending  a  short  distance  from  the  posterior  intertrochanteric  ridge. 
It  is  placed  immediately  below  the  geminus  muscle,  and  its  lower 
border  reaches  the  upper  border  of  the  great  adductor.  In  front  of 

1  M.  gemini  or  gemelli ;  m.  marsupialis ;  m.  ischio-spini-trochanterius ;  gemi- 
nous  muscle. 

2  M.  geminus  or  gemellus  superior.  3  M.  geminus  or  gemellus  inferior. 

4  M.  obturator  externus  ;  external  obturator  muscle. 

5  M.  quadratus  femoris. 


328  THE   MUSCULAR  SYSTEM. 

it  is  the  tendon  of  the  external  obturator,  the  small  trochanter,  and 
the  hip-joint,  and  behind,  it  is  crossed  by  the  sciatic  nerves  and  vessels. 

The  great  gluteal  muscle  is  supplied  by  the  inferior  gluteal  nerve ; 
the  middle  and  small  gluteal,  and  fascial  tensor  muscles  by  the  superior 
gluteal  nerve.  The  pyriform,  internal  obturator,  geminus,  and  quad- 
rate femoral  muscles  are  supplied  by  branches  from  the  sacral  plexus ; 
and  the  external  obturator  muscle  by  the  obturator  nerve. 

The  great  gluteal  muscle  is  remarkable  for  its  large  size  in  com- 
parison with  that  of  quadrupeds,  and  is  related  with  the  erect  con- 
dition of  the  body.  It  is  the  principal  extensor  of  the  hip,  and  by  its 
agency  the  lower  limb  is  brought  into  the  line  of  the  body.  Its  most 
powerful  action  is  to  extend  the  trunk  when  this  is  bent  forward  ;  but 
in  the  erect  condition  the  body  maintains  its  position  chiefly  through 
tension  of  the  ligaments,  while  it  is  balanced  with  the  centre  of  gravity 
slightly  behind  a  vertical  plane  passing  through  the  middle  of  the  hip- 
joint.  The  upper  part  of  the  muscle  may  assist  in  abduction  of  the 
thigh,  while  the  lower  part  acts  as  an  adductor  and  as  a  rotator  out- 
wardly. Through  the  connection  of  the  muscle  with  the  thickest  por- 
tion of  the  femoral  fascia  extended  to  the  tibia,  it  also  serves  to  steady 
the  knee  in  standing.  The  middle  and  small  gluteal  muscles  are  power- 
ful abductors  of  the  thigh  aided  by  the  fascial  tensor,  and  together  they 
rotate  the  limb  inwardly.  They  come  especially  into  action  in  walking, 
in  the  support  of  the  body  on  one  limb,  and  in  the  rotation  of  the 
pelvis  on  the  two  limbs  alternately.  The  fascial  tensor,  from  its  mode 
of  termination  in  the  thickest  portion  of  the  femoral  fascia  extended 
to  the  tibia,  aids  the  great  gluteal  in  steadying  the  knee  when  stand- 
ing. The  pyriform,  internal  obturator  and  geminus,  external  obtu- 
rator, and  quadrate  femoral  muscles  are  all  rotators  of  the  lower  limb 
outward,  in  which  they  may  be  assisted  by  the  lower  portion  of  the 
small  gluteal  muscle.  They  also  act  together  as  abductors  of  the  thigh ; 
but  the  latter  two  may  aid  in  adduction  and  the  last  one  in  flexion. 

MUSCLES   OP   THE   BACK   OF   THE   THIGH. 

The  fleshy  mass  at  the  back  of  the  thigh  is  composed  of  three 
flexors  of  the  leg, —  the  femoral  biceps,  semitendinosus,  and  semi- 
membranosus  muscles. 

The  femoral  biceps1  is  situated  at  the  outer  side  of  the  fleshy 
mass  at  the  back  of  the  thigh,  and  consists  of  two  portions  or  heads. 
The  long  head2  is  fusiform,  and  arises  by  a  strong  tendon  in  common 
with  the  semitendinosus  from  the  lower  impression  behind  the  ischial 
tuberosity,  whence  its  fleshy  fascicles  descend  and  terminate  in  an 
aponeurosis  at  the  lower  back  part  of  the  muscle.  The  short  head,3 
lying  beneath  the  lower  part  of  the  former,  is  lozenge-shaped,  and 

1  M.  biceps  flexor  eruris  ;  m.  flexor  cruris  externus  or  fibularis ;  m.  biceps  femoris. 

2  Caput  longum  bicipitis.  3  C.  brevi  bicipitis. 


THE   MUSCULAR  SYSTEM. 


329 


FIG.  161. 


arises  from  the  outer  margin  of  the  linea  aspera  and  greater  part 
of  the  outer  supracondylar  ridge  and  adjacent  intermuscular  septum, 
whence  the  fascicles  descend  obliquely  outward  and  terminate  in  the 
posterior  aponeurosis.  This  narrows  into  a  strong  tendon,  which  is 
inserted  into  the  outer  part  of  the  head  of  the  fibula,  dividing  into 
two  portions,  which  embrace  the  external  lateral  ligament  of  the  knee- 
joint,  giving  an  offset  forward  to  the 
outer  tuberosity  of  the  tibia  and  a 
thinner  expansion  downward  to  the 
deep  fascia  of  the  leg. 

The  upper  part  of  the  biceps  is 
covered  by  the  great  gluteal  muscle, 
but  elsewhere  is  subcutaneous.  It 
rests  against  the  semimembranosus, 
great  adductor,  and  external  vastus, 
and  covers  the  great  sciatic  nerve. 
Its  inner  border  is  in  contact  with  the 
semitendinosus  and  semimembranosus, 
and  its  lower  'extremity  forms  the 
outer  boundary  of  the  popliteal  space. 
A  bursa  is  commonly  interposed  be- 
tween its  tendon  and  the  external  lat- 
eral ligament  of  the  knee,  and  some- 
times another  between  the  origin  of 
the  long  head  and  that  of  the  semi- 
membranosus. 

The  semitendinosus1  is  situated 
at  the  inner  side  of  the  former,  and 
arises  from  the  ischial  tuberosity,  and 
from  the  tendon  common  to  it  and  the 
biceps  for  about  three  inches,  whence 
its  fusiform  belly  descends  and  grad- 
ually diverges  from  the  biceps,  and 
below  the  middle  of  the  thigh  termi- 
nates in  a  long,  narrow  tendon.  This 
proceeds  along  the  inner  side  of  the 
popliteal  space,  resting  on  the  semi- 
membranosus, to  the  knee,  where  it 
turns  forward  around  the  inner  tuber- 
osity of  the  tibia  and  expands  to  be  inserted  into  the  latter  near  its 
tubercle,  below  the  insertion  of  the  gracilis  and  beneath  that  of  the  sar- 
torius,  giving  an  expansion  downward  to  the  deep  fascia  of  the  leg.  A 
synovial  bursa  is  interposed  between  the  three  tendons  just  indicated 
and  the  internal  lateral  ligament  of  the  knee-joint.  The  belly  of  the 


10 


MUSCLES  OF  THE  BACK  OF  THE  RIGHT 
BUTTOCK  AND  THIGH.  1,  middle  gluteal 
muscle;  2,  great  gluteal  muscle;  3,  exter- 
nal vastus,  covered  by  the  femoral  fascia ; 
4,  long  head  of  the  femoral  biceps;  5, 
its  short  head ;  6,  semitendinosus,  and  7, 
semimembranosus  muscles;  8,  gracilis; 

9,  inner  border  of  the  great  adductor ; 

10,  lower  extremity  of  the  sartorius ;  11, 
popliteal  space ;  12,  gastrocnemius. 


1  M.  semitendinosus  ;  m.  ischio-pretibialis. 


330  THE   MUSCULAR   SYSTEM. 

muscle  is  commonly  crossed  about  its  middle  by  a  thin  tendinous 
intersection. 

The  muscle  is  covered  at  its  origin  by  the  great  gluteal,  and  else- 
where is  subcutaneous.  By  its  deep  surface  it  is  in  contact  with  the 
semimembranosus,  great  adductor,  and  inner  head  of  the  gastrocnemius 
muscles. 

The  semimembranosus l  is  situated  at  the  inner  side  of  the  pre- 
ceding muscles,  between  them  and  the  great  adductor.  It  arises  from 
the  upper  impression  behind  the  ischial  tuberosity  by  a  strong  tendon, 
which  is  grooved  behind  to  accommodate  the  common  tendon  of  the 
adjacent  flexors.  The  tendon  descends  and  expands  in  an  aponeurosis, 
from  which  the  fleshy  fascicles  of  the  muscle  proceed  obliquely  down- 
ward and  inward  and  terminate  in  another  aponeurosis,  which  faces 
the  muscle  inwardly,  and  narrows  into  a  stout  tendon  descending  at 
the  inner  side  of  the  knee  to  be  inserted  into  the  back  part  of  the  inner 
tuberosity  of  the  tibia.  From  the  tendon  of  insertion  proceed  three 
considerable  offsets,  of  which  one  extends  to  the  groove  of  the  tibia 
beneath  the  internal  lateral  ligament  of  the  knee-joint;  the  second 
reinforces  the  capsular  ligament  of  the  latter,  and  is  directed  upward 
and  outward  to  be  inserted  into  the  outer  condyle  of  the  femur ;  and 
the  third  descends  and  expands  as  the  popliteal  fascia. 

The  semimembranosus  rests  against  the  great  adductor,  with  the 
great  sciatic  nerve  descending  behind  along  its  outer  border.  Its  upper 
part  is  covered  by  the  conjoined  biceps  and  semitendinosus,  the  latter 
of  which  lies  on  it  its  whole  length;  and  below  it  is  partially  subcu- 
taneous. Between  its  tendon  of  insertion  and  the  inner  head  of  the 
gastrocnemius  is  a  large  synovial  bursa,  which  commonly  communicates 
with  the  cavity  of  the  knee-joint.  Another  bursa  intervenes  between 
the  tendon  and  the  upper  margin  of  the  inner  tuberosity  of  the  tibia. 

The  femoral  biceps,  semimembranosus,  and  semitendinosus  are  sup- 
plied by  branches  of  the  great  sciatic  nerve.  They  are  flexors  of  the 
leg  upon  the  thigh,  and  when  the  lower  limbs  are  fixed  in  position 
they  are  extensors  of  the  trunk  and  sustain  the  pelvis  on  the  thighs. 
When  the  knee  is  bent,  the  biceps  slightly  rotates  the  leg  outward ;  the 
other  muscles  in  the  opposite  direction. 

The  flexors  of  the  thigh  are  also  called  the  hamstring  muscles ;  the 
tendon  of  insertion  of  the  biceps  being  the  outer  hamstring,  while 
those  of  the  semitendinosus  and  semimembranosus,  together  with  those 
of  the  sartorius  and  gracilis,  are  called  the  inner  hamstrings. 

FASCIAE   OF   THE   LEG  AND  FOOT. 

The  deep  fascia  of  the  leg,  or  the  crural  fascia,2  is  an  aponeu- 
rotic  membrane  investing  the  muscles  of  the  leg,  to  which  it  is  loosely 
attached,  except  where  some  of  them  have  partial  origin  from  its  inner 

1  M.  semimembranosus  ;  m.  ischio-popliti-tibialis.  *  F.  cruralis. 


THE   MUSCULAR   SYSTEM.  331 

surface.  It  is  tightly  attached  to  all  the  subcutaneous  prominences 
and  borders  of  the  bones,  as  the  heads  of  the  tibia  and  fibula,  the  mal- 
leoli,  and  the  front  and  inner  borders  of  the  shaft  of  the  tibia,  where 
it  is  continuous  with  the  periosteum.  At  the  knee  it  is  continuous 
with  the  femoral  fascia,  and  is  reinforced  on  the  inner  side  by  expan- 
sions from  the  tendons  of  the  sartorius,  gracilis,  and  semitendinosus 
muscles,  and  on  the  outer  side  by  an  expansion  from  the  tendon  of  the 
femoral  biceps  muscle.  It  becomes  stronger  approaching  the  ankle- 
joint,  and  is  continuous  with  the  corresponding  fascia  of  the  foot. 
The  fascia  is  thickest  and  most  aponeurotic  in  appearance  at  the  fore 
part  of  the  leg,  where  it  invests  the  anterior  tibialis  and  long  digital 
extensor  muscles,  to  several  of  which  it  gives  partial  origin  above  by 
its  inner  surface.  It  is  thinnest  behind,  where  it  invests  the  muscles 
of  the  calf  and  crosses  the  popliteal  space.  In  the  latter  position  it  is 
strengthened  by  transverse  fibres  binding  the  two  sides  together,  and  is 
perforated  by  the  external  saphenous  vein  as  it  passes  forward  to  join 
the  popliteal  vein.  On  the  outer  side  of  the  leg  it  is  of  intermediate 
thickness,  and  invests  the  peroneal  muscles,  to  which  it  gives  partial 
origin.  In  this  position,  also,  it  is  connected  by  strong  intermuscular 
septa  with  the  fibula,  of  which  one  septum  separates  the  peroneal 
muscles  from  those  of  the  front,  and  the  other  from  those  of  the  back 
of  the  leg.  Besides  other  septa  extending  from  the  inner  surface  of 
the  fascia  between  the  muscles,  a  broad  one,  extended  between  the  bones 
at  the  back  of  the  leg,  separates  the  posterior  tibialis  and  long  digital 
and  hallucal  flexor  muscles  from  those  of  the  calf. 

In  front  and  at  the  sides  of  the  ankle-joint  the  deep  fascia  of  the  leg 
and  foot  are  reinforced  by  bands  of  fibres  forming  the  annular  ligaments. 

The  deep  fascia  at  the  back  of  the  foot,  or  the  dorsal  fascia,1 
is  a  thin  membrane  extending  from  the  crural  fascia  over  the  extensor 
tendons  to  the  toes.  Thin  laminae  of  the  same  extend  between  the  latter 
tendons  and  the  short  digital  extensor,  and  also  beneath  this  muscle. 

The  plantar  fascia,2  or  deep  fascia  of  the  sole  of  the  foot, 
consists  of  three  portions,  which  unite  in  intermuscular  septa  pene- 
trating the  sole  between  the  median  muscles  of  the  latter  and  those 
of  the  great  toe  at  the  inner  part  and  those  of  the  little  toe  at  the  outer 
part  of  the  foot.  The  inner  portion3  of  the  plantar  fascia,  thinner  and 
of  looser  texture  than  the  other  portions,  invests  the  muscles  of  the 
great  toe,  and  is  connected  with  the  bones  along  the  inner  border  of  the 
foot,  where  it  is  continuous  with  the  dorsal  fascia  and  internal  annular 
ligament.  The  outer  portion 4  of  the  fascia  invests  the  muscles  of  the 
little  toe,  and  is  connected  with  the  bones  along  the  outer  border  of  the 
foot,  where  it  is  also  continuous  with  the  dorsal  fascia.  It  is  for  the 
most  part  thin,  but  forms  a  thick,  aponeurotic  band,  extending  between 

1  Aponeurosis  dorsalis  pedis.  2  Aponeurosis  plantaris. 

3  A.  plantaris  interna.  4  A.  plantaris  externa. 


332  THE    MUSCULAR   SYSTEM. 

the  outer  tubercle  of  the  calcaneum  and  the  prominent  base  of  the  fifth 
metatarsal  bone,  giving  partial  origin  to  the  minimal  abductor.  The 
middle  portion1  of  the  plantar  fascia  is  a  strong,  dense,  white,  fan- 
shaped  aponeurosis,  chiefly  composed  of  longitudinal  radiating  fibrous 
bundles  starting  from  the  inner  tubercle  of  the  calcaneum  and  ex- 
panding at  the  fore  part  of  the  metatarsus,  where  it  divides  into  five 
processes.  Each  of  these  divides  into  two  slips,  between  which  the 
flexor  tendons  proceed  to  the  toes ;  and  the  slips  are  fixed  to  each  side 
of  the  base  of  the  first  phalanges  and  contiguous  portion  of  the  trans- 
verse metatarsal  ligament.  The  processes  of  the  fascia  are  intersected 
by  numerous  transverse  fibres,  which  serve  to  strengthen  their  con- 
nection and  give  them  attachment  to  the  adjacent  skin.  Between  the 
processes  the  digital  vessels  and  nerves  and  the  tendons  of  the  lum- 
brical  and  interosseous  muscles  pass.  On  each  side,  the  median  plantar 
fascia  joins  the  lateral  portions  in  the  formation  of  the  intermuscular 
septa,  which  give  partial  origin  to  the  contiguous  muscles.  With  these 
septa  are  connected  thinner  ones,  which  extend  horizontally  between 
the  muscles.  The  upper  surface  of  the  median  plantar  fascia  gives 
partial  origin  behind  to  the  short  digital  flexor. 

The  anterior  annular  ligament,2  situated  in  front  of  the  ankle- 
joint  and  on  the  back  of  the  foot,  is  a  thickened  portion  of  the  crural 
fascia  continuous  with  the  dorsal  fascia  of  the  foot.  Attached  exter- 
nally to  the  upper  fore  part  of  the  calcaneum,  it  is  directed  inwardly 
and  divides  into  two  variable,  divergent  bands,  of  which  the  upper, 
thicker,  and  more  constant  proceeds  to  be  attached  to  the  fore  part  of 
the  internal  malleolus,  while  the  other  is  attached  to  the  inner  side  of 
the  tarsus,  where  it  is  continuous  with  the  plantar  fascia.  The  outer 
extremity  of  the  ligament  forms  a  passage  for  the  tendons  of  the  long 
digital  extensor  and  anterior  peroneal  muscles,  provided  with  a  syno- 
vial  sheath.  The  inner  bands  of  the  ligament  form  two  separate  pas- 
sages for  the  tendons  of  the  hallucal  extensor  and  anterior  tibialis, 
each  provided  with  a  synovial  sheath.  The  anterior  tibial  vessels  and 
nerve  descend  beneath  the  ligament  between  the  position  of  the  long 
digital  extensor  tendons  and  that  of  the  hallucal  extensor. 

Above  the  anterior  annular  ligament  a  variably  broad  and  strong 
band3  of  the  crural  fascia  extends  obliquely  downward  from  the  fibula 
to  the  tibia,  and  serves  to  confine  the  tendons  before  they  turn  forward 
to  the  foot. 

The  internal  annular  ligament4  extends  from  the  internal  mal- 
leolus downward  and  backward  to  the  inner  side  of  the  calcaneum  and 
astragalus,  and  in  its  course  bridges  over  several  bony  grooves  and 
converts  them  into  canals,  through  which  the  flexor  tendons  proceed 

1  Aponeurosis  plantaris  media. 

2  Ligamentum  annulare  anterius  ;  1.  cruciatum. 

3  L.  transversum.  4  L.  annulare  internum ;  1.  laciniatum  int. 


THE    MUSCULAE   SYSTEM.  333 

to  the  sole  of  the  foot.  Above,  it  is  continuous  with  the  crural  fascia, 
especially  with  the  intermuscular  septum  separating  the  deeper  mus- 
cles from  those  of  the  calf.  Below,  it  is  continuous  with  the  plantar 
fascia,  and  gives  partial  origin  to  the  hallucal  abductor.  Of  two 
canals  formed  by  it  behind  the  internal  malleolus,  each  provided  with 
a  synovial  sheath,  one  gives  passage  to  the  tendon  of  the  posterior 
tibialis,  and  the  other  to  that  of  the  long  digital  flexor.  Then  succeeds 
a  space  occupied  by  the  posterior  tibial  vessels  and  nerve ;  and  then 
another  canal,  provided  with  a  synovial  sheath,  for  the  passage  of  the 
tendon  of  the  long  hallucal  flexor.  This  canal  is  formed  by  the  an- 
nular ligament  bridging  over  successive  and  continuous  grooves  of  the 
tibia,  astragalus,  and  calcaneum. 

The  external  annular  ligament,1  of  less  strength  than  the  pre- 
ceding, extends  from  the  end  of  the  outer  malleolus  to  the  outer 
side  of  the  calcaneum,  and  confines  the  tendons  of  the  long  and  short 
peroneal  muscles,  both  in  the  same  canal,  which  is  provided  with  a 
synovial  sheath. 

MUSCLES  OF  THE  INNEK  FOKE  PAKT  OF  THE  LEG  AND  BACK 

OF  THE  FOOT. 

The  fore  part  of  the  leg  is  occupied  in  the  interval  of  the  tibia  and 
fibula  with  four  muscles,  from  which  tendons  proceed  to  the  back  of 
the  foot  and  toes.  The  muscles  are  the  anterior  tibialis,  long  digital 
extensor,  anterior  peroneal,  and  hallucal  extensor.  The  short  digital 
extensor  is  placed  on  the  back  of  the  foot. 

The  anterior  tibialis 2  is  subcutaneous,  and  rests  on  the  tibia.  It  is 
.a  fusiform  muscle,  and  arises  beneath  the  outer  tuberosity  of  the  tibia 
from  the  external  surface  of  the  shaft  for  two-thirds  its  length,  from 
the  adjacent  portion  of  the  interosseous  membrane,  from  the  investing 
fascia,  and  from  the  intermuscular  septum  between  it  outwardly  and 
the  long  digital  extensor.  The  fascicles  descend  and  terminate  in  a 
tendon,  which  appears  in  front  of  the  muscle  at  the  lower  third  of  the 
leg,  passes  through  the  inner  canal  of  the  annular  ligament  in  front 
of  the  tibia,  and  proceeds  on  the  back  of  the  foot  to  be  inserted  into 
the  inner  and  lower  part  of  the  entocuneiform  bone  and  the  contigu- 
ous portion  of  the  base  of  the  first  metatarsal  bone.  The  muscle  lies 
in  contact  outwardly  with  the  long  digital  and  hallucal  extensors, 
with  the  anterior  tibial  vessels  and  nerve  between  them.  Its  tendon 
passes  over  the  ankle-joint  and  the  inner  surface  of  the  tarsus. 

The  long  digital  extensor3  is  a  flat,  semipenniform  muscle,  which 
lies  to  the  outer  side  of  the  former  next  the  fibula.  It  is  also  subcuta- 
neous, and  arises  from  the  outer  tuberosity  of  the  tibia,  the  head  of 
the  fibula  and  its  anterior  surface  for  about  three-fourths  of  its  length, 

1  L.  annulare  externum  ;  1.  laciniatum  ext. 

2  M.  tibialis  anticus  ;  anterior  tibial  muscle  ;  m.  hippicus. 

3  M.  extensor  longus  digitorum  pedis ;  m.  ext.  digitorum  communis  longus. 


334 


THE    MUSCULAR   SYSTEM. 


FIG.  162. 


from  the  adjacent  portion  of  the  interosseous  membrane  above,  from 
the  intermuscular  septa  between  it  and  the  anterior  tibialis  and  peroneal 
muscles,  and  from  the  investing  fascia.  Its  fascicles  descend  obliquely 
forward  and  terminate  in  three  tendons,  and  later,  by  the  division  of 

the  outer  one,  in  four,  which  pass  be- 
neath the  outer  part  of  the  anterior 
annular  ligament  to  the  back  of  the 
foot,  where  they  diverge  to  the  lesser 
toes,  on  which  they  terminate  in  the 
same  manner  as  do  the  extensor  ten- 
dons of  the  fingers.  The  muscle  lies 
in  contact  outwardly  with  the  peroneal 
muscles.  Its  tendons  cross  the  ankle- 
joint,  and  on  the  back  of  the  foot 
spread  over  the  short  digital  extensor. 
.  The  anterior  peroneal  muscle1  is 
placed  below  the  former,  and  appears 
as  a  continuation  of  it,  arising  from 
the  remainder  of  the  shaft  of  the  fib- 
ula, the  contiguous  portion  of  the  in- 
terosseous membrane,  and  the  inter- 
muscular  septum  outwardly  between 
it  and  the  short  peroneal  muscle.  Its 
fleshy  fascicles  continue  the  course  of 
those  of  the  preceding  muscle,  and 
terminate  at  its  fore  part  in  a  tendon 
which  descends  beneath  the  annular 
ligament  in  company  with  those  of  the 
long  digital  extensor,  and  diverges  from 
them  to  be  inserted  into  the  base  of 
the  last  metatarsal  bone.  The  muscle 
is  variable,  is  sometimes  much  larger, 
and  extends  higher,  and  is  sometimes 
much  smaller,  and  occasionally  absent. 
The  hallucal  extensor2  is  a  thin 
triangular  muscle  situated  between  the 
anterior  tibialis  and  long  digital  exten- 
sor, and  for  the  most  part  concealed  by 
them.  It  arises  from  the  middle  half  of  the  deeper  part  of  the  an- 
terior surface  of  the  fibula  and  the  adjacent  portion  of  the  interosseous 
membrane,  descends  the  leg,  becoming  superficial  below,  and  termi- 
nates at  its  fore  part  in  a  tendon  which  passes  through  a  distinct  canal 


MUSCLES  OF  THE  FKONT  OF  THE  LEG  AND 
BACK  OF  THE  FOOT.  1,  tendon  of  the  fem- 
oral rectus ;  2,  subcutaneous  inner  surface 
of  the  tibia ;  3,  anterior  tibialis  muscle ;  4, 
long  digital  extensor;  5,  hallucal  exten- 
sor ;  6,  anterior  peroneal  muscle ;  7,  long 
peroneal  muscle ;  8,  short  peroneal  mus- 
cle ;  9,  borders  of  the  soleus ;  10,  border 
of  the  inner  belly  of  the  gastrocnemius ; 
11,  short  digital  extensor,  beneath  the 
tendons  of  the  long  extensor. 


1  M.  peroneus  tertius  or  anticus. 

2  M.  extensor  proprius  pollicis  pedis ;  m.  ext.  proprius  hallucis  ;  m. 
longus. 


ext.  hallucis 


THE   MUSCULAR  SYSTEM.  335 

of  the  anterior  annular  ligament  between  the  tendons  of  the  anterior 
tibialis  and  long  digital  extensor,  and  proceeds  along  the  inner  side 
of  the  back  of  the  foot  to  be  inserted  into  the  base  of  the  terminal 
phalanx  of  the  great  toe.  In  the  leg  the  muscle  is  in  contact  inwardly 
with  the  anterior  tibialis  and  the  anterior  tibial  vessels,  and  outwardly 
with  the  long  digital  extensor. 

The  short  digital  extensor1  lies  on  the  back  of  the  foot,  and  is 
a  broad,  thin  muscle,  which  consists  of  four  penniform  bellies,  on  the 
same  plane,  arising  together  tendinously  from  the  outer  fore  part  of 
the  calcaneum  and  the  contiguous  portion  of  the  anterior  annular  liga- 
ment. Directed  forward  and  inward,  the  bellies  terminate  in  as  many 
tendons,  of  which  the  first  proceeds  to  the  great  toe  and  joins  that 
of  the  hallucal  extensor  in  its  insertion  into  the  terminal  phalanx, 
while  the  others  proceed  in  the  same  manner  to  the  succeeding  three 
toes  and  join  the  corresponding  tendons  of  the  long  digital  extensor. 
The  muscle  lies  somewhat  obliquely  on  the  tarsus  and  metatarsus,  be- 
neath the  tendons  of  the  long  digital  extensor  and  anterior  peroneal 
muscles.  Its  inner  division  crosses  the  dorsal  pedal  vessels  and  the 
anterior  tibial  nerve. 

All  the  above  muscles  are  supplied  by  the  anterior  tibial  nerve. 
The  anterior  tibialis  and  anterior  peroneal  muscles  are  flexors  of  the 
foot ;  the  action  of  the  others  is  indicated  by  the  names. 

MUSCLES  ON  THE  OUTER  PART  OF  THE  LEG. 

Two  muscles,  the  long  and  short  peroneal,  occupy  the  outer  part 
of  the  leg,  covering  the  fibula,  and  placed  between  the  muscles  of  the 
front  and  back  of  the  leg. 

The  long  peroneal  muscle,2  the  larger  and  more  superficial, 
arises  from  the  head  and  upper  two-thirds  of  the  outer  surface  of  the 
fibula,  from  the  intermuscular  septa  between  it  and  the  muscles  in 
front  and  behind  the  leg,  and  from  the  investing  fascia.  Its  fleshy 
fascicles  descend  and  converge  to  a  long  tendon  appearing  at  the  lower 
outer  part  of  the  muscle,  and  thence  passing  through  the  canal  of  the 
external  annular  ligament  behind  the  outer  malleolus,  where  it  turns 
forward  and  downward  to  the  outer  side  of  the  calcaneum  and  cuboid 
bone,  bound  to  the  former  by  the  fore  part  of  the  external  annular 
ligament.  It  then  turns  inward  beneath  the  cuboid  bone,  through  the 
canal  between  it  and  the  long  plantar  ligament,  and  proceeds  obliquely 
forward  across  the  sole  of  the  foot  to  be  inserted  into  the  outer  part 
of  the  base  of  the  first  metatarsal  bone.  Thus  the  tendon  makes  two 
turns  in  its  course,  and  at  the  second  exhibits  a  fibro- cartilaginous 
thickening,  which  plays  on  the  tubercle  of  the  cuboid  bone.  Rarely, 
in  this  position,  it  contains  an  osseous  nucleus,  a  little  sesamoid  bone. 

1  M.  extensor  brevis  digitorum  pedis  ;  pedal  muscle. 

2  M.  peroneus  longus ;  m.  p.  1.  lateralis. 


336  THE   MUSCULAR   SYSTEM. 

In  the  canal  behind  the  external  malleolus  the  tendon  is  accompanied 
by  that  of  the  short  peroneal  muscle,  both  being  enveloped  in  a  syno- 
vial  sheath,  which  extends  on  the  long  peroneal  tendon  in  the  canal 
at  the  outer  side  of  the  calcaneum.  Another  synovial  sheath  envelops 
the  tendon  in  the  canal  beneath  the  cuboid  bone. 

In  the  leg  the  long  peroneal  muscle  is  subcutaneous ;  its  upper  part 
lying  between  the  long  digital  extensor  in  front  and  the  soleus  and 
long  hallucal  flexor  behind ;  and  its  lower  part  lies  behind  on  the  short 
peroneal  muscle.  Near  its  origin  above,  it  is  interrupted  for  a  short 
distance  in  its  attachment  to  the  fibula  for  the  passage  of  the  peroneal 
nerve  beneath  the  muscle. 

The  short  peroneal  muscle  :  lies  beneath  the  preceding,  and  arises 
from  the  lower  two-thirds  of  the  outer  surface  of  the  fibula  and  the 
intermuscular  septum  on  each  side.  Descending,  it  terminates  in  a 
tendon  which  runs  in  front  of  that  of  the  long  peroneal,  and  accom- 
panies it  through  the  canal  behind  the  external  malleolus.  Thence  it 
turns  forward  and  downward  on  the  outer  side  of  the  calcaneum,  to 
which  it  is  bound  by  the  external  annular  ligament  in  a  separate  canal 
above  that  of  the  long  peroneal  tendon,  and  proceeds  to  be  inserted 
into  the  dorsal  surface  of  the  projection  of  the  base  of  the  fifth  meta- 
tarsal  bone.  The  synovial  sheath  investing  the  tendons  of  both  pero- 
neal muscles  behind  the  outer  malleolus  is  extended  in  a  separate 
process  upon  that  of  the  short  peroneal  in  the  canal  on  the  outer  side 
of  the  calcaneum. 

The  muscle  in  front  is  in  contact  with  the  long  digital  extensor 
and  anterior  peroneal;  behind,  with  the  long  peroneal  and  the  long 
hallucal  flexor. 

The  long  and  short  peroneal  muscles  are  supplied  by  the  musculo- 
cutaneous  branch  of  the  peroneal  nerve.  They  are  extensors  of  the 
foot.  The  three  peroneal  muscles  and  the  extensors  of  the  toes  to- 
gether extend  and  evert  the  foot. 

MUSCLES  ON  THE   BACK  OP  THE   LEG. 

The  muscles  of  the  back  of  the  leg  consist  of  a  superficial  and  a 
deep  group.  The  former  compose  the  calf  of  the  leg,  which  is  one  of 
the  striking  characters  of  the  human  muscular  apparatus,  and  is  related 
with  the  erect  position  and  mode  of  progression  of  man.  The  chief 
muscles,  the  gastrocnemius  and  the  soleus,  with  the  former  divided 
into  two  portions  or  heads,  terminate  in  a  common  tendon,  whence 
they  are  also  regarded  as  one  muscle,  with  the  name  of  the  sural 
triceps.2  The  remaining  muscle,  the  plantaris,  is  very  small,  and 
appears  to  be  a  mere  rudimental  representative  of  a  more  important 
muscle  in  some  lower  animals.  The  muscles  of  the  deep  group  in- 

1  M.  peroneus  brevis ;  m.  p.  b.  lateralis. 

2  M.  triceps  gurae  ;  m.  extensor  pedis. 


THE   MUSCULAR   SYSTEM. 


337 


FIG.  163. 


vested  with  a  layer  of  fascia  beneath  the  former,  are  the  popliteus,  the 
posterior  tibialis,  and  the  long  digital  and  hallucal  flexors. 

The  gastrocnemius,1  the  subcutaneous  muscle  of  the  calf,  is  com- 
posed of  a  pair  of  elliptical  fleshy  bellies 
or  heads  arising  tendinously  from  the  rough 
impressions  behind  the  femur  above  the 
condyles,  over  which  they  converge  and 
descend  side  by  side  to  terminate  in  the 
aponeurosis  of  insertion.  The  tendons  of 
origin  expand  in  superficial  aponeuroses  be- 
hind the  bellies,  from  which  the  fleshy  fas- 
cicles spread  obliquely  forward  and  down- 
ward and  terminate  in  the  aponeurosis  of 
insertion  which  faces  the  bellies  together 
in  front.  The  descending  aponeurosis  leaves 
the  bellies,  about  the  middle  of  the  leg, 
gradually  narrows,  thickens,  and  unites 
with  that  of  the  soleus  muscle  to  form  the 
common  tendon,  named  the  tendon  of 
Achilles.  The  inner  head  is  the  larger, 
arises  by  a  thicker  tendon,  and  descends 
lower ;  the  outer  head  also  partially  arises 
from  the  contiguous  portion  of  the  capsu- 
lar  ligament  of  the  knee-joint. 

The  gastrocnemius  covers  the  plantaris, 
popliteus,  and  soleus  muscles.  Its  heads 
proceed  backward  and  downward  from  be- 
tween the  hamstring  muscles  and  from  the 
lateral  boundaries  of  the  lower  part  of  the 
popliteal  space.  Approaching  each  other, 
they  conceal  the  popliteal  vessels  and  nerve. 
The  outer  head  covers  the  origin  of  the 
plantaris,  which  lies  to  its  inner  side  be- 
tween it  and  the  capsule  of  the  knee ;  and 
is  crossed  externally  by  the  biceps,  with 
the  peroneal  nerve  passing  between  them. 
Beneath  the  inner  head  and  the  inner  con- 
dyle  of  the  femur  a  synovial  bursa  is  inter- 
posed, commonly  communicating  with  the 
cavity  of  the  knee-joint;  and  externally  it  is  crossed  by  the  tendons 
of  the  semimembranosus  and  semitendinosus  muscles. 

The  soleus,  situated  under  or  in  front  of  the  former,  is  a  broad, 
flat  muscle,  named  from  its  resemblance  in  outline  to  a  sole-fish.  It 
arises  tendinously  from  behind  the  head  of  the  fibula  and  the  upper 


SUPERFICIAL  MUSCLES    ON   THE 

BACK  OF  THE  EIGHT  LEG.    1,  femoral 

biceps ;  2,  tendons  of  the  semitendi- 
nosus, semimembranosus,  gracilis, 
and  sartorius ;  3,  popliteal  space ; 
4,  gastrocnemius ;  5,  soleus ;  6,  ten- 
don of  Achilles ;  7,  calcaneum ;  8, 
tendons  of  the  long  and  short  per- 
oneal muscles  passing  behind  the 
outer  ankle ;  9,  tendon  of  the  pos- 
terior tibialis  muscle  and  long  digi- 
tal flexor  passing  behind  the  inner 
ankle. 


1  M.  gemellus  surse. 
22 


338  THE   MUSCULAR   SYSTEM. 

third  of  its  shaft,  from  the  oblique  line  of  the  tibia  below  the  popliteus, 
and  from  the  middle  third  of  the  inner  back  border  of  that  bone,  with 
a  few  fascicles  from  a  tendinous  arch  which  spans  the  popliteal  vessels 
and  nerve  between  the  bones.  The  fleshy  fascicles  descend  obliquely 
backward  and  converge  to  an  aponeurosis  facing  the  muscle  behind, 
gradually  narrowing,  becoming  thicker,  and  uniting  with  that  of  the 
gastrocnemius  to  form  the  deeper  part  of  the  tendon  of  Achilles.  The 
fleshy  fascicles  are  numerous  and  short,  and  continue  to  terminate  in 
the  latter  within  a  short  distance  of  the  heel. 

The  soleus  rests  against  the  posterior  tibialis  and  the  long  digital 
and  hallucal  flexors,  with  the  posterior  tibial  vessels  and  nerve  descend- 
ing between  them  and  covered  by  the  deep  fascia. 

The  tendon  of  Achilles,1  the  thickest  of  all  tendons,  is  formed  by 
the  union  of  the  terminal  aponeuroses  of  the  gastrocnemius  and  soleus. 
Broad  at  its  commencement,  it  narrows  to  a  flattened  cylindrical  cord, 
which  again  slightly  expands  on  the  heel,  and  is  inserted  into  the 
middle  of  the  back  surface  of  the  tuberosity  of  the  calcaneum.  A 
bursa  is  interposed  between  the  tendon  and  the  upper  part  of  the 
latter. 

The  plantaris  is  a  small  fusiform  muscle,  two  or  three  inches  long, 
situated  at  the  inner  side  beneath  the  outer  head  of  the  gastrocnemius. 
It  arises  from  the  femur  beneath  the  latter,  and  from  the  contiguous 
portion  of  the  capsule  of  the  knee-joint,  on  the  back  of  which  it  lies, 
and  terminates  in  a  long,  slender  tendon  which  descends  obliquely  be- 
tween the  gastrocnemius  and  soleus  to  the  inner  margin  of  the  tendon 
of  Achilles,  and  runs  along  this  to  the  heel.  It  ends  variably,  some- 
times in  the  tendon  of  Achilles,  the  adjacent  portion  of  the  deep  fascia, 
or  the  internal  annular  ligament.  The  muscle  is  frequently  absent. 

The  muscles  of  the  calf  are  supplied  by  branches  from  the  popliteal 
nerve.  They  lift  the  heel  and  raise  the  body  on  the  toes  as  in  walking. 
The  gastrocnemius  may  also  act  as  a  flexor  of  the  leg. 

The  popliteus,  a  flat,  triangular  muscle,  is  situated  below  the  back 
of  the  knee-joint,  covered  by  the  gastrocnemius.  It  arises  by  a  rounded 
tendon  from  the  lower  part  of  the  grooved  surface  on  the  outer  side 
of  the  external  condyle  of  the  femur,  under  the  capsular  and  external 
lateral  ligaments  of  the  knee-joint,  and  partly,  also,  from  the  capsule. 
Turning  around  the  groove  behind  the  outer  tuberosity  of  the  tibia, 
between  it  and  the  head  of  the  fibula,  the  fleshy  fascicles  thence  di- 
verge, and  are  inserted  into  the  inner  two-thirds  of  the  triangular  sur- 
face at  the  upper  back  part  of  the  tibia  and  into  an  investing  fascia. 
The  tendon  of  origin  lies  between  the  external  lateral  ligament  and 
the  contiguous  semilunar  cartilage  of  the  knee  invested  by  the  syno- 
vial  membrane,  which  is  prolonged  from  the  joint  upon  the  tendon 
behind  the  outer  tuberosity  of  the  tibia.  The  fascia  investing  the 

1  Tendo  Achillis. 


THE   MUSCULAR   SYSTEM. 


339 


FIG.  164. 


.  muscle  and  attached  to  the  contiguous  bony  margins  is  a  thin  aponeu- 
rosis,  mainly  an  expansion  derived  from  the  tendon  of  insertion  of  the 
semimembranosus. 

The  popliteus  is  supplied  by  a  branch  from  the  popliteal  nerve.  It  is 
the  only  muscle  which  operates  on  the  knee-joint  alone,  and  rotates  the 
leg  inwardly  in  flexion,  in  which  latter  it 
also  assists.  In  the  extended  condition  of 
the  leg  the  tendon  of  origin  lies  below  the 
groove  of  the  femur,  and  occupies  it  only 
when  the  leg  is  flexed. 

The  remaining  three  muscles  extend 
down  the  leg,  below  the  former,  into  the 
foot,  and  are  closely  invested  by  a  deep 
layer  of  the  femoral  fascia  which  sepa- 
rates them  from  the  soleus  and  is  attached 
to  the  adjacent  bony  boundaries. 

The  long  digital  flexor,1  the  inner- 
most of  the  group  of  deep  longitudinal 
muscles,  lies  on  the  tibia.  It  arises  from 
the  intermediate  half  of  the  posterior  sur- 
face of  the  tibia  commencing  below  the 
popliteus,  and  partially  from  a  thin  apo- 
neurosis  covering  the  posterior  tibialis  and 
attached  to  the  inner  border  of  the  fibula. 
The  fleshy  fascicles  pass  obliquely  down- 
ward and  converge  to  a  posterior  tendon, 
which  descends  and  passes  through  a 
canal  behind  the  inner  malleolus.  Thence 
directed  obliquely  forward  and  outward 
beneath  the  arch  of  the  calcaneum  into 
the  sole  of  the  foot,  it  divides  into  four 
tendons,  which  diverge  to  the  lesser  toes 
and  proceed  to  be  inserted  into  the  bases 
of  their  terminal  phalanges.  Behind  the 
inner  malleolus  the  tendon  is  accompa- 
nied by  that  of  the  posterior  tibialis,  but 
through  a  separate  canal  invested  with  a 
distinct  synovial  sheath.  Before  dividing 
the  tendon  receives  a  strong  offset  from 
the  contiguous  tendon  of  the  long  hallucal 
flexor,  then  expands,  and  is  further  rein- 
forced by  the  insertion  of  the  accessory  flexor  of  the  sole  of  the  foot. 
Opposite  the  first  phalanges  each  tendon  passes  through  a  slit  in  the 


DEEP  MUSCLES  OF  THE  BACK  OF  THE 
LEG.  1,  femur;  2,  posterior  portion 
of  the  capsular  ligament ;  3,  tendon 
of  the  semimembranosus  muscle  in- 
serted into  the  head  of  the  tibia,  and 
giving  an  offset  to  the  capsular  liga- 
ment; 4,  5,  internal  and  external 
lateral  ligaments;  6,  popliteus  mus- 
cle; 7,  long  digital  flexor ;  8,  posterior 
tibialis;  9,  long  hallucal  flexor;  10, 

11,  long  and  short  peroneal  muscles ; 

12,  tendon  of  Achilles;  13,  tendons 
of  the  long  digital  flexor  and  pos- 
terior  tibialis   muscles,  just  before 
passing  beneath  the  internal  annular 
ligament. 


1  M.  longus  digitorum  pedis  ;  m.  digitorum  communis  longus ;  m.  flexor  per- 
forans ;  long  or  common  flexor  of  the  toes. 


340  THE   MUSCULAR   SYSTEM. 

corresponding  tendon  of  the  short  digital  flexor,  which  also  occupies 
the  sole  of  the  foot. 

In  the  leg  the  long  digital  flexor  lies  on  the  tibia  and  the  posterior 
tibialis  muscle,  which  it  crosses  below.  Above,  it  is  covered  by  the 
soleus,  and  below  is  subcutaneous.  The  posterior  tibial  vessels  and 
nerve  descend  on  it,  covered  by  the  investing  fascia.  In  the  foot  its 
tendon  crosses  beneath  that  of  the  long  hallucal  flexor,  and  it  is 
covered  beneath  by  the  hallucal  abductor  and  short  digital  flexor. 

The  long  hallucal  flexor,1  the  largest  muscle  of  the  group,  lies  on 
the  fibula  between  the  peroneal  and  posterior  tibialis  muscles.  It  arises 
from  the  lower  two-thirds  of  the  posterior  surface  of  the  fibula,  except 
its  inferior  extremity,  from  the  lower  portion  of  the  interosseous  mem- 
brane, from  the  intermuscular  septum  between  it  and  the  peroneal 
muscles,  and  from  the  aponeurosis  covering  the  posterior  tibialis  mus- 
cle. Its  fascicles  descend  obliquely  and  converge  to  a  posterior  tendon, 
which  descends  and  passes  through  a  canal  behind  the  lower  end  of 
the  tibia,  the  astragalus,  and  beneath  the  sustentacle  of  the  calcaneum, 
and  thence  proceeds  along  the  inner  side  of  the  sole  to  be  inserted  into 
the  base  of  the  terminal  phalanx  of  the  great  toe.  The  canal  traversed 
by  the  tendon  is  completed  by  the  internal  annular  ligament,  and  is 
provided  with  a  synovial  sheath.  In  the  sole,  as  it  passes  forward  above 
the  tendon  of  the  long  digital  flexor,  it  commonly  gives  the  latter  a 
strong  reinforcing  offset.  In  the  great  toe  it  is  enclosed  in  a  digital 
canal  invested  with  a  synovial  sheath.  In  the  leg  the  muscle  is  in  great 
part  covered  by  the  soleus,  but  is  subcutaneous  outside  the  position  of 
the  tendon  of  Achilles,  and  is  in  contact  externally  with  the  peroneal 
muscles.  It  rests  on  the  fibula  and  posterior  tibialis  muscle,  and  covers 
the  peroneal  vessels.  Behind  the  ankle-joint  the  tendon  is  separated 
from  that  of  the  long  digital  flexor  by  an  interval  occupied  by  the 
posterior  tibial  vessels  and  nerve.  In  the  foot  it  is  covered  by  the  hal- 
lucal adductor,  and  proceeds  between  the  heads  of  the  short  hallucal 
flexor.  The  offset  to  the  long  digital  flexor  is  variable  in  size,  and 
sometimes  joins  the  tendons  after  the  division  of  the  chief  one. 

The  posterior  tibialis,2  placed  between  and  beneath  the  two  pre- 
ceding muscles,  arises  from  the  posterior  surface  of  the  tibia,  from  the 
popliteal  line  to  about  its  middle,  beneath  the  origin  of  the  long  digi- 
tal flexor,  from  the  inner  surface  of  the  fibula,  and  from  the  posterior 
surface  of  the  interosseous  membrane,  except  its  lower  portion,  and 
by  a  few  fascicles  from  the  investing  fascia.  The  fleshy  fascicles  pass 
obliquely  downward,  and  converge-  to  a  tendon  which  descends  along 
the  inner  back  border  of  the  muscle,  and  passes  through  a  canal  behind 
the  internal  malleolus.  Thence  the  tendon  is  directed  forward  through 


1  M.  flexor  longus  pollicis  pedis ;  m.  flexor  hallucis  longus ;  long  flexor  of  the 
great  toe. 

2  M.  tibialis  posticus  ;  m.  nauticus. 


THE   MUSCULAK   SYSTEM.  341 

a  canal  over  the  internal  lateral  ligament  of  the  ankle-joint  and  the 
internal  calcaneo-scaphoid  ligament,  and  is  inserted  into  the  prominence 
beneath  of  the  scaphoid  and  entocuneiform  bones,  giving  offsets  to  the 
other  cuneiform  bones,  the  cuboid  bone,  and  the  bases  of  the  inter- 
mediate metatarsal  bones. 

In  the  leg  the  posterior  tibialis  muscle  lies  on  the  interosseous  mem- 
brane of  the  fibula  and  tibia.  Its  lower  part  crosses 'the  tibia  obliquely 
beneath  the  long  digital  flexor,  with  its  tendon  passing  from  in  front 
to  the  inner  side  of  the  tendon  of  the  latter,  enclosed  in  a  separate 
canal  behind  the  internal  malleolus,  and  invested  with  a  synovial  sheath, 
which  extends  into  the  canal  at  the  inner  side  of  the  ankle  and  com- 
municates with  the  calcaneo-scaphoid  articulation. 

The  above  muscles  are  supplied  by  branches  of  the  posterior  tibial 
nerve.  The  long  digital  and  hallucal  flexors,  as  indicated,  are  flexors 
of  the  toes,  but  continuing  their  action  become  extensors  of  the  foot. 
The  posterior  tibialis,  with  the  peroneal  muscles,  is  also  an  extensor  of 
the  foot. 

MUSCLES  OF   THE   FOOT. 

On  the  back  of  the  foot,  besides  the  tendons  continued  from  the 
muscles  on  the  fore  part  of  the  leg,  there  are  the  short  digital  extensor 
and  four  dorsal  interosseous  muscles.  In  the  sole  there  are  numerous 
muscles,  besides  the  tendons  of  the  long  flexors,  forming  groups,  as 
those  of  the  middle  of  the  sole,  those  of  the  great  toe  and  of  the  little 
toe,  and  the  three  plantar  interosseous  muscles. 

The  short  digital  extensor.     See  page  335. 

Median  plantar  muscles.  The  short  digital  flexor1  occupies 
the  middle  of  the  sole,  covered  by  the  plantar  fascia.  It  arises  in  a 
pointed  manner  from  the  fore  part  of  the  inner  tubercle  of  the  calca- 
neum,  from  the  plantar  fascia,  and  from  the  intermuscular  septum  on 
each  side.  Expanding  forward,  it  divides  into  four  portions,  termi- 
nating in  as  many  tendons,  which  diverge  and  proceed  to  the  lesser 
toes  to  be  inserted  into  the  second  phalanges,  each  tendon  being  split 
for  the  passage  of  the  corresponding  tendon  of  the  long  digital  flexor. 

The  arrangement  of  the  tendons  of  the  short  and  long  digital  flexors, 
their  relation  with  the  attachment  of  other  muscles,  and  their  confine- 
ment in  digital  canals,  are  the  same  as  in  the  flexor  tendons  of  the 
fingers  already  described. 

The  accessory  flexor 2  is  covered  by  the  preceding.  It  arises  by 
two  heads,  of  which  the  inner  larger  one  comes  from  the  inner  concave 
surface  of  the  calcaneum  and  contiguous  portion  of  the  calcaneo- 
scaphoid  ligament,  while  the  outer  one  springs  tendinously  from  the 
calcaneum  in  front  of  its  inner  tubercle  and  from  the  long  plantar 
ligament.  Advancing,  the  two  heads  unite,  and  the  muscle  proceeds 

1  M.  flexor  brevis  digitorum  ;  m.  flexor  perforatus  ;  short  flexor  of  the  toes. 
*  M.  flexor  accessorius ;  caro  quadrata  Sylvii-;  massa  carnea  Jacobi  Sylvii. 


342 


THE   MUSCULAR  SYSTEM. 


to  be  inserted  into  the  upper  surface  and  outer  border  of  the  tendon 
of  the  long  digital  flexor.  The  outer  head  is  sometimes  absent. 

The  lumbrical  muscles,1  like  those  of  the  hand,  have  similar 
relations  and  connections.  They  arise  from  the  tendons  of  the  long 
digital  flexor :  the  outer  three  from  the  contiguous  sides  of  the  tendons ; 
the  inner  one  from  the  inner  side  of  the  corresponding  tendon.  Pro- 
ceeding forward,  they  terminate  in  narrow  tendons,  which  expand  and 
join  the  extensor  tendons  on  the  back  of  the  toes  at  the  inner  side  of 
the  first  phalanges. 

Muscles  of  the  great  toe.  Of  these  there  are  four,  mainly  form- 
ing the  fleshy  prominence  on  the  inner  side  of  the  sole. 


FIG.  165. 


FIG.  166. 


MUSCLES  OF  THE  SOLE  OF  THE  FOOT.  1,  cal- 
caneum ;  2,  posterior  extremity  of  the  plantar 
fascia;  3,  hallucal  abductor;  4,  minimal  ab- 
ductor ;  5,  short  digital  flexor ;  6,  tendon  of  the 
long  hallucal  flexor ;  7,  insertion  of  the  lumbri- 
cal muscles,  which  are  seen  to  the  right  of  the 
tendons  of  the  short  digital  flexor. 


DEEP  MUSCLES  OF  THE  SOLE.  1,  attachment  of 
the  plantar  fascia  and  short  digital  flexor ;  2, 
accessory  flexor ;  3,  tendon  of  the  long  digital 
flexor ;  4,  tendon  of  the  long  hallucal  flexor ; 

5,  two  heads  of  the  short  hallucal  flexor; 

6,  hallucal  adductor ;   7,  minimal  flexor ;  8, 
hallucal  transversalis  muscle ;  9,  interosseous 
muscles ;  10,  course  of  the  tendon  of  the  long 
peroneal  muscle,  seen  through  the  long  plantar 
ligament. 


The  hallucal  abductor 2  lies  superficially  along  the  inner  border 
of  the  sole.  It  arises  from  the  inner  tubercle  of  the  calcaneum,  the 
internal  annular  ligament  of  the  ankle,  the  intermuscular  septum  be- 
tween it  and  the  short  digital  flexor,  and  from  the  investing  plantar 
fascia.  The  fascicles  advance  and  converge  to  a  tendon  which  proceeds 

1  M.  lumbricales. 

2  M.  abductor  pollicis  pedis  ;  m.  abductor  hallucis  ;  abductor  muscle  of  the  great 
toe. 


THE   MUSCULAR   SYSTEM.  343 

forward,  is  joined  by  the  contiguous  head  of  the  short  digital  flexor, 
and  is  inserted  into  the  inner  part  of  the  base  of  the  first  phalanx  of 
the  great  toe.  Its  deep  surface  is  in  contact  with  the  tendons  of  the 
posterior  tibialis  and  long  flexor  muscles,  and  with  the  plantar  vessels 
and  nerves. 

The  short  hallucal  flexor l  lies  at  the  inner  side  of  the  metatarsus, 
covered  by  the  preceding  muscle.  It  arises  by  a  tendinous  process  from 
the  inner  border  of  the  cuboid  bone  and  by  an  offset  from  the  posterior 
tibialis  tendon  inserted  into  the  adjacent  portion  of  the  ectocuneiform 
bone.  It  forms  two  muscular  bellies,  which  proceed  together  and 
terminate  in  tendons,  of  which  the  inner  joins  that  of  the  hallucal 
abductor  and  the  outer  one  the  hallucal  adductor  to  be  inserted  into 
the  sides  of  the  base  of  the  first  phalanx  of  the  great  toe.  The  sesa- 
moid  bones  are  embedded  in  the  tendons  of  insertion,  and  play  on  the 
lateral  articular  surfaces  of  the  head  of  the  metatarsal  bone.  The 
tendon  of  the  long  hallucal  flexor  lies  between  the  two  portions  of  the 
short  flexor. 

The  hallucal  adductor 2  lies  beneath  the  metatarsus  to  the  outer 
side  of  the  former.  It  arises  from  the  bases  of  the  intermediate  meta- 
tarsal bones  and  from  the  long  plantar  ligament  sheathing  the  [long 
peroneal  tendon,  and  proceeds  obliquely  forward  and  inward  to  unite 
with  the  outer  tendon  of  the  short  hallucal  flexor  in  its  insertion  into 
the  first  phalanx  of  the  great  toe. 

The  hallucal  transverse  muscle 3  is  placed  at  the  fore  part  of 
the  metatarsus  above  the  flexor  tendons.  It  arises  by  fleshy  fascicles 
from  the  inferior  metatarso-phalangeal  ligaments  of  the  outer  three 
toes  and  from  the  transverse  metatarsal  ligament,  and  proceeds  directly 
inward  to  be  inserted  tendinously,  in  conjunction  with  the  hallucal  ad- 
ductor, into  the  base  of  the  first  phalanx  of  the  great  toe.  The  fascicle 
from  the  little  toe  is  sometimes  absent. 

Muscles  of  the  little  toe.  Of  these  there  are  two,  lying  along 
the  inner  side  of  the  sole  of  the  foot. 

The  minimal  abductor4  is  subcutaneous  at  the  outer  part  of  the 
sole.  It  arises  from  the  outer  tubercle  of  the  calcaneum  and  from  the 
bone  in  advance  of  both  tubercles,  from  the  adjacent  intermuscular 
septum,  and  from  a  strong  band  of  investing  fascia  extended  from  the 
calcaneum  to  the  base  of  the  last  metatarsal  bone.  Thence  the  fasci- 
cles advance  and  converge  to  a  tendon,  which  glides  over  a  smooth 
depression  beneath  the  base  of  the  last  metatarsal  bone,  and  proceeds 
to  be  inserted  into  the  outer  part  of  the  base  of  the  first  phalanx  of 

1  M.  flexor  brevis  pollicis  pedis ;  m.  flexor  brevis  hallucis ;  short  flexor  muscle 
of  the  great  toe. 

2  M.  adductor  pollicis  pedis  ;  m.  adductor  hallucis  ;  adductor  muscle  of  the  great 
toe. 

s  M.  transversus  pedis ;  caput  breve  or  transversum  adductoris  hallucis. 
4  M.  abductor  minimi  digiti ;  m.  abductor  digiti  quinti. 


344  THE    MUSCULAE  SYSTEM. 

the  little  toe.  The  deep  surface  of  the  muscle  lies  in  contact  with  the 
outer  head  of  the  accessory  flexor,  the  minimal  flexor,  the  long  plantar 
ligament,  and  the  long  peroneal  tendon. 

The  minimal  flexor1  lies  at  the  outer  part  of  the  metatarsus 
above  the  preceding.  It  arises  tendinously  from  the  base  of  the  fifth 
metatarsal  bone  and  the  adjacent  portion  of  the  long  plantar  ligament, 
and  proceeds  forward  to  be  inserted  by  a  tendon  into  the  outer  part 
of  the  base  of  the  first  phalanx  of  the  little  toe.  Not  unfrequently 
some  of  its  fascicles  are  inserted  into  the  outer  fore  part  of  the  meta- 
tarsal bone. 

The  interosseous  muscles 2  accord  in  number,  relative  position, 
and  attachments  with  those  of  the  hand. 

The  dorsal  interosseous  muscles 3  are  penniform,  and  occupy 
the  intervals  of  the  metatarsal  bones  on  the  back  of  the  foot.  Each 
arises  from  the  adjacent  sides  of  the  metatarsal  bones,  and  proceeds 
forward,  terminating  in  a  tendon,  which  is  inserted  into  the  base  of  the 
first  phalanx  and  into  the  extensor  tendon  on  the  back  of  the  latter. 
The  first  two  are  inserted  on  each  side  of  the  second  toe,  the  others 
on  the  outer  side  of  the  third  and  fourth  toes.  At  the  proximal  end 
of  each  muscle  is  an  angular  interval,  which  gives  passage  to  the  com- 
municating blood-vessels. 

The  plantar  interosseous  muscles4  arise  from  the  lower  and 
inner  surfaces  of  the  third,  fourth,  and  fifth  metatarsal  bones,  and  are 
inserted  in  the  same  manner  as  the  preceding  muscles  into  the  first 
phalanges  and  the  extensor  tendons  on  the  inner  side  of  the  correspond- 
ing toes. 

Of  the  muscles  of  the  sole  of  the  foot,  the  short  digital  flexor,  the 
hallucal  abductor  and  short  flexor,  and  the  inner  two  lumbrical  muscle& 
are  supplied  by  the  internal  plantar  nerve ;  all  the  others,  including 
the  interossei,  are  supplied  by  the  external  plantar  nerve. 

1  M.  flexor  brevis  minimi  digiti ;  m.  flexor  brevis  digiti  quinti. 

2  M.  interossea  pedis.  3  M.  i.  dorsales.  *  M.  i.  plantares. 


CHAPTEE    YI. 

GENERAL  COMPOSITION  OP  THE  SKIN,  THE  MUCOUS 
MEMBRANES,  THE  GLANDS,  THE  LUNGS,  THE  SEROUS 
AND  SYNOVIAL  MEMBRANES,  AND  THE  LINING  OF 
THE  VASCULAR  SYSTEM. 

MANY  parts  of  the  body  are  composed  of  similar  anatomical  ele- 
ments, arranged  in  the  same  relative  position.  They  are  chiefly  the 
skin,  the  mucous  membranes,  the  glands,  the  lungs,  the  serous  and 
synovial  membranes,  and  the  lining  of  the  vascular  system.  The  ana- 
tomical elements  are  a  cellular  structure,  of  one  or  more  layers,  resting 
on  a  basis  which  is  commonly  composed  of  nbro-connective  tissue,  with 
blood-vessels,  lymphatics,  and  nerves. 

The  cellular  structure  is  composed  of  distinct  cells  united  by  a 
cementing  substance,  and  is  in  some  cases  directly  supplied  with  nerve- 
fibrils.  In  most  parts  it  is 

named  the  epithelium,  in  ^^^^^^^^^^J^ 
others  is  distinguished  as  the 
endothelium,  and  in  the  skin 
is  the  epidermis.  The  basis 
of  support  of  the  cellular 
structure  in  mucous  mem  DIAGRAM  EXHIBITING  THE  RELATIVE  POSITION  OF  THE 

COMMON  ANATOMICAL  ELEMENTS  OF  SEROUS  AND  MUCOUS 

branes    is    distinguished    as       MEMBRANES,  THE  GLANDS,  THE  LUNGS,  AND  THE  SKIN. 

the  mUCOSa,  in  the  skin  as       *>  cellular   layer;    2>  basement   membrane;    3,  fibro- 

connective-tissue  layer,  with  blood-vessels,  4. 
the  corium,  in  glands  and 

other  parts  as  the  membrana  propria,  and  in  serous  and  allied  mem- 
branes as  the  serosa.  It  is  variable  in  thickness  and  strength,  and 
ordinarily  consists  of  fibre-connective  tissue  defined  by  a  delicate  and 
apparently  homogeneous  layer,  the  basement  membrane,  which  is 
composed  of  thin  plates  or  flattened  cells.  To  the  supporting  basis 
generally  the  blood-vessels  are  distributed,  ending  in  capillary  nets  be- 
neath the  basement  membrane ;  and  in  the  same  position  commence 
the  lymphatics.  Nerves,  also,  ordinarily  terminate  in  this  basis,  but  in 
some  cases,  as  in  the  conjunctiva  and  the  skin,  extend  into  the  .cellular 
structure. 

EPITHELIAL   TISSUE. 

The  epithelial  tissue,  or  epithelium,  is  the  distinct  cellular 
structure  which  forms  the  free  surface  of  mucous,  serous,  and  syno- 
vial membranes  and  of  the  skin,  the  essential  glandular  substance, 
and  the  lining  of  the  vascular  system,  including  the  capillaries.  Com- 

345 


346  EPITHELIAL   TISSUE. 

monly,  in  its  more  restricted  sense,  the  term  epithelium  is  applied  to 
the  superficial  cell-structure  of  the  mucous  membranes,  including  the 
lining  of  the  air-cells  of  the  lungs  and  that  of  the  recesses  of  glands. 
The  corresponding  layer  of  the  serous  and  synovial  membranes  and  of 
the  vascular  system  is  often  distinguished  as  the  endothelium  ;  while 
that  of  the  skin  is  named  the  epidermis. 

The  epithelium,  in  general,  is  composed  exclusively  of  cells,  in  one, 
several,  or  many  layers,  and  closely  joined  together  by  a  cementing 
substance.  Blood-vessels  never  enter  the  cell-structure,  but  terminate 
in  capillary  nets  beneath  the  epithelium.  In  some  cases  nerves,  as 
finely-beaded  ultimate  nerve-fibrils,  are  distributed  among  the  cells, 
as  exemplified  in  the  conjunctiva  of  the  eye. 

When  an  epithelium  consists  of  a  single  characteristic  cell-layer  it 
is  called  a  simple  epithelium,  and  when  of  several  or  many  layers  it 
is  a  stratified  epithelium. 

The  epithelial  cells1  differ  greatly  in  shape,  structure,  and  com- 
position in  different  epithelia,  and  often,  likewise,  in  the  same  epithe- 
lium. 

Of  the  simple  epithelia  there  are  several  kinds,  distinguished  as  the 
pavement,  the  columnar,  and  the  polyhedral  epithelium. 

The  pavement  epithelium  2  is  the  most  common  kind,  and  is  ex- 

emplified by  that  of  the  air-cells 

FIG.  168.  of  fae  lungs  and  nearly  all  the  en- 

dothelia.  It  is  composed  of  clear, 
thin  plates,  or  flat,  scale-like  cells, 
cemented  together  at  the  edges. 
Ordinarily  their  limits  are  very 
PAVEMENT  EPITHELIUM,  from  a  serous  mem-  obscure,  but  become  distinctly  de- 


brane,  highly  magnified,  and  seen  to  consist  of  fined  fe  Wack  ]ineg  throUgh  the 
flat,  six-sided,  nucleated  cells.  J 

action  of  a  solution  of  silver  ni- 

trate. In  the  endothelium  of  serous  membranes  the  cells  are,  for  the 
most  part,  hexagonal  with  straight  outlines  ;  in  that  of  the  vascular 
system  they  are  mostly  elongated,  lozenge-shaped  with  sinuous  out- 
lines, or  lanceolate  with  more  even  outlines.  The  cells  have  a  central 
round  or  oval  nucleus,  from  which  they  thin  away  to  the  edge  ;  so  that 
in  profile  section  the  cells  appear  narrow  fusiform.  The  remaining  con- 
tents are  small  in  quantity,  mostly  homogeneous,  and  sometimes  finely 
granular. 

The  simple  columnar  epithelium  3  is  exemplified  by  that  of  the 
entire  alimentary  canal  from  the  termination  of  the  oasophagus,  that  of 
the  nasal  cavities  and  adjacent  part  of  the  pharynx,  of  the  air-passages, 
of  many  ducts  and  recesses  of  glands,  of  the  urethra,  and  of  the  uterus 
and  oviducts.  It  is  composed  of  a  single  layer  of  six-sided  columnar 

1  Epithelia.  2  Tessellated,  squamous,  or  scaly  epithelium. 

8  Cylinder  epithelium. 


EPITHELIAL   TISSUE. 


347 


FIG.  169. 


DIAGRAM  OF  A  VERTICAL  SECTION  OF  MUCOUS  MEM- 
BRANE OF  THE  SMALL  INTESTINE,  highly  magnified. 
1,  fibro-connective-tissue  layer,  in  which  the  blood- 
vessels are  distributed ;  2,  basement  membrane ;  3, 
young  nucleated  cells ;  4,  layer  of  columnar  cells; 
5,  6,  cells  in  the  act  of  being  shed  or  thrown  off ;  7, 
free  ends  of  the  columnar  cells,  exhibiting  their 
six-sided11  form  ;  8,  a  single  columnar  cell,  exhibit- 
ing its  prismatic  form. 


cells,  standing  upright  on  the  surface  of  support  and  closely  con- 
joined. Viewed  laterally,  they  present  a  palisade-like  arrangement, 
and  seen  on  the  free  extremities  they  have  a  six-sided  alveolate  appear- 
ance. The  cells  are  comparatively  soft,  and  the  hexahedral  form  is  due 
to  mutual  pressure,  so  that 
when  isolated  they  are  dis- 
posed to  assume  a  more  cylin- 
drical shape.  They  differ  in 
exact  form,  dimensions,  and 
structure  in  different  positions, 
and  also  vary  more  or  less  in 
the  same  position.  They  are 
mostly  much  longer  than  the 
thickness,  but  in  some  of  the 
narrower  glandular  ducts  are 
so  short  as  to  appear  cubical 
in  the  side  view.  In  many 
positions  they  are  of  uniform 
thickness,  but  vary  with  the 
form  of  the  surface  on  which 
they  stand,  so  that  in  a  tube 
they  will  be  wider  at  the  bot- 
tom of  the  cell  than  at  the  free  end,  so  as  to  conform  to  the  curvature 
of  the  tube.  More  commonly,  columnar  cells  taper  at  their  lower  or 
attached  extremity,  and  the  intervals  between  them  are  occupied  by 
immature  cells,  which  conform  in  shape  to  the  latter.  The  sides  of 
the  cells  are  even,  but  sometimes  are  rendered  more  or  less  uneven  by 
irregular  processes ;  and  the  tapering  extremity  may  be  pointed  at  the 
end,  or  variably  expanded,  or  divided  into  diverging  processes. 

The  columnar  cells  have  a  large,  central,  commonly  oval  nucleus, 

which  in  the  narr<5wer  forms  produces  a 
bulging  at  the  middle  of  the  cell.  They 
are  provided  with  a  delicate  wall,  which 
is  usually  thicker  at  the  free  extremity 
and  thinnest  at  the  bottom.  The  con- 
tents, enclosing  the  nucleus,  consist  of 
a  soft  protoplasm  with  a  clouded  or 
faintly  granular  appearance,  sometimes 
mingled  with  more  distinct  granules. 

In  the  intestinal  epithelium  the  free 
extremity  of  the  columnar  cells  is  de- 
fined by  a  conspicuous  thickening  of  the  wall,  forming  a  terminal  plate, 
which  is  vertically  finely  striated.  The  stria?  are  considered  either  to 
be  minute  pores,  or  lines  of  separation  between  solid  rods  of  which  it 
is  supposed  the  plate  is  composed. 

A  remarkable  variety  is  the  ciliated  columnar  epithelium,  in 


FIG.  170. 


COLUMNAR  EPITHELIUM,  from  the 
mucous  membrane  of  the  small  intes- 
tine. 


348 


EPITHELIAL  TISSUE. 


FIG.  171. 


DIAGRAM  OF  A  VERTICAL  SECTION  OF 
THE  BRONCHIAL  MUCOUS  MEMBRANE, 
highly  magnified.  1,  columnar  cili- 
ated epithelial  cells ;  2,  cilia ;  3,  nu- 
clei ;  4,  young  cells ;  5,  basement 
membrane ;  6,  fibro-connective-tissue 
layer. 


which  the  cells,  instead  of  the  terminal  plate  as  in  those  last  described, 
are  provided  with  a  tuft  of  exceedingly  fine  hair-like  processes,  named 

cilia,1  from  their  resemblance,  in  the  ordi- 
nary view  of  the  cells  under  the  micro- 
scope, to  an  eyelash.  The  cilia,  during 
life  and  for  some  time  after  death,  exhibit 
an  incessant  and  rapid  vibratory  motion, 
and  serve  to  sweep  secretions  from  sur- 
faces. They  are  found  in  most  classes  of 
animals,  in  which  they  often  serve  the 
most  important  functions,  and  in  many  of 
the  lowest  forms  are  the  chief  organs  of 
locomotion.  The  ciliated  epithelium,  in 
man  and  his  class,  lines  the  nasal  cavities 
and  communicating  sinuses,  the  contiguous 
portion  of  the  pharynx,  eustachian  tube, 
and  tympanum,  the  larynx  and  succeeding  air-passages,  the  ventricles 
of  the  brain  in  part  and  the  central  canal  of  the  spinal  cord,  the  epi- 
didymis,  the  uterus,  and  the  oviducts. 

In  the  trachea  the  ciliated  columnar  cells  are  about  -g-^j-  of  an  inch 
long,  and  their  cilia  about  ^  the  length  of  the  cell ;  in  the  epidulymis 
the  cells,  about  the  same  length,  have  their  cilia  more  than  half  that 
of  the  cell. 

Certain  columnar  cells,  found  in  the  smaller  ducts  of  the  salivary 
glands  and  tubules  of  the  kidney,  enlarge  downward  or  towards  their 
base,  and  to  a  variable  extent  from  the  latter  position  present  a  longi- 
tudinally striated  appearance,  which  appears  to  be  due  to  the  cell  being 
divided  into  a  tuft  of  rod-like  processes. 

In  the  columnar  epithelium  there  often  occur,  here  and  there  among 
the  others,  usually  isolated  cells,  which,  from  their  form,  have  been  called 
goblet-cells.2  They  appear  as  the  product 
of  transformation  of  the  ordinary  cells,  with 
the  upper  part  of  the  cell  expanded  by  an 
ovoid  mass  of  clear  mucus,  devoid  of  the 
terminal  covering,  and  with  the  granular 
protoplasm  and  nucleus  confined  to  the 
lower  part  of  the  cell. 

A    simple     polyhedral    epithelium3 
forms  the  essential  cell-structure  of  many 
glands,  occupying  their  commencing  folli- 
cles or  alveoli,  as  in  the  salivary,  lachrymal,  peptic,  duodenal,  and  mam- 
mary glands  and  the  pancreas.     From  its  usual  position,  the  polyhedral 
epithelium,  even  when  not  simple,  as  in  the  sebaceous  glands  and  tes- 


FIG.  172. 


COLUMNAR  EPITHELIUM,  from  an 
intestinal  villus.  a,  goblet  cells ; 
b,  ordinary  columnar  cells. 


1  Gils ;  vibrillae. 

3  Spheroidal  epithelium. 


2  Chalice  or  beaker  cells. 


EPITHELIAL   TISSUE. 


349 


ticje,  or  having  other  relations,  as  in  the  liver,  is  also  called  glandular 
epithelium.1     It  commonly  consists  of  soft,  polyhedral  cells,  of  which 


FIG.  173. 


FIG.  174. 


POLYHEDRAL  EPITHELIUM,  exemplified  by 
secreting  cells  of  the  liver.  The  arrange- 
ment is  ideal.  1,  space  occupied  by  a  blood- 
vessel ;  2,  isolated  cells. 

the  form  is  mainly  due  to  sur- 
rounding pressure,  so  that  when 
isolated  they  assume  a  more 
spheroidal  shape.  They  are  or- 
dinarily composed  of  a  soft, 
granular  protoplasm,  with  a 
central  nucleus,  and  no  definite 
cell- wall;  and  the  protoplasm 
contains  the  peculiar  materials 
which  are  secreted  by  the  glands, 
glandular  epithelium  will  be  given 
While  there  is  no  well-marked 


SECTION  OF  THE  SUBMAXILLARY  GLAND.  Alveoli 
of  connective  tissue  containing  the  secretory  cells, 
—a  polyhedral  epithelium,  a,  cells  containing 
mucus.';  b,  cells^with  granular  protoplasm  ;  c,  cres- 
centic  parietal  cells ;  d,  duct  with  striated  colum- 
nar epithelial  cells. 

A  more  particular  description  of  the 
in  the  special  account  of  the  glands, 
separation  between  the  simple  and 


FIG.  175. 


DIAGRAM  OF  STRATIFIED  EPITHELIUM  OF  THE  CORNEAL  CONJUNCTIVA,  highly  magni- 
fied. 1,  deep  layer  of  columnar  cells ;  2,  layers  of  polyhedral  cells ;  3,  broader  cells  at 
the  surface.  Between  the  deeper  cell  layers  the  intercellular  channels  are  observed. 

the  stratified  epithelium,  and  one  may  be  said  to  merge  into  the 
other,  the  latter  is  distinguished  as  containing  more  than  several,  and 


Secretory  or  secreting  cells. 


350 


EPITHELIAL   TISSUE. 


usually  many,  distinct  layers  of  cells,  which  greatly  differ  from  one  an- 
other in  shape,  in  size,  and  often  in  composition.  The  stratified  epithelia 
of  mucous  membranes  are  those  of  the  conjunctiva  of  the  eye,  of  the 
mouth,  lower  part  of  the  pharynx,  and  oesophagus,  of  the  ureters  and 
urinary  bladder,  and  of  the  vagina,  with  the  lower  portion  of  the  neck 
of  the  uterus.  The  epidermis  belongs  to  the  stratified  epithelium,  is 
remarkable  for  the  great  number  and  variety  of  its  constituent  layers, 
and  will  be  especially  described  in  the  account  of  the  skin. 

The  epithelium  of  the  uterus  and  urinary  bladder  consists  of  com- 
paratively few  layers  of  cells,  and  has  been  distinguished  as  transitional 
epithelium,  though  the  transition  is  really  not  greater  than  in  those 

FIG.  176. 


FIG.  177. 


EPITHELIUM  OFTHE  URINARY  BLADDER,  highly 
magnified.  1,  superficial  layer  of  flattened  poly- 
hedral cells ;  2,  columnar  cells ;  3,  deep  layers 
of  irregular  polyhedral  cells. 


SQUAMOUS  EPITHELIUM,  consisting  of  nucle- 
ated cells,  as  broad  plates  or  scales.  Scraped 
from  the  inside  of  the  mouth,  and  highly 
magnified. 


epithelia  which  consist  of  more  numerous  layers.  It  will  be  more  par- 
ticularly described  in  an  account  of  the  urinary  organs. 

Generally  in  the  stratified  epithelium  the  deepest  layer  is  of  colum- 
nar form,  while  that  which  immediately  follows  consists  of  polyhedral 
cells  of  equal  breadth  and  depth.  In  the  next  layers  the  cells  are  also 
polyhedral,  but  are  successively  larger,  of  greater  breadth  and  propor- 
tionately less  depth,  and  finally  merge  into  superficial  layers  of  squa- 
mous  epithelium,  consisting  of  broad,  flat  scales,  which  do  not,  as  in 
pavement  epithelium,  conjoin  at  the  edges,  but  overlap  one  another. 
The  cells  of  the  different  layers  differ  not  only  in  form  and  size,  but 
also  in  constitution.  The  deeper  cells  consist  of  soft,  granular  masses 
of  protoplasm,  containing  a  large,  distinct  nucleus,  while  the  superficial 
scales  appear  as  clear  corneous  plates,  with  scarcely  any  contents. 

The  cells  of  the  deeper  layers  of  the  stratified  epithelium  are  not 
closely  applied  to  one  another  throughout,  but  are  minutely  ridged, 
and  the  ridges  conjoin  so  as  to  leave  intercellular  channels  communi- 
cating with  one  another  among  the  cells.  Later  researches  would 
indicate  the  existence  of  a  similar  arrangement  in  the  simple  columnar 
epithelium. 

The  deepest  cells  of  the  stratified  epithelium  incessantly  multiply 
through  division,  and  as  the  new  cells  grow  they  compress  and  push 


SEROUS   MEMBRANES. 


351 


FIG.  178. 


away  those  previously  formed.  As  the  older  cells  are  successively 
shifted  towards  the  surface  of  the  epithelium  they  undergo  transfor- 
mation, and  finally  become  the  superficial  scales,  which  are  shed  or 
removed  by  abrasion,  while  other  cells  are  produced  beneath. 

SEKOITS   MEMBRANES. 

The  serous  membranes  *  line  closed  cavities  of  the  body,  and  are 
thence  reflected  upon  and  invest  the  organ  or  organs  contained  within 
the  cavities.  The  lining  membrane  is  named 
its  parietal  portion,  and  the  other  the  re- 
flected or  visceral  portion.  Together  the 
two  portions  of  the  membrane  form  a  closed 
sac,  with  its  cavity  exterior  to  the  organ, 
which,  as  it  were,  is  thrust  from  behind  from 
the  parietal  portion  of  the  sac  into  the  re- 
flected portion.  The  opposed  free  surfaces 
of  the  two  portions  of  the  membrane,  on  the 
interior  of  the  sac,  are  always  maintained 
in  contact,  are  smooth  and  shining,  and  are 
moistened  by  a  thin  liquid,  the  serum. 
This  resembles  the  serum  of  blood,  and  is 
derived  from  the  membrane,  which  it  lubri- 
cates, and  thus  facilitates  the  movements  of 
the  parts  on  each  other.  The  serous  mem- 
branes are  attached  to  the  subjacent  parts 
by  areolar  tissue,  named  the  subserous 
tissue,  which  varies  in  the  firmness  of  its 
connection  in  different  positions,  and  in  some  cases  is  more  or  less  prone 
to  the  accumulation  of  fat.  The  serous  membranes  are  thin,  colorless, 
and  transparent,  permitting  the  subjacent  structures  to  shine  through. 
They  are  moderately  strong,  extensible,  and  elastic,  so  that  they  do 
not  wrinkle  in  the  ordinary  contraction  of  the  parts  with  which  they 
are  connected. 

The  most  extensive  of  the  serous  membranes  is  the  peritoneum, 
lining  the  abdomen  and  reflected  upon  the  contained  viscera.  The 
many  attachments  of  the  latter,  by  means  of  the  doublings  or  folds  of 
the  membrane  passing  from  the  walls  of  the  cavity,  are  usually  called 
ligaments,  though  some  are  called  by  special  names,  as  the  mesentery 
and  mesocolon.  Other  folds  extend  between  the  contiguous  viscera, 
such  as  the  small  and  great  omenta.  The  pleurae  are  serous  mem- 
branes, of  which  one  lines  the  cavity  of  the  chest  on  each  side,  and  is 
thence  reflected  on  and  closely  invests  the  corresponding  lung.  The 
fibrous  bag,  the  pericardium,  enclosing  the  heart,  is  lined  by  the  serous 
pericardium,  and  is  thence  reflected  on  and  invests  the  heart.  The 


DIAGRAM  EXHIBITING  THE  RELA- 
TION OF  A  SEROUS  MEMBRANE,  THE 
PLEURA,  TO  THE  ORGAN  IT  INVESTS 
AND  THE  CAVITY  IT  LINES.  1,  lung  ; 

2,  root  of  the  lung,  which  is  the 
only  attached  portion  of  the 
organ  ;  3,  side  of  the  thorax ;  4, 
diaphragm  ;  5,  parietal  pleura ;  6, 
pulmonary  or  reflected  pleura ;  7, , 
cavity  of  the  pleura. 


1  Membranae  serosse. 


352 


SEROUS    MEMBRANES. 


scrotum  on  each  side  is  lined  by  a  serous  membrane,  the  vaginal  tunic, 
which  thence  invests  the  corresponding  testicle. 

The  serous  membranes  are  composed  of  a  distinct  cellular  layer,  the 
endothelium,  which  occupies  the  free  surface  and  rests  on  the  serosa, 
a  thin  connective-tissue  layer  defined  from  the  former  by  a  delicate 
basement  membrane. 

The  endothelium l  consists  of  a  simple  layer  of  pavement  epithe- 
lium, thin,  clear,  polygonal  plates,  which  are  flattened,  nucleated  cells : 
the  nucleus  being  thicker  than  the  cell  beyond  its  periphery,  in  profile 
the  latter  appears  narrowly  fusiform.  The  cells  of  the  endothelium 
are  united  at  their  edges  by  a  cement  which  has  the  same  refractive 
power  as  the  cells,  so  that  they  seem  to  be  continuous,  but  become 

distinctly    defined    by    sil- 

EIG.  179.  ver  nitrate,  which  blackens 

the  cement.  The  cells  are 
mostly  hexagonal,  but  vari- 
able. The  nucleus,  also  ren- 
dered more  visible  by  cer- 
tain reagents,  as  carmine 
or  haBmatoxylin  solution,  is 
usually  round  and  central. 
The  prolonged  action  of  sil- 
ver nitrate  renders  the  pro- 
toplasmic contents  of  the 
cells  more  evident,  and  gives 
to  them  a  finely  granular 
aspect. 

The  endothelial  cells  of 
the  same  membrane  are  not 
uniform;  as  in  many  posi- 
tions patches  of  larger  cells 
alternate  with  those  of 

smaller  size.  The  larger  cell-areas  generally  lie  on  fibro-connective- 
tissue  bundles  of  the  serosa,  while  the  smaller  cells  occupy  the  inter- 
vals of  the  latter  over  lymphatic  clefts  and  vessels.  There  occurs  here 
and  there  between  the  cells  an  appearance  of  angular  apertures,  called 
pseudostomata,  filled  with  intercellular  cement.  In  the  smaller  cell- 
areas  of  the  pleurae  and  the  peritoneum,  especially  where  this  invests 
the  diaphragm,  and  in  the  great  omentum,  there  appear  true  openings, 
or  stomata.  These  are  surrounded  by  a  circle  of  thicker  and  more 
granular  cells,  and  communicate  between  the  cavity  of  the  serous 
membrane  and  the  subjacent  Ivmphatic  spaces  and  vessels  of  the 
serosa  and  subserous  tissue. 

In  the  growth  and  extension  of  some  of  the  folds  of  the  peritoneum, 


DIAGRAM  or  A  PORTION  OF  THE  PERITONEAL  SURFACE 
OF  THE  DIAPHRAGM.  1, 1,  tendinous  bundles  covered  by 
a  pavement  endothelium  of  polygonal  cells ;  2,  interval 
over  a  lymph-channel  covered  with  smaller  cells;  3, 
pseudostomata,  apparent  openings  filled  with  intercel- 
lular cement ;  4,  stomata,  or  openings  surrounded  by 
granular  cells. 


1  Serous  epithelium. 


SYNOVIAL,   MEMBRANES.  353 

as  in  the  omenta,  the  layers  become  very  thin  and  are  pierced  by  in- 
numerable holes,1  as  if  torn  through  distention.  In  these  cases  the 
endothelium  becomes  folded  around  the  reticular  bands  of  the  sub- 
jacent tissues,  including  the  serosa,  the  subserous  tissue,  with  vessels, 
and  often  more  or  less  fat. 

The  serosa  is  a  delicate  intertexture  of  fibre-connective  tissue  with 
elastic  fibres,  defined  from  the  endothelium  by  a  thin  basement  mem- 
brane, and  continuous  beneath  with  the  subserous  tissue. 

The  capillary  blood-vessels  of  serous  membranes  form  a  wide-meshed 
net,  in  the  serosa  and  subserous  tissue,  communicating  with  numerous 
branches  of  the  nearest  arteries  and  veins  of  the  subjacent  structures 
or  of  the  vessels  passing  between  the  folds  of  the  membrane.  The 
largest  arterial  branches  and  accompanying  veins,  in  many  positions, 
especially  in  the  folds  of  the  peritoneum,  traverse  tracts  of  lymphoid 
tissue,  which  is  most  marked  in  youth,  and  in  the  advance  of  life 
becomes  more  or  less  transformed  into  fat.  Lymphatics  are  abundant 
in  the  serous  membranes,  commencing  in  plexuses  of  the  serosa  and 
subserous  tissue,  and  thence  pursuing  the  course  of  the  blood-vedsels. 
The  nerves,  except  those  which  follow  the  chief  vessels,  are  compara- 
tively few,  and  end  in  fine  plexuses  of  the  subserous  tissue  and  the 
serosa. 

SYNOVIAL   MEMBRANES. 

The  synovial  membranes  are  of  the  nature  of  the  serous 
membranes,  and  have  the  same  function,  that  of  lubricating  surfaces 
which  habitually  move  upon  each  other,  as  in  the  joints  of  the  skele- 
ton and  in  the  grooves  which  give  passage  to  tendons.  They  furnish 
a  liquid,  named  synovia,  which  is  much  more  viscid  than  the  liquid 
of  the  serous  membranes,  resembles  in  its  composition  and  qualities 
the  white  of  egg,  and  is  well  adapted  to  the  purpose  of  reducing 
friction  and  facilitating  motion.  Its  employment  in  the  animal  is 
like  that  of  the  lubricating  oil  in  machinery.  The  synovial  mem- 
branes are  distinguished  as  articular,  and  as  synovial  bursse,  and 
sheaths. 

The  articular  synovial  membrane 2  occupies  the  movable  joints 
of  the  skeleton.  It  closely  and  evenly  lines  the  interior  surface  of  the 
capsular  ligament,  and  is  thence  reflected  on  the  borders  of  the  artic- 
ular cartilages,  but  does  not  extend  over  them.  In  like  manner  in  the 
joints  with  interarticular  cartilages  it  is  reflected  to  the  surfaces  of 
these,  but  does  not  entirely  cover  them.  In  many  of  the  joints  com- 
monly a  fold  of  the  synovial  membrane  projects  into  the  cavity  around 
the  periphery  of  the  articulation.  The  synovial  folds 3  are  strength- 

1  Fenestrated  membrane.  Capsula  synovialis. 

3  Plicae  synoviales,  vasculosse,  or  adiposse  ;  ligamenta  mucosa ;  Haversian  fringes ; 
glands  of  Havers. 

23 


354  SYNOVIAL,   MEMBRANES. 

ened  by  connective  tissue,  and  their  thin  free  border  is  usually  fringed 
with  numerous  irregular  villous  processes.1  The  larger  folds,  like  those 
of  the  knee-joint,  contain  considerable  fat,  and  in  a  measure  serve  as 
cushions.  In  the  foetus  the  synovial  membrane  lines  the  joints 
throughout,  but  subsequently  becomes  obliterated  on  the  opposed  ar- 
ticular cartilages,  apparently  as  if  from  the  friction  to  which  they  are 
subjected. 

The  synovial  bursa 2  is  a  simple  pouch,  in  certain  positions  inter- 
posed between  surfaces  which  move  upon  each  other,  to  alleviate  fric- 
tion. The  pouch  is  closed  and  flattened,  and  is  attached  by  its  exte- 
rior to  the  adjacent  moving  parts,  while  its  interior  opposed  surfaces 
are  in  contact  and  lubricated  with  synovia.  It  is  generally  situated 
between  a  muscle  or  its  tendon,  and  a  bone  or  the  exterior  of  a  joint, 
and  sometimes  between  two  muscles  or  tendons.  Those  contiguous  to 
joints  frequently  communicate  with  them,  so  that  the  bursa  appears 
to  be  a  continuation  of  the  synovial  membrane  of  the  articulation. 
Others,  named  from  their  position  subcutaneous  bursse,  are  placed 
immediately  beneath  the  skin  over  bony  prominences,  as  on  the  elbow 
and  knuckles,  on  the  patella  and  malleoli,  and  on  the  heel.  These  differ 
from  the  former  in  their  less  distinct  character,  and  in  the  more  or 
less  irregular  condition  of  the  interior  surfaces,  which  give  them  the 
appearance  of  a  lacerated  cleft  in  the  surrounding  fibre-connective 
tissue. 

The  synovial  sheath3  lines  bony  and  ligamentous  canals,  and 
invests  the  tendons  traversing  the  latter ;  and  is  intended  to  facilitate 
the  movement  of  the  tendons  in  the  canals.  The  sheath  lines  the 
passage,  to  which  it  is  closely  adherent,  and  is  thence  reflected  on  the 
tendon  or  tendons,  which  it  closely  invests  ;  and  the  intervening  sur- 
faces lie  in  contact,  and  are  lubricated  with  synovia.  The  canals  of 
the  fingers  and  toes,  formed  by  the  phalanges  and  the  vaginal  liga- 
ments, enclosing  the  flexor  tendons,  are  occupied  by  such  a  sheath. 
The  carpal  canal  is  lined  by  a  synovial  sheath,  which  is  complexly 
folded  as  it  invests  the  numerous  tendons  which  pass  through  the 
canal. 

The  synovial  membrane  is  composed  of  a  basis  of  fibro-connective 
tissue  intimately  associated  with  the  similar  tissue  of  the  capsular  lig- 
ament or  other  subjacent  parts.  The  free  surface  consists  of  an  endo- 
thelium  like  that  of  serous  membranes,  but  commonly  is  not  so  dis- 
tinctly obvious ;  is  variously  described,  and  as  a  continuous  complete 
layer  has  been  disputed.  At  the  margin  of  the  articular  synovial 
membrane  its  cells  appear  to  merge  into  the  condition  of  connective- 
tissue  corpuscles. 

1  Villi  synoviales ;  glandulse  articulares,  mucilagineae,  or  Haversii. 

2  Bursa  mucosa  or  synovialis. 

8  Vagina  synovialis ;  vaginal  synovial  membrane. 


MUCOUS   MEMBRANES.  355 

SEKUM. 

Serum  is  a  slightly  viscid,  straw-colored  liquid,  which  in  small 
quantity  moistens  the  smooth,  free  surfaces  of  the  serous  membranes ; 
and  only  occurs  in  the  serous  cavities  in  conspicuous  quantities  as  a 
result  of  disease.  It  serves  to  facilitate  the  movement  of  the  opposed 
surfaces  of  the  organs  and  cavity  containing  them.  In  composition  it 
resembles  the  blood-liquor. 

SYNOVIA. 

Synovia,  the  lubricating  liquid  of  the  joints  and  other  synovial 
cavities,  is  amber-colored  or  colorless,  more  viscid  than  serum,  and 
usually  occurs  in  greater  quantity.  In  composition  it  resembles  serum, 
with  a  proportion  of  mingled  mucin. 

MUCOUS   MEMBKANES. 

The  mucous  membranes1  line  passages  and  cavities  which  com- 
municate with  the  exterior  of  the  body,  where  they  become  continuous 
with  the  skin.  They  constitute  the  lining  of  the  alimentary,  respira- 
tory, urinary,  and  generative  apparatus,  together  with  that  of  the  ducts 
of  glands  which  open  upon  it.  Habitually  subjected  to  the  contact  of 
various  matters,  such  as  the  food  and  air  and  the  different  glandular 
secretions  and  excretions,  they  are  protected  from  undue  irritation  by 
a  viscid  liquid,  the  mucus,  which  bathes  their  surface. 

Mucous  membranes  are  attached  to  subjacent  parts  by  a  layer  of 
fibro-connective  tissue,  distinguished  as  the  submucous  layer,2  differ- 
ing in  thickness  and  density  in  different  positions.  The  attachment  of 
the  mucous  membrane  is  variable  in  degree,  in  some  cases  being  close 
and  firm,  as  in  that  of  the  nasal  cavities,  on  the  dorsum  of  the  tongue, 
in  the  air-passages,  and  in  the  uterus.  In  other  cases,  and  especially  in 
organs  subject  to  considerable  change  of  capacity,  as  in  the  stomach, 
intestines,  and  bladder,  it  is  comparatively  loosely  attached,  and  to 
some  extent  permits  some  shifting  of  the  connected  surfaces.  Thus, 
in  the  contraction  of  the  stomach  or  bladder,  the  mucous  membrane 
is  thrown  into  folds,  which  are  again  obliterated  in  expansion  of  the 
organs.  In  the  small  intestine,  for  the  greater  part  of  its  length,  the 
mucous  membrane  forms  numerous  permanent  folds,  the  connivent 
valves,3  which  are  not  affected  by  changes  of  capacity  of  the  canal. 
In  some  positions  the  mucous  membrane  is  provided  with  a  multitude 
of  minute  processes,  as  exemplified  by  the  papillae  of  the  tongue  and 
the  villi  of  the  small  intestine.  Generally  also  the  mucous  membranes 
are  furnished  with  numerous  minute  glands,  which  are  embedded  in 
the  thickness  of  the  membrane,  and  open  by  their  ducts  on  the  free 
surface. 

1  Membrana  niucosa.  2  Submucosa.  3  Valvulae  conniventes. 


356  MUCOUS   MEMBRANES. 

The  mucous  membranes  are  mostly  thicker  than  the  serous  mem- 
branes, less  elastic,  and  less  transparent.  They  vary  from  gray  and 
various  shades  of  pink  to  bright  red.  The  latter  colors  are  due  to  the 
vascularity,  which  may  be  more  or-  less  obscured  by  the  character  of 
the  epithelium  of  the  membrane.  In  some  they  are  habitually  bright 
red,  as  in  the  nose,  mouth,  and  pharynx ;  variably  pale  or  darker  red 
in  the  stomach  and  intestines,  according  as  these  organs  are  more  active 
or  quiescent ;  and  nearly  or  quite  colorless  and  transparent,  as  in  the 
conjunctiva  in  front  of  the  eyeball. 

The  mucous  membranes  are  composed  of  a  cellular  layer,  the  epi- 
thelium, supported  by  the  mucosa. 

The  epithelium  varies  greatly  in  different  mucous  membranes.  In 
the  mouth  and  throat,  on  the  conjunctiva  of  the  eye  (see  page  349),  and 
in  the  vagina,  it  is  a  stratified  epithelium,  consisting  of  many  layers  of 
cells  of  different  forms  and  constitution.  The  deepest  is  a  single  layer 
of  comparatively  short  columnar  cells,  which  is  followed  by  layers  of 
polyhedral  cells,  which  become  successively  of  greater  relative  breadth, 
while  the  superficial  layers  consist  of  broad,  flat  cells,  or  scales,  often 
distinguished  as  a  squamous  epithelium.  In  the  mucous  membrane  of 
the  urinary  bladder  (see  page  350)  the  epithelium  is  also  stratified,  but 
consists  of  comparatively  few  layers  of  cells,  of  which  the  superficial 
layer  is  not  reduced  to  the  condition  of  thin  scales.  The  air-cells  of 
the  lungs  are  lined  by  a  simple  or  single  layer  of  pavement  epithelial 
cells.  In  most  other  mucous  membranes  the  epithelium  consists  of  a 
single,  superficial  layer  of  comparatively  long,  six-sided,  columnar  cells, 
often  with  one  or  two  strata  of  young  cells  occupying  the  intervals  at 
the  bottom  of  the  usually  tapering  columnar  cells  of  the  surface.  In 
the  gastro-intestinal  mucous  membrane  the  columnar  epithelium  is  of 
plain  character  (see  page  347),  but  in  that  of  the  nasal  and  air-passages, 
in  the  cavity  of  the  uterus  and  oviducts,  and  in  some  other  positions,  it 
is  ciliated  (see  page  348). 

In  mucous  membranes  with  the  ordinary  stratified  epithelium,  in 
which  the  superficial  strata  are  squamous  epithelium,  the  mucus  of 
the  surface  is  mainly  derived  from  minute  racemose  glands  embedded 
in  the  mucous  membrane.  In  those  with  the  columnar  epithelium 
much  of  the  mucus  appears  to  be  derived  from  some  of  the  columnar 
cells,  scattered  here  and  there,  undergoing  transformation  into  the  con- 
dition of  goblet-cells  (see  page  348).  It  is  probable  that  the  columnar 
epithelium  is  incessantly  shed,  through  successive  transformation  of  the 
cells  into  goblet-cells,  which  are  displaced  to  give  room  or  place  to 
newly-developed  cells.  In  the  ordinary  stratified  epithelium  the  squa- 
mous layers  are  incessantly  shed,  while  new  layers  of  this  kind  are  due 
to  transformation  of  the  deeper  polyhedral  layers  of  cells. 

The  mucosa,  or  membrana  propria,  variable  in  thickness,  dis- 
tinctness, and  composition  in  different  mucous  membranes  and  other 
related  structures,  in  general  consists  of  an  interlacement  of  fibro-con- 


MUCOUS   MEMBRANES.  357 

nective  tissue,  defined  by  a  thin,  apparently  homogeneous  layer,  named 
the  basement  membrane,  and  situated  next  the  epithelium.  The 
fibre-connective  tissue  contains  nets  of  capillary  blood-vessels  and  lym- 
phatics and  terminal  plexuses  of  nerves.  It  is  often  mingled  with  some 
elastic  tissue,  which  is  especially  abundant  in  the  mucosa  of  the  air- 
passages.  The  basement  membrane,  sometimes  scarcely  distinguishable 
from  the  fibro-connective-tissue  layer  of  the  mucosa,  appears  to  be 
composed  of  broad,  flat  cells  or  plates  like  those  of  the  serous  endo- 
thelium.  In  other  cases  the  cells  appear  not  to  be  connected  by  their 
edges  continuously,  but  through  branching  processes,  and  in  this  con- 
dition are  barely  distinguishable  from  contiguous  connective-tissue  cor- 
puscles. In  some  of  the  mucous  membranes  the  fibro-connective  tissue 
of  the  mucosa  is  substituted  to  a  variable  degree,  and  notably  in  that 
of  the  stomach  and  intestines,  by  lymphoid  or  adenoid  tissue,1 
which  also  enters  largely  into  the  construction  of  the  lymphatic  glands. 
This  tissue  consists  of  a  reticular  structure  of  branching,  radiated  con- 
nective-tissue cells,  which  may  more  or  less  merge  into  the  ordinary 
condition  of  fibro-connective  tissue,  with  the  interspaces  filled  with 
lymph  or  lymphoid  corpuscles.  In  most  mucous  membranes  the  mu- 
cosa is  defined  from  the  submucous  fibro-connective-tissue  layer  by  a 
muscularis  mucosa,  a  thin  stratum  of  unstriped  muscle-fibres,  gener- 
ally circular  in  their  direction ;  but  in  the  well-developed  layer  of  the 
gastro-intestinal  mucous  membrane,  in  most  positions,  the  circular 
stratum  is  succeeded  by  a  longitudinal  stratum. 

The  mucosa  generally  contains  numerous  minute  glands,  whose 
ducts  open  on  the  surface  of  the  mucous  membrane.  In  the  gastric 
and  intestinal  mucous  membrane,  and  that  of  the  uterus,  the  glands  are 
tubular,  and  densely  packed  in  the  mucosa.  In  other  mucous  mem- 
branes they  are  racemose  glands,  variable  in  number  and  size  in  dif- 
ferent positions,  and  when  large  extend  from  the  mucosa  into  the 
submucous  tissue.  Besides  the  more  extended  lymphoid  tissue  enter- 
ing into  the  composition  of  the  mucosa,  in  some  of  the  mucous  mem- 
branes accumulations  of  the  same  structure  occur,  as  lymphoid 
nodules,  as  exemplified  in  the  solitary  and  agminated  glands  of  the 
intestines. 

The  mucous  membranes  are  abundantly  supplied  with  blood-vessels. 
Arteries  and  veins  form  plexuses  in  the  submucous  fibro-connective- 
tissue  layer,  whence  branches  communicate  with  the  capillary  nets  of 
the  mucosa,  including  those  enveloping  the  numerous  glands  of  the 
latter.  Lymphatics  are  also  numerous,  and  commence  in  lymphatic 
spaces  and  capillary  nets  of  the  mucosa,  whence  larger  vessels,  pro- 
vided with  valves,  proceed  into  the  submucous  layer  in  company  with 
the  blood-vessels.  Nerves  terminate  in  gangliated  plexuses  of  the  sub- 
mucous  layer,  and  thence  extend  into  finer  plexuses  of  the  mucosa. 

1  Cytogenic  tissue. 


358 


GLANDULAR  SYSTEM. 


MUCUS. 

Mucus1  is  a  viscid  liquid,  which  covers  the  surface  of  all  mucous 
membranes  in  variable  quantity,  and  is  produced  or  secreted  by  the 
epithelium,  and  often  also  by  glands  discharging  on  the  surfaces  of 
these  membranes.  It  is  tasteless  and  odorless,  transparent  and  color- 
less, or  more  or  less  clouded,  and  whitish  or  yellowish.  It  consists  of  a 
clear,  homogeneous  liquid,  mingled  with  variable  proportions  of  mucous 
corpuscles  and  cast-off  epithelial  cells.  The  mucous  corpuscles  are 
small  granular  cells,  and  resemble  the  colorless  blood-corpuscles  and 
lymph-corpuscles.  In  most  cases  mucus  also  occurs  mingled  with 
other  secretions,  as  the  saliva,  pancreatic  juice,  bile,  and  urine.  It 
is  a  solution  of  a  peculiar  nitrogenized  substance,  mucin,  with  some 
extractive  and  fatty  matters  and  salts. 

THE   GLANDULAK  SYSTEM. 

The  name  of  gland  has  been  applied  to  many  organs  of  very  dif- 
ferent character,  though  it  is  probable  that  they  were  originally  sup- 
posed to  possess  similar  functions.  Thus,  the  salivary  glands,  which 
produce  saliva,  the  liver,  which  produces  bile,  the  kidneys,  which  elimi- 
nate urine,  the  thyroid,  thymus,  and  suprarenal  bodies,  whose  office  is 
obscure,  the  pituitary  and  pineal  bodies  of  the  brain,  and  the  rounded 
ones  in  the  course  of  the  lymphatic  vessels,  have  all  been  and  yet  con- 
tinue to  be  called  glands. 

A  true  gland2  is  commonly  regarded  to  be  a  distinct  organ,  which 
elaborates  or  separates  from  the  blood  a  peculiar  liquid,  and  discharges 
it  by  a  duct  on  the  surface  of  the  mucous  membranes  or  skin.  The 

FIG.  180. 


DIAGRAM  OF  TWO  SIMPLE  TUBULAR  GLANDS. 
The  dotted  line  1,  the  epithelium  or  secreting 
cells ;  2,  the  basement  membrane  ;  3,  the  fibro- 
connective  tissue  in  which  the  blood-vessels 
are  distributed. 


SIMPLE  FOLLICULAR  GLAND.   References  as  in 
the  preceding  figure. 


liquid  discharged  is  called  a  secre- 
tion, and  the  act  of  producing  it  is 
called  by  the  same  name,  or  if  it 

is  rejected  from  the  body  as  useless  or  harmful,  as  in  the  case  of  urine, 

it  is  distinguished  as  an  excretion. 

The  mucous  and  serous  membranes,  in  their  essential  structure  and 

function,  closely  resemble  glands,  and  these  produce  the  liquids  which 

habitually  bathe  their  surfaces,  the  mucus  and  serum,  likewise  known 

as  secretions. 


1  Myxa  ;  mycus ;  pituita  ;  blenna. 


2  Glans  ;  glandula  ;  aden. 


GLANDULAK   SYSTEM. 


359 


The  larger  glands  are  more  or  less  visibly  isolated,  and  are  invested 
with  a  fibro-connective  envelope  continuous  with  the  matrix  of  the 
gland.  The  small  glands,  which  are  very  numerous,  are  generally 
embedded  in  the  submucous  tissue  of  mucous  membranes  and  in  the 
dermis  or  subcutaneous  connective  tissue. 

In  general  structure  the  glands  consist  of  a  tube,  or  duct,  which 
is  simple  or  branched,  defined  by  a  membrana  propria  lined  by  an 
epithelium,  and  sustained  by  a  matrix  of  fibro-connective  tissue 
with  blood-vessels,  lymphatics,  and  nerves.  Difference  in  the  struc- 
ture of  most  glands  chiefly  depends  on  the  extent  and  arrangement  of 
the  constituent  tubes  and  the  character  of  the  epithelium.  The  tubes 
may  be  simple  or  branched,  of  variable  length,  straight,  tortuous,  or 
convoluted,  and  commencing  in  the  tubular  form,  or  in  that  of  a  club- 
shaped  or  more  distinct  rounded  polyhedral  sac,  called  a  follicle,  or 
an  alveolus.1  A  gland  consisting  of  a  single  tube  of  variable  length 
and  arrangement  is  called  a  simple  gland,  while  those  which  have 
their  duct  more  or  less  branched  are  called  compound  glands.  In 
the  latter  all  the  branches  or  tubes  are  likewise  named  ducts,  and  the 
terminal  tube  or  outlet  is  the  principal  duct.  When  the  ducts  com- 


FIG.  182. 


FIG.  183. 


FIG.  184. 


Fig.  182.  COMPOUND  TUBULAK  GLAND.  References  as  in  Fig.  180. 
Fig.  183.  COMPOUND  FOLLICULAR  GLANDS.  References  as  before. 
Fig.  184.  A  SIMPLE  TUBULAR  GLAND  CONVOLUTED.  Same  references. 

mence  in  the  tubular  form  and  so  continue  throughout  the  glands  are 
named  tubular  glands,  and  when  they  commence  in  follicles  they 
are  distinguished  as  follicular  glands.  The  distinction  is  not  always 
well  marked,  for  the  commencing  tubes  of  a  gland  may  be  variably 
expanded,  and  thus  the  two  kinds  of  glands  may  merge  into  one 
another.  Many  of  the  compound  follicular  glands  in  the  arrange- 
ment of  their  branching  ducts  and  commencing  follicles  resemble  a 
bunch  of  grapes,  whence  from  the  word  raceme,  meaning  a  bunch  or 
cluster,  they  are  called  racemose  glands ;  and  a  large  gland  of  this 
kind  differs  from  a  small  one,  just  as  a  large  cluster  of  grapes  is 
composed  of  a  number  of  small  ones.  The  likeness  is  more  complete 
to  a  bunch  of  raisins;  for  the  follicles  of  the  racemose  glands  are 


1  Folliculus ;  sacculus. 


360 


GLANDULAR  SYSTEM. 


compressed  together  in  the  least  possible  space,  but  are  more  or  less 
separated  by  the  matrix  of  connective  tissue  with  blood-vessels.  The 
compound  glands  are  more  or  less  subdivided  into  small  portions  distin- 
guished as  lobules,1  and  more  or  less  distinct  collections  of  these  form 
larger  divisions,  or  lobes.  The  lobules  consist  of  groups  of  follicles 
or  the  commencing  tubes  of  the  racemose  gland  connected  together  by 
the  ducts  and  the  connective-tissue  matrix  with  the  blood-vessels. 


FIG.  187. 

i 


Fig.  185.  GLAND  OF  COMPLEX  FORM  ;  the  tubes  branching  and  the  commencing  ones  convoluted 
and  dilated  at  the  extremities.  1,  main  tube  or  duct ;  2,  branches ;  3,  convoluted  portions  dilated 
at  the  extremities. 

Fig.  186.  GLAND  OF  COMPLEX  FORM,  whose  arrangement  resembles  that  of  a  bunch  of  grapes. 
1,  duct ;  2,  branches  commencing  in  follicles ;  3,  branch  of  another  lobule. 

Fig.  187.  GLAND  OF  COMPLEX  CHARACTER,  in  which  the  tubes  anastomose,  and  thus  form  a  net- 
work. 1,  duct;  2,  net-work  of  tubes. 

The  epithelium  of  glands  is  always  continuous  at  the  mouth  of  the 
duct  with  that  of  the  mucous  membrane  or  other  surface  on  which  it 
opens.  In  the  simple  tubular  glands,  as  those  of  the  intestines,  the 
lining  epithelium  throughout  is  columnar,  and  not  different  in  appear- 
ance from  that  of  the  mucous  membrane,  with  which  it  is  continuous. 
In  the  gastric  tubular  glands,  both  simple  and  compound,  the  epithelium 
is  likewise  columnar,  but  in  some  of  them  larger  polyhedral  cells  are 
intermingled  or  occupy  the  deeper  recesses.  In  the  racemose  glands 
the  follicles  are  occupied  by  a  layer  of  polyhedral  cells,  which  usually 
fill  the  follicles,  and  are  regarded  as  the  peculiar  glandular  epithelium, 
or  secreting  cells.  The  larger  ducts  are  lined  by  a  distinct  columnar 
epithelium,  which  in  the  smallest  ones,  directly  communicating  with 
the  follicles,  is  of  a  transitional  character.  The  principal  ducts  of  the 
large  racemose  glands  are  lined  with  mucous  membrane,  commonly 
with  a  columnar  epithelium  continuous  with  that  of  the  smaller  ducts, 
and  with  that  of  the  mucous  membrane  on  which  they  open. 

The  membrana  propria  of  the  glandular  ducts  and  their  com- 
mencing tubes  and  follicles,  of  variable  thickness  and  distinctness,  is 


1  Lobuli ;  acini. 


GLANDULAR   SYSTEM.  361 

usually  composed  of  a  delicate,  limiting  basement  membrane,  appar- 
ently homogeneous  or  consisting  of  flat  cells,  and  strengthened  with 
more  or  less  connective  tissue,  which  in  some  cases,  as  in  the  sebaceous 
glands  of  the  skin,  appears  alone  to  be  present.  In  the  coiled  tube 
of  the  sweat-glands  it  is  distinguished  by  containing  a  thin  stratum  of 
longitudinal,  unstriped  muscular  fibres. 

The  more  essential  glandular  structure  is  embedded  in  a  connective- 
tissue  matrix  traversed  by  blood-vessels,  which  communicate  with  cap- 
illary nets  enclosing  the  glandular  tubes  and  follicles,  and  separated 
from  their  epithelium  by  the  membrana  propria. 

The  glands  are  richly  supplied  with  blood-vessels,  lymphatics,  and 
nerves,  which,  for  the  most  part,  accompany  one  another  in  the  course 
of  the  ducts,  the  blood-vessels  to  communicate  with  capillary  nets,  and 
the  lymphatics  with  interspaces  of  the  connective-tissue  matrix  between 
the  tubes  and  follicles  of  the  glands.  In  the  salivary  glands  it  is  stated 
that  the  nerves  have  been  traced  to  be  in  direct  connection  with  the 
secreting  cells. 

The  numerous  true  glands  of  the  intestines,  with  few  exceptions, 
are  simple  tubular  glands,  and  many  of  the  gastric  glands  are  of  the 
same  character,  while  others  more  or  less  divided  are  compound  tubu- 
lar glands.  The  glands  of  the  nasal  mucous  membrane  and  uterus  are 
also  simple  tubular  glands.  Many  of  these  tubular  glands  by  expan- 
sion in  a  club-like  manner  approximate  the  more  distinct  follicular 
glands.  The  sweat-glands  in  general  are  simple  tubular  glands,  and 
are  remarkable  for  the  great  length  of  their  tube,  which  is  coiled  into 
a  mass  in  the  body  of  the  gland,  whence  they  are  sometimes  distin- 
guished as  convoluted  glands. 

To  the  largest  compound  follicular  or  racemose  glands  belong  the 
pancreas,  the  salivary,  lachrymal,  and  mammary  glands.     The  smallest 
are  very  numerous,  and  are,  for  the  most  part,  embedded  in  the  sub- 
mucous  tissue  and  dermis.    These  are  the  mucous  glands  of  the  mouth, 
pharynx,  oesophagus,  trachea,  and  bron- 
chi, the   duodenal    glands,  the   prostate  FIG.  188. 
and    suburethral   glands,    the   palpebral 
glands,  and  the  sebaceous  glands  of  the 
skin. 

The  testicles  are  compound  tubular 
glands,  remarkable  for  the  great  and  very 
conspicuous  length  and  convoluted  con- 
dition of  their  branching  tubular  struc- 
ture. The  commencing  tubules  possess 

r  A     RACEMOSE    GLAND.       1,    duct ;     2, 

few   branches   of    great    length   closely     lobules  composed  of  the  divisions  of 
convoluted    into    elongated,    pyramidal     the  ducts,  commencing  in  follicles, 
lobules.     The  membrana  propria,  defined 

by  a  basement  membrane  of  flat  cells,  is  lined  by  a  stratified  poly- 
hedral epithelium,  while  the  larger  ducts,  also  greatly  convoluted,  are 


362  GLANDULAR   SYSTEM. 

lined  by  a  ciliated  columnar  epithelium,  and  the  main  duct,  or  vas 
deferens,  is  lined  by  mucous  membrane  with  a  plain  columnar  epi- 
thelium. 

The  kidneys  are  compound  tubular  glands  of  peculiar  character, 
especially  in  the  arrangement  of  their  constituent  tubes  and  blood- 
vessels. Their  numerous  long,  branching  tubes  commence  each  in  a 
spherical  sac,  which  is  doubly  reflected  around  a  tuft  of  capillary  blood- 
vessels and  is  lined  by  a  pavement  epithelium.  The  constituent  lobules 
and  lobes  of  the  kidney  are  compactly  united ;  and  the  larger  tubes  ab- 
ruptly end,  on  the  summits  of  the  lobes,  in  the  divisions  of  a  common 
receptacle,  the  pelvis  of  the  kidney  narrowing  to  the  ureter,  which 
corresponds  with  the  principal  duct  of  glands  in  general. 

The  liver,  a  huge  glandular  organ,  is  also  peculiar,  especially  in  the 
arrangement  of  its  secretory  cells  and  their  relation  with  the  ducts. 
The  substance  of  the  liver  is  composed  of  little  polyhedral  lobules1 
compactly  united  together,  and  in  some  animals,  as,  for  example,  the 
hog,  much  more  distinct  than  in  man.  The  lobules  are  composed  of 
the  secretory  cells,  a  polyhedral  epithelium,  arranged  in  a  sponge-like 
intertexture,  with  the  interspaces  occupied  by  a  corresponding  arrange- 
ment of  the  capillary  blood-vessels.  The  ducts  commence  in  an  inter- 
texture  of  canaliculi,  the  biliary  capillaries,2  which  run  among  and 
between  the  secretory  cells,  and  communicate  in  the  intervals  of  the 
lobules  with  larger  passages,  the  interlobular  ducts.  These  anasto- 
mose with  one  another  and  converge  into  the  main  ducts,  which  in 
their  course  from  the  liver  accompany  the  chief  vessels  which  supply 
the  organ.  The  biliary  capillaries  are  variously  regarded  as  tubes  of 
homogeneous  membrana  propria  or  as  mere  intercellular  passages. 
The  smallest  ducts  in  which  the  latter  open  have  a  pavement  epithe- 
lium, which  gradually  assumes  the  columnar  form  in  the  larger  ducts. 
The  largest  ducts  are  lined  by  a  distinct  mucous  membrane  with  a 
columnar  epithelium,  and  provided  with  numerous  minute  racemose 
glands. 

1  Acini.  2  Pori  biliarii  ;  radicles  of  the  bile-ducts. 


OHAPTEE  TIL 

THE  NECK,  THORAX,  AND  ABDOMEN. 

THE  NECK. 

THE  neck l  forms  the  short,  thick,  cylindrical  column  uniting  the 
head  with  the  chest.  In  front,  it  is  bounded  above  by  the  floor  of  the 
mouth,  denned  by  the  base  of  the  mandible,  and  below  by  the  breast, 
from  which  it  is  denned  by  the  upper  border  of  the  sternum  and  the 
clavicles.  Behind,  it  extends  on  the  lower  part  of  the  occiput,  and  is 
continuous  with  the  back  of  the  chest  below.  At  the  sides,  it  extends 
from  the  ear  to  the  shoulder.  Near  its  middle  in  front,  in  the  adult 
male,  is  a  conspicuous  prominence,  Adam's  apple,2  produced  by  the 
projection  of  the  larynx,  which  is  not  prominent  in  the  female  nor  in 
the  boy  before  puberty.  Immediately  above  the  larynx  is  the  hyoid 
bone,  which  may  be  readily  felt  externally.  At  the  bottom  of  the 
neck,  immediately  above  the  sternum,  is  a  depression,  the  jugular 
fossa,  within  which  is  the  trachea  as  it  descends  from  the  neck  into 
the  chest.  Farther  out,  above  the  clavicle,  is  another  depression,  the 
supraclavicular  fossa,  within  which  lie  the  axillary  blood-vessels 
and  nerves  as  they  escape  from  the  chest  into  the  armpit. 

The  bony  axis  of  the  neck  is  formed  by  the  cervical  vertebrae, 
which  are  enclosed  behind  and  laterally  by  a  thick  mass  of  muscles. 
In  front  of  the  vertebrae  in  succession  from  above  are  the  pharynx  and 
oasophagus ;  in  advance  of  these  the  mouth,  tongue,  hyoid  bone,  larynx, 
and  trachea,  with  the  thyroid  gland  and  the  supra-  and  infrahyoid 
muscles;  and  at  the  sides  of  all  these  are  the  great  cervical  blood- 
vessels, lymphatics  and  nerves,  and  the  sterno-mastoid  muscle.  The 
skin  of  the  neck,  thinner  in  front,  is  loosely  attached  by  the  superficial 
fascia  to  the  deep  fascia  and  subjacent  parts,  and  is  readily  raised  in 
folds.  A  thin,  superficial  muscle,  the  platysma,  occupies  the  sides  of 
the  neck,  and  in  aged  people  by  its  anterior  border  forms  with  the 
skin  a  conspicuous  fold  descending  from  the  chin. 

THE   THOEAX. 

The  thorax,  or  chest,3  comprises  the  upper  part  of  the  trunk  of 
the  body  below  the  neck,  and  consists  of  the  skeleton  chest  with  its 
appropriate  muscles  covered  by  the  skin.  With  the  intercostal  spaces 

1  Collum  ;  cervix.  2  Pomum  Adami ;  nodus  gutturis. 

3  Pectus  ;  bosom  ;  breast. 

363 


364  THE   THORAX. 

occupied  by  the  corresponding  muscles  its  front  part  is  mainly  covered 
by  the  pectoral  muscles,  extending  outwardly  along  the  clavicle  to  the 
arm  and  forming  the  thick  anterior  border  of  the  axilla,  or  armpit. 
In  the  median  line,  between  the  greater  pectoral  muscles,  it  is  slightly 
depressed,  as  the  sternal  groove,  in  which  the  sternum  is  subcuta- 
neous. The  groove  expands  below,  and  over  the  ensiform  process,  be- 
tween the  seventh  costal  cartilages,  is  still  more  depressed,  as  the 
infrasternal  fossa,  or  pit  of  the  stomach.1  To  the  outer  side  of 
the  pectorals  the  ribs  are  covered  by  the  great  serratus  muscle,  and 
below,  in  front  and  at  the  side,  are  covered  by  the  abdominal  rectus 
and  external  oblique  muscles.  Behind  the  chest  are  the  dorsal  exten- 
sors, the  supra-  and  infraserratus,  the  rhomboid,  trapezius,  and  latissi- 
mus  muscles.  The  latter,  as  it  ascends,  lies  on  the  great  serratus,  and 
with  the  greater  teres  muscle  forms  the  posterior  border  of  the  axilla. 

The  interior  of  the  chest  forms  the  thoracic  cavity  and  the  upper 
part  of  the  abdominal  cavity,  the  two  being  separated  by  the  dia- 
phragm, which,  from  its  deeply-vaulted  character,  rises  high  up  in  the 
chest;  on  a  level  with  the  junction  of  the  fifth  costal  cartilage  and  rib 
on  the  right,  and  of  the  sixth  on  the  left  side. 

The  thoracic  cavity *  is  chiefly  occupied  by  the  lungs  and  heart, 
the  former  on  each  side  invested  with  a  membrane,  the  pleura,  and  the 
latter  intermediate,  and  enclosed  in  a  membranous  pouch,  the  pericar- 
dium, situated  between  the  two  pleurae.  The  parietal  portions  of  the 
latter,  where  contiguous,  form  a  fore  and  aft  partition  to  the  thoracic 
cavity,  called  the  mediastinum,3  while  the  different  spaces  it  in- 
cludes are  distinguished  as  the  anterior,  middle,  posterior,  and  superior 
mediastina. 

The  anterior  mediastinum 4  is  formed  by  the  two  pleurae  reflected 
from  the  front  of  the  pericardium  to  the  back  of  the  sternum.  Its 
upper  half  is  narrow  where  the  pleurae  nearly  come  into  contact,  but 
it  is  wider  below  where  the  left  pleura  recedes  from  its  fellow,  and 
leaves  a  space  which  is  bounded  behind  by  the  pericardium  and  in 
front  by  the  sternum,  with  the  fifth,  sixth,  and  a  portion  of  the  seventh 
costal  cartilages  of  the  left  side,  and  the  sternal  triangular  muscle. 

The  middle  mediastinum5  is  the  capacious  central  portion  of  the 
whole  mediastinum,  containing  the  heart  with  the  ascending  portion 
of  the  aorta,  the  trunk  of  the  pulmonary  artery,  and  the  lower  half  of 
the  superior  cava,  all  included  in  the  pericardium,  together  with  the 
phrenic  nerves,  arch  of  the  azygos  vein,  and  roots  of  the  lungs,  with 
the  bronchial  lymphatic  glands. 

The  posterior  mediastinum,6  produced  by  the  reflection  of  the 


1  Scrobiculus  cordis  ;  antecardium.  2  Cavum  thoracis. 

3  Septum  or  dissepimentum  thoracis. 

4  Cavum  mediastini  anterius  ;  m.  pectorale.  5  C.  mediastini  medium. 
6  C.  mediastini  posterius  ;  m.  dorsale. 


THE   THORAX. 


365 


pleurae  from  the  pericardium  backward  to  the  sides  of  the  spine,  from 
the  fourth  thoracic  vertebra  downward,  contains  the  descending  por- 
tion of  the  thoracic  aorta,  the  oesophagus  with  the  vagus  nerves,  the 
azygos  and  hemiazygos  veins,  the  thoracic  duct,  and  the  posterior 
mediastinal  lymphatic  glands. 


FIG.  189. 


VIEW  OF  THE  POSTERIOR  MEDIASTINUM,  and  of  the  lungs.  1,  posterior  mediastinum,  bounded 
laterally  by  the  pleurae ;  2,  lower  border  of  the  costal  pleura ;  3,  outline  indicating  the  lower  limit 
of  the  pleural  cavity ;  4,  pleura  covering  the  diaphragm ;  5,  upper  lobe  of  the  right  lung ;  6, 
lower  lobe;  7,  fissure  separating  the  lobes;  8,  middle  lobe;  9,  pharynx;  10,  its  lower  limit; 
11,  oesophagus;  12,  thoracic  aorta,  giving  off  intercostal  arteries;  13,  innominate  artery,  dividing 
into  the  right  common  carotid  and  subclavian  arteries ;  14,  left  subclavian  artery ;  15,  left  com- 
mon carotid  artery  and  the  accompanying  internal  jugular  vein;  16,  azygos  vein;  17,  hemi- 
azygos vein ;  18,  thoracic  duct. 

The  superior  mediastinum  '  is  the  space  between  the  pleurae  from 
above  the  pericardium,  on  a  level  with  the  lower  part  of  the  presternum 
and  fourth  thoracic  vertebra,  extending  through  the  upper  aperture  of 
the  thorax  into  the  root  of  the  neck.  It  contains  the  trachea,  the 
oesophagus,  the  transverse  portion  of  the  aortic  arch,  with  the  innomi- 
nate and  left  carotid  and  subclavian  arteries,  the  innominate  veins  and 
upper  portion  of  the  superior  cava,  the  phrenic,  vagus,  left  recurrent 
laryngeal  and  cardiac  nerves,  the  cardiac  lymphatic  glands,  and  re- 
mains of  the  thymus  gland. 

1  C.  mediastini  superius. 


366 


THE   ABDOMEN. 


FIG.  190. 


THE  ABDOMEN. 

The  abdomen,  or  belly,1  is  that  portion  of  the  trunk  of  the  body 
included  between  the  chest  and  pelvis,  enclosing  a  large  cavity  which 
contains  the  digestive  and  urinary  organs  and  part  of  those  of  the 

generative  apparatus.  Su- 
perficially, its  limits  are 
considered  to  be  the  infe- 
rior margin  of  the  thorax 
above,  and  the  pubis, 
groin,  and  iliac  crest  on 
each  side  below;  but  the 
abdominal  cavity  consid- 
erably exceeds  these  lim- 
its, as  it  includes  the  pel- 
vic cavity  and  ascends 
within  the  chest,  where  it 
is  bounded  by  the  deeply- 
vaulted  diaphragm,  which 
separates  it  from  the  tho- 
racic cavity.  In  the  skel- 
eton it  corresponds  with 
the  great  vacuity  between 
the  thorax  and  pelvis  with 
the  lumbar  vertebrae  be- 
hind. Its  surrounding 

CAVITY  OF  THE  ABDOMEN  LAID  OPEN,  WITH  THE  VISCERA          ,,     .  A      f 

RETAINED  IN  THEIR  RELATIVE  POSITION.    The  straight  lines    wall    IS    Composed    OI    ap- 


indicate  the  regions  of  the  abdomen,    a,  epigastric  region ;  propriate 

b,  hypochondriac  regions ;  c,  umbilical  region  ;  d,  lumbar  ,, 
regions ;  e,  hypogastric  region  ;  /,  iliac  regions.    1,  flaps  of 

the  abdominal  wall  turned  aside;  2,  3,  left  and  right  lobes  skin. 


muscles  and 
together  with  the 
Near  its  centre  in 


front  is  the  umbilicus, 


of  the  liver ;  4,  fundus  of  the  gall-bladder ;  5,  round  liga- 
ment of  the  liver ;  6,  part  of  the  suspensory  ligament  of  the 

liver;  7,  8,  stomach;  9,  commencement  of  the  duodenum;  or  navel,  the  cicatrix  re- 

10,  spleen;  11,  great  omentum;  12  small  intestine ;  13,  <*-  mainin  from  the  attach- 
cum ;  14,  vermiform  appendix ;  15,  ascending  colon ;  16, 

transverse  colon ;  17,  descending  colon ;  18,  sigmoid  flex-  ment  of  the  umbilical  COrd 

ure;   19,  epiploic  appendages;   20,  folds   indicating  the  of  ^e  foetus.      It  is  SOine- 

course  of  the  remains  of  the  urachus  and  umbilical  ar-  .     ' 

teries;  21,  diaphragm.  what    variable    in    exact 

position,  but  is  always 

below  the  middle  line  between  the  pit  of  the  stomach  and  the  pubes, 
and  generally  slightly  above  the  level  of  the  iliac  crests. 

(For  a  description  of  the  muscles  of  the  abdominal  walls,  see 
page  270.) 

For  convenient  reference  in  speaking  of  the  position  of  the  abdom- 
inal viscera,  the  cavity  of  the  abdomen  is  divided  into  regions.  This  is 
done  by  drawing  two  parallel  lines  on  a  level  with  the  lowest  lateral 


1  Venter ;  gaster ;  paunch. 


THE   PERITONEUM.  367 

margin  of  the  thorax  and  the  highest  point  of  the  iliac  crest  on  each 
side,  while  two  other  lines  are  drawn  to  intersect  the  former  ascending 
vertically  from  the  middle  of  the  groin  on  each  side.  The  lines  thus 
divide  the  abdomen  into  nine  regions,  of  which  the  intermediate  three, 
from  above  downward,  are  the  epigastric,1  umbilical,2  and  hypo- 
gastric3  regions,  and  the  others  are  the  right  and  left  hypochon- 
driac,* lumbar,5  and  iliac6  regions.  The  position  within  the  pubes 
is  also  called  the  pubic  region,  that  within  the  groin  on  each  side 
the  inguinal  region,  and  that  within  the  pelvis  the  pelvic  region. 

The  hypochondriac,  epigastric,  and  hypogastric  regions  are  often 
more  briefly  named  each  as  the  hypochondrium,  the  epigastrium, 
and  the  hypogastrium.  Most  of  the  viscera  are  more  or  less  mova- 
ble, and  therefore  variable  in  exact  position  according  to  the  move- 
ments to  which  they  are  subjected  in  respiration,  the  passage  of  the 
contents  of  the  bowels,  or  otherwise,  but  ordinarily  they  occupy  the 
regions  as  follows : 

The  stomach  occupies  the  left  hypochondriac  and  epigastric  regions. 

The  duodenum  occupies  the  epigastric  and  umbilical  regions,  and  the 
remainder  of  the  small  intestine  and  mesentery  occupy  the  umbilical, 
hypogastric,  and  adjacent  portions  of  the  lumbar  and  iliac  regions. 

The  head  of  the  colon  occupies  the  right  iliac  region,  and  the  rest 
of  the  gut  ascends  through  the  right  lumbar  into  the  right  hypochon- 
driac region ;  thence  arches  through  the  umbilical  into  the  left  hypo- 
chondriac region,  and  descends  through  the  left  lumbar  into  the  left 
iliac  region,  where  it  forms  its  sigmoid  flexure  and  ends  in  the  rectum, 
which  occupies  the  back  part  of  the  pelvic  cavity. 

The  liver  occupies  the  right  hypochondriac,  epigastric,  and  a  little 
portion  of  the  left  hypochondriac  region.  The  gall-bladder  is  in  the 
epigastric  region. 

The  pancreas  occupies  the  epigastric  extending  into  the  left  hypo- 
chondriac region. 

The  spleen  lies  in  the  left  hypochondriac  region  and  slightly  in  the 
epigastric  region. 

The  kidneys  occupy  the  lumbar  regions,  with  adjacent  portions 
of  the  umbilical,  epigastric,  and  hypochondriac  regions. 

The  suprarenal  bodies  are  in  the  epigastric  region. 

The  urinary  bladder  occupies  the  fore  part  of  the  pelvic  cavity,  and 
in  the  distended  condition  rises  into  the  hypogastric  region. 

The  uterus  and  vagina  occupy  a  position  between  the  bladder  and 
rectum  in  the  pelvic  cavity. 


1  Regie  epigastrica,  cardiaca,  or  stomachica. 

2  K.  umbilicalis,  gastrica,  or  mesogastrica ;  mesogastrium. 

3  K.  hypogastrica  ;  venter  parvus  or  imus. 

4  R.  hypochondriaca  or  subcartilaginea. 

5  R.  lumbaris  or  lumbalis  ;  lumbi;  lendis  ;  loins;  flanks;  reins.          6  R.  iliaca. 


368 


THE   PERITONEUM. 


THE   PEKITONEUM. 

The  cavity  of  the  abdomen  is  lined  throughout  by  a  serous  mem- 
brane, the  peritoneum,1  which  is  reflected  from  behind  and  above 
upon  the  different  viscera,  so  as  to  give  them  an  investment  and  attach 
them  by  folds,  which  serve  to  retain  them  in  position  and  give  passage 
to  their  vessels  and  nerves. 

The  peritoneum  is  the  most  extensive  of  the  serous  membranes,  and 

is  a  strong,  uncolored,  transparent 
membrane  attached  to  the  subja- 
cent structures  by  areolar  tissue. 
Its  free  surface  is  smooth,  moist, 
and  shining,  and  is  provided  with 
a  pavement  epithelium.  The 
parietal  portion,2  or  that  lining 
the  abdominal  cavity,  is  thickest, 
and  is  closely  attached  to  adja- 
cent fasciae  and  muscles,  more 
especially  along  the  linea  alba 
and  to  the  diaphragm,  and  ad- 
hering most  tightly  to  the  tendi- 
nous portion  of  the  latter.  The 
visceral  portion3  aifords  a  more 
or  less  complete  investment  to 
the  organs  to  which  it  closely  and 
evenly  adheres,  forming  their  se- 
rous coat. 

Like  other  serous  membranes, 
the  peritoneum  forms  a  closed 
sac,  but  is  rendered  much  more 
complex  in  its  arrangement  from 
the  many  foldings  produced  by 
its  reflection  upon  the  viscera  it 
invests.  In  tracing  its  extension 
in  any  direction,  its  continuity 
everywhere  is  obvious.  Thus  pro- 
ceeding from  the  anterior  wall 
of  the  abdomen  outwardly,  it 
reaches  the  ascending  and  de- 
scending colon,  invests  these  in  front  and  at  the  sides,  and  passes  in- 
ward over  the  kidneys  to  the  spine,  where  it  produces  the  mesentery, 
a  wide-spreading  fold,  which  invests  the  whole  length  of  the  jejunum 
and  ileum.  In  the  right  iliac  region  it  invests  the  commencement  of 


DIAGRAM  OF  THE  APPARENT  ARRANGEMENT  OP 
THE  COURSE  OF  THE  PERITONEUM  IN  A  VERTICAL 
SECTION  OF  THE  ABDOMEN,  the  peritoneum  repre- 
sented by  the  thick,  black  line.  1,  upper  seg- 
ment of  the  sacrum ;  2,  first  lumbar  vertebra ;  3, 
thoracic  vertebrae;  4,  diaphragm;  5,  liver;  6, 
stomach ;  7,  transverse  colon ;  8,  small  intestine ; 
9,  duodenum  ;  10,  pancreas ;  11,  rectum  ;  12,  va- 
gina and  uterus :  13,  urinary  bladder ;  14,  pubis ; 
15,  greater  cavity  of  the  peritoneum;  16,  lesser 
cavity ;  17,  section  of  a  lateral  ligament  of  the 
liver ;  18,  gastro-hepatic  omentum :  the  arrow  in- 
dicates the  communication,  at  the  right  border 
of  the  latter,  of  the  great  and  lesser  cavities  of  the 
peritoneum  ;  19,  great  omentum ;  20,  transverse 
mesocolon;  21.  mesentery;  22,  recto-uterine 
pouch ;  23,  vesico-uterine  pouch ;  24,  portion  of 
peritoneum  lining  the  anterior  wall  of  the  ab- 
domen. 


1  Membrana  abdominis. 
3  L.  visceralis  or  interim. 


2  Lamina  parietalis  or  externa. 


THE    PERITONEUM.  369 

the  csecum  and  the  vermiform  appendix,  and  in  the  left  iliac  region  the 
sigmoid  flexure  of  the  colon,  forming  its  broad  fold,  the  mesocolon. 
Descending  from  the  mesentery  and  colon  on  each  side,  the  peritoneum 
enters  the  pelvis,  invests  the  upper  part  of  the  rectum,  and  is  thence 
reflected  on  the  bladder,  forming  between  them  the  recto-vesical 
pouch.  From  the  summit  of  the  bladder  it  is  reflected  to  the  front 
of  the  abdomen,  producing,  in  the  pubic  and  inguinal  regions,  slight 
folds  on  the  remains  of  the  urachus  and  on  the  umbilical  arteries  of  the 
foetus.  In  the  female  the  peritoneum  is  reflected  from  the  rectum  to 
the  upper  part  of  the  vagina  and  thence  over  the  uterus,  from  which  it 
proceeds  to  the  bladder.  It  thus  forms  two  pouches,  the  recto-uterine 
and  the  vesico-uterine  ;  and  between  the  sides  of  the  uterus  and  the 
sides  of  the  pelvic  cavity  it  forms  two  additional  folds,  the  broad  liga- 
ments of  the  uterus. 

Above  the  mesentery  the  peritoneum  forms  the  transverse  meso- 
colon, a  broad  fold  which  encloses  the  transverse  colon  and  is  continuous 
on  each  side  with  the  ascending  and  descending  mesocolon,  below  with 
the  mesentery,  and  above  with  the  great  omentum. 

Following  the  extension  of  the  peritoneum  from  the  front  of  the 
upper  part  of  the  abdomen,  it  spreads  over  the  vault  of  the  diaphragm, 
and  thence  descends  and  invests  the  liver,  stomach,  and  spleen,  and 
forms  between  them  their  ligaments.  From  the  transverse  fissure  of 
the  liver  it  descends,  as  the  small  omentum,  to  the  small  curvature  of 
the  stomach,  whence  it  completely  invests  the  organ  and  departs  from 
its  great  curvature  as  the  great  omentum.  This  descends  like  an 
apron  in  front  of  the  bowels,  doubles  on  itself,  and  ascends  to  join 
the  transverse  colon  and  mesocolon,  on  which  it  continues  upward 
to  the  pancreas,  where  its  layers  separate,  one  to  go  to  the  posterior 
border  of  the  liver,  the  other  to  turn  downward  and  become  continuous 
with  the  upper  layer  of  the  mesocolon.  From  the  fundus  of  the 
stomach  the  peritoneum  proceeds  as  the  gastro-splenic  omentum  to  the 
hilus  of  the  spleen,  and  thence  is  continuous  with  the  investment  of 
this  organ. 

The  peritoneum  forms  the  following  processes,  folds,  or  doublings 
of  the  membrane,  which  serve  as  attachments  for  the  viscera,  and  often 
.as  convenient  means  for  the  passage  of  the  vessels  and  nerves  to  and 
from  the  organs : 

The  suspensory,  coronary,  and  lateral  ligaments  of  the  liver. 

The  hepatico-renal  and  hepatico-colic  ligaments. 

The  phrenico-splenic,  phrenico-gastric,  and  phrenico-colic  ligaments. 

The  small  and  great  omentum. 

The  mesentery,  mesocolon,  and  mesorectum. 

The  recto-vesical  folds  of  the  male. 

The  recto-uterine  and  vesico-uterine  folds  and  the  broad  ligaments 
-of  the  uterus. 

The  suspensory  ligaments  of  the  bladder. 

24 


370  THE    PERITONEUM. 

The  suspensory  ligament l  of  the  liver  is  a  strong  fold  of  the 
peritoneum,  which  extends  from  the  median  line  of  the  diaphragm  to 
the  liver,  between  the  right  and  left  lobes,  and  thence  descending  is 
attached  along  the  linea  alba  to  the  umbilicus.  It  is  widest  at  the  an- 
terior notch  of  the  liver,  and  thence  diminishes  in  a  falciform  manner 
towards  the  posterior  notch,  in  front  of  which  its  two  layers  diverge 
as  the  fore  part  of  the  coronary  ligament.  The  anterior  portion  also 
narrows  in  its  descent  to  the  umbilicus,  and  encloses  in  its  free  border 
the  round  ligament.  The  right  layer  of  the  upper  portion  of  the  sus- 
pensory ligament  is  reflected  from  the  corresponding  side  of  the  dia- 
phragm to  the  upper  surface  of  the  right  lobe  of  the  liver,  and  in  like 
manner  the  left  layer  is  reflected  from  the  diaphragm  to  the  left  lobe. 
The  usual  position  of  the  ligament  is  not  vertical,  but  oblique,  its  left 
side  lying  on  the  left  lobe  of  the  liver,  and  its  right  side  in  contact  with 
the  diaphragm  and  front  wall  of  the  abdomen,  with  the  free  border  of 
the  descending  portion  directed  to  the  right. 

The  lateral  ligaments  are  transverse  folds  of  peritoneum  attaching 
the  posterior  border  of  the  liver  to  the  diaphragm.  The  right  lateral 
ligament 2  forms  a  short  attachment  to  the  right  lobe,  its  two  layers 
starting  from  the  right  and  diverging  inwardly  from  each  other,  the 
upper  layer  reflected  from  the  upper  surface  of  the  diaphragm  to  that 
of  the  liver,  and  continuous  with  the  fore  part  of  the  coronary  liga- 
ment ;  and  the  lower  layer  reflected  from  the  ascending  portion  of  the 
diaphragm  to  the  under  surface  of  the  liver,  and  forming  the  lower 
part  of  the  coronary  ligament.  In  the  interval  of  the  two  layers, 
widening  from  the  right  to  the  posterior  notch  of  the  liver,  the  surface 
of  the  right  lobe  is  devoid  of  the  serous  coat,  and  is  attached  to  the 
adjacent  part  of  the  diaphragm  by  connective  tissue.  The  left  lateral 
ligament,3  of  greater  length  than  the  former,  is  a  close  peritoneal  fold, 
attaching  the  posterior  border  of  the  left  lobe  of  the  liver  to  the  dia- 
phragm, extending  from  the  posterior  notch  of  the  former  outwardly 
in  front  of  the  termination  of  the  oesophagus.  It  is  continuous  in- 
wardly with  the  coronary  ligament.  Its  length  permits  more  mobility 
to  the  left  lobe  than  to  any  other  portion  of  the  liver. 

The  coronary  ligament 4  is  not  a  distinct  structure,  and  is  variously 
described.  It  may  be  regarded  as  the  attachment  of  the  liver  to  the 
diaphragm  by  the  diverging  portions  of  the  suspensory  ligament  and 
the  intermediate  portions  of  the  lateral  ligaments,  including  the  inter- 
vening connective-tissue  attachment  of  the  two  organs. 

The  hepatico-renal  ligament 5  is  a  narrow  fold,  which  starts  be- 
neath the  liver  on  the  right  of  the  caudate  lobe,  and  descends  in  front 
of  the  right  suprarenal  body  to  the  upper  extremity  of  the  correspond- 
ing kidney. 

1  Ligamentum  suspensorium  ;  broad  or  falciform  ligament. 

2  L.  triangulare  dextrum.  3  L.  t.  sinistrum. 

4  L.  coronarium  ;  1.  c.  dextrum  et  sinistrum.  5  Ligamentum  hepatico-renale. 


THE   PERITONEUM.  371 

The  hepatico-colic  ligament x  is  also  a  narrow,  crescentic  fold, 
which  descends  from  the  back  of  the  liver  on  the  right  of  the  gall- 
bladder to  the  hepatic  flexure  of  the  colon. 

The  phrenico-splenic  ligament2  is  a  short,  triangular  fold,  de- 
scending from  the  diaphragm  to  the  upper  end  of  the  spleen. 

The  phrenico-gastric  ligament 3  is  also  a  short,  triangular  fold, 
which  descends  from  the  diaphragm  on  the  left  of  the  oesophagus  to 
the  fundus  of  the  stomach. 

The  phrenico-colic  ligament 4  is  a  narrow,  strong  fold,  which  de- 
scends from  the  diaphragm  below  the  spleen  to  the  splenic  flexure  of 
the  colon. 

The  small  omentum,  or  gastro-hepatic  omentum,5  is  a  thin, 
transparent  doubling  of  the  peritoneum,  extending  between  the  trans- 
verse fissure  of  the  liver  and  the  small  curvature  of  the  stomach, 
reaching  from  the  cardia  to  the  pylorus.  On  the  right  it  forms  a  free 
border,  which  extends  between  the  transverse  fissure  of  the  liver  and 
the  commencement  of  the  duodenum,  and  encloses  the  vessels  ascend- 
ing to  the  former,  with  the  accompanying  ducts  and  nerves.  Behind 
it,  above,  lies  the  caudate  lobe  of  the  liver ;  and  on  the  left  a  fold  of  it 
descends  from  the  oesophagus  to  the  pancreas.  Between  its  layers  the 
coronary  blood-vessels  and  accompanying  lymphatics  and  nerves  run 
along  the  small  curvature  of  the  stomach.  The  free  border  of  the  small 
omentum  is  the  anterior  boundary  of  the  omental  foramen,6  bounded 
behind  by  the  inferior  cava,  above  by  the  caudate  lobe  of  the  liver,  and 
below  by  the  duodenum.  The  foramen  will  admit  the  finger,  and 
through  it  the  greater  portion  of  the  peritoneal  sac  communicates  and 
is  continuous  with  the  smaller  portion,  the  omental  sac.  This  ex- 
tends behind  the  stomach  into  the  great  omentum,  is  bounded  in  front 
by  the  small  omentum  and  its  extension  on  the  posterior  wall  of  the 
stomach,  below  by  the  doubling  of  the  great  omentum,  and  behind  by 
the  ascending  layer  of  the  latter,  continuous  above  with  the  posterior 
layer  of  the  small  omentum. 

The  gastro-splenic  omentum 7  is  a  doubling  of  the  peritoneum, 
extending  from  the  fundus  of  the  stomach  to  the  hilus  of  the  spleen, 
continuous  above  with  the  phrenico-gastric  ligament,  and  below  with 
the  great  omentum.  It  encloses  the  short  gastric  vessels. 

The  great  omentum,  or  gastro-colic  omentum,8  is  a  broad, 
double  fold  of  the  peritoneum,  which  falls  from  the  great  curvature  of 
the  stomach  in  front  of  the  intestines  to  the  lower  part  of  the  cavity  ; 
occasionally  a  little  way  below  the  umbilicus,  and  sometimes  even  into 
the  pelvic  cavity.  It  extends  lower  on  the  left  than  on  the  right,  and 

1  L.  hepatico-colicum.  2  L.  phrenico-splenicum. 

3  L.  phrenico-gastricum.  *  L.  pleuro-colicum  or  costo-colicum. 

5  O.  minus  or  gastro-hepaticum ;  small  epiploon. 

6  Foramen  of  Winslow  ;  f.  Duverneyi  or  omenti  minoris. 

7  Ligamentum  gastro-lienale.  8  O.  majus  or  gastro-colicum ;  great  epiploon. 


372 


THE    PERITONEUM. 


FIG.  192. 


in  fat  than  in  lean  people,  and  is  further  varied  by  the  elevation  or  de- 
pression of  the  stomach.  It  is  squarish,  thin,  more  or  less  cribriform, 
and  variably  loaded  with  an  irregular  net-work  of  dull-yellow  fat.  At 
the  fundus  of  the  stomach  it  is  continuous  with  the  gastro-splenic 
omentum,  and  terminates  below  in  an  irregular  border.  It  consists  of 
four  layers  in  great  part  confluent  or  blended  together,  and  encloses  a 
space,  the  omental  sac.  Two  of  the  layers  descend  from  the  greater 
curvature  of  the  stomach  and  quickly  unite  in  a  single  lamina,  which 
continues  to  the  lower  border  of  the  omentum,  then  doubles  on  itself, 
and  ascends  behind,  blends  with  the  descending  portion,  and  again 
separates  to  become  attached  to  the  transverse  colon.  From  this  it 
goes  backward  attached  to  the  mesocolon,  and  ascends  in  front  of 
the  pancreas,  where  it  divides  into  the  two  original  layers,  of  which 
one  continues  upward  to  the  posterior  border  of  the  liver,  while  the 
other  turns  downward  and  becomes  continuous  with  the  upper  layer 
of  the  transverse  mesocolon.  The  great  omentum  thus  forms  the 

omental  sac,1  the  cavity  of  which 
lies  between  its  descending  and 
ascending  portions,  and  between 
the  transverse  colon  and  meso- 
colon behind,  and  the  back  of  the 
stomach  in  front,  and  communi- 
cates by  the  omental  foramen  with 
the  greater  pouch  of  the  perito- 
neum. Prior  to  birth  the  omental 
sac  is  entire  and  its  interior  free ; 
and  in  this  condition,  when  inflated, 
the  omentum  appears  as  a  large, 
thin,  transparent  pouch  protruding 
from  between  the  stomach  and  the 
transverse  colon.  Subsequently, 
the  cavity  of  the  sac  below  the 
position  of  the  colon  becomes  in 
great  part  obliterated,  and  the 
omentum  in  its  growth  becomes 
proportionately  much  attenuated 
and  is  rendered  cribriform  from  the  production  of  innumerable  holes 
in  the  membrane.  In  the  early  part  of  foetal  life  the  ascending  portion 
of  the  omentum  is  free  from  the  transverse  colon  and  mesocolon,  and 
ascends  over  them  to  the  position  of  the  pancreas,  where  it  divides 
into  the  two  component  layers  as  before  described.  The  great  omen- 
tum contains  more  or  less  fat,  which  is  proportioned  in  quantity  with 
the  condition  of  the  person ;  and  is  especially  collected  along  the 
course  of  the  vessels,  giving  to  the  omentum  a  striking  reticular  ap- 


DlAGRAM  OF  THE  COURSE  OF  THE  PERITO- 
NEUM IN  THE  FCETUS.  4,  diaphragm ;  5,  liver ; 
6,  stomach;  7,  transverse  colon;  8,  small  in- 
testine ;  9,  duodenum ;  10,  pancreas ;  15,  greater 
cavity  of  the  peritoneum;  16,  lesser  cavity; 
17,  right  or  left  lateral  ligament;  18,  gastro- 
hepatic  omentum;  19,  great  omentum;  20, 
transverse  mesocolon ;  21,  mesentery. 


1  Bursa  omenti  minoris. 


THE    PERITONEUM. 


373 


pearance.  When  in  large  quantity  it  forms  irregular,  knotted  ridges 
pendent  from  the  omentum.  The  lower  portion  of  the  latter  is  a 
common  element  of  inguinal  hernia. 

While  there  are  lymphatic  vessels  in  the  great  omentum,  it  contains 
no  glands,  except  along  its  attachment  to  the  great  curvature  of  the 
stomach. 

FIG.  193. 


17 

18 


VIEW  OF  THE  ABDOMINAL  VISCERA;  with  the  greater  part  of  the  small  intestine  removed, 
and  the  liver  and  stomach  turned  upward.  1,  under  surface  of  the  liver ;  2,  gall-bladder ;  3, 
diaphragm ;  4,  stomach,  posterior  surface ;  5,  caudate  lobe  of  the  liver ;  6,  duodenum ;  7,  pan- 
creas ;  8,  spleen ;  9,  jejunum ;  10,  ileum ;  11,  caecum ;  12,  vermiform  appendix ;  13,  ascending 
colon ;  14, 14,  transverse  colon ;  15,  descending  colon ;  16,  sigmoid  flexure ;  17,  rectum ;  18,  urinary 
bladder;  19,  hepatic  artery,  giving  off  pyloric,  hepatic,  pancreatico-duodenal,  and  right  gastro- 
epiploic  branches  ;  20,  gastric  artery  to  small  curvature  of  the  stomach  ;  21,  splenic  artery ;  22, 
superior  meseiiteric  vessels ;  23,  24,  cut  edge  of  the  mesentery  between  the  divided  ends  of  the 
jejunum  and  ileum. 

The  mesentery1  is  the  most  extensive  and  strongest  of  the  peri- 
toneal folds,  and  encloses  and  suspends  the  entire  small  intestine,  except 
the  duodenum.  Its  upper  border,  called  the  root  of  the  mesentery,2 
about  six  inches  long,  is  attached  obliquely  across  the  spine  in  front  of 
the  great  vessels,  from  the  left  of  the  second  lumbar  vertebra  to  the 
right  sacro-iliac  articulation.  From  the  root  it  rapidly  expands  down- 


1  Mesenterium. 


2  Kadix  mesenterii. 


374  THE   PERITONEUM. 

ward  and  forward  in  a  fan-like  and  ruffled  manner,  and  at  its  distal 
border  encloses  the  whole  length  of  the  jejunum  and  ileum,  while  at 
its  widest  part  it  is  from  four  to  six  inches.  It  is  continuous  above 
with  the  transverse  mesocolon,  on  each  side  with  the  ascending  and 
descending  portions  of  the  latter,  and  below  extends  towards  the 
promontory  of  the  sacrum.  It  consists  of  two  layers  directed  right 
and  left  and  united  by  a  considerable  layer  of  areolar  tissue,  which  is 
traversed  by  the  superior  mesenteric  blood-vessels,  numerous  lymphatics, 
and  nerves,  and  also  contains  many  lymphatic  glands.  It  further  con- 
tains a  variable  quantity  of  fat  proportioned  to  the  condition  of  the 
individual,  sometimes  in  fat  persons  causing  the  mesentery  to  be  a 
half-inch  or  more  in  thickness. 

The  mesocolon  comprehends  the  peritoneal  attachment  of  the 
colon  to  the  adjacent  abdominal  wall,  almost  completely  encircles  the 
small  intestine  and  mesentery,  and  is  inwardly  continuous  with  the 
root  of  the  latter.  The  ascending  mesocolon1  is  commonly  very 
short,  and  incompletely  invests  the  corresponding  portion  of  the  colon, 
which  is  not  covered  by  it  behind.  It  invests  the  commencement  of 
the  caecum  and  its  vermiform  appendix,  and  furnishes  this  with  a  fold 
connected  with  the  inner  side  of  the  former.  The  transverse  meso- 
colon2 is  attached  across  the  abdomen  opposite  the  pancreas,  inclining 
downward  on  each  side,  and  completely  invests  the  transverse  colon  at 
its  fore  part.  It  is  shortest  at  the  extremities,  where  it  attaches  the 
hepatic  and  splenic  flexures  to  the  contiguous  portion  of  the  diaphragm, 
and  widens  to  the  middle,  where  it  is  about  four  inches  in  length,  and 
permits  free  downward  and  upward  movement  of  the  transverse  arch 
of  the  colon.  It  is  formed  by  two  peritoneal  layers,  which  enclose  the 
latter,  and  is  greatly  strengthened  by  the  close  adherence  of  the  as- 
cending portion  of  the  great  omentum.  The  descending  mesocolon,3 
continuous  with  the  former  and  commencing  above  with  the  phrenico- 
colic  ligament,  like  that  of  the  right  side,  gives  an  imperfect  investment 
to  the  descending  colon.  In  the  left  iliac  region  the  mesocolon  from 
extreme  shortness  above  gradually  extends  in  a  broad  fold,  which  con- 
forms to  and  completely  invests  the  sigmoid  flexure  of  the  colon.  Be- 
tween the  layers  of  the  mesocolon  and  their  attachments  are  the  colic 
and  sigmoid  branches  of  the  superior  and  inferior  mesenteric  blood- 
vessels, together  with  their  accompanying  lymphatic  vessels  and  numer- 
ous glands  and  nerves  of  the  colon. 

The  broad  mesocolon  of  the  sigmoid  flexure  of  the  colon  gradually 
subsides  below  into  the  mesorectum,  which  is  short,  directed  obliquely 
to  the  right,  and  attaches  the  rectum  to  the  front  of  the  sacrum.  It 
almost  completely  invests  the  commencement  of  the  rectum,  but  in  its 
farther  descent  gradually  retires  from  behind,  covering  the  rectum 
at  the  sides  and  in  front,  and  finally  only  in  the  latter  position,  near 

1  M.  ascendens  or  dextrum.      2  M.  transversum.      3  M.  descendens  or  sinistrum. 


THE   PERITONEUM.  375 

the  middle  of  its  length,  whence  it  is  reflected  on  the  bladder.  In 
this  manner  is  formed  the  recto-vesical  pouch,  bounded  laterally 
by  the  lunate  recto-vesical  folds.1  Between  the  layers  of  the  meso- 
rectum  the  superior  hemorrhoidal  blood-vessels,  with  the  accompanying 
lymphatics  and  nerves,  pursue  their  course  associated  with  lymphatic 
glands  and  more  or  less  fat. 

From  the  posterior  surface  of  the  bladder  the  peritoneum  ascends 
to  the  summit,  and  thence  to  the  front  of  the  pelvis  and  anterior  ab- 
dominal wall.  Within  the  latter  it  produces  three  slight  folds,  the  sus- 
pensory ligaments  of  the  bladder,2  which  ascend  and  converge 
from  the  pubic  and  inguinal  regions  to  the  umbilicus. 

In  the  female  the  lower  extension  of  the  mesorectum  is  reflected 
to  the  contiguous  upper  part  of  the  vagina  and  the  uterus,  forming  the 
recto-uterine  pouch,3  defined  laterally  by  the  lunate  recto-uterine 
folds.4  Covering  the  uterus,  the  peritoneum  produces  on  each  side  a 
fold,  the  broad  ligament  of  the  uterus,  directed  to  the  side  of  the 
pelvic  cavity.  From  the  front  of  the  organ  it  is  reflected  upon  the 
bladder,  forming  the  vesico-uterine  pouch,  of  less  depth  than  the 
former,  and  defined  laterally  by  lunate  vesico-uterine  folds. 

1  Plicae  recto-vesicales  or  semi-lunares  Douglasii. 

2  Ligamenta  suspensoria  vesiose. 

3  Recto-vaginal  pouch  ;  pouch  of  Douglas. 

4  Plicae  recto-uterinae 


OHAPTEE   YIII. 

THE  ALIMENTARY  APPARATUS. 

THIS  consists  of  the  alimentary  canal,  about  thirty  feet  in  length,  or 
between  five  and  six  times  that  of  the  body,  extending  from  the  mouth 

Fio.  194. 


VERTICAL  SECTION,  ANTEROPOSTERIOKLY.  EXPOSING  THE  CAVITIES  OF  THE  NOSE,  MOUTH,  PHARYNX, 
AND  LARYNX.  1,  oval  cartilage  of  the  left  nostril;  2,  triangular  cartilage;  3,  separation  between 
the  two ;  4,  prolongation  of  the  oval  cartilage  along  the  column  of  the  nose ;  5,  superior  meatus  of 
the  nose;  6,  middle  meatus ;  7,  inferior  meatus ;  8,  sphenoidal  sinus;  9,  arch  bounding  the  eusta- 
chian  tube ;  10,  orifice  of  the  latter ;  11,  lateral  recess  of  the  pharynx ;  12,  soft  palate,  ending  below 
in  the  uvula;  13,  vestibule  of  the  mouth  between  the  lips  and  jaws;  14,  roof  o£  the  mouth,  or 
hard  palate ;  15,  communication  of  the  cavity  of  the  mouth  with  the  vestibule  ;  16,  tongue;  17, 
fibrous  partition  in  the  median  line  of  the  latter;  18,  genio-glossal  muscle ;  19,  genio-hyoid  mus- 
cle ;  20,  mylo-hyoid  muscle ;  21,  anterior  pillar  of  the  palate ;  22,  posterior  pillar  of  the  palate ; 
23,  tonsil ;  24,  glands  of  the  tongue ;  25,  floor  of  the  fauces ;  26,  27,  pharynx ;  28,  cavity  of  the 
larynx;  29,  ventricle  of  the  larynx;  30,  epiglottis;  31,  hyoid  bone;  32,  33,  thyroid  cartilage;  34, 
thyro-hyoid  membrane ;  35,  36,  cricoid  cartilage ;  37,  vocal  membrane. 

to  the  anus.     The  first  portion  consists  of  the  mouth,  with  the  organs 
of  mastication,  including  the  teeth,  with  the  jaws  and  muscles  which 
376 


THE   ALIMENTAKY   APPAEATUS.  377 

act  on  the  latter,  the  tongue,  and  the  salivary  glands.  The  second  por- 
tion consists  of  the  pharynx  and  oesophagus,  as  the  organs  of  swallow- 
ing ;  and  the  third  portion  consists  of  the  stomach  and  intestines,  with 
the  pancreas  and  liver,  as  the  organs  of  digestion,  contained  within  the 
abdomen. 

THE   MOUTH. 

The  mouth *  is  included  by  the  lips,  cheeks,  palate,  and  floor,  and 
opens  behind  by  a  passage  named  the  fauces  into  the  pharynx,  or 
throat.  The  cavity  of  the  mouth 2  is  lined  throughout  by  mucous 
membrane,  except  upon  the  teeth,  which,  when  closed  together,  divide 
the  cavity  into  two  portions,  the  outer  one  being  called  the  vestibule.3 
The  cavity  within  the  position  of  the  lower  jaw  is  occupied  by  the 
tongue,  attached  to  the  floor  of  the  mouth. 

The  lips 4  enclose  the  orifice  of  the  mouth,5  and  their  union  forms 
the  angles,  or  corners,6  of  the  mouth.  They  are  formed  by  the  oral 
sphincter  and  other  muscles  converging  to  the  orifice,  covered  by  the 
skin  outwardly,  merging  into  the  oral  mucous  membrane  inwardly. 
The  thin,  bright-red  skin  at  the  border  of  the  lips  adheres  directly  to  the 
oral  sphincter  by  a  layer  of  connective  tissue  free  from  fat.  It  is  fur- 
nished with  numerous  minute  vascular  papillae,  which  are  embedded 
in  the  investing  epithelium ;  and  some  of  the  papilla  are  provided  with 
tactile  corpuscles.  Embedded  in  the  submucous  connective-tissue  layer 
of  the  lining  mucous  membrane  are  the  labial  glands,7  which  form 
an  almost  continuous  layer,  and  produce  a  more  or  less  uneven  condition 
of  the  inner  surface  of  the  lips  that  may  be  felt  by  the  tip  of  the  tongue. 
They  are  rounded,  polyhedral,  racemose  glands,  of  a  pinkish  color, 
secrete  mucus,  and  by  their  ducts  open  on  the  surface  of  the  mucous 
membrane. 

Between  the  lips  and  the  jaws,  in  the  median  line,  the  mucous  mem- 
brane forms  a  little  fold,  the  labial  frsenum,8  which  connects  the  lip 
with  the  gum  ;  the  upper  one  being  more  produced. 

The  cheeks 9  have  a  nearly  similar  composition  to  the  lips,  the  fore 
part  having  for  its  basis  the  buccinator  and  contiguous  muscles,  and 
the  back  part  the  ramus  of  the  mandible  with  its  muscles,  all  covered 
by  the  skin  and  lined  by  the  oral  mucous  membrane.  Between  the 
buccinator  and  the  skin,  and  extending  backward  between  the  former 
and  the  ramus  of  the  mandible,  the  space  is  commonly  occupied  by 
more  or  less  soft  adipose  tissue,  the  disappearance  of  which  in  emacia- 
tion produces  the  "hollow  cheek."  Numerous  small  buccal  glands,10 

1  Os  ;  stoma.  2  Cavum  oris  ;  spatium  oris. 

*  Vestibulum.  *  Labia. 

5  Orificium,  apertura,  rima,  or  hiatus  oris. 

6  Commissures  ;  commissura  labiorum. 

7  Glandulae  labiales.  8  Fraenulum  labii. 

9  Genae  ;  malae.  10  Glandulae  buccales. 


378  THE   ALIMENTARY   APPARATUS. 

like  the  labial  glands,  are  embedded  in  the  submucous  areolar  tissue  of 
the  cheek. 

Forming  the  inner  boundary  of  the  vestibule  of  the  mouth  are 
the  arching  alveolar  borders  of  the  jaws  supporting  the  teeth.  These 
borders  are  closely  invested  with  a  smooth,  dense,  and  highly-vascular 
mucous  membrane,  forming  the  gums.1  They  are  attached  by  firm 
connective  tissue  to  the  periosteum  of  the  subjacent  bones.  Around 
the  neck  of  each  tooth  the  gum  forms  a  narrow  doubling,  or  collar, 
free  from  the  tooth. 

The  palate,  or  roof  of  the  mouth,2  comprises  two  portions,  the 
hard  and  soft  palate.  The  hard  palate,3  included  within  the  arch  of 
the  upper  jaw,  has  for  its  foundation  the  inner  surface  of  the  alveolar 
border  and  the  palate  plates  of  the  maxilla?  and  palate  bones.  It  is 
deeply  vaulted,  but  is  much  reduced  in  old  age  by  the  loss  of  the  teeth 
and  alveolar  border.  It  is  invested  with  a  firm  mucous  membrane,  con- 
tinuous with  the  adjacent  gum,  and  is  attached  by  a  dense  connective 
tissue  to  the  subjacent  periosteum,  along  the  alveolar  border  and  the 
median  line  of  the  palate.  The  intermediate  subjacent  space  on  each 
side  is  occupied  by  a  compact  layer  of  racemose  glands  embedded  in 
connective  tissue  closely  adherent  to  the  periosteum.  The  glandular 
layer  increases  in  thickness  behind,  and  extends  into  the  soft  palate. 
The  free  surface  of  the  mucous  membrane  is  transversely  rugose  at  its 
fore  part,  is  smooth  behind,  and  is  divided  by  a  feeble  median  ridge,  or 
raphe,  ending  in  a  little  papilla  beneath  the  incisive  foramen  immedi- 
ately behind  the  interval  of  the  middle  incisors.  Many  minute  aper- 
tures, the  orifices  of  the  palatine  glands,*  are  scattered  over  the 
surface,  the  larger  and  more  numerous  being  situated  near  the  com- 
mencement of  the  soft  palate. 

The  soft  palate 5  is  a  movable  flap,  which  extends  from  the  hard 
palate  obliquely  downward  and  backward  between  the  mouth  and 
posterior  nares  into  the  pharynx.  The  lower  surface  is  concave  and 
smooth,  and  is  divided  in  the  median  line  by  a  continuation  of  the 
raphe  of  the  hard  palate.  The  upper  surface  is  convex  and  some- 
what more  prominent  along  the  middle.  The  posterior  free  border 
is  prolonged  into  a  median,  blunt,  conical  process,  the  uvula,6  and  it 
curves  outward  on  each  side  in  the  formation  of  the  posterior  pillar 
of  the  palate. 

The  soft  palate  is  invested  with  mucous  membrane,  continuous 
below  with  that  of  the  hard  palate  and  sides  of  the  fauces,  and  above 
with  that  of  the  posterior  nares.  Its  foundation  is  an  aponeurotic  and 


1  Gingivse  ;  carnicula.  2  Palatum ;  fossa  palatina. 

3  Palatum  durum.  *  Glandulae  palatinae. 

5  Palatum  molle,  mobile,  or  pendulum;    velum  palati,    palatinum,  pendulum 
palati,  or  staphylinum  ;  claustrum  palati ;  veil  of  the  palate. 

6  Uva ;  uvigera ;  staphyle ;  columella,  or  columna  oris  ;  sublingua ;   palate. 


THE   ALIMENTARY   APPARATUS.  379 

partially  fleshy  layer,  beneath  the  upper  surface,  pertaining  to  the  pal- 
atine muscles,  attached  to  the  palate  plates  of  the  palate  bones.  Below 
the  aponeurosis  is  a  thick  extension  of  the  glandular  layer  of  the  hard 
palate,  continuous  on  the  two  sides  and  thinning  away  behind.  A 
thinner  layer  of  the  same  kind  of  glands  occupies  the  upper  part  of 
the  soft  palate.  The  uvula  is  formed  by  the  uvular  muscles  extending 
from  above  the  palatine  aponeurosis,  enclosed  by  a  softer  prolongation 
of  the  mucous  membrane  of  the  soft  palate. 

The  soft  palate  on  each  side  joins  the  triangular  niche  of  the  fauces, 
in  which  is  lodged  the  tonsil,  and  is  defined  in  front  and  behind  by  the 
pillars  of  the  palate.1  The  anterior  pillar  is  a  fold  of.  mucous 
membrane  enclosing  the  palato-glossal  muscle,  starting  from  the  base 
of  the  uvula  and  curving  from  beneath  the  soft  palate  outward,  down- 
ward, and  forward  to  the  side  of  the  tongue,  which  it  joins  about  its 
posterior  third.  The  posterior  pillar,  in  like  manner,  starts  from  the 
uvula  and  curves  outward  as  the  posterior  border  of  the  soft  palate, 
and  continues  downward  to  the  side  of  the  pharynx.  It  encloses  the 
palato-pharyngeal  muscle,  and  is  more  prominent  than  the  former. 

The  wedge-shaped  space  across  the  -mouth  between  the  niches 
for  the  tonsils  constitutes  the  fauces,  or  passage-way,  from  the  mouth 
into  the  pharynx,  its  floor  being  formed  by  the  posterior  third  of  the 
tongue.  The  anterior  pillars  of  the  palate  together  form  the  ante- 
rior palatine  arch,  or  the  isthmus  of  the  fauces,2  through  which 
may  be  seen  the  tonsil  on  each  side,  the  uvula  above,  and  behind  the 
posterior  palatine  arch,3  formed  by  the  posterior  pillars  of  the 
palate. 

The  arteries  of  the  palate  are  the  superior  palatine  of  the  in- 
ternal maxillary  artery  and  the  inferior  palatine  of  the  facial  artery. 
The  veins  from  the  superior  palatine  join  the  pterygoid  plexus,  and 
with  those  of  the  tonsil  join  the  inferior  palatine  of  the  facial  vein. 
The  lymphatics  proceed  to  the  side  of  the  fauces,  and  join  the  glands 
at  the  side  of  the  hyoid  bone  and  styloid  muscles.  The  nerves  are 
the  palatine  and  naso-palatine  branches  of  the  spheno-palatine  gan- 
glion. 

The  floor  of  the  mouth  is  mainly  formed  by  the  muscles  included 
within  the  arch  of  the  mandible,  the  mylo-hyoid,  the  genio-hyoid,  and 
the  digastric  muscles,  together  with  the  attachment  of  those  of  the 
tongue,  which  lies  on  the  floor.  Its  free  surface  in  the  mouth  is  cov- 
ered by  the  mucous  membrane  continuous  with  the  lower  gum  and 
reflected  from  the  mandible  to  the  under  part  of  the  sides  and  tip  of  the 
tongue.  In  the  median  line  it  forms  a  narrow  fold,  the  lingual  frae- 
num,4  extended  between  the  symphysis  of  the  mandible  and  the  under 
part  of  the  tip  of  the  tongue.  Beneath  the  sides  of  the  latter  it  covers 

1  Half  arches  of  the  palate.  2  Arcus  palatinus  anticus. 

3  Arcus  palatinus  posticus.  4  Fraenulum  or  vinculum  lingua?. 


380 


THE   ALIMENTAEY   APPARATUS. 


the  sublingual  gland,  the  position  of  which  is  indicated  by  a  ridge, 
between  the  mandible  and  the  attachment  of  the  tongue. 

The  mucous  membrane  lining  the  cavity  of  the  mouth,  for  the 
most  part  bright  red,  varies  in  thickness  and  firmness  in  different  posi- 
tions. It  is  thicker  on  the  lips  and  cheeks  than  on  the  floor,  the  soft 
palate,  and  the  palatine  arches,  and  is  firmer  on  the  gums  and  hard  pal- 
ate than  elsewhere ;  the  difference  being  mainly  due  to  the  greater  or  less 
density  of  the  subjacent  connective-tissue  layer.  It  is  provided  with  a 
stratified  epithelium,  of  which  the  deepest  layer  consists  of  columnar 
cells,  the  succeeding  layers  of  larger  polyhedral  cells,  while  the  more 
superficial  layers  form  a  squamous  epithelium  of  broad,  flat  scales  over- 
lapping at  the  borders.  The  squamous  epithelium  varies  in  thickness 
in  different  positions,  and  proportioned  with  its  thickness  the  mucous 
membrane  appears  less  red  and  more  or  less  white.  The  subjacent 
mucosa  is  well  marked,  and  is  everywhere  provided  with  minute  con- 
ical papillae,  which  are  mostly  buried  in  the  deeper  part  of  the  epithe- 
lium. At  the  borders  of  the  gums  and  on  the  rugose  fore  part  of  the 
hard  palate  they  are  more  numerous,  larger,  and  more  or  less  promi- 
nent. The  papilla  are  processes  of  the  mucous  membrane  supplied 
with  nerves,  and  each  with  a  looped  capillary  blood-vessel. 

THE  GLANDS  OF  THE  MOUTH. 

Besides  the  special  salivary  glands,  whose  ducts  open  into  the 
cavity  of  the  mouth,  there  are  numerous  small  racemose  glands,  which 

are  situated  in  most  posi- 
tions embedded  in  the  sub- 
mucous  layer  of  connective 
tissue  of  the  lining  mucous 
membrane  and  secrete  mu- 
cus. They  constitute  the 
labial  and  buccal  glands, 
and  many  of  those  of  the 
palate  and  tongue.  Asso- 
ciated with  the  latter,  and 
found  also  in  a  similar  posi- 
tion of  the  pharynx,  are 
numerous  glands,  which 
may  be  distinguished  as 
follicular  lymphoid  glands.  The  simple  form  of  these,  as  repre- 
sented in  the  adjoining  figure,  consists  of  a  flask-like  follicle  or  crypt, 
which  is  formed  by  an  inflection  of  the  mucous  membrane  surrounded 
by  a  connective-tissue  layer,  in  which  are  embedded  numerous  rounded 
nodules  of  lymphoid  tissue.  These  glands  are  commonly  more  or  less 
conspicuous  at  the  posterior  third  of  the  tongue,  where  their  orifices 
are  distinctly  visible,  and  they  give  to  the  surface  an  uneven  appear- 
ance. The  tonsils  are  compound  glands  of  the  same  character. 


FIG.  195. 


SECTION  OF  A  FOLLICULAE  LYMPHOID  GLAND,  a,  oral 
mucous  membrane  continued  into  the  follicular  gland ; 
6,  papillae ;  e,  cavity  of  the  follicle ;  d,  mouth  of  the  fol- 
licle ;  e,  nodules  of  lymphoid  tissue ;  /.  connective-tissue 
layer :  highly  magnified. 


THE   ALIMENTARY   APPARATUS.  381 


THE  TONSILS. 

The  tonsil1  is  a  flattened,  oval  body,  which  occupies  the  niche  at 
the  side  of  the  fauces  between  the  anterior  and  posterior  pillars  of  the 
palate.  It  is  of  variable  size,  often  as  a  result  of  disease  which  causes 
more  or  less  enlargement,  but  normally  is  about  two-thirds  of  an  inch 
long,  scarcely  half  an  inch  broad,  and  of  less  thickness.  It  is  placed 
with  its  length  upright,  with  its  free,  broad  surface  directed  inward, 
and  its  outer  surface  resting  against  the  superior  constrictor  of  the 
pharynx,  to  which  it  is  attached  by  connective  tissue.  Its  inner  sur- 
face, projecting  into  the  fauces,  presents  a  somewhat  honey-combed 
aspect,  due  to  a  number  of  variably-sized  shallow  recesses,  or  crypts, 
into  which  open  smaller  ones.  The  crypts  are  lined  throughout  by  a 
continuation  of  the  oral  mucous  membrane,  and  have  thick  walls  of 
connective  tissue,  in  which  are  embedded  numerous  nodular  masses 
of  lymphoid  tissue. 

The  tonsil  externally  lies  near  the  internal  carotid  artery ;  and  in 
relation  with  the  outside  of  the  neck  it  is  placed  just  within  the  posi- 
tion of  the  angle  of  the  lower  jaw. 

The  tonsils  are  supplied  by  the  dorsal  branch  of  the  lingual  artery, 
the  inferior  palatine  and  tonsillar  branches  of  the  facial,  and  the  su- 
perior palatine  branch  of  the  internal  maxillary  artery.  The  veins  form 
the  tonsillar  plexus,  which  joins  the  inferior  palatine  branch  of  the  facial 
vein.  The  lymphatics  are  abundant,  and  join  the  deep  cervical  glands. 

MUSCLES   OF   THE   PALATE. 

The  palato-glossal  muscle  2  is  a  small,  fleshy  fascicle  within  the 
anterior  pillar  of  the  palate.  It  arises  within  the  lower  surface  of  the 
soft  palate,  united  with  the  muscle  of  the  opposite  side,  and  descends  to 
the  side  of  the  tongue,  where  it  blends  with  the  stylo-glossal  muscle. 

The  palato-pharyngeal  muscle,3  in  the  same  manner,  occupies 
the  posterior  pillar  of  the  palate.  It  is  a  long,  fleshy  fascicle,  which 
arises  within  the  soft  palate  in  an  expanded  manner  on  both  sides  of 
the  aponeurosis  of  the  palatal  tensor  and  connected  with  the  opposite 
muscle.  Descending  to  the  side  of  the  pharynx  at  the  inner  side  of 
the  middle  constrictor,  it  expands  and  unites  with  the  stylo-pharyn- 
geal  muscle,  to  be  inserted  with  it.  It  receives  a  narrow  slip,  which 
descends  from  the  lower  end  of  the  eustachian  tube  and  has  been 
described  as  a  separate  muscle.* 

1  Tonsilla  ;  amygdala  ;  glandula  colli ;  almond  of  the  throat. 

2  M.  palato-glossus,  glosso-palatinus,  or  glosso-staphylinus  ;  m.  constrictor  isthmi 
faucium. 

3  M.  palato-pharyngeus  or  pharyngo-palatinus ;   m.  thyreo-palatinus  ;   m.  con- 
strictor isthmi  faucium  posterior  superior. 

*  M.  salpingo-pharyngeus  ;  m.  levator  pharyngis  internus. 


382 


THE  ALIMENTAEY  APPARATUS. 


14 


The  palatal  elevator1  is  a  columnar  muscle  placed  in  the  wall  of 
the  pharynx,  at  the  outer  side  of  the  posterior  nares.  It  arises  ten- 
dinously  from  beneath  the  apex  of  the  temporal  pyramid  and  the  con- 
tiguous part  of  the  eustachian  tube.  Descending  obliquely  forward 

and  inward  at  the  side  of  the 
pharynx,  it  enters  the  soft  pal- 
ate and  expands  above  the 
aponeurosis  of  the  palatal  ten- 
sor, to  which  it  is  attached  in 
advance,  and  joins  its  fellow  in 
the  median  line.  The  muscle 
lies  in  contact  externally  with 
the  palatal  tensor  and  superior 
constrictor;  and  internally  with 
the  mucous  membrane  of  the 
pharynx. 

The  palatal  tensor2  is  a 
thin,  fleshy  band,  situated  to 
the  outer  side  of  the  former. 
It  arises  from  the  scaphoid 
fossa  at  the  base  of  the  ento- 
pterygoid process,  the  sphe- 
noidal  spine,  and  the  outer  side 
of  the  eustachian  tube.  De- 
scending on  the  outer  side  of 
the  entopterygoid  process,  it 
winds  around  its  hook  inwardly, 
and  expands  within  the  soft 
palate  in  an  aponeurosis,  which 
unites  with  that  of  the  opposite 
side,  and  is  inserted  into  a  trans- 
verse ridge  of  the  palate  plate  of 
the  palate  bone.  Externally  it 
lies  in  contact  with  the  internal 
pterygoid  muscle,  and  internally 
is  next  the  palatal  elevator,  sepa- 
rated from  it  by  the  entoptery- 
goid process  and  the  superior  constrictor  of  the  pharynx.  In  the  soft 
palate  its  aponeurosis  is  beneath  the  insertion  of  the  palatal  elevator 
and  the  uvular  muscle. 

The  uvular   muscle,3   together  with   that  of  the   opposite  side, 

1  M.  levator  palati ;    m.  1.  p.  mollis ;   m.  peristaphylinus   internus  ;   m.  petro- 
staphylinus ;  m.  petro-salpingo-staphylinus. 

2  M.  tensor  palati ;   m.  circumflexus  palati ;    m.  peristaphylinus  externus  ;  m. 
pterygo-staphylinus ;  m.  spheno-salpingo-staphylinus. 

3  M.  uvulae;  m.  azygos  uvulae;  m.  palato-staphylinus. 


13    12 

MUSCLES  OF  THE  PALATE.  The  pharynx  laid 
open  and  viewed  from  behind.  1,  basilar  process ; 
2,  roof  of  the  pharynx ;  3,  posterior  nasal  orifice ; 
4,  cartilaginous  eustachian  tube  ;  5,  entopterygoid 
process,  ending  in  a  hook ;  6,  the  fauces ;  7,  uvula; 
8,  tonsil;  9,  epiglottis;  10,  thyroid  cartilage;  11, 
aryteno-epiglottic  fold;  12,  arytenoid  cartilage; 
13,  notch  between  the  arytenoid  cartilages;  14, 
palatal  elevator  muscle ;  15,  palatal  tensor ;  16,  ex- 
pansion of  its  tendon  of  insertion  in  the  soft  palate ; 
17,  uvular  muscle ;  18,  palato-pharyngeal  muscle ; 
19,  stylo-pharyngeal  muscle;  20,  superior  con- 
strictor of  the  pharynx. 


THE   ALIMENTARY   APPARATUS.  383 

forms  the  fleshy  interior  of  the  uvula.  It  arises  from  the  posterior 
nasal  spine  and  the  contiguous  aponeurosis,  and,  closely  connected  with 
its  fellow,  descends  at  the  back  of  the  soft  palate  into  the  uvula. 

The  palato-glossal  and  palato-pharyngeal  muscles  are  probably  sup- 
plied by  the  adjacent  pharyngeal  plexus  of  nerves.  The  palatal  tensor 
receives  a  branch  from  the  otic  ganglion,  and  the  palatal  elevator  arid 
uvular  muscles  from  the  petrosal  branch  of  the  vidian  nerve. 

THE    TONGUE. 

The  tongue l  is  a  muscular  organ  covered  with  an  extension  of  the 
oral  mucous  membrane,  and  provided  with  conspicuous  papillse  which 
are  the  chief  organs  of  taste.  Ordinarily  at  rest,  it  occupies  the  space 
within  the  position  of  the  mandible  and  the  teeth  on  the  floor  of  the 
mouth.  The  free  portion,  called  the  body,  is  bounded  by  the  rounded 
sides  and  tip,  which  are  often  somewhat  impressed  by  contact  with 
the  teeth.  Its  posterior  part  attached  to  the  hyoid  bone  is  the  root ; 
and  it  is  also  attached  its  entire  length  beneath  by  means  of  the  genio- 
glossal  muscles  to  the  mental  tubercle  of  the  mandible.  The  upper 
surface,  dorsum,  or  back  of  the  tongue,  is  convex,  and  is  marked 
by  a  slight  median  furrow,  the  raphe,  which  indicates  the  bilateral 
symmetry  of  the  organ.  The  raphe  usually  ceases  behind  in  a  pit,  the 
caecal  foramen,  situated  about  an  inch  from  the  root  of  the  tongue. 

The  mucous  membrane  beneath  the  sides  and  tip  of  the  tongue  is 
like  that  elsewhere  in  the  mouth,  and  is  comparatively  loosely  attached 
to  the  subjacent  muscular  structure.  It  is  sufficiently  thin  to  see 
through  it,  on  each  side,  the  ranine  vein,  which  runs  forward  below  the 
tip,  and  has  close  to  it  externally  the  ranine  artery.  To  the  outer  side 
of  the  position  of  these  vessels  there  is  not  unfrequently  a  narrow, 
irregular,  and  somewhat  fringed  fold  of  the  membrane  ;  and  in  the 
median  line  under  the  tip  of  the  tongue  is  the  more  distinct  fold,  or 
lingual  fraenum. 

The  dorsum,  or  back,  of  the  tongue,  on  the  anterior  two-thirds 
of  its  surface,  is  velvety,  or  covered  with  a  white  fur,  which  is  due 
to  numerous  little  eminences,  named  from  their  function  the  papillae 
of  taste.2  Of  these,  visible  to  the  naked  eye,  there  may  be  distin- 
guished three  kinds,  different  in  size  and  shape,  and  named  the  cir- 
cumvallate,  fungiform,  and  conical  papillse.  They  are  generally  beset 
with  others  which  are  minute,  and  are  like  those  found  everywhere  in 
the  oral  mucous  membrane  concealed  beneath  the  epithelium.  Simple 
in  their  character,  the  larger  ones  are  regarded  as  compound  papilla. 
Besides  the  foregoing,  some  little  folds  of  the  mucous  membrane,  de- 
scribed as  the  foliate  papillae,3  are  situated  on  the  side  of  the  tongue 
immediately  in  advance  of  the  termination  of  the  anterior  pillar  of  the 
palate. 

1  Lingua ;  glossa  ;  glotta.  2  P.  gustatoriae.  3  P.  foliatae. 


384 


THE  ALIMENTARY  APPARATUS. 


The  circumvallate  papillae,1  the  largest  kind,  are  few,  usually 
about  nine,  but  often  one  to  three  more  or  less.  They  form  an  angular 
series  at  the  limit  of  the  papillary  layer  behind.  Each  has  the  shape 
of  a  reversed,  truncated  cone,  and  occupies  a  corresponding  pit  of  the 
mucous  membrane  surrounded  by  a  thick,  prominent  ring,  which  gives 


FIG.  197. 


VIEW  OF  THE  DORSUM  OF  THE  TONGUE.  1, 2,  V-like  row  of  the  circumvallate  papillae ;  3,  fungi- 
form  papillae ;  4,  5,  conical  papillae ;  6,  6,  floor  of  the  fauces,  with  numerous  lymphoid  follicu- 
lar  glands ;  7,  tonsils  ;  8,  summit  of  the  epiglottis ;  9,  the  middle  glosso-epiglottic  frsenum,  with 
depressions  on  each  side  bounded  externally  hy  the  lateral  frsena. 

the  papilla  the  appearance  of  being  enclosed  by  a  wall,  and  hence  its 
name.  The  top  of  the  papilla  is  rounded  and  beset  with  many  minute, 
simple  papillae  concealed  beneath  a  thick,  stratified  epithelium,  which 
is  thinner  on  the  sides  of  the  papilla.  The  surrounding  wall  has  a 
similar  construction. 

1  P.  circumvallatse,  vallatse,  maximae,  truncatae,  calyciformes,  mucosee,  or  lenticulares. 


THE  ALIMENTARY  APPARATUS. 


385 


The  fungiform  papillae,1  smaller  than  the  former,  are  scattered 
over  the  dorsum  of  the  tongue,  and  are  more  numerous  approaching 
the  lateral  borders,  and  especially  the  tip.  They  are  rendered  con- 
spicuous by  their  redder  color  contrasted  with  the  more  or  less  whitish 
appearance  of  the  conical  papilla  occupying  the  intervals  of  the  former. 
They  are  rounded  eminences  narrowed  at  their  attachment,  resembling 
a  young  mushroom,  whence  the  name.  They  are  covered  with  minute 
simple  papilla?  covered  by  a  smooth,  stratified  epithelium. 

FIG.  198. 


DIAGRAM  OF  THE  PAPILLAE  OF  TASTE.  1,  conical  papillae;  2,  fungiform  papilla;  3,  simple 
papillse,  which  also  surmount  the  former ;  4,  epithelial  hair-like  processes ;  5,  isolated  squamous 
epithelial  cells  forming  the  latter :  highly  magnified. 

The  conical  papillae,2  the  smallest  and  most  numerous,  densely 
crowd  the  space  unoccupied  by  the  former.  They  are  generally  ar- 
ranged in  oblique  lines  diverging  on  each  side  forward  from  the  raphe, 
but  gradually  become  more  transverse  towards  the  tip  of  the  tongue. 
They  vary  in  size,  and  are  largest  and  more  slender  towards  the  lateral 
borders  of  the  tongue.  Many  are  small,  and  merge  into  the  character 
of  the  simple  papilla?.  They  are  conical  or  cylindro-conical.  and  mostly 
terminate  in  a  group  of  simple  papilla?,  from  which  the  epithelium 
extends  in  long,  hair-like  processes,  which  give  to  each  conical  papilla 
the  appearance  of  a  pencil  or  small  brush.  It  is  especially  these  pro- 
cesses, varying  in  degree  of  production,  which  give  to  the  back  of  the 
tongue  its  whitish,  velvety,  or  furred  appearance. 

The  papillse  of  taste  have  the  compound  structure  of  the  simple 
papilla?,  and  contain  nets  of  capillary  vessels  with  a  loop  for  each 
simple  papilla  they  possess.  The  fungiform  and  circumvallate  papilla? 
also  receive  numerous  medullated  nerve-fibres. 

Embedded  in  the  epithelium  at  the  base  of  the  circumvallate,  the 
foliate,  and  many  of  the  fungiform  papilla?,  there  occur  peculiar  micro- 

1  P.  fungiformes,  clavatse,  capitatae,  mediae,  or  semilenticulares. 
a  P.  conicae,  filiformes,  minimaa,  pyramidales,  or  villosae. 

25 


386  THE   ALIMENTAEY   APPARATUS. 

scopic  bodies,  named  taste-buds.1  These  are  ranged  in  rows,  and 
consist  of  ovoidal  masses  of  cells,  which  are  placed  perpendicularly  in 
the  epithelium  resting  on  the  basement  membrane,  with  the  narrower 
extremity  reaching  the  free  surface  of  the  epithelium.  The  adjacent 
portion  of  the  latter  forms  a  special  cover  for  each  bud,  consisting  of  a 
layer  of  flat,  fusiform  scales  overlapping  at  the  edges  and  arranged  par- 
allel with  those  composing  the  bud.  The  outer  cells  of  the  taste-bud 
are  likewise  fusiform,  slightly  flattened,  and  provided  with  a  large 
central,  oval  nucleus.  The  interior  cells,  named  gustatory  cells,  are 
similar,  but  are  much  more  slender,  and  have  filamentous  ends,  of 
which  the  outer  one  projects  slightly  beyond  the  summit  of  the  bud, 
and  the  inner  one,  sometimes  divided,  is  connected  with  a  terminal 
nerve-fibril. 

The  mucous  membrane  at  the  posterior  part  of  the  dorsum  of  the 
tongue,  forming  the  floor  of  the  fauces,  is  quite  different  in  character 
from  the  papillary  layer  in  advance.  It  is  connected  laterally  with  the 
niche  of  the  tonsil  and  behind  with  the  epiglottis,  between  which  and 
the  root  of  the  tongue  it  produces  three  folds,  the  glosso-epiglottic 
fraena.  The  middle  one  of  these  is  narrow  and  prominent,  while 
those  at  the  sides  are  low  and  rounded ;  and  between  them  the  root  of 
the  tongue  forms  two  shallow  recesses.  The  surface  of  the  mucous 
membrane  presents  a  variably  prominent  mammillated  appearance, 
with  a  central  aperture  to  each  mammilla.  The  submucous  connective 
tissue,  mingled  with  lymphoid  tissue,  forms  a  considerable  layer,  con- 
taining numerous  small  racemose  glands  and  simple  lymphoid  follicular 
glands,  which  produce  the  mammillated  appearance  of  the  contiguous 
surface  of  the  tongue.  The  lymphoid  glands,  like  the  tonsils,  are  liable 
to  enlargement,  giving  a  more  conspicuous  mammillary  condition  of 
the  surface  of  the  tongue,  each  mammilla  also  presenting  an  enlarged 
central  aperture.  The  racemose  glands  are  like  those  of  the  lips  and 
palate,  and  extend  between  the  contiguous  bundles  of  muscular  fibres, 
while  their  ducts  open  on  the  surface  of  the  mucous  membrane  between 
the  lymphoid  glands  and  also  into  their  recesses.  They  exist  elsewhere 
in  the  tongue,  as  around  the  circumvallate  papillae  and  also  the  csecal 
foramen,  into  which  their  ducts  open ;  others  are  beneath  the  sides  of 
the  tongue,  and  a  considerable  group  under  the  tip  close  to  the  ranine 
blood-vessels. 

MUSCLES   OF   THE  TONGUE. 

The  genio-glossal  muscle 2  forms  with  its  fellow  the  chief  part 
of  the  middle  of  the  tongue.  It  arises  tendinously  from  the  mental 
tubercle  of  the  mandible,  whence  its  fleshy  fascicles  diverge  in  a  fan- 
like  manner  upward  and  backward  to  be  inserted  into  the  upper  part 
of  the  body  of  the  hyoid  bone,  above  which  some  extend  backward  to 
the  side  of  the  pharynx,  but  in  great  part  enter  the  tongue  and  extend 

1  Taste-goblets.  2  M.  genio-glossus ;  m.  genio-hyo-glossus. 


THE  ALIMENTARY  APPARATUS. 


387 


forward  to  the  tip.  Internally,  it  is  in  contact  with  the  muscle  of  the 
opposite  side,  but  is  separated  behind  and  below  by  the  fibrous  septum 
of  the  tongue.  Externally,  it  is  in  contact  with  the  infralingual,  hyo- 
glossal,  and  stylo-glossal  muscles,  the  lingual  vessels,  the  hypo-glossal 
and  gustatory  nerves,  and  the  sublingual  gland.  Its  anterior  border 
occupies  the  lingual  fra3num,  and  its  posterior  lower  border  is  in  contact 
with  the  genio-hyoid  muscle. 

The  hyo-glossal  muscle1  lies  to  the  outer  side  of  the  former. 
Flat  and  quadrate,  it  arises  from  the  side  of  the  body  and  cornua  of 
the  hyoid  bone,  and  ascends  to  the  side  of  the  tongue,  where  it  extends 
towards  the  tip.  The  portion  ascending  from  the  hyoid  body  expands 
at  the  side  of  the  tongue  to  the  outer  side  of  that  from  the  cornua.  Its 
different  portions,  variably  distinct  according  to  the  attachment  and 
direction  of  its  fascicles,  have  been  described  as  separate  muscles.2  In- 
ternally, it  is  in  contact  with  the  infralingual  and  genio-glossal  muscles, 
the  middle  constrictor  of  the  pharynx,  and  the  lingual  vessels  and  the 
glosso-pharyngeal  nerve.  Externally,  it  is  connected  with  the  stylo- 
glossal  and  palato-glossal  muscles,  and  is  in  contact  with  the  stylo- 
hyoid  and  digastric  muscles, 

and  with  the  lingual  vessels,  FIG.  199. 

the  sublingual  gland,  and  the 
duct  of  the  submaxillary  gland. 

The  infralingual  mus- 
cle 3  is  a  longitudinal,  fusiform, 
fleshy  bundle  extending  from 
the  hyoid  bone  to  the  tip  of 
the  tongue,  between  the  upper 
part  of  the  genio-glossal  and 
hyo-glossal  muscles.  At  the 
root  of  the  tongue  its  fibres 
are  intercalated  with  those  of 
the  stylo-glossal  and  genio- 
glossal  muscles  and  of  the  mid- 
dle constrictor  of  the  pharynx. 

The  stylo-glossal  mus- 
cle/ the  shortest  and  smallest 
of  those  from  the  styloid  pro- 
cess, arises  tendinously  from 
the  fore  part  near  its  end,  and 
from  the  stylo-maxillary  liga- 
ment. Descending,  it  curves  forward,  and  terminates  in  the  lateral 


SIDE  VIEW  OF  THE  MUSCLES  OF  THE  TONGUE.     1,  2, 

stylo -glossal  muscle;  3,  infralingual  muscle;  4, 
dorsum  of  the  tongue  ;  5,  6,  hyo-glossal  muscle ;  7, 
genio-glossal  muscle  ;  8,  stylo-pharyngeal  muscle  ; 
9,  genio-hyoid  muscle ;  10,  mylo-hyoid  muscle. 


1  M.  hyo-glossus  ;  m.  basio-cerato-chondro-glossus. 

2  M.  basio-glossus,  cerato-glossus,  and  chondro-glossus. 

3  M.  lingualis ;  m.  lingualis  inferior,  or  lingualis  longitudinal  is  inferior. 

4  M.  stylo-glossus. 


388  THE   ALIMENTARY    APPARATUS. 

border  of  the  tongue,  with  its  fibres  decussating  with  those  of  the  hyo- 
glossal  muscle.  It  is  in  contact  internally  with  the  superior  constrictor 
of  the  pharynx,  the  tonsil,  and  the  hyo-glossal  muscle ;  externally  with 
the  parotid  gland,  the  internal  pterygoid  muscle,  the  sublingual  gland, 
and  the  mucous  membrane  of  the  tongue. 

The  fleshy  portion  of  the  body  of  the  tongue  above  is  very  com- 
pactly composed  of  interlacing  bundles  of  fibres  of  the  different  mus- 
cles which  enter  into  the  construction  of  the  organ  ;  but  the  lower  por- 
tion is  formed  alone  by  the  chief  muscles,  the  bundles  of  which  in  this 
position  do  not  interlace,  but  are  distinct  and  easily  separable,  as  in 
the  voluntary  muscles  generally.  The  intervals  of  the  interlacing 
bundles  of  muscular  fibres  are  occupied  by  delicate  connective  with 
adipose  tissue.  The  muscles  of  the  two  sides  of  the  tongue  are  sepa- 
rated below  by  a  distinct  fibro-connective  tissue,  septum,  extending 
from  the  hyoid  bone  to  the  tip,  and  fading  away  above  in  the  more 
compact  muscular  structure.  Between  the  hyo-glossal  and  genio- 
glossal  muscles,  and  extending  on  each  side  of  the  infralingual  muscle, 
is  another  fibro-connective  tissue  layer,  attached  behind  to  the  hyoid 
bone. 

Besides  the  former  muscles,  others,  which  intersect  them  in  the  more 
compact  portion  of  the  body  of  the  tongue,  are  distinguished  as  the 
superficial,  transverse,  and  vertical  lingual  muscles. 

The  superficial  lingual  muscle l  forms  a  stratum  on  each  side  of 
the  tongue  beneath  the  mucous  membrane  of  the  dorsum,  consisting  of 
longitudinal  fibres  running  forward  from  the  root  and  curving  towards 
the  tip,  between  the  ascending  bundles  of  the  geriio-  and  hyo-glossal 
muscles. 

The  transverse  lingual  muscle,2  beneath  the  former,  consists  of 
numerous  fibres,  which  curve  from  the  septum  of  the  tongue  outwardly 
to  the  border,  between  the  ascending  bundles  of  the  genio-  and  hyo- 
glossal  muscles. 

The  vertical  lingual  muscle 3  consists  of  bundles  of  fibres,  which 
descend  obliquely,  and  curve  outwardly  from  the  dorsum  to  the  under 
surface  of  the  side  of  the  tongue,  decussating  with  the  superficial  and 
transverse  lingual  muscles  and  ascending  bundles  of  the  genio-glossal 
muscles. 

The  arteries  of  the  tongue  are  chiefly  branches  of  the  lingual,  but 
it  is  also  supplied  by  branches  of  the  facial  and  ascending  pharyngeal 
arteries.  Its  veins  terminate  in  the  facial  and  internal  jugular  veins. 
The  main  lymphatics  follow  the  ranine  vein,  and,  after  passing  through 
one  or  two  little  lymphatic  glands  at  the  side  of  the  hyo-glossal  muscle, 
end  in  the  deep  cervical  glands.  The  nerves  are  the  gustatory  branch 
of  the  trigeminal  nerve,  which  supplies  the  mucous  membrane  and 

1  M.  superficialis  linguse ;  m.  longitudinalis  superior ;  m.  chondro-glossus. 

2  M.  transversus  linguse ;  m.  transversalis.  3  M.  verticalis  linguae. 


THE   ALIMENTARY   APPARATUS.  389 

papillae  of  taste  at  the  fore  part  and  side  of  the  tongue ;  the  lingual 
branch  of  the  glosso-pharyngeal  nerve,  which  sends  filaments  to  the 
mucous  membrane  at  the  posterior  part  of  the  tongue,  and  especially 
to  the  circumvallate  papillae;  and  the  hypoglossal  nerve,  which  is 
distributed  to  the  muscles. 

THE   SALIVAEY   GLANDS. 

The  glands  which  secrete  the  saliva  consist  of  three  on  each  side 
of  the  face,  named  the  sublingual,  submaxillary,  and  parotid  glands. 
They  are  distinctly  lobulated,  racemose  glands ;  are  of  a  dull,  pinkish- 
white  color,  and  are  attached  to  the  contiguous  parts  by  areolar 
tissue. 

The  sublingual  gland,1  the  smallest  of  the  salivary  glands,  lies 
along  the  floor  of  the  mouth,  extending  from  the  lingual  fraanum  back- 
ward, and  producing  a  ridge  of  the  mucous  membrane  between  the 
tongue  and  lower  gum.  It  is  elongated  elliptical,  flattened  parallel 
with  the  mandible,  and  is  about  an  inch  and  a  half  long.  It  rests  below 
on  the  mylo-hyoid,  and  inwardly  on  the  genio-glossal  muscle,  with  the 
lingual  nerve  and  submaxillary  duct  between  them.  Its  anterior  ex- 
tremity is  close  to  its  fellow,  and  behind  it  is  joined  by  a  process  of 
the  submaxillary  gland.  Its  lobules  are  loosely  united,  and  it  has  a 
variable  number  of  ducts,2  commonly  from  a  dozen  to  twenty,  which 
open  along  the  ridge  of  the  mouth. 

The  arteries  of  the  sublingual  gland  are  branches  of  the  submental 
and  lingual,  and  its  veins  join  the  ranine  vein.  The  nerves  are  numer- 
ous, and  derived  from  the  gustatory. 

The  submaxillary  gland,3  the  second  in  size  of  the  salivary  glands, 
lies  partly  within  and  below  the  base  of  the  mandible  in  advance  of 
the  angle,  covered  by  the  skin,  platysma,  and  fascia  of  the  neck.  It 
occupies  a  hollow,  formed  within  by  the  mylo-hyoid  and  hyo-glossal 
muscles,  below  by  the  anterior  belly  of.  the  digastric  muscle,  and  be- 
hind by  the  stylo-maxillary  ligament,  which  separates  it  from  the 
parotid  gland.  The  facial  artery,  in  its  course  to  the  face,  passes 
through  a  channel  in  its  back  and  upper  border.  It  is  of  irregular, 
rounded,  massive  shape,  with  a  prolongation  turning  around  the  back 
border  of  the  mylo-hyoid  muscle,  and  often  another  directed  upward 
and  backward. 

The  submaxillary  duct,4  about  two  inches  long,  leaves  the  gland 
on  the  inner  side,  passes  back  around  the  posterior  border  of  the  mylo- 
hyoid  muscle,  accompanied  by  a  process  of  the  gland,  and  runs  for- 
ward above  the  muscle,  below  and  to  the  inner  side  of  the  sublingual 
gland  to  the  lingual  frsenum.  Here  it  ends  by  a  narrowed  orifice  on  a 

1  Glandula  sublingualis.  2  Ductus  Kivini. 

3  Gl.  submaxillaris,  maxillaris,  or  angularis. 
*  Duct  of  Wharton  ;  ductus  Whartonianus. 


390  THE   ALIMENTARY    APPARATUS. 

little  papilla  beneath  the  tip  of  the  tongue.  The  duct  is  a  line  or  more 
thick,  and  has  a  comparatively  thin  wall. 

The  arteries  and  veins  are  branches  of  the  facial,  submental,  and 
lingual.  The  nerves  are  numerous,  and  mainly  derived  from  the  gusta- 
tory nerve,  including  those  from  the  submaxillary  ganglion ;  and  others 
are  from  the  sympathetic  on  the  facial  artery. 

The  parotid  gland,1  the  largest  of  the  salivary  glands,  is  situated 
at  the  side  of  the  face,  in  advance  of  the  ear.  It  occupies  the  deep 
interval  between  the  ramus  of  the  mandible  and  the  mastoid  process, 
extending  inward  to  the  styloid  process  and  its  muscles,  and  from  the 
zygoma  to  the  angle  of  the  jaw.  Its  fore  part  spreads  and  thins  away 
on  the  masseter  muscle,  and  its  back  part  rests  on  the  sterno-mastoid 
muscle,  and  fills  the  space  between  the  articulation  of  the  jaw  and  the 
mastoid  process.  Below  and  behind  it  is  in  contact  with  the  digastric 
muscle,  and  in  front  extends  between  the  pterygoid  muscles.  Its  shape 
conforms  to  the  space  it  occupies,  and  it  is  a  little  convex  externally, 
and  covered  by  the  skin,  fascia,  and  partially  by  the  platysma  muscle. 
Its  lobules  are  smaller  than  in  the  other  glands,  and  are  more  closely 
united  by  the  interlobular  connective  tissue. 

The  parotid  duct,2  emerging  from  the  fore  part  of  the  gland,  pro- 
ceeds across  the  masseter  muscle,  closely  adherent  to  it,  parallel  with 
the  zygoma,  and  about  the  breadth  of  a  finger  below.  Turning  over 
the  anterior  border  of  the  masseter  inwardly,  it  pierces  the  buccinator, 
and  continues  a  short  distance  obliquely  forward  next  the  mucous 
membrane  of  the  cheek,  and  opens  by  a  contracted  orifice,  on  a  little 
papilla,  into  the  vestibule  of  the  mouth,  opposite  the  second  upper 
molar  tooth.  Its  length  is  about  two  and  a  half  inches,  its  diameter 
scarcely  the  eighth  of  an  inch,  and  its  wall  is  thicker  than  that  of  the 
submaxillary  duct. 

A  small  detached  portion  of  the  gland,  or  an  accessory  gland3  of 
variable  size,  usually  lies  on  the  masseter  in  advance  of  the  main  gland, 
below  the  zygoma  ;  and  by  its  duct  joins  the  main  duct. 

Ascending  through  the  parotid  gland,  behind  the  ramus  of  the  jaw, 
is  the  external  carotid  artery,  which  divides  within  it  into  the  temporal 
and  internal  maxillary  arteries,  the  former  emerging  from  the  gland 
above,  the  latter  from  within,  behind  the  neck  of  the  mandible.  From 
the  back  of  the  gland  emerges  the  posterior  auricular  artery,  and  from 
its  fore  part  the  transverse  facial  artery.  More  superficially  the  tem- 
poral vein  enters  the  gland,  and  is  joined  by  the  internal  maxillary  to 
form  the  temporo-maxillary  vein.  This  divides  into  two  branches,  of 
which  one  joining  the  posterior  auricular  vein  forms  the  external 
jugular  vein,  emerging  from  the  lower  part  of  the  gland,  while  the 
other  branch  also  passes  from  the  latter  to  join  the  facial  artery.  The 

1  Glandula  parotis  or  parotidea. 

2  Duct  of  Steno  or  Stenon ;  ductus  Stenonianus.  8  Gl.  socia  parotidis. 


THE   ALIMENTARY   APPARATUS. 


391 


FIG.  200. 


facial  nerve  enters  the  gland  behind  and  divides  within  it  into  branches, 
which  emerge  from  the  fore  part.  Branches  of  the  great  auricular 
nerve  also  pierce  the  gland. 

The  arteries  which  supply  the  parotid  gland  come  directly  from  the 
external  carotid,  and  from  contiguous  branches  to  other  parts.  The 
veins  correspond  with  them.  The  lymphatics  join  the  deep  and  super- 
ficial ones  of  the  neck.  One  or  two  lymphatic  glands  lie  on  the  surface 
of  the  parotid,  and  often  one  or  two  are  embedded  in  its  substance. 
The  nerves  are  derived  from  the  sympathetic  on  the  external  carotid 
artery,  and  also  from  the  facial,  auriculo-temporal,  and  great  auricular 
nerves. 

The  salivary  glands  are'  compound  racemose  glands,  possessing  a 
common  structure,  though  each  exhibits  certain  important  differences. 
They  consist  of  a  close  aggre- 
gation^of  polyhedral  lobes  and 
lobules,  the  latter  of  which  con- 
sist of  a  similar  aggregation  of 
smaller  ones,  composed  of  the 
peculiar  gland-substance.  The 
lobes  and  lobules  are  invested 
with  and  held  together  by  fibro- 
connective  tissue,  which  also  sup- 
ports the  vessels,  nerves,  and 
ducts  of  the  gland.  The  prin- 
cipal duct  divides  and  subdivides, 
and  furnishes  each  lobe  and  lob- 
ule with  a  branch,  the  branches, 
for  convenience,  being  called  the 
lobar  ducts.  These  communicate 
within  each  lobule  with  the  in- 
tralobar  duct,  which  ramifies  and 
finally  enters  into  communica- 
tion with  the  alveoli  or  follicles 
containing  the  secreting  cells  of 
the  gland. 

The  lobar  ducts  are  lined  with  a  layer  of  columnar  epithelial  cells, 
longitudinally  striated,  and  with  an  oval  nucleus  in  the  outer  part  of 
the  cells.  The  epithelium  includes  a  relatively  large  passage,  and  rests 
on  a  thin  basement  membrane,  sustained  by  fibro-connective  tissue  pro- 
portioned in  quantity  with  the  size  of  the  duct.  In  the  largest  ducts, 
including  the  principal  one,  unstriped  muscular  fibres  enter  into  the 
construction  of  the  wall. 

The  larger  intralobar  ducts *  have  a  relatively  smaller  passage,  and 
are  lined  by  a  layer  of  columnar  cells,  remarkable  for  their  strongly 


SECTION  OF  THE  SUBMAXILLARY  GLAND.  Alveoli 
of  connective  tissue  containing  the  secretory  cells, 
—a  polyhedral  epithelium,  o,  cells  containing 
mucus ;  b,  cells  with  granular  protoplasm ;  c,  cres- 
centic  parietal  cells ;  d,  duct  with  striated  colum- 
nar epithelial  cells. 


Salivary  tubes  of  Pfluger. 


392  THE   ALIMENTARY   APPARATUS. 

striated  condition,  which  is  most  obvious  along  the  inner  or  deeper 
part  of  the  cells  and  gives  them  the  appearance  of  a  short  brush. 
Their  nucleus  is  spherical  or  oval,  and  nearly  central.  The  smaller 
intralobar  ducts J  become  successively  narrower,  and  the  epithelial  cells 
shorter,  polyhedral,  and  clear,  and  then  more  flattened  as  they  join 
the  alveoli.  The  epithelium  of  the  intralobar  ducts  rests  on  a  mem- 
brana  propria  consisting  of  a  delicate  basement  membrane  sustained 
by  fibro-connective  tissue,  gradually  decreasing  with  the  division  of 
the  ducts. 

The  alveoli,2  which  directly  communicate  with  the  latter,  are  rela- 
tively wider  branching  tubes  of  variable  length,  lined  by  the  secreting 
cells.  These  rest  on  a  delicate  membrana  propria  continuous  with 
that  of  the  intralobar  ducts,  and  united  with  the  least  proportion  of 
fibro-connective  tissue  between  the  alveoli,  and  sustaining  the  capillary 
blood-vessels  of  the  latter.  The  alveoli  are  of  two  kinds,  those  which 
yield  a  ropy  liquid,  the  mucus  of  the  saliva,  hence  called  the  mucous 
alveoli,  and  those  which  produce  a  more  watery  secretion,  distin- 
guished as  the  serous  alveoli.  The  serous  alveoli  are  lined  with  poly- 
hedral cells,  with  a  dense  granular  protoplasm,  and  a  peripheral  spher- 
ical nucleus.  The  cells  nearly  fill  the  alveoli,  and  during  secretion, 
they  become  thicker  and  the  passage  of  the  alveoli  narrower.  The 
mucous  alveoli  have  a  greater  calibre  than  the  former,  the  lining  mucous 
cells  being  longer  and  the  passage  larger.  The  cells  are  transparent, 
and  contain  a  soft,  obscurely  granular  protoplasm,  with  a  compressed 
basal  nucleus.  During  secretion  the  cells  swell  and  become  more  trans- 
parent, from  the  production  of  mucus  in  the  protoplasm.  At  the 
bottom  of  the  alveoli,  beneath  the  former  cells,  are  others,  called  the 
parietal  cells,3  which  are  smaller,  granular,  and  polyhedral,  but  in 
section  appear  crescentic. 

In  the  parotid  gland  the  substance  is  composed  entirely  of  serous 
alveoli,  and  therefore  secretes  pure  saliva.  The  sublingual  gland  con- 
tains only  mucous  alveoli,  and  is  therefore  a  mucous  gland.  The  sub- 
maxillary  gland  consists  of  lobules  of  serous  alveoli,  and  smaller  ones 
of  mucous  alveoli,  besides  others  in  which  the  two  kinds  of  alveoli  are 
intermingled. 

The  alveoli  of  the  salivary  glands  are  surrounded  by  close  nets  of 
capillary  blood-vessels,  and  between  them  and  the  alveoli  are  lymph- 
spaces,  which  communicate  with  plexuses  of  lymphatic  vessels  trav- 
ersing the  interlobular  connective  tissue.  The  nerves,  consisting  of 
medullated  fibres,  also  form  a  plexus  in  the  latter,  and  associated  with 
them  are  minute  ganglia. 


1  Intermediary  or  terminal  ducts.  2  Acini. 

3  Crescents  of  Gianuzzi. 


THE   ALIMENTARY   APPARATUS.  393 


SALIVA. 

Saliva  is  the  mixed  secretion  of  the  various  glands  whose  ducts 
open  into  the  mouth,  and  is  a  glairy  and  usually  more  or  less  frothy 
and  turbid  liquid.  Under  the  microscope,  independently  of  remains 
of  food  and  cryptogamous  growths,  it  is  observed  to  contain  epithelial 
scales,  salivary  corpuscles,  and  fine  granules.  Its  reaction  in  health  is 
alkaline,  especially  when  the  secretion  is  abundant.  The  materials 
detected  in  it  are  chiefly  mucin,  with  small  quantities  of  globulin  and 
serum-albumin.  It  also  contains  a  minute  proportion  of  a  substance 
named  ptyalin,  which,  though  it  has  not  been  satisfactorily  isolated, 
manifests  its  power  as  a  ferment,  by  which  the  saliva  converts  starch 
into  sugar. 

Parotid  saliva  is  a  clear,  limpid  liquid  without  viscidity.  It  con- 
tains globulin  and  some  other  forms  of  albumin,  but  little  or  no  mucin. 
Ptyalin  is  indicated  by  its  powerful  action  on  starch.  It  also  contains 
calcium  carbonate  and  potassium  sulpho-cyanide.  It  is  free  of  cor- 
puscles. . 

Submaxillary  saliva  is  viscid,  and  contains  mucin,  abundance  of 
corpuscles,  and  amorphous  particles  of  proteid  material.  Ptyalin  is 
also  indicated  by  greater  activity  on  starch  than  in  the  former.  It 
is  also  more  alkaline  than  parotid  saliva. 

The  epithelial  scales  of  the  saliva,  single  and  in  little  groups,  are 
portions  of  the  detached  epithelium  of  the  mucous  membrane  in  all 
parts  of  the  mouth.  They  are  transparent,  polygonal  plates,  with  a 
clear,  circular,  or  oval  central  nucleus. 

The  salivary  corpuscles  are  pale,  spherical  bodies,  resembling  the 
colorless  corpuscles  of  the  blood.  They  contain  one  or  several  nuclei 
and  numerous  fine  granules,  which  under  high  power  of  the  microscope 
are  observed  to  be  in  an  incessant  state  of  agitation  or  of  molecular 
movement.  They  resemble  the  mucous  corpuscles  of  the  mucous  mem- 
branes generally,  and  with  them  are  probably  to  be  regarded  as  lymph- 
corpuscles  modified  by  the  condition  in  which  they  are  found. 

THE   TEETH. 

Man,  and  most  other  animals  of  his  class,  in  the  course  of  life  are 
provided  with  two  diiferent  sets  of  teeth,  of  which  the  first  that  make 
their  appearance  in  infancy  are  called  the  temporary,  or  milk  teeth, 
and  those  which  displace  and  succeed  them  from  childhood  to  maturity 
are  distinguished  as  the  permanent  teeth.  To  the  first  set  there 
are  twenty  teeth,  ten  in  each  jaw,  and  to  the  second  set  thirty-two 
teeth,  sixteen  in  each  jaw.  The  teeth  form  an  unbroken  row  above 
and  below,  and  on  each  side  they  form  a  series  of  several  different 
kinds,  which  are  named  incisors,  canines,  premolars,  and  molars.  In 
zoology,  in  defining  the  chief  characters  of  mammalia,  it  is  usual  to 


394  THE   ALIMENTARY   APPARATUS. 

indicate  the  number  and  kind  of  teeth  of  each  lateral  series  in  a  for- 
mula. Thus,  the  dental  formula  of  man  and  his  nearest  relatives,  the 
higher  apes,  is  expressed  as  follows : 

21  23 

Permanent  teeth in.  —  ca.  -  premol.  —  mol.  —  =  16  X  2  =  32. 

21  23 

Temporary  teeth in.  -  ca.  -  mol.  -  =  10  X  2  =  20. 

2t  \  2t 

A  tooth  consists  of  two  principal  parts,  that  displayed  in  the  living 
mouth,  white  and  glistening,  and  projecting  from  the  red  gums  at  the 
border  of  the  jaws,  named  the  crown,1  and  another  part  implanted  in 
the  socket,  or  alveolus,  and  named  the  fang,  or  root.2  The  place  of 
union  of  the  crown  and  fang,  scarcely  constricted  and  embraced  by  the 
edge  of  the  gum,  is  called  the  neck. 

The  crown  is  of  various  shapes  in  the  different  teeth  :  in  the  incisors 
being  chisel-like  and  adapted  to  cutting ;  in  the  canines,  conical-pointed 
and  fitted  for  piercing ;  and  in  the  premolars  and  molars  cuboidal  and 
provided  with  tubercles,3  and  suited  to  crushing  the  food.  The  fangs 
are  from  one  to  three  in  the  different  teeth,  and  are  long,  conical  pro- 
cesses by  which  the  teeth  are  firmly  implanted  in  the  sockets,  to  which 
they  are  attached  by  thin,  vascular,  connective  tissue  continuous  with 
the  periosteum  of  the  alveoli  and  the  submucous  tissue  of  the  gum. 
The  tapering  shape  of  the  fangs  accurately  fitting  their  sockets  is 
favorable  to  the  diffusion  of  pressure  communicated  through  the  teeth, 
while  it  is  entirely  removed  from  the  point  of  the  fang  at  which  the 
vessels  and  nerves  enter  the  latter. 

THE   PERMANENT   TEETH. 

The  teeth  in  both  jaws  form  unbroken  arches,  a  condition  which 
is  peculiar  to  man  among  existing  animals  of  the  same  class.  The 
lower  teeth  are  vertical,  though  the  molars  have  a  slight  inward  incli- 
nation. The  upper  teeth  are,  for  the  most  part,  vertical,  though  the 
molars  have  a  slight  outward  inclination,  and  the  front  teeth,  chiefly 
the  incisors,  project  obliquely  to  a  variable  degree  in  different  indi- 
viduals and  races.  The  arches  formed  by  the  teeth  are  nearly  of  equal 
extent,  but  the  upper  is  slightly  the  larger,  and  includes  the  lower  one 
within  its  outer  limit.  They  start  on  the  same  line  behind,  but  the 
upper  arch  extends  laterally  a  little  to  the  outside  of  the  lower  arch 
and  overlaps  it  in  front  from  the  oblique  projection  of  the  incisors. 
When  the  mouth  is  closed,  while  the  upper  incisors  overlap  the  lower 
ones  and  adjacent  sides  of  the  canines,  the  other  teeth  above  and  below 
alternate,  so  that  the  point  of  the  upper  canine  occupies  the  angle 
between  the  lower  canine  and  first  premolar,  the  first  upper  premolar 
the  angle  between  the  lower  ones,  and  so  on  to  the  last  upper  molar, 

1  Corona.  2  Radix.  3  Cusps  ;  lobes. 


THE   ALIMENTARY   APPARATUS. 


395 


which  is  in  contact  alone  with  the  last  lower  molar.  In  the  movement 
of  the  jaw  bringing  the  condyles  on  the  articular  eminences,  the  lower 
molars  are  shifted  past  the  last  upper  ones,  on  the  upper  molars  and 
premolars  in  advance ;  and  the  edges  of  the  lower  incisors  are  pushed 
in  advance  of  those  above. 

The  incisors,1  two  on  each  side  above  and  below,  have  a  single, 
long,  conical  fang,  usually  straight  and  compressed  at  the  sides,  most  in 
the  lower  teeth  and  least  in  the  upper  first  tooth.  The  crown,  as  long 
as,  or  a  little  longer  than,  in  all  the  other  teeth  except  the  canines,  is 
wedge-shaped  and  slightly  gouge-like,  longer  than  broad,  widest  at  the 
biting  edge,  and  narrowing  to  the  base,  where  it  is  thicker  than  wide. 
The  front  surface  is  convex  but  flattened  mesially  towards  the  biting 


UPPER  AND  LOWER  PERMANENT  TEETH,  EX- 
TERIOR VIEW.  1,  first  incisors;  2,  canines;  3, 
first  premolars ;  4,  middle  molars. 


LATERAL  VIEW  of  the  same  teeth  as  in  the  pre- 
ceding figure. 


edge,  and  is  conical  in  outline,  with  rounded  apex  next  the  fang.  The 
posterior  surface  curves  backward  to  the  prominently  convex  base,  is 
variably  concave,  and  sometimes  in  the  upper  teeth  slightly  ridged. 
The  biting  edge,  the  thinnest  part  of  the  crown,  is  transversely  some- 
what convex  or  nearly  straight  and  variably  tuberculate.  The  sides 
of  the  crown  are  curved  triangular  in  outline,  and  convex  but  flattened 
towards  the  base. 

The  upper  incisors  are  of  more  robust  proportions  than  the  lower, 
and  have  a  broader  and  more  gouge-like  crown  ;  the  posterior  surface 
being  more  concave  and  defined  by  more  prominent,  lateral  borders, 
and  sometimes  marked  by  from  two  to  four  slight  longitudinal  folds 


1  Dentes  incisives,  incisores,  or  primores. 


396  THE   ALIMENTARY   APPARATUS. 

or  ridges.  The  cutting  edge  is  more  rounded  transversely,  especially 
at  the  outer  corner,  and  is  also  more  variably  tuberculate. 

The  lower  incisors  are  more  slender,  and  have  a  narrower  crown 
with  a  straighter  cutting  edge,  which  is  pretty  uniformly  divided  into 
three  little  tubercles.  The  fang  is  strongly  compressed  laterally  and 
sometimes  feebly  grooved. 

The  first  upper  incisor  is  commonly  the  longest,  is  the  largest  in 
other  respects,  and  has  the  fang  scarcely  compressed.  The  crown  has 
the  edge  variably  tuberculated,  sometimes  slightly,  and  at  other  times 
distinctly  divided  into  from  three  to  five  little  eminences.  The  second 
upper  incisor,  also  the  second  in  size,  is  a  reduced  likeness  of  the  former, 
but  has  the  more  rounded  cutting  edge  divided  into  three  or  four  little 
eminences. 

The  first  lower  incisor,  commonly  the  smallest,  though  sometimes 
as  long  as  those  above,  has  the  cutting  edge  the  most  rectangular.  The 
second  lower  incisor,  usually  larger  than  the  former,  is  about  the  length 
of  the  corresponding  upper  tooth,  but  is  sometimes  longer,  though  less 
robust  and  less  rounded  at  the  cutting  edge. 

From  the  attrition  to  which  the  incisors  are  subjected,  the  tubercles 
of  the  biting  edges  soon  disappear,  and  as  the  wearing  continues  the 
edges  of  the  crowns  gradually  widen  fore  and  aft,  but  are  reduced  in 
the  opposite  direction.  As  the  edges  of  the  upper  teeth  overlap  those 
below,  they  are  both  worn  away  in  a  bevelled  manner,  and  thus  main- 
tain a  condition  adapted  to  cutting  the  food.  As  may  be  observed  in 
skulls  of  barbarous  races,  in  whom  the  teeth  are  better  preserved  and 
longer  retained,  as  the  crowns  of  the  incisors  wear  away  the  abraded 
surfaces,  from  narrow,  transversely  elliptical,  become  successively  oval, 
nearly  circular,  and  finally  fore  and  aft  oval. 

The  canines,1  of  which  there  is  one  on  each  side  above  and  below, 
are  commonly  the  longest  of  the  teeth,  though  occasionally  they  do  not 
exceed  the  first  upper  incisor.  The  fang  is  usually  longer  and  more 
robust,  is  straight,  and  is  laterally  compressed,  especially  in  the  lower 
ones,  in  which  it  is  also  sometimes  feebly  grooved.  The  crown  is  ovoid 
with  the  length  greatest,  and  with  the  thickness  from  without  inward 
as  great  as,  or  even  slightly  exceeding,  the  breadth.  It  is  commonly 
longer  and  thicker  than  that  of  the  incisors,  except  the  first  upper  one, 
than  which  it  is  slightly  shorter  and  of  less  breadth.  The  base  in  sec- 
tion is  oval,  with  the  longer  diameter  from  without  inward,  and  the 
biting  extremity  tapers  to  a  conical  point.  The  outer  surface,  more 
convex  than  in  the  incisors,  is  rhombic-ovate  in  outline,  rounded  next 
the  fang,  and  angular  towards  the  point.  The  inner  surface  slopes  in- 
ward from  the  latter  to  the  thick,  convex  base,  and  on  each  side  is  de- 
pressed between  a  low  median  ridge  and  the  lateral  prominent  border. 

1  Cuspid  teeth  ;  dentes  cuspidati,  canini,  angulares,  laniarii,  oculares,  or  mor- 
dentes  ;  eye  teeth  and  stomach  teeth. 


THE   ALIMENTAEY   APPARATUS.  397 

The  point  of  the  crown,  about  a  third  of  the  length,  is  produced  in 
an  angular  ridge,  which  extends  from  the  summit  on  each  side  to  the 
greatest  width  of  the  crown,  and  separates  the  outer  and  inner  surfaces. 

As  the  point  of  the  upper  canine  and  adjacent  incisor  overlap  the 
point  of  the  lower  canine,  the  latter  is  worn  outwardly  and  the  former 
inwardly.  Both  become  blunted,  and  by  the  time  the  incisors  are  worn 
square  at  the  biting  border  the  canines  are  reduced  nearly  to  the  same 
level. 

The  premolars,1  two  on  each  side  above  and  below,  are  shorter 
than  the  canines,  but  in  other  measurements  differ  but  little.  They 
are  commonly  nearly  of  the  same  size,  and  mostly  have  a  single  fang, 
laterally  compressed  and  variably  grooved,  especially  in  the  upper 
teeth,  in  which  it  is  sometimes  more  or  less  divided,  usually  in  the 
second  upper  premolar,  but  occasionally  in  the  first  one  or  in  both. 
The  crown  is  shorter  than  in  the  canines,  and  commonly  also  than  in 
the  incisors.  It  is  somewhat  keg-shaped,  narrowest  next  the  fang,  and 
at  the  biting  extremity  divided  into  a  pair  of  broad,  pyramidal  tuber- 
cles,2 of  which  the  outer  one  is  the  larger.  The  outer  and  inner  sur- 
faces of  the  crown  have  about  the  same  convexity  and  outline  reduced 
in  length  like  the  outer  one  of  the  canines.  From  the  points  of  each 
pair  of  tubercles  ridges  proceed  in  opposite  directions,  encircle  the 
crown,  and  define  the  triturating  surface  from  the  sides.  The  tritu- 
rating surface  is  depressed,  and  more  or  less  divided  into  a  pair  of  lat- 
eral pits  by  an  intermediate  ridge  proceeding  from  the  points  of  the 
tubercles. 

The  crown  of  the  upper  premolars  is  laterally  compressed,  the  trit- 
urating surface  is  quadrate  oval,  and  the  tubercles  are  nearly  alike, 
though  the  inner  one  is  slightly  the  smaller.  The  crown  of  the  lower 
premolars  is  but  slightly  compressed  laterally,  is  oval  in  cross-section 
at  the  base,  and  nearly  or  quite  circular  at  the  triturating  surface. 
The  tubercles  are  nearly  alike,  though  usually  the  inner  one  of  the  first 
premolar  is  less  developed  than  in  the  others,  and  is  sometimes  reduced 
to  the  condition  of  a  thick  basal  ridge  to  the  outer  tubercle,  conjoined 
to  the  point  of  the  latter  by  an  intermediate  ridge. 

The  outer  tubercle  of  the  premolar  crown  is  homologous  with  the 
greater  part  of  the  canine  crown,  while  the  inner  tubercle  is  homol- 
ogous with  the  inner  basal  ridge  of  the  latter. 

The  molars,3  of  which  there  are  three  on  each  side  above  and 
below,  are  the  largest  of  the  teeth,  and  are  variable  in  size  and  form, 
especially  the  last  one,  which,  from  its  not  making  its  appearance  until 
near  maturity,  is  commonly  called  the  "wisdom  tooth."*  The  lower 
molars  are  a  little  the  larger,  and  together  occupy  as  much  space  as 

1  Small  molars  ;  bicuspid  teeth  ;  dentes  bicuspidati.  2  Cusps  ;  lobes. 

3  Dentes  molares,  multicuspidati,  or  maxillares  ;_  true  or  large  molars  ;  grinders. 

4  Dens  sapientise  ;  d.  serotinus. 


398  THE   ALIMENTARY    APPARATUS. 

the  upper  ones  together  with  half  the  adjacent  premolar.  The  molars 
of  each  series  usually  exhibit  successively  a  slight  reduction  in  size, 
but  sometimes  the  second  is  the  largest,  and  rarely  they  successively 
increase. 

The  crown  of  the  upper  molars  is  cuboid al  or  rhombic,  with  rounded 
sides,  and  about  two-thirds  the  length  of  the  breadth,  the  diameters 
of  which  are  nearly  equal.  Thickest  about  the  middle,  it  diminishes  to 
the  base  and  to  the  triturating  surface,  which  is  composed  of  four,  or 
three,  pyramidal  tubercles  with  angular-ridged  borders,  which  define 
the  triturating  surface  from  the  sides  of  the  crown. 

Commonly  there  are  four  tubercles  occupying  the  corners  of  the 
triturating  surface  of  the  crown  of  the  first  and  second  molars,  and 
three  tubercles  in  the  last  molar ;  but  frequently  there  are  also  only 
three  to  the  second  molar.  In  the  crown  with  four  tubercles,  the 
antero-internal  is  the  largest,  and  is  usually  extended  so  as  to  join  the 


TRITURATING  SURFACE  OF  MOLAR  TEETH.  1,  first  upper  molar,  right  side;  2,  view  of  another 
specimen ;  3,  second  upper  molar,  right  side  ;  4,  first  lower  molar,  right  side ;  5,  view  of  another 
specimen  ;  6,  second  lower  molar,  right  side. 

postero-external  tubercle,  while  the  others  are  extended  at  the  fore  and 
back  part  of  the  crown  to  join  both  the  former.  This  arrangement 
gives  to  the  triturating  surface  the  appearance  of  a  winding,  sigmoid 
ridge,  with  the  enclosed  intervals  or  valleys  opening  at  the  outer  and 
inner  sides  of  the  crown.  The  sides  of  the  tubercles  sloping  from  their 
angular  summits  into  the  valleys  are  variably  marked  by  lesser  ridges. 
In  the  crown  with  three  tubercles  it  is  less  square,  more  narrowed 
inwardly,  and  usually  wider  from  without  inward  than  fore  and  aft. 
Two  of  the  tubercles  are  external,  and  nearly  equal,  while  the  third  is 
internal  and  much  larger  than  the  others,  which  it  joins  by  its  angular 
ridged  summit  at  the  fore  and  back  part  of  the  crown. 

In  the  molar  of  three  tubercles  these  are  homologous  with  the  outer 
pair  and  antero-internal  one  in  the  molar  of  four  tubercles,  of  which  the 
postero-internal  is  undeveloped  or  rudimentary  in  the  tri-tuberculate 
crown. 


THE   ALIMENTARY   APPARATUS.  399 

The  crown  of  the  lower  molars,  about  the  same  length  and  trans- 
verse breadth  as  in  the  upper  teeth,  is  wider  fore  and  aft.  Commonly, 
in  the  first  and  second  molars  the  triturating  surface  is  formed  by  five 
tubercles,  like  those  of  the  upper  teeth,  differing  little  in  size,  and  ar- 
ranged in  an  outer  row  of  three  and  an  inner  row  of  two.  In  the  last 
molar  there  are  usually  four  tubercles,  occupying  the  corners  of  the 
crown,  and  this  is  also  frequently  the  condition  in  the  second  molar. 
Occasionally  all  the  lower  molars  exhibit  five  tubercles. 

The  upper  molars  have  three  fangs,  of  which  two  are  external, 
vertical,  or  slightly  divergent,  and  straight  or  somewhat  bent ;  and  the 
third  internal,  thicker,  and  longer  than  the  former,  and  directed  upward 
and  inward,  often  grooved,  and  sometimes  forked  at  the  end.  In  the 
last  molar  the  fangs  are  commonly  more  or  less  confluent,  and  often 
united  in  a  single  cone  with  variable  traces  of  division. 

The  lower  molars  have  a  pair  of  broad  fangs  placed  one  behind  the 
other  and  grooved,  usually  parallel  and  somewhat  bent,  or  straight  and 
slightly  divergent.  In  the  last  of  the  series  the  two  fangs  are  often 
more  or  less  confluent. 

The  wisdom  tooth  is  exceedingly  variable  in  its  condition  of  develop- 
ment, and  often  differs  on  the  two  sides  of  the  jaws,  as  it  does  also  in 
different  individuals.  Its  size  or  degree  of  development  is  related  with 
the  size  of  the  jaws. 

From  attrition  the  tubercles  of  the  premolars  and  molars  are  gradu- 
ally worn  away,  so  that  finally  the  triturating  surfaces  of  the  teeth 
become  flat,  or  slightly  excavated  in  the  lower  teeth,  and  proportion- 
ately prominent  in  the  upper  ones.  With  the  obliteration  of  the 
tubercles  little  islets  of  dentine  appear,  and  with  the  further  wear  of 
the  teeth  the  latter  widen  and  become  confluent,  and  ultimately  the 
triturating  surface  exhibits  a  broad  expanse  of  dentine  bordered  with 
enamel.  In  the  wear  of  the  crown  beyond  the  middle  of  its  length  it 
gradually  diminishes  in  breadth,  as  is  the  case  likewise  with  the  canines 
and  incisors. 

Ordinarily  the  crowns  of  the  teeth  of  each  jaw  near  their  biting 
border  and  triturating  surface  are  in  close  contact  with  one  another 
throughout  the  series,  but  are  separated  by  considerable  angular  inter- 
vals approaching  the  fangs.  As  the  crowns  are  worn  away  they  main- 
tain their  close  apposition,  and  form  together  a  continuous  triturating 
surface,  while  the  intervals  next  the  fangs  are  narrowed  as  well  as 
shortened. 

THE   TEMPORAKY  TEETH. 

Of  the  ten  temporary  teeth 1  in  each  jaw,  the  series  of  five  on 
each  side  of  the  median  line  consists  of  two  incisors,  a  canine,  and 
two  molars,  or  the  same  number  and  kind  of  the  former  two  as  in 

1  Milk  teeth  ;  deciduous  teeth  ;  denies  lactei,  caduci,  or  temporarii. 


400 


THE  ALIMENTARY  APPARATUS. 


the  permanent  set,  with  no  premolars  and  one  molar  less.  They  are 
smaller  than  the  permanent  teeth,  but  are  broader  in  proportion  to 
their  length. 

The  incisors  and  canines  have  the  same  proportions  among  themselves 
as  in  the  permanent  set,  which  they  also  resemble  in  form,  but  have 
their  crown  in  general  proportionately  broader,  and  do  not  have  the 
fangs  laterally  compressed.  The  crown  of  the  first  upper  incisor  is  of 
greater  breadth  than  the  length,  which  is  about  equal  to  the  thickness 
at  base.  The  crown  of  the  second  upper  incisor  has  the  length  and 
breadth  about  equal  and  the  thickness  somewhat  less.  In  the  lower 
incisors  the  length  of  the  crown  exceeds  the  breadth,  especially  in  the 
second  one,  and  the  thickness  is  least.  The  fang  of  the  first  upper 


6789 

THE  TEMPORARY  TEETH  OF  ONE  SIDE.  1, 2,  upper  and  lower  incisors ;  3,  upper  and  lower  canine ; 
4,  5,  upper  and  lower  molars ;  6,  7,  triturating  surface  of  the  lower  molars ;  8,  9,  triturating  sur- 
face of  the  upper  molars. 

incisor  is  thicker  fore  and  aft  than  from  side  to  side,  but  in  the  others 
is  more  uniform. 

The  crown  of  the  upper  canine,  larger  than  that  of  the  incisors, 
has  an  equal  breadth  and  a  less  thickness.  The  crown  of  the  lower 
canine  is  longer  and  narrower  than  that  of  the  upper  one,  and  has  the 
thickness  nearly  equal  to  the  breadth. 

The  molars  are  constructed  on  the  plan  of  the  permanent  ones,  but 
have  a  proportionately  shorter  crown  and  smaller  fangs,  of  which  they 
possess  the  same  number  above  and  below  as  in  the  permanent  teeth, 
but  differ  strikingly  in  their  greater  divergence  from  one  another. 

The  crown  of  the  first  upper  molar  variably  approximates  both  in 
size  and  form  an  upper  premolar,  which  it  often  resembles,  with  the 
outer  tubercle  pushed,  as  it  were,  partially  in  advance  of  the  inner  one. 
In  other  instances  the  outer  tubercle  presents  more  or  less  disposition 
to  the  production  of  two  accessory  tubercles,  and  in  this  way  approaches 


THE   ALIMENTAEY   APPAEATUS.  401 

more  nearly  the  condition  of  the  second  molar.  The  latter  ordinarily 
approximates  in  size  and  shape  an  upper  permanent  molar,  with  the 
four  tubercles  disposed  to  assume  the  arrangement  of  an  S-like  ridge, 
but  with  the  summits  more  contracted.  The  crown  of  the  second  lower 
molar  approximates  in  size  and  form  the  five  tuberculate  permanent 
lower  molars,  but  is  more  contracted  at  the  triturating  surface.  The 
crown  of  the  first  lower  molar  is  a  reduced  representative  of  the  second 
one. 

The  first  upper  molar  has  its  crown  horizontally  half  oval  or  tri- 
lateral and  convex  inwardly.  The  triturating  surface  is  formed  by 
three  tubercles,  of  which  the  inner  one  is  largest,  most  distinct,  and 
demiconical.  The  outer  pair  are  but  feebly  separated,  and  of  these  the 
posterior  is  the  smaller  and  least  distinct.  A  ridge  in  front  connects 
the  anterior  with  the  inner  tubercle,  and  is  sometimes  so  much  produced 
as  to  form  an  accessory  tubercle. 

The  second  upper  molar,  considerably  larger  than  the  former,  has 
a  more  quadrate  crown,  which  is  nearly  like  that  of  the  permanent 
upper  molars.  The  triturating  surface  is  formed  in  the  same  manner 
as  in  the  latter,  but  is  frequently  varied  from  a  less  proportionate  de- 
velopment of  the  postero-internal  lobe  and  a  variably  greater  pro- 
duction of  the  anterior  ridge  of  the  crown,  which  may  appear  as  an 
accessory  tubercle. 

The  first  lower  molar  has  a  horizontally  ovoid  crown,  widest  behind, 
and  considerably  narrowed  in  front  approaching  the  triturating  surface, 
which  is  obscurely  divided  into  four  tubercles.  Of  these  the  posterior 
,  pair  are  much  the  smaller,  especially  the  inner  one.  The  ridged  sum- 
mit of  the  outer  tubercles,  at  the  front  and  back  of  the  crown,  curves 
inwardly  to  the  inner  tubercles.  The  second  lower  molar,  also  consider- 
ably larger  than  the  former,  likewise  resembles  the  lower  permanent 
molars  in  the  shape  and  construction  of  its  crown. 

STRUCTURE   OF   THE   TEETH. 

The  teeth  contain  a  soft  substance,  the  dental  pulp,  and  the  pulp 
cavity  occupying  the  central  portion  of  the  crown  nearly  conforms  to 
this  in  shape,  and  tapers  in  each  fang  into  a  canal  which  opens  by  a 
small  orifice  at  the  point  of  the  latter.  The  cavity  in  the  incisors  is 
extended  towards  each  corner  of  the  crown,  in  the  canine  towards  the 
summit,  and  in  the  premolars  and  molars  towards  the  tubercles.  "When 
two  fangs  are  confluent  a  separate  canal  occupies  each.  The  pulp  cavity 
is  largest  in  the  young  tooth,  and  gradually  decreases  with  the  advance 
of  life. 

The  dental  pulp '  is  a  soft,  red,  highly  vascular  and  sensitive  sub- 
stance, the  basis  of  which  is  formed  by  numerous  nucleated  cells,  which 
divide  into  fine  filaments  and  freely  interlace  together.  The  peripheral 

1  Pulpa  dentis. 
26 


402 


THE   ALIMENTARY   APPARATUS. 


FIG.  205. 


portion  consists  of  a  layer  of  nucleated  columnar  cells,  named  the  odon- 
toplasts.  These  divide  into  filaments  at  their  inner  extremity,  and 
interlace  with  the  other  cells;  and  at  their  outer  extremity  they  give 
off  one  or  more  filaments,  which  penetrate  the  dentinal  tubules.  The 
capillary  blood-vessels  of  the  pulp  form  a  close  net  beneath  the  odonto- 
plasts,  and  non-medullated  nerve-fibrils  extend  from  the  pulp  between 
the  latter  towards  the  tooth. 

The  arteries  of  the  dental  pulp  are  derived  from  the  dental  branches 
of  the  internal  maxillary  artery,  and  the  veins 
are  corresponding  companions.  The  nerves 
are  derived  from  the  dental  branches  of  the 
superior  and  inferior  maxillary  divisions  of 
the  trigeminal  nerve. 

The  hard  substance  of  the  teeth  is  com- 
posed of  three  different  tissues,  dentine, 
enamel,  and  cementum. 

The  dentine,  or  ivory,1  forms  the  chief 
bulk  of  a  tooth,  and  is  an  apparently  homoge- 
neous, yellowish -white  substance  more  dense 
than  bone.  It  resembles  the  latter  in  chemical 
composition,  but  contains  a  greater  propor- 
tion of  bone-earth,  amounting  to  nearly  three- 
fourths  of  the  whole.  The  bone-earth.  72  per 
cent.,  consists  of  calcium  phosphate,  66.7,  cal- 
cium carbonate,  3.3,  magnesium  phosphate 
and  other  salts,  including  calcium  fluoride,  2. 
The  bone-cartilage,  28  per  cent.,  like  that  of 
bones,  is  resolved  into  gelatin  by  boiling. 

Sections  of  dentine  prepared  for  the  mi- 
croscope and  viewed  by  transmitted  light 
exhibit  numerous  fine,  black,  parallel  lines  traversing  a  translucent 
matrix ;  the  black  lines  being  due  to  tubules  filled  with  air.  By  re- 
flected light  the  lines  appear  white  on  a  dark  ground.  The  dentinal 
tubules2  commence  on  the  surface  of  the  pulp  cavity,  where  their  ori- 
fices come  into  contact  with  the  dental  pulp,  and  thence  they  radiate 
everywhere  through  the  dentine  to  its  exterior  surface.  They  pursue 
a  generally  parallel  undulating  course  with  two  or  three  gentle  curva- 
tures, and  also  run  in  an  extended  or  open  spiral.  Largest  at  their 
commencement  in  the  pulp  cavity,  they  slightly  diverge  and  repeatedly 
fork  as  they  proceed  outwardly,  taper  and  end  in  the  finest  branches 
at  the  periphery  of  the  dentine.  They  are  of  nearly  uniform  diameter, 
and  are  separated  from  one  another  about  two  or  three  times  their 
thickness.  From  their  sides  emanate  innumerable  minute  twigs,  which 
diverge  into  the  intertubular  substance,  where  they  imperceptibly  end. 


VERTICAL  SECTION  OF  A  MOLAR 
TOOTH,  moderately  magnified. 
1,  enamel,  the  lines  of  which  in- 
dicate the  arrangement  of  its 
columns;  2,  dentine,  the  lines 
indicating  the  course  of  its  tu- 
bules; 3,  thin  lamina  of  the 
dentine  forming  the  wall  of  the 
pulp  cavity,  the  dots  indicating 
the  orifices  of  the  dentinal  tu- 
bules ;  4,  cementum. 


1  Tooth-bone  ;  proper  tooth-substance.  2  Canaliculi  dentium  ;  calcigerous  tubes. 


THE   ALIMENTARY   APPARATUS. 


403 


The  tubules  have  a  relatively  thick  wall1  distinct  from  the  intertu- 
bular  dentine,  appearing  in  cross-section  as  a  ring  surrounding  the  ori- 
fices. They  contain  homogeneous  soft  filaments  projecting  from  the 
odontoplasts  of  the  dental  pulp.  The  terminal  tubules  mostly  end  in 
the  peripheral  layer  of  dentine,2  where  they  communicate  with  narrow, 
irregular  intervals  occupied  by  soft  substance,  apparently  uiicalcified 
dentine.  The  intervals  are  limited  by  botryoidal  walls  composed  of 
minute  globules  of  dentine,  whence  they  are  called  interglobular 
spaces.  Many  of  the  dentinal  tubules  traverse  these  spaces  and 
enter  the  adjacent  enamel  or  cementum. 

The  dentinal  tubules  at  their  commencement  measure  about  4  .*0-p 
of  an  inch  in  thickness. 

When  the  bone-earth  has  been  removed  from  teeth  the  dentinal 
cartilage  is  separable  into  laminae  parallel  with  the  surfaces  of  the 
pulp  cavity,  indicating  its  mode  of  original  production.  In  sections 

FIG.  206. 


Fig.  206.  VERTICAL  SECTION  OF  THE  FANG  OF  A  CANINE  TOOTH,  exhibiting  the  structure  of  the 
dentine  and  cement.  1,  inner  extremities  of  the  dentinal  tubules ;  2,  outer  extremities  of  the 
tubules,  terminating  in  interspaces  at  the  boundary  of  the  dentine ;  3,  cementum ;  4,  lacunae  like 
those  of  bone.  Highly  magnified. 

Fig.  207.  SECTION  OF  DENTINE,  cutting  across  the  direction  of  its  tubules,  very  much  magni- 
fied. The  tubules  are  seen  to  have  thick  walls,  distinct  from  the  intertubular  substance. 

of  teeth  prepared  for  the  microscope,  variable  lines  are  often  observed 
conforming  with  the  direction  of  the  laminae  indicated.  These  lines3 
exhibit  interglobular  spaces  like  those  of  the  periphery  of  the  dentine, 
but  of  greater  capacity  and  apparently  of  like  nature. 

The  enamel  *  forms  the  glistening  white,  exposed  surface  of  the 
teeth,  and  it  is  not  only  the  hardest  part  of  the  latter,  but  of  all  or- 
ganic tissues,  and  is  therefore  admirably  adapted  to  prevent  rapid 
wearing  of  the  teeth.  Where  these  are  most  exposed  to  attrition  it  is 
about  one-sixteenth  of  an  inch  thick,  and  towards  the  bottom  of  the 
crown  it  thins  away  to  a  sharp  circular  edge  at  the  neck  of  the  tooth. 

The  enamel  contains  the  smallest  proportion  of  bone-cartilage, 
amounting  to  about  3.5  per  cent.,  while  all  the  rest  is  bone-earth,  con- 
sisting of  calcium  phosphate,  89.8 ;  calcium  carbonate,  4.4 ;  magnesium 
phosphate  and  other  salts,  including  a  trace  of  calcium  fluoride,  1.3 
per  cent. 

1  Dentinal  sheath.  2  Granular  layer.  s  Incremental  lines. 

4  Substantia  vitrea,  adamantina,  or  filamentosa ;  crusta  adamantina. 


404  THE   ALIMENTARY   APPARATUS. 

The  enamel  is  very  brittle,  and  is  very  liable  to  crack,  even  during 
life,  from  undue  pressure  or  the  application  of  extreme  cold.  In  pre- 
pared specimens  of  teeth  it  is  also  readily  cracked  through  drying  or 
violence.  The  broken  edge  exhibits  a  vertical  fibrous  appearance,  due 
to  the  enamel  being  composed  of  narrow  columns,  which  are  applied  by 
one  end  to  the  dentine  in  shallow  impressions  of  the  surface,  and  by 
the  other  end  form  the  free  surface  of  the  crown.  The  columns  are  six- 
sided,  and  closely  united  by  a  small  proportion  of  homogeneous  cement- 
ing substance.  They  are  slightly  flexuose  and  divergent  in  their  course, 
and  have  others  interposed  in  the  intervals  towards  the  free  surface.  In 
the  unworn  teeth  the  columns  are  invested  on  the  surface  of  the  enamel 
with  a  thin,  homogeneous  layer,  called  the  cuticle,  which,  through  treat- 
ment with  silver  nitrate,  exhibits  the  outlines  of  non-nucleated  epithe- 
lial cells.  The  diameter  of  the  enamel  columns  is  about  -5-^  of  an  inch. 

At  the  attached  surface  of  the  enamel  irregular  intervals  extend  from 
the  dentine  a  variable  distance  outwardly  among  the  enamel  columns. 

FIG.  208.  FIG.  209.  FIG.  210. 


3 

Fig.  208.  CROWN  OF  A  CANINE  TOOTH,  fore  and  aft  section,  the  fang  undeveloped.  1,  layer  of 
enamel ;  2,  dentine ;  3,  pulp  cavity.  Magnified  two  diameters. 

Fig.  209.  THREE  ENAMEL  COLUMNS,  highly  magnified ;  exhibiting  the  six-sided  prismatic  and 
waving  character. 

Fig.  210.  SECTION  OF  ENAMEL,  highly  magnified,  at  right  angles  to  the  course  of  its  columns ; 
exhibiting  the  six-sided  character  of  the  latter. 

In  thin  sections  of  the  teeth  the  enamel  exhibits  alternate  light  and 
darker  stripes  extending  through  its  thickness,  and  narrow,  concentric, 
brownish-colored  lines.  The  enamel  columns  are  also  crossed  by  alter- 
nate darker  and  lighter  shadings. 

The  cementum  l  occurs  in  small  proportion  in  the  human  teeth, 
but  is  largely  produced  and  is  an  important  factor  in  the  teeth  of  many 
large  herbivorous  animals,  as  the  ox,  the  horse,  and  the  elephant.  It 
consists  of  osseous  tissue  with  little  modification  of  structure,  and 
forms  a  thin  layer  to  the  exterior  surface  of  the  dentine  of  the  fangs. 
It  gradually  thickens  towards  the  end  of  the  latter,  and  increases  with 
the  advance  of  age,  when  it  often  forms  accumulations  at  the  end 
of  the  fangs,  obstructing  the  entrance  to  the  pulp  cavity.  It  is  lami- 
nated, and  contains  branching  corpuscles  like  those  of  ordinary  bone, 
but  larger  and  less  regular.  When  the  cementum  is  thicker  than  usual 

1  Cement ;  crusta  petrosa ;  crusta  ostoides  radicis  ;  cortical  substance. 


THE   ALIMENTARY   APPARATUS. 


405 


it  may  also  contain  vascular  canals.  In  the  temporary  teeth  the 
cementum  is  thinner  and  its  corpuscles  fewer. 

In  old  teeth  the  surface  of  the  pulp  cavity  is  formed  of  a  variably 
thick  layer  of  a  substance  different  from  dentine,  and  partaking  of  the 
character  of  this  and  of  bone,  whence  its  name  of  osteo-dentine. 
It  occurs  after  adult  age,  and  in  much  worn  molar  teeth  is  sometimes 
observed  extending  to  the  centre  of  the  triturating  surface.  It  is  de- 
rived from  the  calcification  of  the  remains  of  the  dental  pulp,  which 
sometimes  occurs  to  such  an  extent  as  to  obliterate  the  pulp  cavity. 

The  development  of  the  teeth  commences  in  the  embryo  about  the 
seventh  week.  At  this  time  the  border  of  the  jaws  is  covered  by  a 


DIAGRAM  OF  THE  MODE  or  DEVELOPMENT  OF  THE  TEETH,  a,  section  across  the  dental  groove; 
b,  dental  papilla  developed  in  the  latter ;  c,  the  groove  deepened  and  processes  forming  which 
ultimately  close  it ;  d,  the  papilla  become  the  dental  pulp  and  the  groove  becoming  closed ;  e, 
dental  sac  containing  a  dental  pulp,  which  is  the  rudiment  of  the  crown  of  a  temporary  incisor; 
the  cavity  above  is  reserved  for  a  permanent  incisor;  /,  the  crown  of  the  temporary  incisor  fully 
formed,  and  the  reserved  cavity  for  the  permanent  tooth  moving  backward ;  g,  fang  of  the  tem- 
porary incisor  produced,  and  origin  of  the  dental  papilla  of  the  future  permanent  tooth ;  h,  erup- 
tion of  the  temporary  incisor,  and  the  alveoli  produced  for  both  teeth;  i,  the  temporary  incisor 
occupying  its  functional  position,  and  the  crown  of  the  permanent  incisor  developed. 

thick  layer  of  epithelium,  of  which  the  deeper  portion1  occupies  a 
groove2  in  the  subepithelial  embryonic  connective  tissue.  An  increased 
growth  of  the  epithelium  gives  rise  to  the  enamel-germs3  of  the 
temporary  teeth,  which  appear  as  flask-shaped  accumulations  of  cells 
occupying  corresponding  recesses  of  the  jaws  and  attached  by  their 
neck  to  the  epithelium  at  the  edge  of  the  latter.  With  the  appearance 
of  the  enamel-germs  a  vascular  eminence,  the  dental  papilla,  project- 
ing into  them,  is  developed  from  the  subepithelial  connective  tissue  at 
the  bottom  of  the  recess  occupied  by  each  germ.  The  dental  papilla 
assumes  the  shape  of  the  future  crown,  and  is  covered  by  the  enamel- 
germ  inserted  upon  it,  cup-like  in  form,  and  now  separated  by  the  ob- 

1  Common  enamel-germ.          2  Primitive  dental  groove.          3  Special  enamel-germs. 


406 


THE  ALIMENTAKY  APPARATUS. 


FIG.  212. 


literation  of  its  neck  from  the  epithelium  at  the  edge  of  the  jaws.  The 
dental  papilla  and  enamel-germ  together  form  the  tooth-germ,  during 
the  production  of  which  it  becomes  enclosed  in  a  vascular  membrane, 
the  dental  sac,  continuous  with  the  papilla  of  the  tooth-germ,  and 
developed  from  the  subepithelial  connective  tissue  of  the  recess  occu- 
pied by  the  latter.  The  bony  jaws  first  appear  as  an  open  gutter  con- 
taining the  dental  sacs  with  their  enclosed  tooth-germs.  The  gutter 
soon  becomes  divided  into  compartments  with  narrowed  openings, 
through  which  the  dental  sacs  adhere  to  the  gum.  The  alveoli  are 
formed  at  a  later  period,  in  accordance  with  the  production  of  the 
fangs  of  the  teeth  and  the  growth  of  the  alveolar  border  of  the  jaws. 
The  dental  sacs  consist  of  an  outer  vascular  fibro-connective-tissue 

layer  attached  to  the  con- 
tiguous periosteum  and  gum, 
and  an  inner  more  vascular 
layer  united  with  the  former 
by  soft,  jelly-like,  connective 
tissue.  The  blood-vessels 
are  derived  from  the  dental 
arteries  which  run  along 
the  bottom  of  the  sacs,  and 
partly  from  those  of  the 
gums. 

The  dental  papilla,  having 
assumed  the  shape  and  size 
of  the  crown  of  the  future 
tooth,  is  henceforth  distin- 
guished as  the  dental  pulp. 
After  its  production  it  begins 
to  harden  or  calcify,  and  is 
thus  converted  into  dentine, 
while  at  the  same  time  the 
enamel  is  produced  from  the 
enamel-germ  or  organ  on  its 
exterior.  Calcification  com- 
mences in  the  appearance  of 
little,  thin  shells  of  dentine 
on  the  prominent  points  of 
the  dental  pulp,  correspond- 
ing in  number  with  those 
points.  Thus  there  is  one  for 
the  incisors  and  canine,  two 
for  the  premolars,  and  from 
three  to  five  for  the  molars. 

The  little  shells  expand  at  the  edges,  and  where  there  are  more  than 
one,  as  in  the  molars,  they  become  confluent.      Continuing  to   grow 


DEVELOPMENT  OF  TEETH  IN  THE  PIG.  1, 2,  sections  fore 
and  aft  of  the  maxilla  with  tooth-germs  from  a  young 
embryo ;  3,  from  an  older  embryo,  a,  epithelium  of  the 
gum ;  b,  deeper  layer ;  c,  deepest  layer  of  columnar 
cells ;  d,  enamel-germ,  and  later,  e,  enamel  organ  con- 
nected by  a  stem  with  the  gum ;  /,  dental  papilla ;  g, 
inner,  and  h,  outer,  layers  of  the  dental  sac ;  i,  section  of 
a  vessel ;  k,  osseous  structure  of  the  jaw. 


THE   ALIMENTAEY   APPARATUS. 


407 


around  the  edge  of  the  shell,  this  also  grows  in  thickness  by  the  calci- 
fication of  the  pulp,  which  proportionately  decreases.  "While  the  den- 
tinal  shells  grow,  in  like  manner  the  enamel  extends  step  by  step  with 
them,  and  also  increases  in  thickness.  After  the  crown  is  completed 
the  pulp  becomes  slightly  narrowed  at  the  neck,  and  then  grows  in 
length  in  a  tapering  manner  to  form  the  basis  of  the  fangs.  Where 
there  are  more  than  one  of  these  to  a  tooth  the  pulp  divides  at  the  base 
of  the  crown,  and  then  each  portion  grows  in  the  manner  of  that  of 
the  single-fanged  teeth.  Step  by  step  with  the  elongation  of  the  pulp 
the  calcification  extends  in  length  and  thickness  in  the  production  of 
the  fang,  and  finally,  in  the  complete  tooth,  the  pulp  is  reduced  to  the 
condition  usually  observed  occupying  the  pulp  cavity.  Calcification 
of  the  temporary  teeth  commences  about  the  end  of  the  fourth  month 
of  the  embryo,  and  about  the  middle  period  caps  of  dentine  have  been 
formed  on  all  of  them. 

The  description  of  the  development  of  the  temporary  teeth  from 
the  tooth-germs  also  applies  to  that  of  the  permanent  teeth. 

Production  of  the  dental  tissues.  The  description  of  the  den- 
tal pulp  of  the  mature  teeth  applies  to  the  same  before  its  calcification. 
In  the  production  of  the  dentine  the  peripheral  layer  of  columnar  cells, 
the  odontoplasts,  are  chiefly  concerned.  These  project  from  their  outer 


FIG.  213. 


VERTICAL  SECTION  OF  THE  GERM  OF  A  MOLAR  TOOTH,    a,  vascular  papilla;  6,  odontoplasts ;  c, 
dentine  pervaded  with  tubules ;  d,  enamel ;  e,  cuticle. 

extremity  filamentous  processes,  around  which  the  matrix  of  the  den- 
tine is  formed  by  the  calcification  of  an  intervening  homogeneous 
substance,  probably  derived  from  the  odontoplasts.  As  the  calcifica- 
tion proceeds  from  without  inwardly  the  body  of  the  odontoplasts 
recedes,  leaving  extensions  as  the  dentinal  filaments,  which  occupy  the 
dentinal  tubules.  In  this  recession  of  the  odontoplasts  they  probably 
continue  to  grow,  but  probably  also  are  succeeded  by  others  produced 
successively  in  the  dental  pulp.  The  calcification  occurs  in  minute 


408  THE    ALIMENTARY   APPARATUS. 

spherical  nodules,  and  in  positions  in  which  the  process  is  incomplete 
the  so-called  interglobular  spaces  occur. 

The  cells  of  the  enamel-germ,  at  first  soft  and  rounded  polyhedral, 
multiply  by  division,  and  then  undergo  transformation,  after  which  it 
is  called  the  enamel  organ.1  The  central  cells  become  stellate,  re- 
taining their  central  nucleus  and  anastomosing  by  their  rays,  the  inter- 
vals of  which  are  occupied  by  a  clear,  jelly-like  liquid.  The  cells  next 
the  dental  pulp  form  a  close  layer2  of  six-sided  columns,  while  those 
on  the  inner  surface  of  the  dental  sac  form  a  pavement  of  six-sided 
blocks.  Into  the  enamel  organ  project  numerous  processes  of  the  den- 
tal sac,  minute  papillae  resembling  those  of  the  oral  mucous  membrane. 
The  columnar  cells  of  the  enamel  organ  by  calcification  form  the  enamel 
columns,  and  as  the  process  proceeds  the  cells  either  grow  or  else  are 
succeeded  by  the  production  of  others.  The  enamel  organ  gradually 
disappears,  and  its  outer  layer  of  pavement-cells  is  supposed  to  be 
the  source  of  the  cuticle  of  the  tooth.  The  cementum  is  formed  from 
the  connective-tissue  investment  of  the  fang,  as  in  the  production  of 
bone  from  the  periosteum. 

Eruption  of  the  temporary  teeth.  At  birth  the  crowns  of  the 
temporary  teeth  enclosed  within  their  sacs  occupy  compartments  within 
the  jaw,  with  somewhat  narrowed  apertures,  through  which  the  sacs 
adhere  to  the  gum.  The  eruption,  or  cutting,  of  the  teeth  commences 
from  six  to  nine  months  after  birth,  and  is  usually  completed  at  the 
end  of  the  second  year.  The  lower  teeth  commonly  precede  the  upper 
ones  in  their  appearance,  commencing  with  the  central  incisors.  After 
a  few  months  the  lateral  incisors  appear,  then  the  first  molars,  and 
after  four  or  five  months  more  the  canines,  and  lastly  the  second 
molars.  The  eruption  of  the  teeth  is  concurrent  with  the  growth  of 
the  fangs.  It  is  preceded  by  an  absorption  of  part  of  the  wall  of  the 
cavity  containing  the  tooth,  after  which  a  restoration  of  the  osseous 
structure  occurs  and  forms  the  alveolus  around  the  fang  of  the  tooth. 
Before  the  eruption,  the  gum  undergoes  some  change,  the  edge  be- 
coming harder  and  sharper,  but  as  the  teeth  approach  the  edge  this 
becomes  tumid  and  purplish,  and  a  whitish  spot  on  line  is  seen  through 
the  vascular  gum,  soon  followed  by  the  emergence  of  the  tooth. 

Development  of  the  permanent  teeth.  Ten  permanent  teeth 
in  each  jaw  succeed  the  temporary  teeth,  and  three  others  are  added 
farther  back  on  each  side  above  and  below.  The  former  appear  towards 
the  end  of  the  fourth  month  of  the  embryo  as  enamel-germs  springing 
from  the  neck  of  those  of  the  temporary  teeth.  They  grow  within  the 
jaw  as  club-shaped  bodies  behind  the  position  of  the  germs  of  the  tem- 
porary teeth,  and  subsequently  pursue  the  same  course  of  development 
as  the  latter.  The  new  germs  in  like  manner  become  enclosed  in  den- 
tal sacs,  which  adhere  by  a  narrow  neck  to  the  back  of  the  temporary 

1  Organon  adamantine.  2  Membrana  adamantinae. 


THE   ALIMENTARY   APPARATUS.  409 

dental  sacs.  As  the  permanent  dental  sacs  with  their  germs  continue 
to  grow  they  recede  more  deeply  in  the  jaw,  but  retain  their  connection 
with  the  gum  by  a  long  pedicle,1  which  previously  formed  the  neck  of 
attachment  to  the  temporary  dental  sac,  and  originally  was  the  neck 
of  the  enamel-germ.  The  upper  permanent  teeth  are  developed  in 
recesses  above  and  behind  the  upper  temporary  teeth,  and  the  lower 
permanent  teeth  below  and  behind  the  lower  temporary  teeth.  The 
recesses  are  separated  from  the  alveoli  of  the  temporary  teeth,  and 
each  communicates  by  a  canal 2  for  the  pedicle  of  the  dental  sac,  which 
opens  at  the  edge  of  the  jaw  behind  the  corresponding  temporary  tooth. 
The  permanent  teeth  are  separated  from  the  temporary  teeth  by  a  thin 
osseous  partition,  which,  as  well  as  the  fang  of  the  contiguous  tempo- 
rary tooth,  is  absorbed  when  the  former  is  about  to  protrude.  As  this 
occurs  the  temporary  tooth  is  shed  and  the  permanent  tooth  takes  its 
place.  The  absorption  of  the  fangs  of  the  temporary  teeth  appears  not 
to  be  the  result  of  direct  pressure,  but  occurs  through  the  agency  of 
absorbing  cells  or  osteoclasts  in  contact  with  the  fangs. 

The  additional 'permanent  teeth,  which  are  the  three  permanent 
molars,  have  no  predecessors,  but  are  developed  in  succession  in  the  jaws 
back  of  the  other  teeth.  The  epithelial  production  at  the  border  of  the 
jaws,  from  which  were  developed  the  enamel-germs  of  the  temporary 
teeth,  is  persistent  back  of  the  latter,  and  about  the  fifteenth  week  of 
the  embryo  gives  origin  to  the  enamel-germ  of  the  first  permanent  molar. 
Long  after,  about  seven  months  subsequent  to  birth,  another  germ  ap- 
pears, that  for  the  second  permanent  molar,  projecting  back  from  the 
neck  of  the  former.  After  another  long  period,  during  which  the  first 
and  second  permanent  molars  have  considerably  advanced  in  their 
development,  about  the  third  year,  a  third  germ,  that  of  the  wisdom 
tooth,  appears  back  of  the  others.  The  subsequent  development  of  these 
teeth  is  the  same  as  that  described  in  the  others. 

Calcification  in  the  permanent  teeth  commences  with  the  first 
molars  about  five  or  six  months  after  birth  ;  with  the  central  incisors 
a  little  later;  the  lateral  incisors  and  canines  about  eight  or  nine 
months ;  the  premolars  two  years  or  more  ;  the  second  molars  five  or 
six  years ;  and  the  wisdom  teeth  about  twelve  years. 

The  eruption  of  the  permanent  teeth  usually  occurs  in  the  following 
order,  the  lower  preceding  the  upper  ones  : 

First  molars * 6  years. 

Central  incisors 7 

Lateral      " 8 

First  premolars 9 

Second      "          10 

Canines 12 

Second  molars 12  to  13  y«ars. 

Third         "         17  "  25      " 

1  Gubernaculum  dentis.  2  Iter  dentium. 


410  THE   ALIMENTARY   APPAEATUS. 

About  the  sixth  year,  previous  to  shedding  the  temporary  incisors, 
the  jaws  contain  the  greatest  number  of  teeth.  At  that  time,  besides 
the  temporary  teeth,  the  crowns  of  all  the  permanent  teeth  are  pro- 
duced, except  those  of  the  wisdom  teeth. 

THE   PHAKYNX. 

The  pharynx,1  or  throat,  is  a  musculo-membranous  pouch,  situated 
back  of  the  nasal  cavities,  mouth,  and  larynx,  extending  from  the  base 
of  the  skull  to  the  lower  part  of  the  latter,  and  to  the  sixth  cervical 
vertebra.  It  is  about  five  inches  long,  the  upper  two-thirds  being 
half  cylindrical,  from  one  and  a  half  to  two  inches  wide  in  different 
positions,  and  mostly  less  fore  and  aft,  except  opposite  the  mouth. 
From  the  hyoid  bone  it  narrows  in  a  funnel-like  manner  to  its  termi- 
nation, where  it  is  narrowest.  It  lies  behind  against  the  cervical 
vertebra3  and  prevertebral  muscles,  attached  to  them  by  loose  connec- 
tive tissue,  which  permits  easy  movement  of  the  pharynx.  Opening 
into  its  fore  part  in  succession  from  above  downward  are  the  posterior 
nares,  the  fauces,  and  the  opening  of  the  larynx.  Projecting  into  it 
obliquely  downward  and  backward  is  the  soft  palate,  with  the  uvula, 
which,  in  the  act  of  swallowing,  is  drawn  upward,  so  as  to  separate 
the  upper  from  the  lower  part  of  the  pharynx,  and  thus  prevent  the 
egress  of  the  food  through  the  nares.  On  each  side  of  the  latter  it 
communicates  with  the  eustachian  tube. 

Above,  the  pharynx  is  attached  to  the  occipital  basilar  process  be- 
tween the  prerecti  muscles,  and  on  each  side  to  the  under  part  of  the 
apex  of  the  temporal  pyramid.  Thence  it  is  attached  in  front,  in  suc- 
cession, to  the  entopterygoid  process,  the  pterygo-maxillary  ligament, 
the  inside  of  the  mandible,  and  the  sides  of  the  tongue,  hyoid  bone, 
thyroid  and  cricoid  cartilages.  It  is  also  connected  above  with  the 
soft  palate  and  styloid  process.  From  its  basilar  attachment  it  extends 
forward  to  the  sphenoidal  body,  and  thence  is  prolonged  in  a  recess 
outward  to  the  apex  of  the  temporal  pyramid.  Below  the  soft  palate, 
the  floor  of  the  fauces  forms  its  anterior  sloping  surface,  and  below 
this,  the  posterior  surface  of  the  larvnx  within  the  embrace  of  the 
thyroid  cartilage. 

The  wall  of  the  pharynx  is  about  a  tenth  of  an  inch  thick,  and  is 
externally  invested  by  the  pharyngeal  fascia,  a  thin  connective-tissue 
layer,  loosely  connected  with  the  contiguous  parts,  the  prevertebral 
fascia  behind,  and  the  sheaths  of  the  principal  cervical  vessels  and 
nerves  at  the  sides  of  the  neck.  The  succeeding  coat  of  the  pharynx 
is  muscular,  and  consists  of  three  pairs  of  constrictors,  together  with 
the  stylo-  and  palato-pharyngeal  muscles. 

Succeeding  the  muscular  coat  within  is  a  fibro-connective-tissue  layer, 
thin  and  inconspicuous  below,  but  strong  above,  where  it,  together  with 

1  Gula  ;  ingluvies  ;  pharus. 


THE   ALIMENTARY  APPARATUS.  411 

the  pharyngeal  fascia,  supplies  the  deficiency  of  the  muscular  layer 
and  attaches  the  pharynx  to  the  base  of  the  skull ;  a  more  compact 
band  extending  between  the  prerecti  muscles  to  the  basilar  process. 

The  lining  mucous  membrane  of  the  pharynx,  continuous  with  that 
of  the  different  communicating  cavities,  is  variably  red  and  highly 
vascular  throughout.  From  opposite  the  fauces  downward  to  the 
oesophagus  it  is  like  that  of  the  mouth,  both  as  regards  its  minute 
papillae  and  its  stratified  epithelium.  Its  upper  part,  to  the  base  of 
the  uvula,  is  furnished  like  that  of  the  nose  with  a  ciliated  columnar 
epithelium.  Numerous  racemose  mucous  glands,  the  pharyngeal 
glands,  are  found  everywhere  in  the  submucous  tissue,  the  ducts  of 
which  open  on  the  surface  of  the  mucous  membrane.  Follicular  lym- 
phoid  glands  are  also  numerous,  and  give  the  surface  of  the  pharynx 
a  more  or  less  slightly  mammillated  aspect.  A  patch  of  these  bodies 
extends  between  the  orifices  of  the  eustachian  tubes  across  the  back 
of  the  pharynx. 

The  arteries  of  the  pharynx  are  derived  from  the  pharyngeal,  in- 
ferior palatine,  pterygo-palatine,  and  thyroid  arteries.  The  veins  form 
the  pharyngeal  plexus,  which  joins  the  internal  jugular  through  the 
pharyngeal  vein.  The  nerves  are  derived  from  the  glosso-pharyngeal, 
the  pharyngeal  branch  of  the  vagus,  and  branches  from  the  first 
cervical  ganglion  of  the  sympathetic. 

MUSCLES   OF   THE    PHARYNX. 

The  muscular  layer  of  the  wall  of  the  pharynx  is  composed  of  three 
pairs  of  laminar  muscles,  the  constrictors,  whose  fibres  pursue  a 
generally  transverse  direction ;  and  two  pairs  of  longitudinal  muscles, 
the  elevators  of  the  pharynx, — the  stylo-pharyngeal  and  the  palato- 
pharyngeal  muscles.  The  constrictors  arise  at  the  side  of  the  mouth, 
the  tongue,  the  hyoid  bone,  and  the  pharynx,  thence  pass  to  the  back 
of  the  pharynx,  overlapping  from  below  upward,  and  terminate  at  the 
median  line  in  a  narrow,  tendinous  raphe,  and  partially  by  continuity 
through  the  fibres  of  the  muscles  of  the  two  sides. 

The  superior  constrictor,1  a  thin,  pale,  quadrilateral  muscle,  occu- 
pies the  upper  part  of  the  pharynx.  It  arises  from  the  lower  third  of 
the  entopterygoid  process,  including  its  hook,  from  the  pterygo-maxil- 
lary  ligament  or  tendinous  intersection  of  the  buccinator  muscle,  from 
the  posterior  extremity  of  the  alveolar  process  of  the  mandible,  and 
from  the  side  of  the  tongue  in  connection  with  the  genio-glossal  muscle. 
From  this  origin  the  fibres  pass  around  the  side  to  the  back  of  the 
pharynx,  and  unite  in  a  median,  aponeurotic  raphe,  common  to  this  and 
the  opposite  muscle.  The  raphe  is  prolonged  above  to  be  attached  to 
the  basilar  process,  and  the  upper  part  of  the  muscle  curves  to  it  from 
beneath  the  palatal  elevator  and  the  eustachian  tube.  The  upper 

1  M.  constrictor  pharyngis  superior. 


412  THE   ALIMENTARY   APPARATUS. 

margin  of  the   muscle   is  attached  to  the  base  of  the  skull  by  the 
pharyngeal  fascia. 

The  middle  constrictor,1  thicker  and  darker  than  the  former,  is 
a  fan-shaped  muscle,  and  occupies  the  middle  portion  of  the  pharynx. 
It  arises  from  the  cornua  of  the  hyoid  bone  and  from  the  stylo-hyoid 
ligament,  whence  it  widely  spreads  on  the  side  and  back  of  the  pharynx, 
and  terminates  in  the  median  raphe,  with  many  of  its  fibres  joining 

FIG.  214.  FIG.  215. 


Fig.  214.  POSTERIOR  VIEW  OF  THE  MUSCLES  OF  THE  PHARYNX.  1,  section  of  the  base  of  the 
skull  in  advance  of  the  cervical  vertebrae ;  2,  3,  posterior  border  and  angle  of  the  lower  jaw  ;  4, 
internal  pterygoid  muscle ;  5,  styloid  process  giving  attachment  to  6,  the  stylo-pharyngeal  muscle ; 
7,  larynx;  8,  inferior  constrictor  of  the  pharynx;  9,  middle  constrictor;  10,  superior  constrictor. 

Fig.  215.  SIDE  VIEW  OF  THE  MUSCLES  OF  THE  PHARYNX.  1,  trachea;  2,  cricoid  cartilage;  3, 
vocal  membrane  ;  4,  thyroid  cartilage ;  5,  thyro-hyoid  membrane  ;  6,  hyoid  bone ;  7,  stylo-hyoid 
ligament;  8,  oasophagus;  9,  inferior  constrictor  of  the  pharynx;  10,  middle  constrictor;  11,  supe- 
rior constrictor;  12,  position  at  which  the  stylo-pharyngeal  muscle  passes  into  the  interval 
between  the  superior  and  middle  constrictors ;  13,  upper  extremity  of  the  pharynx ;  14,  pterygo- 
maxillary  ligament ;  15,  buccinator  muscle ;  16,  oral  sphincter ;  17,  mylo-hyoid  muscle. 

those  of  the  opposite  muscle.  Its  upper  part  ascends  behind  the  supe- 
rior constrictor,  with  which  it  becomes  more  or  less  blended,  while  the 
lower  part  descends  within  the  inferior  constrictor,  with  which  it  in 
like  manner  becomes  somewhat  blended. 

The  inferior  constrictor,2  the  thickest  and  broadest  of  the  three 
muscles,  occupies  the  lower  part  of  the  pharynx.  It  arises  from  the 
side  of  the  larynx,  and  passes  around  the  side  to  the  back  of  the 
pharynx,  where  it  unites  with  its  fellow  in  the  median  line,  the  fibres 
of  one  passing  among  those  of  the  other.  The  lower  fibres,  nearly 
horizontal  in  their  course,  are  in  continuous  series  with  those  of  the 
transverse  muscular  layer  of  the  oesophagus  ;  the  upper  ones  becoming 

1  M.  constrictor  pharyngis  medius;  m.  hyo-pharyngeus  ;  m.  cerato-  and  chondro- 
pharyngeus. 

2  M.  c.  pharyngis  inferior;  m.  crico-thyro-pharyngeus ;  m.  thyreo-  and  crico- 
pharyngeus. 


THE   ALIMENTARY   APPARATUS.  413 

successively  more  ascending  overlap  those  of  the  middle  constrictor. 
At  the  origin  of  the  muscle  from  the  side  of  the  larynx  it  is  attached 
to  the  upper  border  and  lateral  oblique  line  of  the  thyroid  cartilage, 
and  to  the  side  of  the  cricoid  cartilage  above  and  below  the  crico-thy- 
roid  muscle ;  often  also  to  a  tendinous  arch  spanning  the  latter.  Com- 
monly some  of  its  fibres  are  continuous  with  those  of  the  sterno-thyroid 
and  crico-thyroid  muscles. 

The  constrictors  of  the  pharynx  rest  against  the  cervical  vertebrae 
and  prevertebral  muscles,  separated  from  these  and  the  prevertebral 
fascia  by  the  investing  pharyngeal  fascia.  To  the  outer  side  of  the 
constrictors  lie  the  carotid  vessels,  the  internal  jugular  vein,  and  the 
sympathetic  and  vagus  nerves.  At  the  outer  side  of  the  superior  con- 
strictor descends  the  stylo-pharyngeal  muscle,  which  enters  the  wall  of 
the  pharynx  between  the  former  and  the  middle  constrictor.  The 
palato-pharyngeal  muscle  descends  to  the  inner  side  of  the  superior 
constrictor,  with  the  tonsil  resting  on  the  latter  in  advance  of  the 
former.  The  middle  constrictor  is  separated  from  the  superior  con- 
strictor by  the  lower  expanded  portion  of  the  stylo-pharyngeal  muscle. 
The  inferior  constrictor  is  in  contact  at  its  fore  part  externally  with 
the  sterno-thyroid  muscle  and  the  thyroid  body. 

The  palato-pharyngeal  muscle  is  described  in  the  account  of  the 
muscles  of  the  soft  palate.  See  page  381. 

The  stylo-pharyngeal  muscle,1  the  longest  and  largest  of  the  three 
styloid  muscles,  lies  behind  and  to  the  inner  side  of  them.  It  arises 
tendinously  from  the  inner  side  of  the  base  of  the  styloid  process,  and 
descends  obliquely  to  the  outer  side  of  the  pharynx,  which  it  enters 
between  the  superior  and  middle  constrictors.  Joined  by  the  palato- 
glossal  muscle  it  spreads  beneath  the  lining  membrane  of  the  pharynx, 
within  the  middle  and  inferior  constrictors,  extending  to  the  larynx, 
where  many  of  its  fibres  are  inserted  into  the  posterior  border  of  the 
thyroid  cartilage.  It  is  in  contact  externally  with  the  stylo-glossal 
muscle,  the  external  carotid  artery,  the  parotid  gland,  and  the  middle 
and  inferior  constrictors.  Internally  it  is  in  contact  with  the  internal 
carotid  artery,  the  internal  jugular  vein,  the  superior  constrictor  and 
palato-pharyngeal  muscles,  and  the  mucous  membrane  of  the  pharynx. 

The  constrictors  of  the  pharynx  are  supplied  by  the  pharyngeal 
plexus  of  nerves ;  the  inferior  constrictor,  in  addition,  by  the  superior 
laryngeal  nerve.  The  stylo-pharyngeal  muscle  is  supplied  by  a  branch 
of  the  glosso-pharyngeal  nerve. 

The  muscles  of  the  pharynx  are  invested  externally  by  the  pharyn- 
geal fascia,  which  extends  above  the  superior  constrictor  to  the  base  of 
the  skull,  and  is  continuous  from  the  former  with  the  buccal  fascia 
investing  the  buccinator  muscle. 

The  muscles  of  the  soft  palate  and  pharynx,  together  with  those  of 

1  M.  stylo-pharyngeus  ;  m.  levator  or  dilatator  pharyngis. 


414  THE  ALIMENTARY  APPARATUS. 

the  tongue  and  others  attached  to  the  hyoid  bone,  form  the  mechanism 
of  swallowing.  The  first  step  of  the  process  is  effected  through  the 
muscles  of  the  tongue,  by  which  this  organ  presses  the  food  against  the 
palate  and  foi*ces  it  backward  into  the  fauces.  The  hyoid  bone,  with 
the  larynx  and  the  pharynx,  are  at  the  same  time  raised  by  their 
appropriate  elevators.  The  food  passing  through  the  fauces  into  the 
pharynx,  the  soft  palate  is  lifted  and  the  posterior  pillars  approximated, 
while  the  uvula  closes  the  interval,  and  thus  shuts  the  communication 
with  the  posterior  nares.  The  orifice  of  the  larynx  is  also  closed  by 
apposition  with  the  epiglottis ;  and  an  inclined  plane  is  formed  over 
the  latter,  down  which  the  food  is  pressed  into  the  oesophagus  by  the 
successive  contraction  of  the  constrictors  of  the  pharynx. 

THE   (ESOPHAGUS. 

The  oesophagus,  or  gullet,1  is  a  musculo-membranous  tube  descend- 
ing from  the  pharynx  through  the  lower  part  of  the  neck  and  back 
part  of  the  thorax  into  the  abdomen,  where  it  expands  in  the  stomach. 
It  commences  opposite  the  sixth  cervical  vertebra,  and  follows  the 
course  of  the  spine  to  about  the  tenth  thoracic  vertebra,  where  it 
passes  through  an  aperture  of  the  diaphragm.  It  is  from  nine  to  ten 
inches  long,  and  is  the  narrowest  portion  of  the  alimentary  canal,  for 
the  most  part  being  less  than  an  inch  in  diameter.  Inflated,  it  is 
cylindrical,  but  gradually  expanding  below  to  the  cesophageal  orifice 
of  the  diaphragm,  where  it  is  slightly  constricted,  and  then  widely 
expanded  into  the  stomach.  It  is  narrowest  in  the  first  few  inches 
of  the  course ;  and  in  the  condition  of  rest  is  collapsed  fore  and  aft 
throughout,  and  scarcely  three-fourths  of  an  inch  wide.  It  follows 
the  flexures  of  the  corresponding  portion  of  the  spine ;  besides  which, 
starting  from  the  median  line  in  the  rteck.  it  inclines  slightly  to  the 
left,  then  to  the  fifth  thoracic  vertebra  gradually  again  assumes  a 
median  position,  and  once  more  deviates  to  the  left  and  forward  to 
reach  the  cesophageal  orifice  of  the  diaphragm. 

In  the  neck  and  upper  part  of  the  chest  the  oesophagus  adheres  to 
the  spine  and  prevertebral  muscles  by  loose  connective  tissue,  but  lower 
passes  in  front  of  the  aorta.  In  the  neck  it  lies  behind  the  trachea, 
slightly  more  to  the  left  side,  with  the  inferior  laryngeal  nerve  ascend- 
ing between  them  on  each  side,  and  here,  also,  lying  in  contact  with  the 
sheath  of  the  carotid  artery.  In  the  thorax  it  is  successively  covered  by 
the  lower  part  of  the  trachea,  the  adjacent  portion  of  the  left  bronchus, 
and  the  pericardium.  At  first  placed  to  the  right  of  the  aorta,  it  after- 
wards passes  in  front,  inclining  to  the  left,  to  reach  the  cesophageal  ori- 
fice ;  and  the  azygos  vein  lies  behind  and  to  its  right.  Placed  between 
the  pleura,  it  is  in  contact  with  both ;  and  the  thoracic  duct  ascending 
on  the  vertebrae  from  right  to  left  lies  beneath  it.  The  vagus  nerves 

1  Gula ;  fistula  ventriculi. 


THE   ALIMENTAEY   APPARATUS.  415 

descend  in  its  fibro-connective  sheath  and  form  a  plexus  around  it,  the 
chief  trunk  of  the  left  one  passing  down  in  front,  that  of  the  right  pass- 
ing down  behind.  The  wall  of  the  oesophagus,  slightly  thicker  than  that 
of  the  pharynx,  in  its  collapsed  condition  is  scarcely  two  lines  thick. 
Besides  an  investing  sheath  of  loose  fibro-connective  tissue  with  elastic 
fibres,  attached  to  the  adjacent  parts,  it  is  composed  of  three  coats. 

The  external,  muscular  coat  consists  of  an  outer  longitudinal  and 
an  inner  circular  layer,  an  arrangement  which  prevails  through  the 
whole  of  the  alimentary  canal ;  but  the  coat  is  thicker  than  elsewhere, 
excepting  at  the  pyloric  orifice  of  the  stomach  and  the  lower  extremity 
of  the  large  intestine.  The  longitudinal  layer  commences  in  three 
bands,  of  which  one  in  front  is  attached  to  the  median  ridge  behind 
the  cricoid  cartilage,  and  the  others  are  continuous  laterally  with  the 
inferior  constrictors  of  the  pharynx.  The  circular  layer  at  its  com- 
mencement is  continuous  with  the  latter  muscles,  but  is  separated  by 
the  lateral  bands  of  the  longitudinal  layer.  At  the  termination  of  the 
oesophagus  both  layers  are  continuous  with  those  of  the  stomach. 

The  muscular  coat  is  of  a  darker  red  color  at  the  upper  part  of 
the  oesophagus,  where  it  consists  of  striped  muscle-fibres ;  but  it  be- 
comes paler  below,  and  the  latter  are  gradually  replaced  by  unstriped 
fibres,  which  occur  almost  alone  in  the  lower  part. 

The  middle,  fibrous,  or  submucous  coat  is  a  layer  of  fibro- 
connective  tissue,  much  thinner  than  the  former,  and  unites  it  loosely 
with  the  internal  coat.  It  contains  the  chief  vessels  of  the  latter  and 
the  oesophageal  glands. 

The  internal  coat,  the  lining  mucous  membrane,  is  of  firm  text- 
ure, and  in  the  condition  of  rest  is  thrown  into  fine  longitudinal  folds, 
which  disappear  with  the  distention  of  the  oesophagus.  It  is  pale  red  at 
its  commencement,  but  becomes,  for  the  greater  part  of  its  extent,  gray 
or  nearly  white.  It  is  provided  with  a  stratified  epithelium  like  that  of 
the  mouth  and  pharynx,  and,  as  in  these,  is  also  furnished  with  minute 
papillae,  fewer  and  smaller,  and  likewise  embedded  beneath  the  epithe- 
lium. The  mucosa  is  defined  by  a  deeper  muscularis  mucosa?,  consist- 
ing of  a  thin  stratum  of  longitudinal,  unstriped  muscle-fibres,  incom- 
plete at  the  upper  part  of  the  oesophagus,  but  continuous  in  its  lower  part. 

The  oesophageal  glands  are  minute  racemose  glands  embedded 
in  the  submucous  fibrous  coat,  generally  scattered,  and  most  numerous 
in  the  lower  part  of  the  oesophagus.  They  open  by  long,  slanting  ducts 
upon  the  surface  of  the  mucous  membrane. 

The  blood-vessels  of  the  oesophagus  generally  pursue  a  longitudinal 
course,  and  are  connected  with  three  systems  of  capillaries,  of  which 
one  pertains  to  the  mucous  membrane,  a  second  to  the  oesophageal 
glands,  and  a  third  to  the  muscular  coat.  Lymphatics  are  found  es- 
pecially in  the  mucous  and  submucous  coats.  The  nerves  form  a  gan- 
gliated  plexus  between  the  layers  of  the  muscular  coat  as  elsewhere 
in  the  alimentary  canal,  but  the  nerve-cells  and  groups  are  both  larger, 


416  THE    ALIMENTARY    APPARATUS. 

and  are  associated  with  many  medullated  nerve-fibres  derived  from 
the  vagus  nerves. 

The  arteries  are  branches  of  the  inferior  thyroid,  the  bronchial,  the 
aorta,  and  the  coronary  artery.  The  veins  form  a  plexus  in  the  fibrous 
coat,  and  join  the  inferior  thyroid,  pericardiac,  azygos,  and  gastric 
coronary  veins.  The  nerves  are  mainly  derived  from  the  vagus,  but 
some  fine  branches  also  come  from  the  thoracic  portion  of  the  sympa- 
thetic nerve. 

THE    OKGANS   OF  DIGESTION. 

The  succeeding  portions  of  the  alimentary  apparatus,  consisting  of 
the  organs  concerned  chiefly  in  the  digestion  of  the  food,  are  contained 
in  the  abdomen.  They  are  the  stomach,  small  intestine,  and  large  in- 
testine as  continuations  of  the  alimentary  canal,  and  two  glands,  the 
pancreas  and  liver,  which  discharge  their  secretions  into  the  small 
intestine. 

THE   STOMACH. 

The  stomach,1  the  most  capacious  portion  of  the  alimentary  canal, 
the  principal  receptacle  of  the  food,  in  which  it  undergoes  the  most 
active  digestion,  is  situated  in  the  upper  part  of  the  abdominal  cavity, 
in  the  left  hypochondrium  and  epigastrium.  On  the  right  it  is  con- 
nected with  the  O3sophagus,  which  opens  into  it  shortly  after  passing 
through  the  cesophageal  orifice  of  the  diaphragm.  The  communication, 
called  the  cardiac  orifice,  or  the  cardia,2  is  circular,  and  opens  down- 
ward from  the  stomach  like  an  inverted  funnel.  On  the  left  and  in  a 
lower  and  more  advanced  position  the  stomach  joins  the  duodenum, 
the  circular  communication  being  named  the  pyloric  orifice,  or  the 
pylorus.3 

The  stomach  is  a  curved  conical  pouch  with  a  hemispherical  base, 
the  fundus,4  which  is  directed  to  the  left  side  as  the  cardiac  ex- 
tremity,5 while  the  narrower  portion  to  the  right  is  the  pyloric  ex- 
tremity.6 It  is  situated  with  its  long  axis  very  oblique,  extending 
from  the  left  hypochondrium  downward  and  to  the  right  in  the  epi- 
gastrium, verging  on  the  right  hypochondrium.  Its  small  curva- 
ture7 is  the  superior  border  between  the  cardia  and  pylorus,  three  or 
four  inches  long,  concave,  and  looking  upward,  backward,  and  to  the 
right.  The  greater  curvature,8  much  longer  than  the  former,  is  con- 
vex, and  looks  in  the  opposite  direction,  downward,  forward,  and  to 
the  left.  The  fundus  extends  two  or  three  inches  to  the  left  of  the 
oesophagus,  and  lies  in  contact  with  the  spleen  behind  and  the  dia- 
phragm above  and  in  front.  The  pyloric  end  lies  beneath  the  liver, 
and  curves  upward  from  right  to  left  and  backward,  producing  a 

1  Stomachus  ;  ventriculus  ;  gaster. 

2  CEsophageal  orifice  ;  upper  or  left  orifice  ;  os  ventriculi,  ostium  oesophageum. 
s  Intestinal  orifice  ;  lower  or  right  orifice ;  ostium  duodenale. 

*  Cul-de-sac  ;  great  tuberosity.  5  Cardiac  or  splenic  end. 

6  Pars  pylorica.  7  Curvatura  inferior.  8  C.  superior. 


THE   ALIMENTARY   APPARATUS. 


417 


bulge,  named  the  pyloric  antrum,1  situated  to  the  right  and  below 
the  pylorus.  The  latter  is  indicated  by  a  slight  external  constriction, 
and  is  a  circular  orifice  directed  backward  into  the  duodenum  and  pro- 
vided with  a  sphincter  and  valve.  Occasionally,  the  pyloric  extremity 
of  the  stomach  is  slightly  constricted  an  inch  or  two  from  the  pylorus. 

PIG.  216. 


VIEW  OF  THE  ABDOMINAL  VISCERA  :  the  liver  raised  to  show  its  under  surface,  and  the  great 
omentum  removed.  1,  upper  surface  of  the  liver;  2,  under  surface;  3,  round  ligament;  4,  gall- 
bladder ;  5,  diaphragm ;  6,  oesophagus ; ;  7,  stomach  ;  8,  gastro-hepatic  omentum  ;  9,  spleen  ;  10, 
gastro-splenic  omentum  ;  11,  descending  portion  of , the  duodenum ;  12,  small  intestine,  jejunum, 
and  ileum  ;  13,  csecum  ;  14,  vermiform  appendix ;  15,  transverse  colon ;  16,  sigmoid  flexure ;  17, 
urinary  bladder. 

The  anterior  and  posterior  surfaces  of  the  stomach  are  free,  smooth, 
and  convex,  the  former  looking  variably  forward  and  upward,  the  latter 
in  the  opposite  direction.  The  anterior  surface  is  in  contact  with  the 
diaphragm,  the  under  surface  of  the  liver,  and  the  front  of  the  abdom- 
inal wall  in  the  epigastrium,  from  which  this  is  called  the  pit  of  the 
stomach.2  The  posterior  surface  lies  on  the  transverse  mesocolon, 
above  the  transverse  colon ;  and  behind  the  former  are  the  pancreas, 
spleen,  left  kidney,  and  suprarenal  body,  the  great  vessels  in  front  of 
the  spine,  and  the  crura  of  the  diaphragm. 

1  Antrum  pylori  or  pyloricum ;  lesser  cul-de-sac  ;    lesser  tuberosity. 

2  Scrobiculus  cordis  ;  procardium  ;  anticardium. 

27 


418  THE   ALIMENTARY   APPARATUS. 

The  exact  position  of  the  stomach  is  variable,  and  is  influenced 
by  its  state  of  distention  and  that  of  the  intestines,  and  also  by  the 
respiration  ;  falling  and  rising  with  the  action  of  the  diaphragm  and 
the  abdominal  muscles  below.  With  the  expansion  in  taking  food,  its 
greater  curvature  rises  and  is  directed  more  forward,  while  the  anterior 
surface  is  directed  upward  and  the  posterior  surface  more  downward. 
The  cardia  is  fixed  in  position  in  front  and  to  the  left  of  the  last  tho- 
racic vertebra,  being  closely  attached  to  the  cesophageal  orifice  of 
the  diaphragm  by  the  reflection  of  the  peritoneum  from  one  to  the 
other.  The  pyloric  extremity,  on  the  other  hand,  is  very  movable. 
When  the  stomach  is  empty  the  pylorus  occupies  nearly  a  median  posi- 
tion in  the  vicinity  of  the  last  thoracic  vertebra,  but  in  the  distended 
condition  of  the  organ  may  be  shifted  several  inches  to  the  right.  The 
empty  stomach  occupies  a  small  portion  of  the  left  hypochondrium 
beneath  the  left  lobe  of  the  liver  and  with  the  spleen  behind  it.1 

The  size  of  the  stomach  varies  greatly  under  many  different  con- 
ditions, and,  while  it  may  sometimes  have  the  capacity  of  a  gallon  or 
more,  it  is  occasionally  reduced  almost  to  the  calibre  of  the  small  intes- 
tine. It  is  commonly  smaller  in  women,  in  persons  habitually  in- 
sufficiently fed,  and  to  a  much  greater  degree  in  the  sick  after  long 
fasting ;  and  is  larger  in  habitually  big  feeders.  Ordinarily,  in  a  mod- 
erately distended  state,  it  is  about  ten  inches  long,  and  nearly  half  as 
wide  where  largest ;  often  a  little  the  wider  between  the  curvatures, 
and  with  a  capacity  approximating  half  a  gallon.  The  same  stomach 
empty  may  be  two  or  three  inches  less  in  length  and  one  or  two  in 
width,  and  collapsed  fore  and  aft. 

The  curvatures  of  the  stomach  are  attached  along  their  course  by 
folds  of  the  peritoneum,  which  invest  the  organ  and  attach  it  to  adja- 
cent parts.  From  along  the  small  curvature  passes  the  gastro-hepatic 
omentum  to  the  transverse  fissure  of  the  liver.  Along  the  greater  curva- 
ture is  appended  the  great  omentum,  continuous  on  the  fundus  with  the 
gastro-splenic  omentum,  attached  also  to  the  spleen ;  and  at  the  left  of 
the  cardia  is  a  small  fold,  the  gastro-phrenic  ligament,  extended  between 
the  oesophagus  and  diaphragm.  Between  the  layers  of  the  omenta  the 
principal  vessels  and  nerves  of  the  stomach  run  along  its  curvatures. 

The  wall  of  the  stomach  varies  in  thickness  with  the  size  of  the 
organ,  being  thinnest  in  the  large  or  distended  state,  and  it  also  varies 
in  different  positions,  becoming  gradually  thicker  as  the  capacity  de- 
creases from  the  fundus  to  the  pylorus. 

In  the  cardiac  extremity  it  is  much  thinner  than  that  of  the  oesoph- 
agus ;  at  the  middle  it  is  about  a  line  or  more,  decreasing  to  less  than 
half  a  line  in  the  fundus,  and  increasing  towards  the  pylorus  to  two  or 

1  From  the  proximity  of  the  stomach  to  the  heart,  separated  only  by  the  left  lobe 
of  the  liver  and  the  diaphragm,  the  pain  of  .gastralgia,  often  accompanied  with  pal- 
pitation, is  commonly  referred  to  the  heart. 


THE   ALIMENTARY   APPARATUS.  419 

three  lines.     The  weight  of  the  stomach  is  estimated  at  four  and  a 
half  ounces  in  the  male,  and  less  in  the  female. 

Pour  different  coats  compose  the  wall  of  the  stomach,  closely  united, 
and  named  in  succession  from  without  the  serous,  muscular,  fibrous,  and 
mucous  coats. 

The  external,  serous  coat,1  derived  from  the  peritoneum,  is  a  thin, 
uniform,  smooth,  transparent,  and  elastic  layer,  closely  investing  the 
stomach,  except  a  narrow  space  along  the  curvatures,  which  is  traversed 
by  the  chief  vessels  of  the  organ,  between  the  layers  of  the  omenta. 

The  muscular  coat 2  is  the  thickest,  and  is  that  upon  which  the 
varying  thickness  of  the  wall  of  the  stomach  chiefly  depends.  The 
decrease  in  size  of  the  stomach  is  due  to  contraction  of  the  muscular 
coat,  and  hence  this  is  proportioned  in  thickness  to  the  size  of  the 
organ  and  to  the  thickness  of  the  wall  in  different  positions.  It  is  of 
a  reddish-brown  color,  visible  through  the  serous  coat,  and  is  composed 
of  comparatively  long,  unstriped  muscle-fibres,  which  are  arranged  in 
three  layers,  named  from  the  direction  of  the  latter  the  longitudinal, 
circular,  and  oblique  layers.  The  external  longitudinal  layer  is  con- 
tinuous with  that  of  the  oesophagus,  from  which  the  fibres  spread  upon 
the  stomach,  mostly  along  the  curvatures,  and  especially  the  short  one, 
where  they  are  best  marked.  Upon  the  front  and  back  surfaces  they 
are  thinly  diffused,  and  become  indistinct  approaching  the  pyloric  ex- 
tremity, where  they  again  appear  more  evident,  and  form  a  continuous 
layer,  proceeding  to  the  pylorus  and  duodenum.  The  circular  layer, 
most  uniformly  continuous  upon  the  stomach,  consists  of  thin  rings 
with  narrow  intervals  encircling  the  course  of  the  organ  from  the 
fundus  to  the  pylorus,  gradually  becoming  smaller  and  thicker  ap- 
proaching the  latter,  where  they  accumulate  in  a  stout  annular  bundle, 
which  is  the  pyloric  sphincter.3  At  its  commencement  the  circular 
layer  is  continuous  with  that  of  the  oesophagus  to  the  right  of  the 
cardia,  whence  it  spreads  over  the  fundus,  gradually  extending  from 
left  to  right.  The  oblique  layer  of  muscular  fibres,  less  complete  or 
extensive  than  the  former,  is  best  produced  on  the  fundus,  to  the  left 
of  the  cardia,  where  it  is  continuous  with  the  circular  layer  of  the 
oesophagus,  and  thence  spreads  on  the  front  and  back  of  the  stomach 
within  the  circular  layer,  with  which  its  fibres  become  continuous 
approaching  the  greater  curvature. 

The  fibrous,  or  submucous,  coat4  of  the  stomach  is  a  consider- 
able, compact,  extensible  layer  of  areolar  tissue,  composed  of  a  basis 
of  fibro-connective-tissue  bundles  intersecting  one  another  and  mingled 
with  elastic  fibres.  Besides  contributing  to  the  strength  of  the  organ, 
it  gives  especial  support  to  the  less  tenacious  mucous  membrane,  and 
contains  extensive  plexuses  of  the  chief  arteries,  veins,  and  lymphatics, 

1  Tunica  serosa.  2  T.  musculosa ;  stratum  musculare. 

3  Musculus  sphincter  pylori.       4  Fibrous  coat ;  tunica  fibrosa,  nervosa,  or  nervea. 


420  THE   ALIMENTARY   APPARATUS. 

directly  connected  with  the  vessels  of  the  latter,  and  associated  with  a 
gangliated  plexus  of  nerves. 

The  lining  mucous  membrane  '  of  the  stomach,  comparatively 
thick,  is  a  moderately  firm,  inelastic  layer,  quickly  changing  color  and 
softening  after  death.  During  digestion  it  is  more  or  less  rose-red,  but 
in  the  empty  state  of  the  stomach  is  gray  or  yellowish  gray.  In  the 
fresh  condition  after  death  it  is  usually  reddish,  but  soon  becomes  paler. 

FIG.  217. 


SURFACE  OF  THE  MUCOUS  MEMBRANE  OF  THE  STOMACH.    1,  rugae ;  2,  mammillated  surface. 

It  presents  a  closely-  and  finely-mammillated  appearance,  which  is 
especially  well  marked  in  the  pyloric  extremity,  but  becomes  indis- 
tinct in  the  aged,  and  is  also  effaced  by  softening  after  death. 

As  the  mucous  membrane,  together  with  its  submucous  basis,  is 
possessed  of  little  elasticity,  in  the  contraction  of  the  muscular  coat 
and  consequent  decrease  of  the  stomach  it  is  thrown  into  numerous 
wrinkles  or  rugae,2  which  are  obliterated  with  the  expansion  of  the 
organ.  The  rugse  are  most  marked  along  the  greater  curvature  and  in 
the  pyloric  extremity,  and  generally  pursue  a  longitudinal  and  more  or 
less  tortuous  and  reticular  course.  In  advanced  life  they  often  appear 
stained  along  their  course,  so  that  this  is  evident  after  their  obliteration 
through  distention  of  the  organ. 

The  pyloric  valve 3  is  a  thick,  annular  fold  of  the  mucous  mem- 
brane with  the  submucous  coat  investing  the  pyloric  sphincter.  It  en- 
closes a  circular  orifice,  usually  central,  but  sometimes  more  or  less 
eccentric.  In  the  dried  preparation,  the  valve  appears  as  a  circular 
diaphragm  with  a  circular  orifice. 

The  mucous  membrane  consists  of  the  epithelium  and  the  mucosa 
with  the  gastric  glands  and  its  muscularis  mucosae. 

The  epithelium  of  the  stomach  consists  of  a  single  layer  of  six- 
sided  columnar  cells,  commencing  abruptly  at  the  cardia,  spreading 

1  Tunica  mucosa.  2  Plicae.  s  Valvula  pylori. 


THE  ALIMENTARY  APPARATUS. 


421 


FIG.  218. 


throughout  to  the  pylorus,  and  extending  into  the  mouths  and  ducts 
of  the  gastric  glands.  The  cells  have  a  delicate  wall  and  protoplasmic 
contents,  appearing  more  or  less  granular  in  the  deeper  part  and  clearer 
in  the  outer  part.  An  oval  nucleus  occupies  their  deeper  part.  During 
digestion  they  become  more  clear,  and  many  pass  more  or  less  into 
the  condition  of  mucus-secreting 
goblet-cells.  They  are  supported 
on  a  basement  membrane  of  flat 
cells,  from  which  branching  pro- 
cesses ascend  among  the  colum- 
nar cells  and  descend  into  the 
mucosa.  Between  their  often 
narrower  attached  extremities 
the  intervals  are  occupied  by 
smaller,  immature  cells  of  round 
or  oval  outline. 

The  mucosa  consists  of  a 
small  proportion  of  fibro-con- 
nective-tissue  matrix,  in  which 
are  closely  embedded  the  gastric 
glands  vertically  arranged,  and 
with  their  ducts  opening  upon 

the  free  surface  of  the  mucous  membrane,  to  which  they  give  a  minutely 
cribriform  appearance. 

The  gastric  glands  are  tubular,  and  are  proportioned  in  length 


MAMMILLAE  OF  THE  MUCOUS  MEMBRANE  OF  THE 
STOMACH,  moderately  magnified,  exhibiting  the 
orifices  of  the  gastric  glands. 


FIG.  219. 


FIG.  220. 


SMALL  PORTION  OF  THE  MUCOUS  MEMBRANE  OF 
THE  STOMACH,  WITH  THE  GASTRIC  GLANDS.  1, 
the  glands ;  2,  orifices  of  the  glands ;  3,  epithe- 
lium of  the  mucous  membrane:  moderately 
magnified. 


to  the  thickness  of  the  mucous 
membrane,  being  shortest  in  the 
fundus  and  longest  in  the  pyloric 
extremity.  They  further  present 
important  differences,  which  have 
led  to  their  being  distinguished 
as  the  cardiac  or  peptic  glands  and  the  pyloric  glands. 


A  GASTRIC  GLAND,  highly  magnified.  1,  large 
polyhedral  cells  at  the  bottom  of  the  gland, 
gradually  merging  2  into  the  columnar  cells  3, 
at  the  upper  part  of  the  gland. 


THE  ALIMENTARY  APPARATUS. 


The  cardiac  glands1  have  comparatively  short  ducts,  gener- 
ally from  one-third  to  one-sixth  of  the  length  of  a  gland,  abruptly 
narrowing  below,  and  communicating  generally  with  two  or  three 
slender  flask-shaped  tubules,  which  are  nearly  straight  or  slightly 
tortuous,  and  end  in  round,  expanded,  and  more  or  less  curved  ex- 
tremities. Approaching  the  cardia,  the  ducts  are  relatively  shorter 
and  the  communicating  tubules  longer.  Approaching  the  pyloric 
extremity,  the  ducts  become  longer  and  approximate  the  character 
of  the  pyloric  glands. 

The  pyloric  glands  have  comparatively  long  ducts,  a  half  or  more 
the  length  of  a  whole  gland,  and  likewise  abruptly  narrowed  below  and 


FIG.  221. 


FIG.  222. 


BOTTOM  OF  A  GASTRIC  GLAND,  highly  magni- 
fied.   1,  columnar  cells ;  2,  parietal  cells. 

communicating  with  two  or  three 
tubules.  These  are  also  slender 
flask-shaped,  and  are  more  or  less 
tortuous  or  convoluted  and  have 
a  more  capacious  passage  than  in 
the  former. 

The  ducts  of  the  gastric  glands 
are  lined  with  an  extension  of  the 
columnar  epithelium,  the  cells 
of  which  become  proportionately 
smaller  in  the  narrowed  bottom 
part  of  the  ducts.  In  the  tu- 
bules of  the  pyloric  glands  the 
lining  cells 2  are  also  columnar,  but 
shorter,  thicker,  more  opaque,  and 
proportionate  in  size  with  the  en- 
largement of  the  tubules  towards 
their  expanded  terminations.  In 

the  tubules  of  the  cardiac  glands  the  lining  epithelium  is  of  the  same 
general  character,  but  in  addition  they  contain  scattered,  isolated  cells, 


A  CARDIAC  GASTRIC  GLAND  OF  THE  DOG,  highly 

magnified.  1,  columnar  epithelium  of  the 
mucous  membrane  of  the  stomach ;  2,  colum- 
nar epithelium  of  the  mucous  membrane  of 
the  duct ;  3,  tubules  of  the  gland ;  4,  columnar 
epithelium ;  5,  parietal  or  peptic  cells. 


Peptic  glands  ;  fundus  or  oxyntic  glands. 


2  Principal  or  central  cells. 


THE  ALIMENTARY  APPARATUS.  423 

named  from  their  relative  position  parietal  cells.1  These  are  situated 
beneath  the  lining  epithelium  on  the  membrana  propria,  which  they 
often  cause  to  bulge  more  or  less  externally.  They  are  compressed 
spheroidal  and  somewhat  polygonal,  more  opaque  and  granular  than 
the  columnar  cells,  and  contain  a  clear,  central,  compressed-spherical 
or  oval  nucleus. 

Beneath  the  gastric  glands  the  mucosa  is  a  thin  fibro-connective- 
tissue  layer,  which  is  succeeded  by  the  muscularis  mucosse  of  variable 
thickness  in  different  positions.  In  some  positions  it  consists  of  a 
single  layer  of  longitudinal  unstriped  muscle-fibres,  in  others  of  an 
outer  longitudinal  and  an  inner  circular  layer,  and  again  with  an  ad- 
ditional inner  longitudinal  layer.  Many  bundles  of  the  muscle-fibres 
ascend  in  the  mucosa  and  pass  between  the  gastric  glands. 

The  stomach  is  a  very  vascular  organ,  more  especially  its  mucous 
membrane.  Its  arteries  are  derived  from  the  coronary,  right  and  left 
gastro-epiploic,  short  gastric,  and  pyloric  arteries,  all  derived  from  the 
coeliac  axis.  From  along  the  curvatures  the  arteries  diverge  in  front 
and  behind  the  stomach,  and  enter  between  the  serous  and  muscular 
coats,  whence  they  penetrate  the  latt'er  and  ramify  and  inosculate  in 
the  submucous  coat,  in  which  they  form  an  extensive  retiform  plexus. 
From  this  numerous  small  arteries  proceed  to  the  mucous  membrane, 
ramifying  and  anastomosing  in  the  mucosa,  and  terminating  in  fine 
capillary  nets  surrounding  the  tubules  and  ducts  of  the  gastric  glands, 
and  finally  in  a  coarser  net  around  the  mouths  of  the  latter.  From 
these  nets  veins  pass  through  the  mucosa  and  join  an  extensive  plexus 
of  the  submucous  coat,  from  which  emanate  the  companion  veins  of 
the  arteries  terminating  in  the  splenic  and  superior  mesenteric  veins, 
and  directly  also  into  the  portal  vein. 

Lymphatics  are  very  numerous  in  the  mucous  membrane  of  the 
stomach,  commencing  as  a  plexus  of  lacunar  spaces  among  the  tubules 
of  the  gastric  glands,  many  of  which,  as  well  as  the  contiguous  capillary 
blood-vessels,  they  enclose.  Near  the  free  surface  of  the  membrane, 
lymphatic  vessels  commence  in  loops  and  club-like  expansions,  and  de- 
scend to  the  bottom  of  the  mucosa,  where  they  join  a  fine  plexus  of 
vessels  which  communicates  with  a  coarser  plexus  in  the  submucous 
coat.  In  the  latter  plexus  the  vessels  are  provided  with  valves,  and 
from  it  proceed  vessels,  which  pass  through  the  muscular  coat,  and 
thence  follow  the  arteries  and  veins  in  their  course  along  the  curva- 
tures of  the  stomach,  where  they  traverse  lymphatic  glands. 

A  capillary  system  of  blood-vessels  also  pertains  to  the  muscular 
coat  of  the  stomach,  and  still  a  third  to  the  serous  coat,  both  of  which 
communicate  with  the  contiguous  arteries  and  veins. 

The  nerves  of  the  stomach  are  derived  from  the  terminal  branches 
of  the  vagus  nerves,  and  from  branches  of  the  sympathetic  accompany- 

1  Peptic  cells  ;  superadded  or  oxyntic  cells. 


424  THE   ALIMENTARY   APPARATUS. 

ing  the  arteries  from  the  solar  plexus.  The  nerves  form  gangliated 
plexuses  between  the  layers  of  the  muscular  coat  and  in  the  submucous 
coat. 

THE   SMALL  INTESTINE. 

The  small  intestine,  or  gut,1  is  a  long,  cylindrical  tube,  extending 
from  the  pylorus  of  the  stomach  to  the  large  intestine.  It  is  of  variable 
length,  ordinarily  in  the  adult  about  twenty  feet,  but  ranging  between 
fifteen  and  twenty-five  feet  or  more.  (In  a  well-proportioned  muscular 
man,  of  six  feet  and  about  forty  years  of  age,  the  small  intestine, 
detached  from  the  mesentery,  measured  twenty-six  feet  three  inches, 
and  the  large  intestine  measured  six  feet  nine  inches ;  in  all,  thirty- 
three  feet.)  It  occupies  the  middle  and  lower  portions  of  the  abdomen, 
and  is  suspended  from  the  spine  by  the  mesentery  in  numerous  coils 
movable  in  any  direction.  It  is  surrounded  by  the  large  intestine  ex- 
cept below,  and  is  covered  by  the  great  omentum,  which  separates  it 
from  the  front  wall  of  the  abdomen.  It  is  regarded  as  consisting  of 
three  portions,  named  the  duodenum,  jejunum,  and  ileum,  which,  though 
merging  into  one  another,  in  the  main  present  certain  differences. 

The  duodenum  2  is  the  shortest  and  least  variable  in  length,  the 
widest,  and  most  fixed  portion  of  the  small  intestine ;  from  eight  to  ten 
inches  long,  and  varying  between  one  and  a  half  to  two  inches  wide. 
It  forms  an  arch  with  its  convexity  directed  to  the  right,  and  embracing 
the  head  of  the  pancreas  in  its  concavity  to  the  left.  From  the  pylorus 
it  passes  upward,  backward,  and  to  the  right  beneath  the  liver,  descends 
in  front  of  the  right  kidney,  and  then  makes  a  sigmoid  curve  inwardly 
across  the  spine,  and  merges  in  the  jejunum  to  the  left  of  the  second 
lumbar  vertebra. 

The  ascending  portion  of  the  duodenum,  about  two  inches  long, 
is  free  and  movable,  and  invested  with  the  peritoneum  of  the  gastro- 
hepatic  omentum.  It  is  in  contact  in  front  and  above  with  the  liver 
and  neck  of  the  gall-bladder,  and  behind  with  the  bile-duct,  the  hepatic 
artery,  and  the  portal  vein.  The  descending  portion,  about  three 
inches  long,  and  the  most  expanded,  turns  abruptly  downward  from 
the  neck  of  the  gall-bladder,  in  front  of  the  right  kidney  and  its  ves- 
sels, as  low  as  the  third  lumbar  vertebra.  It  is  firmly  attached  inwardly 
to  the  head  of  the  pancreas,  and  is  covered  only  on  its  anterior  surface 
by  the  peritoneum,  in  front  of  which  are  the  hepatic  flexure  of  the 
colon  and  the  mesocolon.  The  bile  and  pancreatic  ducts  enter  its 
inner  side  a  little  below  the  middle.  The  transverse  portion,  the 
longest  and  narrowest  of  the  duodenum,  curves  inward  and  upward 
across  the  spine  from  the  third  lumbar  vertebra  on  the  right  to  the 
second  on  the  left,  where  it  becomes  the  jejunum.  Behind,  it  rests  on 
the  aorta,  inferior  cava,  and  crura  of  the  diaphragm ;  above,  it  is  in 

1  Intestinum  tenue,  or  gracile  ;  enteron  ;  small  bowel. 

2  Ventriculus  succenturiatus. 


THE   ALIMENTARY   APPARATUS.  425 

contact  with  the  pancreas,  and  thence  is  crossed  in  front  by  the  supe- 
rior mesenteric  blood-vessels.  It  lies  behind  the  root  of  the  transverse 
mesocolon,  and  receives  no  peritoneal  investment  except  at  its  termi- 
nation. 

The  small  intestine  succeeding  the  duodenum  is  suspended  by  the 
mesentery,  which  furnishes  it  with  a  complete  investment  through- 
out. Its  upper  third  or  two-fifths  comprise  the  jejunum,  while  the 
remainder  is  the  ileum.1  Narrower  and  more  uniformly  cylindrical 
than  the  duodenum,  it  nevertheless  gradually  decreases,  so  that  while 
the  upper  portion  of  the  jejunum  is  from  one  and  a  quarter  to  one  and 
a  half  inches  in  diameter  the  lower  portion  of  the  ileum  is  from  a 
quarter  to  half  an  inch  less.  The  jejunum  is  situated  more  deeply, 
higher,  and  to  the  left,  while  the  ileum  is  more  superficial,  lower,  and 
to  the  right.  The  former  is  mainly  confined  to  the  umbilical  and  left 
lumbar  and  iliac  regions,  while  the  latter  occupies  part  of  the  umbili- 
cal, the  right  lumbar  and  iliac,  hypogastric,  and  pelvic  regions.  From 
the  latter  the  ileum  ascends  obliquely  to  the  right  over  the  correspond- 
ing psoas  muscle,  and  terminates  on  the  inner  side  of  the  large  intes- 
tine, which  commences  in  the  right  iliac  region.  The  mobility  of  the 
jejunum  and  ileum  renders  their  coils  liable  to  incessant  change  in 
position  according  to  their  variable  distention,  or  that  of  the  stomach, 
large  intestine,  and  bladder ;  and  they  are  further  influenced  by  the 
respiratory  movements.  While  the  jejunum  gradually  merges  into  the 
ileum,  in  general  it  presents  a  darker  appearance,  has  a  thicker  wall,  and 
feels  considerably  thicker  when  seized  between  the  finger  and  thumb, 
due  mainly  to  the  numerous  interior  folds  or  connivent  valves  which 
are  included  in  the  pressure. 

The  wall  of  the  small  intestine  is  thinner  than  that  of  any  other 
part  of  the  alimentary  canal,  and,  like  that  of  the  stomach,  is  com- 
posed of  four  coats,  except  that  the  external  or  serous  coat  is  deficient 
on  the  greater  part  of  the  descending  portion  and  on  the  transverse 
portion  of  the  duodenum.  To  the  jejunum  and  ileum  it  provides  a 
continuous  and  close  investment,  leaving  only  a  narrow  interval  along 
the  attachment  of  the  mesentery,  where  the  vessels  and  nerves  pass 
to  and  from  the  intestine. 

The  muscular  coat,  thinner  than  that  of  the  stomach,  and  be- 
coming thinner  on  the  ileum  than  on  the  jejunum,  consists  of  two 
layers,  an  outer  longitudinal  and  an  inner  circular.  The  longitudi- 
nal layer  is  continuous  but  very  thin,  and  is  best  produced  along  the 
distal  border,  or  that  opposite  the  attachment  of  the  mesentery.  The 
circular  layer  is  thicker  and  more  distinct,  especially  on  the  jejunum. 

The  fibrous,  or  submucous,  coat2  is  like  that  of  the  stomach, 
but  is  thinner  and  more  closely  connected  with  the  mucous  coat.  It 
contains  the  larger  plexuses  of  blood-vessels  and  lymphatics  directly 

1  Ileon  ;  intestinum  circumvolution.  ^Submucosa. 


426 


THE  ALIMENTARY  APPARATUS. 


connected  with  those  of  the  latter,  and  also  serves  as  a  bed  for  many 
of  its  glands. 

The  lining  mucous  membrane  has  a  soft,  velvety  appearance, 
due  to  its  surface  being  closely  covered  with  little  processes,  the  villi, 
which  stand  up  like  the  pile  of  velvet.  It  is  very  vascular,  though 
ordinarily  it  is  pale  red,  and  becomes  still  paler,  passing  to  gray  in  the 
i!eum.  From  near  its  commencement,  and  for  more  than  half  the 
length  of  the  intestine,  it  is  provided  with  numerous  transverse  folds, 
named  the  connivent  valves.  It  consists  of  the  epithelium  and 
the  mucosa  with  numerous  glands  and  its  muscularis  mucosse. 


FIG.  223. 


FIG.  224. 


COLUMNAR  EPITHELIUM,  from  the  mucous 
membrane  of  the  small  intestine:  highly  mag- 
nified. 


COLUMNAR  EPITHELIUM,  from  an  intestinal 
villus.  a,  goblet  -  cells ;  b,  columnar  cells: 
highly  magnified. 


The  epithelium  consists  of  a  single  uniform  layer  of  columnar 
cells,  like  those  of  the  stomach,  but  peculiar  in  that  each  cell  terminates 
in  a  thick  plate,  which  is  vertically  striate;  the  striae  seeming  to  be 
due  either  to  fine  pores  or  to  a  division  of  the  plate  into  minute  rods. 
Among  the  columnar  cells  many  are  to  be  observed  in  the  condition 
of  mucus-secreting  goblet-cells. 

The  mucosa  consists  of  a.  basis  of  ordinary  fibro-connective  tissue 
with  lymphoid  tissue  defined  by  basement  membrane  of  the  usual  con- 
stitution. In  it  are  embedded  the  enteric  glands,  and  it  is  defined 
from  the  submucous  coat  by  the  muscularis  mucosse.  This  in  some 
positions  consists  of  a  single  layer  of  longitudinal  unstriped  muscle- 
fibres,  but  in  others  of  an  additional  inner,  thin,  circular  layer. 

The  connivent  valves  (valvulce  conniventes)1  are  narrow  folds  of 
the  intestinal  mucous  membrane  strengthened  by  processes  of  the  sub- 
mucous  coat.  They  are  crescentic,  and  generally  encircle  the  intes- 
tine from  one-half  to  about  three-fourths  way  round,  and  lie  backward, 
so  that  where  they  are  numerous  and  close  together  they  present  a 
somewhat  imbricate  appearance.  They  are  widest  along  the  middle, 
and  taper  at  the  extremities.  The  longest  measure  about  two  and  a 
half  inches  by  one-fourth  of  an  inch  wide,  and  where  most  numerous 
are  separated  about  their  own  width.  They  commence  with  the  de- 
scending portion  of  the  duodenum,  become  most  numerous  and  largest 
in  the  transverse  portion  and  in  the  upper  portion  of  the  jejunum, 
whence  they  continue  into  the  ileum,  gradually  decreasing  both  in 


1  Valves  of  Kerkring  ;  v.  c.  Kerkringii ;  plicae  conniventes. 


THE  ALIMENTARY  APPARATUS. 


427 


FIG.  225. 


number  and  size,  and  finally  disappear  in  the  lower  portion  of  the 
latter,  where  the  mucous  membrane  is  comparatively  even.  Unlike 
the  rugse  of  the  stomach,  they  are  permanent  and  not  affected  by  the 
contraction  or  expansion  of  the  intestine,  nor  are  they  active  during 
life,  as  the  muscular  coat  of  the  latter  does  not  enter  into  their  compo- 
sition. In  dried  preparations  they 
project  straight  inward  from  the 
wall  of  the  intestine  as  narrow, 
crescentic  partitions.  Their  pres- 
ence retards  the  passage  of  the 
food,  and  greatly  increases  the  ex- 
tent of  surface  for  absorption.  It 
is  a  remarkable  fact  that  they  are 
peculiar  to  man,  even  in  the  higher 
apes  existing  only  in  a  rudimentary 


condition. 

The  mucous  membrane  of  the 
connivent  valves  is  the  same  as 
elsewhere  in  the  small  intestine, 


SMALL  PORTION  OF  THE  MUCOUS  MEMBRANE 

FROM  THE  UPPER  PART  OF  THE  JEJUNUM,  mod- 

erately  magnified.  1,  villi,  resembling  conni- 
vent valves  in  miniature;  2,  enteric  glands; 
their  orifices,  3,  opening  on  the  free  surface  of 
the  mucous  membrane;  4,  fibre-connective 

being  provided  with  villi  and  both    tissue  of  the  mucosa. 
enteric  and  solitary  glands. 

The  villi1  thickly  cover  the  surface  of  the  mucous  membrane  from 
the  pyloric  valve  to  the  ileo-colic  valve.     It  is  estimated  that  in  the 

FIG.  226. 


PORTION  OF  THE  MUCOUS  MEMBRANE  FROM  THE  ILEUM,  moderately  magnified,  exhibiting  the 
villi  on  its  free  surface,  and  between  them  the  orifices  of  the  enteric  glands.  1,  portion  of  an 
agminated  gland ;  2,  a  solitary  gland ;  3,  the  mucosa. 

upper  part  of  the  intestine  there  are  from  ten  to  eighteen  in  the  space  of 
a  square  millimetre,  and  eight  to  fourteen  in  the  same  space  in  the  ileum, 
amounting  in  all  to  about  four  millions.  They  are  generally  conical, 
finger-like,  and  tongue-like  in  shape,  and  vary  in  proportionate  length 
and  breadth.  They  commonly  range  from  one-fiftieth  to  one-twenty- 
fifth  of  an  inch  in  length.  They  are  of  greatest  breadth  in  the  duo- 
denum and  the  commencement  of  the  jejunum,  where  many  appear 
laminar,  like  minute  connivent  valves,  more  or  less  flexuose,  inter- 
twining, and  often  dividing  and  joining  one  another.  Lower  in  the 
jejunum  they  become  slightly  longer  and  relatively  much  narrower. 


Villi  intestinorum  ;  intestinal  villosities. 


428 


THE  ALIMENTARY  APPARATUS. 


The  villi  are  processes  of  mucous  membrane,  composed  of  a  matrix 
of  fibre-connective  and  lymphoid  tissue  containing  vessels,  and  covered 
by  the  common  intestinal  epithelium.  Each  villus  contains  beneath 
the  basement  membrane  a  net  of  fine  capillary  vessels,  supplied  by  an 
artery  ascending  from  the  mucosa  and  terminating  in  a  vein  descend- 
ing to  the  venous  plexus  of  the  latter.  Each  also  contains  centrally 
usually  a  single  cylindrical  or  clavate1  lacteal  of  much  greater  calibre 

FIG.  227. 


DIAGRAM  OF  THE  STRUCTURE  OF  THE  MUCOUS  MEMBRANE  OF  THE  ILEUM,  highly  magnified.  1, 
epithelium  forming  the  free  surface  of  the  mucous  membrane  ;  2,  basement  membrane ;  3,  the 
mucosa,  composed  of  fibro-connective-tissue ;  4,  villi  covered  with  epithelium ;  5,  a  villus  de- 
prived of  one-half  of  its  epithelium,  and  exhibiting  through  its  basement  layer  the  blood-vessels ; 
6,  a  villus  partially  deprived  of  its  epithelium;  7,  villi  totally  deprived  of  their  epithelium,  but 
retaining  their  basement  membrane;  8,  enteric  glands  embedded  in  the  mucosa;  9,  orifices  of 
the  enteric  glands  opening  on  the  free  surface  of  the  mucous  membrane  between  the  villi ;  10, 
section  of  an  enteric  gland,  with  its  epithelial  lining;  11,  enteric  glands  stripped  of  the  latter, 
but  retaining  their  basement  membrane ;  12,  one  of  the  glands  in  section,  without  its  epithelium; 
13,  capillaries  surrounding  the  orifices  of  the  enteric  glands;  14,  an  artery  ;  15,  a  vein  ;  1C,  lym- 
phatics or  lacteals ;  17,  commencement  of  the  latter  within  the  villi ;  18,  capillary  blood-vessels 
of  the  villi. 

than  the  surrounding  blood-capillaries.  It  commences  in  a  blind  ex- 
tremity below  the  top  of  the  villus,  and  descends  to  the  lymphatic 
plexus  beneath.  The  broader  villi  contain  two  or  more  lacteals  uniting 
in  loops  or  plexuses.  Accompanying  each  lacteal  are  some  ascending 
unstriped  muscle-fibres,  which  at  their  upper  ends  radiate  to  the  base- 
ment membrane  of  the  villus. 

Glands  of  the  small  intestine.  The  bodies  commonly  named 
as  such  are  the  enteric,  the  duodenal,  the  solitary,  and  the  agminated 
glands. 

The  enteric,  or  tubular,  glands l  are  minute  and  very  numerous, 


1  Glandulae  entericae,  mucosae,  or  Lieberkuhnii  ;  crypts,  follicles,  or  glands  of 
Lieberkiihn ;  cryptae  minimae  or  mucosse. 


THE   ALIMENTARY   APPARATUS. 


429 


and  are  embedded  vertically  in  the  mucosa  of  the  intestinal  mucous 
membrane.  They  are  simple,  cylindrical,  slightly  flask-shaped  tubes, 
closed  at  the  bottom,  and  opening  on  the  surface  of  the  mucous  mem- 
brane in  the  intervals  of  the  villi.  They  are  related  in  size  with 
the  thickness 'of  the  mucous  membrane,  and  are  uniform  in  any  par- 
ticular position.  They  are  longest  in  the  duodenum  and  shortest  in 
the  ileum,  and  usually  range  from  one-sixty-sixth  to  one-fiftieth  of 
an  inch  long.  Their  wall  consists  of  a  membrana  propria  lined  with  a 
columnar  epithelium  like  that  of  the  intestine  generally. 


FIG.  228. 


FIG.  229. 


•  PORTION  OF  THK  DUODENUM,  viewed  from 
without,  natural  size.  1,  thickness  of  the  duo- 
denum; 2,  3,  longitudinal  and  transverse  layers 
of  the  muscular  coat ;  4,  fibrous  coat ;  5,  exte- 
rior of  the  mucous  membrane  with  the  duo- 
denal glands. 


A  VERTICAL  SECTION  OF  THE  DUODENUM,  highly 

magnified.  1,  a  fold-like  villus;  2,  epithelium 
of  the  mucous  membrane ;  3,  orifices  of  the  tu- 
bular enteric  glands,  4 ;  5,  orifice  of  a  duodenal 
racemose  gland,  6 ;  7,  two  follicles  of  the  latter, 
more  highly  magnified,  exhibiting  the  secre- 
tory cells  lining  their  internal  surface. 


The  duodenal  glands1  are  little  spheroidal,  racemose  glands  em- 
bedded in  the  submucous  coat  of  the  duodenum,  with  their  ducts 
ascending  between  the  enteric  glands  and  opening  on  the  surface 
with  them  between  the  villi.  They  are  largest  and  most  numerous 
in  the  ascending  portion  of  the  duodenum,  where  they  form  a  more  or 
less  continuous  patch,  decrease  in  number  and  size  in  the  descending 
portion,  and  disappear  in  the  transverse  portion.  They  are  variable 
both  in  number  and  size  in  different  persons,  and  usually  range  from 
one-hundredth  to  one-twenty-fifth  of  an  inch  in  diameter.  They  are 
best  exposed  to  view  from  the  outside  by  dissecting  away  the  serous 
and  muscular  coats. 

The  solitary  glands2  are  soft,  white,  spheroidal,  or  ovoidal  bodies 
scattered  here  and  there,  alone  as  the  name  indicates,  over  the  inner 
surface  of  the  small  intestine.  They  usually  range  from  one-fiftieth  to 
one-tenth  of  an  inch,  and  are  rather  more  numerous  in  the  ileum.  They 
are  partially  embedded  in  the  submucous  coat,  protrude  through  the 


1  Glands  of  Brunner  ;  glandulae  Brunnerianae  or  conglomerate  intestinorum. 

2  Glandulae  solitariae  or  sporacles. 


430 


THE  ALIMENTARY  APPARATUS. 


muscularis  mucosse  into  the  mucosa,  and  cause  the  investing  epithelium 
to  project  above  the  general  level  of  the  mucous  membrane.  They  are 
surrounded  by  enteric  glands,  and  frequently  have  villi  upon  them. 
Bach  consists  of  an  egg-shaped  nodule  of  lymphoid  tissue, — that  is  to 
say,  a  matrix  of  stellate  connective-tissue  corpuscles  with  the  inter- 
spaces occupied  with  lymphoid  corpuscles.  Though  considered  and 
named  follicles,  they  are  not  actually  separated  from  the  adjacent 
lymphoid  tissue  of  the  mucosa,  but  are  defined  by  a  surrounding 


PIG.  230. 


FIG.  231. 


PORTION  OF  THE  MUCOUS  MEMBRANE  FROM 
THE  UPPER  PART  OF  THE  iLEUM,  exhibiting  the 
appearance  presented  to  the  naked  eye  when 
the  specimen  is  floated  in  water.  1,  2,  3,  4, 
an  agminated  gland ;  5,  connivent  valves ;  the 
short  lines  everywhere  covering  the  surface  of 
the  mucous  membrane,  including  the  valves 
and  the  gland,  represent  villi ;  6,  7,  8,  solitary 
glands. 


PORTION  OF  THE  ILEUM,  viewed  from  without ; 
the  serous  and  muscular  coats  removed  over  the 
position  of  an  agminated  gland.  1,  exterior  sur- 
face of  the  ileum ;  2,  cut  edge  of  the  serous  and 
muscular  coats ;  3,  exterior  surface  of  the  mu- 
cous membrane  and  fibrous  coat ;  4,  an  agmi- 
nated gland,  exhibiting  its  nodules  of  lym- 
phoid tissue ;  5,  position  of  connivent  valves. 


plexus  of  capillary  blood-vessels   and   lymphatics,  from  which   finer 
capillaries  extend  into  the  interior  of  the  nodules. 

The  agminated  glands,  or  glands  of  Peyer,1  are  patches  of  lym- 
phoid nodules  like  the  solitary  glands,  and  for  the  most  part  occupy  the 
ileum.  They  are  commonly  elliptical,  of  very  variable  size,  and  situated 
opposite  the  attachment  of  the  mesentery  in  a  single  row,  with  their 
length  parallel  to  that  of  the  intestine.  They  number  generally  from 
twenty  to  thirty  or  more,  and  range  from  half  an  inch  to  three  or  four 
inches  in  length,  by  half  an  inch  to  three-fourths  in  width,  while  a  few 
of  the  smallest  are  only  two  or  three  lines  broad.  They  are  ordinarily 
largest  and  nearer  together  in  the  lower  part  of  the  ileum,  and  are 
fewer  in  the  upper  part  of  the  intestine,  being  smallest  and  often  cir- 
cular in  the  jejunum.  They  are  more  or  less  sharply  or  obscurely  de- 


1  Glandulse  agminatae ;  g.  mucosae  coagminatae ;  g.  Peyeri,  Peyerianese,  or  sociae 
Peyeri ;  aggregate  glands  ;  patches  or  plaques  of  Peyer. 


THE   ALIMENTAEY   APPAEATUS.  431 

fined,  slightly  or  scarcely  prominent,  and  usually  even  and  not  crossed 
by  connivent  valves.  The  mucous  membrane  continuous  over  them  is 
thinner  and  more  tightly  adherent  to  the  subjacent  parts  than  else- 
where, and  is  usually  provided  with  fewer  villi.  Sometimes  the  glands 
appear  more  prominent  and  better  defined,  and  the  mucous  membrane 
covering  them  is  tortuously  plicated  and  more  villous  than  usual.  Con- 
nivent valves  approaching  the  glands  usually  cease  at  their  border.  The 
constituent  lymph-nodules  lie  on  the  same  plane,  and,  like  the  solitary 
glands,  are  partially  embedded  in  the  submucous  coat,  and  protrude 
through  the  muscularis  mucosae  into  the  mucosa,  but  not  to  the  extent 
of  the  solitary  glands,  which  commonly  appear  more  prominent  than 
the  nodules  of  the  agminated  glands.  The  latter  have  the  same  con- 
stitution as  the  former,  and  in  the  intervals  they  merge  into  the  more 
diffused  lymphoid  tissue  of  the  mucosa,  which  in  these  positions  also 
include  some  of  the  enteric  glands  surrounding  the  nodules.  The 
latter  are  defined  by  plexuses  of  capillary  blood-vessels,  from  which 
finer  capillaries  extend  into  the  interior  of  the  nodules.  Plexuses  of 
lymphatics  likewise  surround  them. 

In  the  position  occupied  by  the  agminated  glands  the  submucous 
coat  is  denser  than  elsewhere,  and  is  more  closely  connected  with  the 
mucosa,  so  that  when  air  is  forced  into  the  submucous  coat  of  the 
intestine  it  meets  with  greater  resistance  to  its  entrance  beneath  the 
glands. 

Both  the  agminated  and  solitary  glands  are  best  developed  during 
growth  and  maturity,  but  after  middle  life  are  less  well  marked,  and 
in  old  age  become  more  or  less  atrophied.  They  are  remarkable  for 
their  susceptibility  to  disease,  especially  in  typhoid  fever,  in  which 
they  become  greatly  enlarged,  and  are  very  liable  to  ulceration,  often 
extending  through  and  perforating  the  intestine.1 

The  arteries  of  the  small  intestine  are  chiefly  derived  from  the 
superior  mesenteric,  and  the  commencement  of  the  duodenum  receives 
branches  from  the  gastro-duodenal  branch  of  the  hepatic  artery.  The 
branches  of  the  superior  mesenteric  artery  reach  the  intestine  along 
the  attachment  of  the  mesentery,  diverging  in  front  and  behind,  and 
entering  between  the  serous  and  muscular  coats.  Penetrating  the 
latter,  they  ramify  freely  in  the  submucous  coat,  and  inosculate  around 
the  intestine  in  a  plexus.  From  this,  branches  proceed  to  the  mucous 
membrane,  and  end  in  the  capillaries  of  its  mucosa,  of  the  villi,  and  of 
the  various  glands.  Branches  also  proceed  to  the  capillaries  of  the 
muscular  coat  and  to  those  beneath  the  serous  coat.  The  corresponding 
veins  return  from  the  capillary  plexuses  to  the  large  venous  plexus  of 


1  In  a  young  soldier  who  died  in  Satterlee  Hospital  in  1862,  in  whom  the  agmi- 
nated glands  were  well  produced,  comparatively  even,  and  the  lymph-nodules  unusu- 
ally distinct,  in  a  gland  an  inch  and  a  quarter  long  and  half  an  inch  wide  there 
were  counted  about  two  hundred  and  sixty  nodules. 


432  THE   ALIMENTARY   APPARATUS. 

the  submucous  coat,  whence  veins  accompany  the  arteries  finally  to 
empty  in  the  superior  mesenteric  vein. 

The  lymphatics  form  plexuses  of  vessels  in  the  mucosa  between 
and  around  the  enteric  glands,  receive  the  lacteals  from  the  villi,  com- 
municate with  plexuses  around  the  lymph-nodules  forming  the  solitary 
and  agminated  glands,  and  unite  with  a  plexus  of  coarser  vessels  in 
the  submucous  coat.  Plexuses  also  exist  in  the  muscular  coat  and 
beneath  the  serous  coat.  From  the  different  plexuses  the  chief  vessels 
proceed  to  the  mesenteric  border  and  conjoin  to  form  the  lacteal  vessels 
traversing  the  mesentery. 

The  nerves  of  the  small  intestine  are  derived  from  the  superior 
mesenteric  plexus  emanating  from  the  solar  plexus  of  the  sympathetics 
united  with  branches  from  the  vagus  nerves.  Accompanying  the 
superior  mesenteric  artery  and  its  divisions  the  plexus  is  expended  in 
branches  diverging  to  the  intestine.  Entering  the  muscular  coat,  they 
form  an  extensive  gangliated  plexus1  between  the  longitudinal  and 
circular  layers ;  the  fibres  of  the  plexus  being  mostly  non-medullated. 
From  the  plexus  proceed  branches  to  the  submucous  coat,  in  which 
they  form  another  gangliated  plexus,2  and  from  both,  fine  branches  pass 
to  the  mucosa,  the  two  layers  of  the  muscular  coat,  and  beneath  the 
serous  coat,  to  form  still  finer  plexuses. 

THE   LAKGE    INTESTINE. 

The  large  intestine,3  as  expressed  by  the  name,  is  the  larger  con- 
tinuation of  the  canal  succeeding  the  small  intestine,  and  extending 
from  the  termination  of  the  ileum  to  the  anus.  Of  variable  length,  it 
is  usually  from  five  to  six  feet;  and  is  also  of  variable  diameter  in 
different  persons  and  in  different  parts  of  the  intestine,  varying  from 
an  inch  and  a  half  to  two  or  three  inches  in  the  largest  portion.  It 
comprises  two  divisions,  the  colon  and  the  rectum,  the  former  occupying 
the  abdomen,  the  latter  the  pelvis. 

The  colon  *  is  largest  at  its  commencement,  and  decreases,  often 
somewhat  irregularly,  to  its  termination  in  the  rectum.  It  is  not  an 
even  cylindrical  tube  like  the  small  intestine,  but  presents  three  rows 
of  pouches  separated  by  constrictions  of  the  wall,  which  are  produced 
by  narrow  folds  projecting  into  the  intestine,  and  caused  by  three  equi- 
distant bands  running  along  the  colon  from  its  commencement  to  the 
rectum.  It  nearly  surrounds  the  small  intestine  at  the  boundaries  of 
the  abdomen,  and  is  attached  to  the  posterior  wall  of  the  latter  by  a 
fold  of  the  peritoneum  named  the  mesocolon.  It  commences  in  the 
right  iliac  region,  ascends  through  the  lumbar  to  the  right  hypo- 

1  Plexus  of  Auerbach ;  p.  myentericus.  2  Plexus  of  Meisner. 

3  Intestinum  crassum,  amplum,  or  plenum. 

4  Colum  ;  intestinum  majus,  grande,  cellulatum,  or  laxum. 


THE   ALIMENTAEY   APPARATUS. 


433 


chondriac  region  beneath  the  liver;  thence  curves  across  to  the  left 
hypochondriac  region  beneath  the  spleen,  and  descends  through  the 
lumbar  to  the  left  iliac  region,  where  it  produces  a  loose  S-like  fold,  and 


FIG.  232. 


VIEW  OF  THE  ABDOMINAL  VISCERA;  with  the  greater  part  of  the  small  intestine  removed, 
and  the  liver  and  stomach  turned  upward.  1,  under  surface  of  the  liver ;  2,  gall-bladder ;  3, 
diaphragm ;  4,  stomach,  posterior  surface ;  5,  caudate  lobe  of  the  liver ;  6,  duodenum ;  7,  pan- 
creas; 8,  spleen;  9,  jejunum;  10,  ileum;  11,  caecum;  12,  vermiform  appendix;  13,  ascending 
colon ;  14, 14,  transverse  colon  ;  15,  descending  colon ;  16,  sigmoid  flexure ;  17,  rectum ;  18,  urinary 
bladder ;  19,  hepatic  artery,  giving  off  pyloric,  hepatic,  pancreatico-duodenal,  and  right  gastro- 
epiploic  branches  ;  20,  coronary  artery  to  small  curvature  of  the  stomach ;  21,  splenic  artery;  22, 
superior  mesenteric  vessels ;  23,  24,  cut  edge  of  the  mesentery  between  the  divided  ends  of  the 
jejunum  and  ileum. 

ends  in  the  rectum,  at  the  border  of  the  pelvis,  in  front  of  the  left  sacro- 
iliac  articulation. 

The  head  of  the  colon,1  below  the  entrance  of  the  ileum,  is  called 
the  caecum,  and  the  remainder  is  divided  into  the  ascending,  transverse, 
and  descending,  and  the  sigmoid  flexure  of  the  colon. 

The  caecum,2  the  broadest  portion  of  the  colon,  is  a  capacious  sac 
two  or  three  inches  in  length  and  as  wide  as  the  greater  length.  It 
is  pouched,  like  the  rest  of  the  colon,  and  at  its  inner  back  part  is 
extended  in  a  cone,  which  is  abruptly  prolonged  into  a  vermiform 


1  Caput  coli ;  initium  or  saccus  intestini  crassi,  or  coli. 

28 


The  blind  gut. 


434 


THE   ALIMENTARY   APPARATUS. 


appendix.1     This  is  usually  from  three  to  six  inches  long,  about  the 

thickness   of   a   goose-quill,   com- 

FIG.  233.  monly  turns  upward,  and  after  a 

variable  flexuose  course  terminates 
in  a  blind,  free,  rounded'  end.  At 
birth  it  is  less  abrupt  at  its  com- 
mencement, and  appears  more  evi- 
dently a  continuation  of  the  caecum. 
It  is  peculiar  to  man  and  some  of 
his  nearest  allies,  the  higher  apes, 
but  exists  also  in  the  wombat,  an 
animal  at  the  opposite  limit  of  the 
same  class.  It  is  regarded  as  a 
rudiment  of  the  greatly  elongated 
Cfficum  of  most  herbivorous  mam- 
mals. Sometimes  it  is  short,  and 
rarely  it  is  altogether  absent. 

The  csecum  occupies  the  right 
iliac  fossa,  to  which  it  is  closely,  or 
more  or  less  loosely,  attached.  In 
the  former  case  it  is  covered  in 
front  and  on  the  sides  by  the  peri- 
toneum reflected  to  the  fossa,  and 
is  attached  behind!  by  areolar  tissue 

to  the  investing  fascia  of  the  iliac  muscle ;  in  the  latter  case  the  peri- 
toneum invests  the  caecum  to  a  greater  degree,  and  attaches  it  behind 
by  a  doubling  called  the  mesocsecum.  A  fold  of  the  peritoneum  also 
extends  from  the  vermiform  appendix  to  the  adjacent  extremity  of  the 
csecum,  serving  to  retain  it  in  a  more  fixed  position. 

The  ileum,  ascending  from  right  to  left  and  backward  across  the 
psoas  muscle,  joins  the  colon  on  the  inner  side  above  the  csecum.  The 
communication  with  the  colon  is  guarded  by  the  ileo- colic  valve,* 
which  is  composed  of  two  crescentic  membranous  segments,  directed 
from  the  ileum  into  the  colon,  one  above  the  other.  Their  convex  at- 
tached border  corresponds  with  the  junction  of  the  latter,  whence  they 
converge  within  the  colon,  and  terminate  with  their  concave  free  edge 
directed  obliquely  to  the  right  and  forward.  Their  extremities  unite 
in  a  tapering  fold,3  which  extends  for  some  distance  in  front  and  be- 
hind round  the  interior  of  the  colon.  The  upper  segment  of  the  valve 
is  horizontal,  and  the  lower  is  larger,  and  slopes  from  its  free  edge 
downward  into  the  ileum.  The  aperture  of  the  valve  is  horizontal, 


THE  C.ECUM  LAID  OPEN,  TO  EXPOSE  THE  ILEO- 

COLIC  VALVE,  a,  Termination  of  the  ileum; 
b,  slit-like  orifice  between  the  two  folds  of  the 
ileo-colic  valve;  c,  caecum;  d,  vermiform  ap- 
pendix ;  e,  ascending  colon. 


1  A.  or  appendicula  vermiformis  or  vermicularis  ;  appendix  caeci ;  additamentum 
coli ;  vermicular  process  ;  digital  appendix. 

*  Ileo-caecal  valve;  valvula  coli,  caeci,  ilei,  Bauhini,  Fallopii,  Tulpii,  or  Varolii ; 
operculum  ilei.  3  Frenum  or  retinaculum  Morgagni. 


THE   ALIMENTARY   APPARATUS.  435 

curving  fore  and  aft,  and  looking  into  the  colon  obliquely  to  the  right 
and  forward.  It  varies  with  the  condition  of  the  valve,  being  elliptical 
if  this  is  relaxed  and  is  narrowed  to  a  fissure  or  is  closed  if  the  valve  is 
stretched.  It  ordinarily  appears  like  a  button-hole,  with  the  anterior 
corner  rounded  and  the  posterior  corner,  more  to  the  right,  acute.  The 
termination  of  the  ileum,  included  by  the  convergent  segments  of  the 
valve,  is  funnel-like,  the  surfaces  of  the  segments  being  concave,  while 
on  the  side  next  the  colon  they  are  correspondingly  convex. 

The  ascending  colon1  proceeds  from  the  position  of  the  ileo-colic 
valve  through  the  adjacent  lumbar  into  the  right  hypochondriac  region 
beneath  the  liver  and  to  the  right  of  the  gall-bladder,  where  it  turns 
abruptly  forward  and  to  the  left  to  become  the  transverse  colon.  It 
lies  against  the  quadrate  lumbar  muscle  and  right  kidney,  to  which  it 
is  attached  by  areolar  tissue  and  by  the  peritoneum,  which  covers  it  in 
front  and  at  the  sides,  and  is  thence  reflected  to  the  abdominal  wall. 
Sometimes  the  latter  membrane  invests  it  more  completely,  and  forms 
a  narrow  mesocolon,  giving  it  some  mobility.  In  front  of  the  ascending 
colon  are  the  abdominal  wall  and  the  convolutions  of  the  ileum. 

The  transverse  colon,2  the  longest  and  most  movable  portion  of 
the  large  intestine,  produces  a  broad  coil  curving  forward  from  the  left 
to  the  right  hypochondrium,  whence  it  is  also  called  the  arch  of  the 
colon.  It  commonly  crosses  the  upper  part  of  the  umbilical  region, 
but  often  descends  to  the  umbilicus  and  sometimes  much  lower.  Its 
extremities  are  deeply  tucked  in  in  the  hypochondriac  regions,  where 
they  form  with  the  ascending  and  descending  colon  the  hepatic3  and 
splenic  flexures.4  It  is  suspended  from  the  posterior  abdominal  wall 
by  the  transverse  mesocolon,  a  broad  duplicature  of  the  peritoneum, 
which  almost  completely  invests  it.  The  splenic  flexure  is  further 
maintained  by  a  fold  of  the  same,  the  phreno-colic  ligament,5  which 
extends  with  a  free  curved  border  from  the  colon  to  the  diaphragm  in 
the  vicinity  of  the  tenth  rib.  The  transverse  colon  lies  beneath  the 
liver,  stomach,  and  spleen,  resting  behind  on  the  transverse  mesocolon 
and  below  on  the  small  intestine,  with  the  great  omentum  and  the 
abdominal  Avail  in  front. 

The  descending  colon,6  more  deeply  situated  than  the  ascending 
colon,  passes  down  through  the  left  hypochondriac  and  lumbar  regions 
to  the  sigmoid  flexure.  It  is  closely  attached  to  the  left  crus  of  the 
diaphragm  and  kidney  by  areolar  tissue  and  by  the  peritoneum  cover- 
ing it  in  front  and  thence  reflected  on  the  sides  to  the  wall  of  the  ab- 
domen. It  is  concealed  in  front  by  convolutions  of  the  jejunum. 

The  sigmoid  flexure 7  is  the  narrowest  portion  of  the  colon,  and 
occupies  the  left  iliac  fossa,  commencing  from  the  descending  colon  at 

1  Colon  ascendens  or  dextrum  ;  right  lumbar  colon. 

2  C.  transversum.  s  Flexura  prima,  dextra,  or  hepatica  coli. 
4  F.  secunda,  sinistra,  or  lienalis.              5  Costo-colic  or  pleuro-colic  ligament. 

6  C.  descendens  or  sinistrum.  7  Flexura  sigmoidea  or  iliaca. 


436  THE   ALIMENTARY   APPARATUS. 

the  iliac  crest  and  terminating  in  the  rectum  at  the  left  sacro-iliac 
articulation.  It  pursues  an  S-like  curve,  whence  its  name,  and  is 
attached  to  the  iliac  fossa  by  a  wide  peritoneal  fold,  which  allows  of 
free  movement.  It  lies  within  the  front  wall  of  the  abdomen,  covered 
by  a  few  coils  of  the  jejunum ;  and  when  the  bladder  is  empty  for  the 
most  part  falls  into  the  pelvis. 

The  wall  of  the  colon  is  thicker  than  that  of  the  small  intestine, 
and  becomes  slightly  thicker  as  it  becomes  narrower  in  approaching 
the  termination.  It  possesses  the  same  number  and  kinds  of  coats  as 
the  stomach  and  small  intestine. 

The  serous  coat  is  of  the  usual  character,  but  is  peculiar  in  that 
it  has  attached  here  and  there  along  its  course  little  long-necked 
pouches,  the  epiploic  appendages,1  which  are  processes  of  the  mem- 
brane, and  are  disposed  to  accumulate  fat  within  them.  It  does  not 
invest  the  colon  so  completely  as  in  the  small  intestine,  being  especially 
deficient  along  the  back  of  the  ascending  and  descending  portions. 

The  muscular  coat,  like  that  of  the  small  intestine,  consists  of  two 
layers,  but  the  fibres  of  the  external  layer  are,  for  the  most  part,  col- 
lected into  three  bands,  about  the  third  of  an  inch  wide,  which  start 
from  the  base  of  the  vermiform  appendix,  and  thence  extend  nearly 
equidistant  from  one  another  along  the  colon  to  its  termination,  where 
they  widen  and  become  a  continuous  longitudinal  layer  on  the  rectum. 
From  the  commencement  of  the  bands  the  longitudinal  fibres  are  also 
extended  as  a  continuous  layer  on  the  vermiform  appendix.  In  the 
intervals  of  the  bands  of  the  colon  the  wall  is  provided  with  a  very 
thin  layer  of  longitudinal  fibres.  The  internal  muscular  layer  is  thin, 
and  consists  of  circular  fibres,  which  are  more  numerous  in  the  con- 
strictions of  the  intestine.  When  the  longitudinal  bands  are  cut  at 
the  constrictions,  these  are  obliterated. 

The  fibrous  coat  of  the  colon  is  thicker  than  that  of  the  small 
intestine,  but  is  otherwise  like  it. 

The  mucous  membrane  is  dull  white,  slightly  thicker  and  firmer 
pIG  234  than  that  of  the  small  intestine.  It  becomes 

slightly  and  irregularly  rugose  in  the  relaxed 
or  empty  condition,  and  smooth  in  the  ex- 
panded condition.  It  has  the  same  structure 
as  that  of  the  small  intestine,  but  is  entirely 
devoid  of  villi,  and  the  tubular,  or  colic, 
glands2  are  longer  and  relatively  more  nu- 
SECTION  OF  THE  MUCOUS  MEM-  merous  than  the  enteric  glands.  The  mouths 

BEANE  OF  THE  COLON.     1.  free  SUT-  f,    ,-,  i         j  .  ,  i  r.  r>   ji 

face  exhibiting  the  orifices  of  the  of  the  glands  opening  on  the  surface  of  the 
colic  glands,  2;  3,  mucosa:  mod-  membrane  give  it  a  minutely  cribriform  ap- 
erateiy  magnified.  pearance.  Solitary  glands  are  in  like  man- 

ner scattered  over  the  surface,  but  are  less  prominent  than  in  the  small 

1  Appendices  epiploicae ;  omentula.  2  Crypts  of  Lieberkiihn. 


THE   ALIMENTARY   APPARATUS.  437 

intestine.  They  are  most  numerous  in  the  caecum,  and  especially  in 
the  vermiform  appendix,  where  they  form  a  continuous  layer  as  in  the 
agminated  glands  of  the  ileum. 

The  ileo-colic  valve  is  composed  of  doublings  of  the  mucous  mem- 
brane strengthened  by  extensions  of  the  submucous  coat  and  with 
muscular  fibres  from  the  circular  layer  of  the  adjacent  muscular  coat : 
the  longitudinal  layer  continuing  uninterruptedly  across  the  position 
of  the  valve.  The  mucous  membrane  of  the  valve  on  the  side  of  the 
ileum  is  covered  with  villi  as  elsewhere  in  the  small  intestine,  but  is 
devoid  of  them  on  the  opposite  side  directed  into  the  colon. 

The  muscularis  mucosas  consists  of  an  outer  longitudinal  and  an  inner 
circular  layer,  and  occasionally  sends  fibres  between  the  colic  glands. 

The  distribution  and  arrangement  of  the  blood-vessels  and  capil- 
laries in  the  coats  of  the  colon  are  the  same  as  in  the  stomach.  The 
arrangement  of  the  nerves  is  the  same  as  in  the  small  intestine,  except 
that  the  gangliated  plexuses1  possess  larger  ganglia. 

The  arteries  of  the  colon  are  the  colic  and  sigmoid  branches  of  the 
superior  and  inferior  mesenteries,  which  approach  and  enter  the  colon 
from  the  mesocolon,  in  the  same  manner  as  the  arteries  enter  the  wall  of 
the  small  intestine.  The  veins  correspond  with  the  arteries,  and  join 
the  inferior  and  superior  mesenteric  branches  of  the  portal  system. 
The  lymphatics  are  numerous,  and  emerging  from  the  colon  enter 
glands  along  the  attachment  of  the  mesocolon.  The  nerves  are  de- 
rived from  the  superior  and  inferior  mesenteric  plexuses  of  the  sym- 
pathetic, accompanying  the  corresponding  arteries. 

The  rectum,2  the  terminal  division  of  the  large  intestine,  occupies 
the  back  part  of  the  pelvis  behind  the  urinary  bladder  in  the  male ; 
with  the  uterus  and  vagina  intervening  in  the  female.  From  its  com- 
mencement in  the  sigmoid  flexure,  at  the  brim  of  the  pelvis  in  front  of 
the  left  sacro-iliac  articulation,  it  curves  downward  to  the  right,  and 
applies  itself  to  the  middle  of  the  sacrum,  and  then  follows  the  curve 
of  this  and  the  coccyx,  and  continues  in  the  same  direction  below  the 
latter  to  near  the  perineal  centre,  when  it  makes  another  curve  back- 
ward to  the  anus.  It  is  not  sacculated  like  the  colon,  but  is  club- 
shaped,  narrowest  at  its  commencement  and  gradually  widening  to 
near  its  termination,  where  it  is  most  expanded,  and  then  abruptly 
narrows  to  the  anus,  which  is  a  dilatable  aperture  enclosed  by  the  anal 
sphincter.  It  is  about  seven  or  eight  inches  long,  but  of  very  variable 
calibre,  in  some  measure  due  to  habit  of  the  person.  In  those  in  whom 
it  is  habitually  empty  it  is  more  contracted ;  in  those  who  are  costive 
or  who  habitually  restrain  the  passage  of  the  contents  it  becomes  more 
or  less  expanded.  Commonly,  it  measures  about  one  and  a  half  inches 
at  its  narrowest  part,  and  from  two  and  a  half  to  three  inches  at  its 
widest  part. 

1  Plexuses  of  Auerbach  and  of  Meisner.  *  Intestinum  rectum. 


438  THE   ALIMEXTAKY   APPAEATUS. 

Commonly,  the  rectum  exhibits  a  few  variable  and  partial  con- 
strictions, apparently  like  those  of  the  colon ;  usually  two  to  the  right 
and  an  intermediate  one  to  the  left.  They  correspond  with  crescentic 
folds  projecting  into  the  intestine  and  varying  in  exact  position,  num- 
ber, and  width.  When  there  are  three  of  these  folds,  the  first  is  high 
up  to  the  right  and  the  least  produced  ;  the  second  is  lower  and  to  the 
left ;  while  the  third  is  about  on  the  level  of  the  base  of  the  bladder, 
mostly  the  largest,  and  is  situated  to  the  right  extending  in  front. 
Sometimes  there  are  four  folds,  and  sometimes  they  are  reduced  to  two 
or  one,  .and  rarely  none  exist.  These  rectal  folds1  are  permanent 
even  in  excessive  distention  of  the  bowel.  They  probably  serve  to  aid 
in  retaining  the  contents  of  the  rectum. 

The  upper  portion  of  the  rectum  is  invested  by  the  peritoneum, 
which  forms  a  duplicature,  the  mesorectum,  attaching  it  behind  to 
the  pelvis.  Lower,  the  peritoneum  covers  the  rectum  only  at  the  sides 
and  in  front,  and  finally  only  in  the  latter  position,  whence,  in  the  male, 
it  is  reflected  on  the  bladder,  which  in  the  distended  condition  comes 
into  contact  with  the  rectum,  but  otherwise  portions  of  the  small 
intestine  or  the  sigmoid  flexure  of  the  colon  fall  into  the  pelvis  between 
them.  In  the  female1,  in  a  similar  manner,  the  peritoneum  is  reflected 
to  the  uterus,  which  intervenes  between  the  rectum  and  bladder.  Be- 
low the  position  at  which  the  peritoneum  ceases  on  the  rectum,  this  is 
connected  to  the  surrounding  parts  by  areolar  tissue,  which  in  approach- 
ing the  anus  becomes  more  or  less  loaded  with  fat.  Behind,  it  is 
attached  to  the  sacrum  and  coccyx,  and  on  each  side  of  these  to  the 
coccygeal  and  anal  elevator  muscles ;  and  in  front,  in  the  male,  it  is 
attached  to  the  fundus  of  the  bladder,  the  seminal  vesicles,  and  the 
prostate  gland  ;  and  in  the  female  to  the  vagina.  Approaching  the 
anus,  it  is  connected  with  the  anal  elevator  muscles,  and  finally  is 
embraced  by  the  anal  sphincter. 

The  wall  of  the  rectum  is  considerably  thicker  than  that  of  the 
colon,  and  is  composed  of  an  extension  of  the  same  coats.  The  serous 
coat  is  less  complete,  only  forming  an  investment  for  its  upper  part 
and  producing  the  mesorectum,  and  thence  extending  a  short  distance 
downward  on  the  sides  and  farther  in  front.  Where  it  ceases,  the 
rectum  below  is  invested  with  a  layer  of  fibro-connective  tissue,  the 
rectal  fascia,  in  which  the  main  blood-vessels  ramify,  and  which  is 
connected  with  the  surrounding  parts. 

The  muscular  coat  is  comparatively  thick,  and  gradually  increases 
and  becomes  redder  approaching  the  anus.  The  external  longitudinal 
layer  is  thick,  and  spreads  uniformly  around  the  rectum,  and  at  the 
lower  extremity  continues  between  the  sphincters,  thinning  away  to 
the  skin  at  the  verge  of  the  anus.  The  internal  circular  layer  gradually 
augments  approaching  the  anus,  where  it  is  a  couple  of  lines  thick, 

1  Valves  of  the  rectum. 


THE   ALIMENTARY   APPARATUS.  439 

and  forms  the  internal  sphincter,  within  the  position  of  the  anal 
sphincter. 

The  fibrous  coat  is  well  produced,  and  adheres  most  tightly  to  the 
mucous  membrane  and  rather  loosely  to  the  muscular  coat. 

The  mucous  membrane  is  thicker  and  firmer  than  that  of  the 
colon,  and  assumes  a  red  color,  which  becomes  of  a  deeper  hue  towards 
the  anus.  In  the  contracted  condition  of  the  rectum  it  is  more  or  less 
irregularly  rugose,  the  ruga?  being  supported  by  the  submucosa,  as  in 
the  stomach,  and  they  are  likewise  effaced  in  distention  of  the  bowel. 
At  the  lower  extremity  it  is  produced  in  longitudinal  folds,  the  rectal 
columns,1  shorter  or  longer,  and  united  in  festoons2  at  the  verge  of 
the  anus.  The  columns  are  supported  by  bundles  of  longitudinal  mus- 
cular fibres  of  the  submucous  coat,  connected  below  with  the  termina- 
tion of  the  longitudinal  layer  of  the  muscular  coat  below  the  internal 
sphincter. 

The  structure  of  the  coats  of  the  rectum,  the  glands  of  the  mucous 
membrane,  and  the  supply  and  arrangement  of  the  vessels  and  nerves, 
are  the  same  as  in  the  colon. 

The  arteries  of  the  rectum  are  the  superior  hemorrhoidal  branch 
of  the  inferior  mesenteric  artery,  the  middle  hemorrhoidals  of  the 
internal  iliac  arteries,  and  the  inferior  hemorrhoidals  of  the  pudic 
arteries.  After  entering  beneath  the  serous  coat  and  into  the  rectal 
fascia  below,  the  branches  penetrate  the  muscular  coat,  furnishing  it 
in  their  course,  and  enter  the  submucous  coat,  in  which  they  ramify 
and  inosculate,  forming  a  plexus  extending  to  the  anus.  The  lower 
branches,  after  penetrating  the  muscular  coat,  mostly  descend  longi- 
tudinally. The  veins  are  very  numerous,  and  closely  inosculate  in  the 
submucous  coat,  forming  the  hemorrhoidal  plexus,  from  which  the  main 
veins  pursue  the  course  of  the  arteries,  partly  conveying  the  blood 
through  the  lower  hemorrhoidal  veins  into  the  pudic  and  internal  iliac 
veins  and  partly  by  the  superior  hemorrhoidal  vein  into  the  inferior 
mesenteric  vein.  The  lymphatics  enter  glands  behind  the  rectum 
and  into  those  of  the  loins.  The  nerves  are  numerous,  partly  derived 
from  the  inferior  mesenteric  and  hypogastric  plexuses  and  partly  from 
the  sacral  plexuses. 

The  anus,  the  terminal  orifice  of  the  alimentary  canal,  is  closed 
by  the  action  of  the  anal  sphincter  muscle,  which  surrounds  it.  It  is 
invested  with  the  skin  continuous  with  the  mucous  membrane,  puck- 
ered in  the  contracted  condition.  The  ski-n  is  thin,  reddish  brown, 
devoid  of  subcutaneous  fat,  and  furnished  with  papilla?  and  sebaceous 
glands. 

For  the  muscles  of  the  anus,  see  the  Perineum. 

1  Columnse  rectae  Morgagnii.  2  Valvulae  semilunares  Morgagnii. 


440  THE   ALIMENTARY    APPARATUS. 

GASTKIC   JUICE. 

The  gastric  juice,1  derived  from  the  epithelium  and  glands  of  the 
mucous  membrane  of  the  stomach,  is  a  clear,  viscid  liquid  with  a  peculiar 
odor  and  acid  taste.  It  is  a  solution  chiefly  of  a  ferment,  pepsin,  with 
ordinarily  free  hydrochloric  acid,  and  mineral  salts.  It  is  especially  a 
powerful  solvent  of  the  proteids. 

INTESTINAL  JUICES. 

The  intestinal  juices,2  derived  from  the  epithelium  and  glands  of 
the  mucous  membrane  of  the  small  and  large  intestines,  are  usually 
clear,  viscid  liquids,  with  albumin  and  mucin,  and  are  alkaline  in  re- 
action. Our  knowledge  of  them  is  very  obscure. 

THE   PANCREAS. 

The  pancreas 3  is  a  reddish,  cream-colored  gland  closely  connected 
to  the  duodenum,  into  which  its  duct  opens  and  pours  its  secretion. 
It  lies  behind  the  stomach,  across  the  spine,  resting  against  the  great 
blood-vessels  in  front  of  the  latter  and  the  crura  of  the  diaphragm. 
Its  right  extremity,  the  largest  portion,  named  the  head,4  occupies  the 
concavity  of  the  duodenum,  to  which  it  is  closely  attached.  The  re- 
maining portion,  the  body,5  extends  to  the  left,  for  some  distance  of 
nearly  uniform  depth,  and  then  diminishes  to  the  lilunt  end,  or  tail,6 
which  usually  is  in  contact  with  the  spleen.  Sometimes  the  body  is 
narrowest  where  it  leaves  the  head,  and  widens  to  the  tail. 

The  pancreas  conforms  in  shape  to  the  space  it  occupies  between 
adjacent  organs,  and  is  an  elongated,  irregular,  fore  and  aft  flattened 
prismatic  body,  which  has  been  likened  to  a  dog's  tongue  in  shape. 
It  commonly  measures  about  six  to  eight  inches  long,  from  an  inch  to 
an  inch  and  a  half  in  depth,  and  from  one-half  to  three-fourths  of 
an  inch  thick,  and  is  estimated  to  weigh  from  two  to  three  and  a  half 
ounces. 

The  anterior  surface,  covered  by  the  upper  layer  of  the  transverse 
mesocolon,  lies  in  contact  with  the  stomach.  The  posterior  surface  is 
attached  by  areolar  tissue  to  the  inferior  cava,  aorta,  portal  vein,  supe- 
rior mesenteric  vessels,  and  the  crura  of  the  diaphragm,  and  by  its  left 
extremity  to  the  corresponding  kidney  and  suprarenal  body.  The  upper 
border  is  grooved  to  accommodate  the  splenic  vein,  and  along  it,  above, 
runs  the  corresponding  artery.  The  lower  border  to  the  right  rests  on 
the  transverse  colon,  and  to  the  left  on  the  junction  of  the  duodenum  and 
jejunum.  The  superior  mesenteric  vessels  descend  behind  the  pancreas, 

1  Succus  gastricus.  2  Succus  entericus  or  intestinalis. 

3  Pancratium  ;  glandula  salivalis  abdominis  ;  sweetbread. 

4  Caput  pancreatis,  pancreas  parvum ;  lesser  pancreas. 

6  Corpus  pancreatis.  6  Cauda  pancreatis. 


THE   ALIMENTARY   APPARATUS. 


441 


more  or  less  embedded  in  its  substance,  and  emerge  forward  between  it 
and  the  termination  of  the  duodenum.  The  bile-duct  descends  behind 
the  head  of  the  pancreas,  usually  in  a  groove  or  canal  of  the  latter 
between  it  and  the  duodenum. 

The  pancreatic  duct1  extends  along  the  interior  of  the  gland  from 
left  to  right,  nearer  its  anterior  surface  and  lower  border,  receives 
many  branches  in  its  course,  bends  a  little  downward  in  the  head,  from 
which'  it  receives  its  largest  branch,2  and  then  emerges  from  the  gland. 


7   25 


•24 


25  3  *  8  4  238  5 
VISCERA  OF  THE  UPPER  PART  OF  THE  ABDOMEN  ;  the  stomach  removed  and  the  liver  raised  to 
show  its  under  surface.  1,  oesophagus  with  cardiac  extremity  of  the  stomach  ;  2,  commence- 
ment of  the  duodenum ;  3,  descending  portion  ;  4,  transverse  portion;  5,  line  passing  over  the 
commencement  of  the  jejunum  to  the  pancreas ;  6,  6,  head  of  the  pancreas ;  7,  tail  of  the  pan- 
creas; 8,  8,  principal  duct ;  9,  accessory  duct;  10,  right  lobe  of  the  liver;  11,  left  lobe  ;  12,  quad- 
rate lobe ;  13,  caudate  lobe ;  14,  gall-bladder ;  15,  hepatic  duct ;  16,  cystic  duct ;  17,  common  bile- 
duct;  18,  portal  vein  ;  19,  ereliac  axis;  20,  coronary  artery;  21,  hepatic  artery;  22,  splenic  artery; 
23,  superior  mesenteric  artery  and  vein ;  24,  spleen ;  25,  kidney ;  26,  ureter. 

Joining  the  left  side  of  the  bile-duct,  together  they  descend  obliquely 
through  the  wall  of  the  duodenum,  behind  and  to  the  inner  side,  and 
open  into  the  gut  by  a  common  orifice  on  the  summit  of  a  papilla, 
usually  about  four  inches  from  the  pylorus. 

Sometimes  the  pancreatic  and  biliary  ducts  open  separately  into  the 
duodenum,  and  occasionally  the  branch  from  the  head  of  the  pancreas 
opens  independently  into  the  latter  some  distance  from  the  main  duct. 

The  pancreas  is  a  large,  much-lobulated,  compound  racemose  gland, 
in  general  construction  resembling  the  salivary  glands.  It  is  less  con- 


1  Ductus  pancreatus  or  "Wirsungianus  ;  duct  of  Wirsung. 


2  D.  Santorini. 


442  THE   ALIMENTAEY   APPARATUS. 

sistent  than  the  latter,  and  its  numerous  angular  lobules  are  less  com- 
pactly associated.  It  is  invested  with  a  thin  connective-tissue  capsule, 
by  which  it  adheres  to  adjacent  parts,  and  from  which  partitions  extend 
between  and  unite  the  lobules  and  their  lesser  divisions,  and  serve  to  sus- 
tain the  blood-vessels  and  ducts  of  the  organ.  The  main  duct  is  provided 
with  a  fibro-connective-tissue  coat  lined  by  a  thin,  smooth  membrane 
furnished  with  a  columnar  epithelium.  The  smaller  ducts  have  the 
same  composition,  with  more  delicate  coats  and  the  cells  of  the  epithe- 
lium becoming  shorter.  The  intralobular  ducts  are  likewise  nearly 
similar,  and  resemble  those  of  the  salivary  glands,  but  with  their  short 
columnar  cells  clearer  and  devoid  of  the  strongly  striated  appearance. 
In  the  smaller  ramifications  the  cells  become  flattened,  and  thus  con- 
tinue into  the  alveoli.  These  are  relatively  large,  branching,  flexuose, 
or  even  convoluted  gland-tubules,  lined  by  stout,  blunt,  pyramidal  cells, 
with  the  narrower  extremity  next  the  lumen,  or  passage,  of  the  alveolus. 

When  the  gland  is  stimulated  to  activity  the  cells  swell,  and  subse- 
quently the  granular  portion  of  their  contents  diminishes  while  the 
clearer  portion  increases.  In  rest  the  former  enlarges  at  the  expense 
of  the  latter,  but  on  the  whole  the  cells  increase  in  size. 

The  capillary  blood-vessels  form  close  nets  around  the  alveoli,  and 
the  lymphatics  commence  in  clefts  of  the  fibro-connective  tissue  around 
and  among  them,  as  in  the  salivary  glands. 

The  pancreas  receives  its  arteries  from  many  branches,  which  are 
derived  from  the  splenic  and  pancreatico-duodenal  branches  of  the 
hepatic  and  superior  mesenteric.  The  veins  join  the  splenic  and 
superior  mesenteric.  The  lymphatics  join  the  lumbar  vessels  and 
glands.  The  nerves  are  derived  from  the  solar  plexus. 

PANCKEATIC   JUICE. 

The  pancreatic  juice,1  the  secretion  of  the  pancreas,  is  a  clear, 
colorless,  and  viscid  liquid,  strongly  alkaline,  and  at  a  low  temperature 
gelatinizes.  It  is  a  solution  principally  of  albumin,  with  a  substance 
resembling  casein  and  called  alkali-albumin,  and  a  number  of  salts, 
among  which  sodium  carbonate  predominates.  It  is  a  powerful  food- 
solvent  ;  dissolves  the  proteids,  saponifies  fats,  and  converts  starch  into 
sugar. 

THE   LIVEK. 

The  liver2  is  the  largest  of  glandular  organs,  and  the  most  bulky  of 
the  abdominal  viscera.  It  occupies  the  greater  part  of  the  right  hypo- 
chondrium,  and  extends  through  the  upper  part  of  the  epigastrium  a 
little  way  into  the  left  hypochondrium.  It  closely  conforms  in  shape 
to  the  space  it  fills,  and  is  attached  by  folds  of  the  peritoneum  to  the 
diaphragm,  but  elsewhere  is  free,  and  has  a  smooth,  shining  surface, 

1  Succus  pancreaticus.  2  Hepar ;  jecur;  glandula  hepatica  or  biliaria. 


THE   ALIMENTARY   APPARATUS.  443 

due  to  the  serous  coat  with  which  it  is  invested.  It  is  half-ovoidal  in 
shape,  with  the  upper  surface  convex  and  closely  applied  to  the  dia- 
phragm, and  the  under  surface  irregularly  slightly  concave,  and  resting 
on  the  stomach,  duodenum,  transverse  colon,  and  right  kidney.  The 
posterior  border  to  the  right  is  the  thickest  part,  and  is  convex;  the 
anterior  border  is  acute ;  and  the  left  border  is  the  thinnest  part  and 
acute. 

The  liver  is  of  firm  consistence,  but  rather  friable,  due  to  the  rela- 
tively small  proportion  of  connective  tissue  which  enters  into  its  com- 
position. It  is  of  a  deep  reddish-brown  color,  but  variable,  and  often 
mottled  with  purple.  In  fatty  degeneration  it  assumes  a  yellow-clay 
color.  Variable  in  size,  it  commonly  measures  about  ten  to  twelve 

FIG.  236. 


INFERIOR  SURFACE  OF  THE  LIVER.  1,  right  lobe ;  2,  left  lobe ;  3,  posterior  margin ;  4,  anterior 
margin  ;  5,  quadrate  lobe;  6,  caudate  lobe;  7,  isthmus,  or  caudate  process,  connecting  the  latter 
with  the  right  lobe ;  8,  9,  longitudinal  fissure ;  10,  transverse  fissure ;  11,  portal  vein  ;  12,  hepatic 
artery;  13,  common  bile-duct  formed  by  the  union  of  the  hepatic  and  cystic  ducts;  14,  gall- 
bladder; 15,  inferior  cava;  16,  hepatic  veins;  17,  round  ligament;  18,  anterior  part  of  the  sus- 
pensory ligament. 

inches  broad,  six  or  seven  inches  fore  and  aft,  and  from  two  and  a  half 
to  three  and  a  half  inches  where  thickest  to  the  right  behind,  and  di- 
minishing to  a  few  lines  approaching  the  left  border.  Its  ordinary 
weight  is  from  three  to  four  pounds  ;  about  a  sixth  to  a  fifth  less  in  the 
female.  Its  specific  gravity  is  1.06,  but  may  be  more  in  lean  and  less 
in  fat  persons. 

The  liver  is  divided  into  two  unequal  portions,  which,  though  con- 
tinuous in  structure,  are  distinguished  as  the  right  and  left  lobes, 
separated  by  notches  in  the  anterior  and  posterior  borders,  by  the 
suspensory  ligament  above,  and  the  longitudinal  fissure  below. 

The  right  lobe,1  much  the  larger,  occupies  the  right  hypochon- 
drium,  reaching  higher  in  the  thorax  and  lower  in  the  abdomen  than 
the  left  lobe,  which  is  not  more  than  a  fifth  or  less  the  size  of  the 

1  Lobus  dexter ;  large,  or  colic  lobe. 


444  THE   ALIMENTARY   APPARATUS. 

former.  Its  upper,  smooth,  and  prominently  convex  surface  is  accu- 
rately adapted  to  the  diaphragm,  and  equally  conforms  to  the  base  of 
the  right  lung,  from  which  it  is  separated  by  the  latter.  Its  under  sur- 
face, irregularly  and  slightly  concave,  has  attached  to  it  in  a  fossa 1  the 
gall-bladder,  which  extends  fore  and  aft,  with  its  fundus  usually  pro- 
jecting a  little  beyond  the  anterior  border  of  the  liver,  where  this  is 
commonly  slightly  emarginate.  The  fossa  for  the  gall-bladder  divides 
the  under  surface  of  the  right  lobe  into  two  unequal  portions,  of  which 
the  smaller,  to  the  right  of  the  fossa,  is  named  the  quadrate  lobe.2 
It  reaches  the  anterior  border  of  the  liver,  is  bounded  on  the  left  by 
the  longitudinal  fissure,  and  behind  by  the  transverse  fissure.  Its 
smooth  under  surface  lies  over  the  pyloric  end  of  the  stomach  and  the 
commencement  of  the  duodenum,  and  is  slightly  impressed  by  them. 
The  remaining  portion  of  the  under  surface  of  the  right  lobe  exhibits 
in  front  a  slight  impression  of  the  transverse  colon,3  another  behind  of 
the  right  kidney,4  and  a  small  one  adjacent  to  the  gall-bladder  of  the 
descending  portion  of  the  duodenum.6  The  posterior  border  of  the 
right  lobe  presents  a  considerable  surface,  which  includes  the  greater 
part  of  the  posterior  notch  of  the  liver,  and  a  wide  patch  tapering  to 
the  right,  destitute  of  the  serous  coat  and  closely  adherent  to  the 
diaphragm  by  connective  tissue.  At  the  lower  left  corner  is  a  small 
surface  impressed  by  the  right  suprarenal  body. 

The  posterior  notch  of  the  liver  is  a  wide,  concave  recess  between 
the  right  and  left  lobes,  mainly  pertaining  to  the  former,  and  embracing 
the  crura  of  the  diaphragm,  together  with  the  inferior  cava,  aorta,  and 
oesophagus.  To  the  right  it  forms  a  deep,  vertical  groove,  occupied  by 
the  inferior  cava,  which  is  closely  attached  to  the  liver,  and  receives 
from  it  the  hepatic  veins  as  they  emerge  from  the  organ.  Some- 
times the  hepatic  substance  extends  partially  or  completely  around  the 
cava,  enclosing  it  in  a  canal.  To  the  left  of  the  caval  groove  the  notch 
is  occupied  by  a  somewhat  detached  portion  of  the  right  lobe,  named 
the  caudate  lobe.6  It  is  of  quadrate  form,  and  extends  beneath 
the  liver,  is  bounded  on  the  left  by  the  longitudinal  fissure,  and  in 
front  below  by  the  transverse  fissure,  between  which  and  the  caval 
groove  it  is  connected  by  an  isthmus 7  with  the  under  surface  of  the 
right  lobe.  It  is  smooth  and  invested  with  the  serous  coat,  and  by 
its  posterior  surface  is  applied  to  the  crura  of  the  diaphragm  in  front 
of  the  aorta.  Behind  its  upper  left  corner  the  oesophagus  joins  the 
stomach. 

1  Fossa  or  impressio  vesicalis. 

2  Lobus  quadratus,  anterior,  anonymus,  innominatus,  or  accessorius. 

3  Faciecula  or  impressio  colica.  4  F.  or  i.  renalis.  6  F.  or  i.  duodenalis. 

6  Lobus  caudatus,  Spigelii,  Eustachii,  posterior,  or  posticus  papillaris ;  tubercu- 
lum   papillare ;    Spigelian,   small,   duodenal,   or   pancreatic   lobe;    posterior   portal 
eminence. 

7  Caudate  lobe ;  eminentia  caudata,  longitudinalis,  or  radiata. 


THE   ALIMENTARY   APPARATUS.  445 

The  left  lobe l  of  the  liver,  variable  in  size,  comparatively  thin  and 
rounded  triangular,  occupies  the  upper  part  of  the  epigastrium,  reach- 
ing a  little  way  into  the  left  hypochondrium.  It  lies  beneath  the  heart, 
separated  by  the  diaphragm,  through  which  its  upper  convex  surface 
is  somewhat  impressed  by  the  former.  Its  lower  surface  is  impressed 
by  the  fore  part  of  the  cardiac  extremity  of  the  stomach,  and  its  pos- 
terior border  to  the  right  forms  part  of  the  posterior  notch  of  the  liver, 
and  is  next  the  termination  of  the  oesophagus. 

The  anterior  notch2  of  the  liver  is  a  deep  angular  incision  in  the 
front  border  between  the  right  and  left  lobes,  continuous  beneath  with 
the  longitudinal  fissure.  It  is  situated  several  inches  to  the  right  of 
the  ensiform  process  of  the  sternum,  and  receives  the  attachment  of 
the  suspensory  ligament. 

The  longitudinal  fissure3  is  a  deep  furrow  beneath  the  liver, 
extending  between  the  anterior  and  posterior  notches,  and  separating 
the  right  and  left  lobes.  The  anterior  longer  portion,4  between  the 
quadrate  and  left  lobes,  is  often  crossed  by  a  bridge5  of  hepatic  sub- 
stance uniting  the  two.  It  is  traversed  by  a  fibrous  cord,  named  the 
round  ligament,6  which  is  the  remnant  of  the  obliterated  umbilical 
vein  of  the  foetus,  ascending  from  the  umbilicus  and  connected  behind 
with  the  portal  vein.  The  posterior  portion 7  of  the  same  fissure,  between 
the  caudate  and  left  lobes,  is  traversed  by  a  narrower  cord,8  remaining 
from  the  obliterated  ductus  venosus  of  the  ftstus,  connected  in  front 
with  the  portal  vein  and  behind  with  the  inferior  cava. 

The  transverse  fissure,9  another  deep  furrow,  starts  from  the 
former  behind  its  middle,  and  proceeds  directly  to  the  right,  between 
the  quadrate  and  caudate  lobes,  and  then  commonly  bends  forward  and 
ends  near  the  centre  of  the  right  lobe.  It  is  the  chief  portal  of  the 
liver,  giving  passage  to  the  portal  vein  and  the  hepatic  artery,  hepatic 
duct,  lymphatics,  and  nerves  of  the  organ. 

The  ligaments  of  the  liver  consist  mainly  of  folds  or  reflections  of 
the  peritoneum  attaching  it  to  the  adjacent  parts.  For  a  description 
of  the  ligaments,  see  page  370. 

The  liver  above,  conforming  to  the  vault  of  the  diaphragm,  rises  on 
the  right  to  a  level  with  the  junction  of  the  fifth  costal  cartilage  with 

1  Lobus  sinister.  *  Incisura  umbilicalis  or  interlobularis. 

3  Fossa  longitudinalis  or  umbilicalis  ;  sulcus  antero-posterior  jecoris,  umbilicalis 
jecoris,  or  sinister ;  great  or  horizontal  fissure. 

4  Umbilical  fissure ;    fossa  longitudinalis  sinistra  anterior ;  fossa  pro  ligamento 
terete  or  vena  umbilicale. 

5  Pons  or  isthmus  hepatis. 

6  Ligamentum  teres,  umbilicale  hepatis,  or  chordae  venae  umbilicalis. 

7  Fissure  of  the  ductus  venosus ;   fossa  longitudinalis  sinistra  posterior ;    fossa 
pro  ligamento  or  ductu  venoso. 

8  Ligamentum  venosum. 

9  Fossa  transversa ;  porta  or  hilus  hepatis ;  sulcus  intermedius. 


446  THE   ALIMENTARY   APPARATUS. 

the  sternum ;  on  the  left  to  a  level  with  the  junction  of  the  sixth  cos- 
tal cartilage  and  sternum.  On  the  right  side  it  is  under  cover  of  the 
ribs  from  the  seventh  to  the  eleventh,  and  in  front  under  the  costal 
cartilages  from  the  sixth  to  the  ninth,  and  the  ensiform  process.  It 
descends  a  short  distance  below  the  ribs,  costal  cartilages,  and  ensiform 
process,  where  it  is  covered  by  the  anterior  abdominal  wall.  The  thin 
edge  of  the  base  of  the  right  lung,  descending  between  the  diaphragm 
and  its  attachment  to  the  ribs,  intervenes  between  the  surface  of  the 
chest  and  the  mass  of  the  liver.  The  front  border  of  the  right  lobe  of 
the  liver  from  the  anterior  notch  slopes  downward  and  outward,  follow- 
ing the  line  of  the  lower  ribs ;  that  of  the  left  lobe  from  the  notch 
curves  upward  and  backward  to  the  left  of  the  termination  of  the 
esophagus. 

The  position  of  the  liver  is  liable  to  change  under  diiferent  con- 
ditions. It  is  affected  by  the  position  of  the  body ;  descending  an  inch 
or  more  below  the  margin  of  the  chest  in  the  upright  position,  and 
retiring  an  inch  or  more  above  in  the  recumbent  position.  In  respira- 
tion it  falls  and  rises  with  the  movements  of  the  chest,  varying  in 
degree  with  the  extent  of  inspiration  and  expiration  and  the  position 
of  the  body,  whether  erect  or  lying  down.  It  is  further  affected  by 
the  condition  of  the  bowels,  whether  full  or  empty,  and  in  like  manner 
by  the  presence  of  abdominal  tumors  and  disease  of  the  lungs  or 
heart.  Tight-lacing  in  females  forces  it  below  the  ribs  permanently, 
sometimes  to  such  a  degree  that  it  nearly  reaches  the  iliac  crest  and 
becomes  impressed  by  the  ribs 

STRUCTURE   OF    THE  LIVER. 

The  liver  is  closely  and  evenly  invested  with  a  transparent  mem- 
branous covering,  which  consists  of  a  serous  and  a  fibrous  coat.  The 
external  serous  coat  is  derived  from  the  peritoneum,  and  is  a  thin, 
transparent  layer  which  everywhere  invests  the  organ,  except  along 
the  posterior  border  of  the  right  lobe,  in  the  posterior  notch,  and  in 
the  fossa  for  the  gall-bladder.  The  fibrous  coat  is  a  thin  fibro-con- 
nective-tissue  layer,  inseparably  connected  with  the  former  and  with 
that  of  the  hepatic  substance.  It  is  thicker  where  the  organ  is  devoid 
of  the  serous  coat,  and  especially  in  the  fissures  of  the  liver,  where  it 
is  continuous  with  the  sheath  of  the  blood-vessels. 

The  liver,  or  hepatic  substance,  besides  its  larger  vessels  and 
ducts,  is  chiefly  composed  of  small,  polyhedral  masses,  or  lobules,1 
compactly  united  together.  The  lobules,  about  the  one-tenth  of  an 
inch  in  diameter,  on  the  surface  of  the  liver  give  to  it  a  uniformly 
maculated  appearance,  and  on  torn  surfaces  a  coarsely  granular  aspect. 
In  some  animals,  notably  the  hog,  the  lobules  are  more  distinctly 

1  Acini. 


THE   ALIMENTARY   APPARATUS. 


447 


marked  from  the  greater  proportion  of  connective  tissue  which  defines 
and  connects  them  together.  In  the  tree-rat  (Capromys*)  of  Cuba  the 
liver  is  subdivided  into  numerous  lobules,  which  lie  close  together  but 
are  quite  detached,  and  are  conjoined  by  the  larger  branches  of  the 
blood-vessels  and  duct.  It  represents  the  common  form  of  the  liver 
of  most  vertebrates  in  an  unravelled  condition. 

The  hepatic  lobules  are  composed  of  a  sponge-like  intertexture  of 
the  secretory  cells  of  the  liver,  the  interspaces  of  which  are  occupied 
by  a  similar  sponge-like  .arrangement  of  capillary  blood-vessels.  In 
their  relation  with  the  larger  blood-vessels,  the  lobules  are  closely 


FIG.  237. 


FIG.  238. 


Fig.  237.  PORTION  OF  THE  LIVER  OF  THE  HOG,  exhibiting  the  lobular  structure  and  the  section 
of  a  hepatic  vein,  somewhat  magnified,  a,  Large  branch  of  the  hepatic  vein ;  the  orifices  belong 
to  other  branches ;  b,  branches  exhibiting  through  their  thin  walls  the  outlines  of  the  lobules; 
the  dots  in  the  centre  of  the  latter  are  orifices  of  the  intralobular  veins  commencing  within  the 
lobules. 

Fig.  238.  PORTION  OF  THE  LIVER  OF  THE  HOG,  exhibiting  the  lobular  structure.  The  large 
vessel  is  a  branch  of  the  portal  vein,  the  outlines  of  the  lobules  being  seen  through  its  transpa- 
rent wall.  The  orifices,  large  and  small,  seen  in  the  portal  vein,  are  fine  branches  sent  between 
the  lobules.  The  two  vessels  lying  to  the  left  of  the  portal  vein  are  branches  of  the  hepatic  artery 
and  duct. 

adherent  to  their  exterior ;  and  in  the  smaller  vessels,  in  which  the 
walls  are  translucent,  the  outlines  of  the  lobules  are  visible  through 
them. 

In  the  relationship  of  the  blood-vessels  of  the  liver,  those  which 
enter  the  transverse  fissure,  the  portal  vein,  and  hepatic  artery,  accom- 
panied by  the  hepatic  duct,  ramify  together  in  a  generally  ascending 
and  diverging  manner,  and  terminate  in  branches  at  the  periphery  of 
the  lobules.  The  hepatic  veins  in  general  pursue  a  course  at  right 
angles  to  the  other  vessels,  and  converge  to  emerge  at  the  posterior 


448 


THE  ALIMENTARY  APPARATUS. 


FIG.  239. 


notch  of  the  liver.  The  general  arrangement  of  the  former  vessels  in 
relation  to  the  latter  is  comparable  to  a  group  of  three  upright  trees 
with  their  boughs  spreading  in  all  directions,  and  intermingled  with 

those  of  another  tree  which  had 
fallen  upon  them. 

The  portal  veins  terminate  in 
the  intervals  of  the  hepatic  lob- 
ules, as  the  interlobular  veins, 
which  directly  communicate  Avith 
the  capillaries  within  the  lobules. 
The  hepatic  veins,  on  the  other 
hand,  commence  in  each  lobule  as 
an  intralobular  vein,  which  re- 
ceives the  capillaries  of  the  latter 
and  proceeds  through  its  axis,  to 
open  at  the  base  of  the  lobule  into 
a  larger  branch  of  the  hepatic 
veins. 

The  capillaries  of  the  hepatic 
lobules  are  but  little  smaller  than 

the  contiguous  columns  of  hepatic 
SECTION  OF  SEVERAL  LOBULES  OF  THE  LIVER  ° 

OF  THE  RABBIT,  the  vessels  injected,  and  the  Cells,    of   which    Only   One    pr    two 

preparation  magnified.    The  capillaries  com-  form  tne  thickness  of  a  Column, 
municate  with   the   interlobular   and   intra-  m. 

lobuiar  veins.  J-ne  hepatic  cells,  which  form 

the  secretory  substance  of  the  liver, 

are  polyhedral,  and  range  from  about  y^r  to  -g-^  of  an  inch  in  diameter. 
They  are  composed  of  granular  protoplasm,  without  a  distinct  cell-wall, 
and  possess  a  clear  central  nucleus,  or  occasionally  two  nuclei. 

The  intertexture  of  hepatic 
cells  is  accompanied  by  a  similar 
arrangement  of  fine  tubes,  the  bile 
canaliculi,1  which  are  regarded 
by  some  observers  as  formed  of  a 
homogeneous  membrane,  and  by 
others  as  being  simple  intercel- 
lular passages.  The  canaliculi  at 
the  periphery  of  the  lobules  open 
into  or  become  continuous  with 
the  bile  or  hepatic  ducts,  com- 
mencing between  the  lobules. 

The  liver  differs  from  all  other 
organs  of  the  body  in  the  fact  that,  besides  receiving  blood  through  an 
artery,  it  also  does  so  in  addition  by  a  much  larger  vessel,  the  portal 
vein,  which  derives  its  blood  from  the  veins  of  the  stomach,  intestines, 


FIG.  240. 


HEPATIC  OR  SECRETING  CELLS  OF  THE  LIVER. 
The  arrangement  is  ideal.  1.  space  occupied 
by  a  capillary  blood-vessel ;  2,  isolated  cells : 
highly  magnified. 


1  Pori  biliarii ;  tubuli  biliferi ;  bile  capillaries. 


THE   ALIMENTARY   APPARATUS. 


449 


pancreas,  and  spleen.  The  hepatic  artery,  besides  being  smaller  than 
the  portal  vein,  which  it  accompanies,  is  also  very  small  in  proportion 
to  the  size  of  the  organ  it  supplies ;  and  is  the  remaining  portion  of 
that  artery  after  giving  off  a  large  branch,  the  gastro-duodenal  artery. 
The  hepatic  artery  and  portal  vein  ascend  together,  enclosed  in  the 
right  border  of  the  small  omentum,  the  former  lying  in  front  of  the 
latter  vessel,  and  both  divide  into  a  right  and  a  left  branch,  which  enter 
the  transverse  fissure  of  the  liver,  and  are  distributed  through  the 


FIG.  241. 


FIG.  242. 


3 


Fig.  241.  DIAGRAM  OF  A  TRANSVERSE  SECTION  OF  A  HEPATIC  LOBULE,  exhibiting  the  relative 
position  of  the  vessels  and  intertexture  of  hepatic  cells.  1,  intralobular  hepatic  vein ;  2,  inter- 
lobular  portal  vein ;  3,  capillaries ;  4,  hepatic  artery ;  5,  hepatic  cells ;  6,  commencement  of  a_ 
bile-duct. 

Fig.  242.  DIAGRAM  OF  THE  COMMENCEMENT  OF  THE  BILE-DUCTS  IN  THE  CANALICULI.  1,  hepatic 
cells ;  2,  biliary  canaliculi ;  3,  biliary  canaliculi  ending  in  a  bile-duct,  4 ;  5,  capillaries  with  blood- 
corpuscles  ;  6,  orifices  of  others. 

corresponding  lobes  of  the  liver.  The  hepatic  duct  pursues  the  same 
course  as  the  hepatic  artery  and  portal  vein,  and  its  right  and  left 
branches  emerge  from  the  liver  in  the  transverse  fissure,  where  they 
unite  at  an  obtuse  angle  in  a  trunk,  which  descends  in  front  of  the 
vein  and  to  the  right  of  the  artery.  The  duct,  smaller  than  the  latter 
vessel,  about  an  inch  and  a  half  long  and  about  one-sixth  of  an  inch 
wide,  is  joined  by  the  cystic  duct  from  the  gall-bladder,  to  form  the 
common  bile-duct.1 

The  portal  vein,  hepatic  artery,  and  hepatic  duct,  in  their  distribu- 
tion throughout  the  liver,  occupy  corresponding  passages  in  its  sub- 
stance, called  the  portal  canals,  and  they  are  together  invested  with 

1  Ductus  communis  choledochus. 
29 


450  THE   ALIMENTARY   APPARATUS. 

a  thin  connective-tissue  sheath,1  which  also  includes  the  accompanying 
lymphatics  and  nerves. 

The  hepatic  artery  mainly  supplies  the  walls  of  the  vessels  and 
ducts  and  the  nerves  of  the  portal  canals,  while  its  blood  is  returned 
through  the  capillaries  of  the  hepatic  lobules  into  the  hepatic  veins. 

The  hepatic  veins,  which  pursue  an  independent  course  from  the 
other  vessels  of  the  liver,  have  no  connective-tissue  sheath,  and  by  their 
thin  wall  adhere  intimately  to  the  hepatic  substance  they  traverse.  Of 
the  three  trunks,  commonly  one  proceeds  from  the  right,  another  from 
the  left,  and  the  third  from  the  quadrate  lobe,  though  the  latter  often 
joins  that  of  the  right  lobe  near  its  termination.  Besides  these  a 
number  of  small  veins  from  the  contiguous  part  of  the  liver  open 
directly  into  the  inferior  cava. 

The  hepatic  ducts 2  commence  in  the  intervals  of  the  hepatic  lobules, 
where  they  receive  the  biliary  canaliculi,  and  freely  anastomose  with 
one  another.  At  their  commencement  they  are  composed  of  a  mem- 
brana  propria  with  a  small  proportion  of  fibro-connective  tissue,  and 
are  lined  by  flattened  epithelial  cells,  while  their  lumen,  or  passage,  is 
continuous  with  the  biliary  canaliculi.  As  the  ducts  become  larger  the 
epithelium  becomes  columnar,  and  they  are  sustained  by  a  greater  pro- 
portion of  connective  tissue.  The  larger  ducts,  including  the  trunks, 
are  lined  with  mucous  membrane  having  a  columnar  epithelium,  and 
are  provided  with  a  vascular  connective-tissue  coat,  and  an  outer  layer 
of  unstriped  muscular  fibres,  mostly  circular  in  their  arrangement. 
The  ducts  are  also  furnished  with  numerous  minute  glands,  which  in 
a  measure  are  proportioned  to  the  size  of  the  ducts.  The  smallest 
glands  consist  of  a  single  follicle  or  of  several,  while  the  larger  ones 
have  the  usual  arrangement  of  racemose  glands. 

The  Ijonphatics  of  the  liver  are  exceedingly  numerous.  Within  the 
lobules  of  the  liver  they  commence  as  cleft-like  spaces  between  the 
hepatic  cells  and  capillary  blood-vessels,  the  spaces  being  limited  by 
flat,  branching  connective-tissue  corpuscles.  The  spaces  communicate 
with  nets  of  lymphatic  vessels  between  and  around  the  lobules,  and 
these  nets  communicate  with  larger  plexuses  of  the  portal  canals,  in 
which  they  surround  the  blood-vessels  and  ducts,  while  the  larger  lym- 
phatic vessels  traverse  their  connective-tissue  sheath  and  emerge  at  the 
transverse  fissure  of  the  liver.  Lymphatics  also  pursue  the  course  of 
the  hepatic  veins,  on  which  they  form  plexuses  communicating  with 
those  between  the  lobules  of  the  liver.  A  subserous  plexus  also  exists 
at  the  surface  of  the  liver ;  the  vessels  from  the  upper  surface  passing 
through  the  ligaments  of  the  liver  to  join  the  thoracic  lymphatics, 
while  those  of  the  under  surface  join  the  deep  lymphatics  emerging  at 
the  transverse  fissure. 

1  Capsule  of  Glisson  ;  capsula  communis  Glissoni. 

2  Interlobular  ducts  ;  pori  biliarii. 


THE   ALIMENTARY   APPARATUS.  451 

The  nerves  of  the  liver  are  derived  partly  from  the  coeliac  plexus 
and  partly  from  the  vagus  nerves,  especially  the  left  one.  They 
enter  the  liver  upon  the  hepatic  artery  and  accompany  it  in  its  dis- 
tribution, but  their  mode  of  termination  has  not  been  satisfactorily 
determined. 

The  gall-bladder1  is  a  pyriform,  membranous  pouch,  a  recepta- 
cle for  gall  or  bile,  occupying  a  fossa  beneath  the  right  lobe  of  the 
liver.  It  is  situated  obliquely  fore  and  aft  with  its  fundus  "directed 
forward,  downward,  and  to  the  right,  and  usually  projecting  a  little 
beyond  the  anterior  border  of  the  liver,  while  the  neck  is  directed  in 
the  opposite  direction  to  the  transverse  fissure.  Its  upper  surface  is 
attached  to  the  liver  by  areolar  tissue,  and  its  under  surface  and  fundus 
are  covered  by  peritoneum  reflected  from  the  adjacent  surface  of  the 
liver.  The  fundus  touches  the  front  abdominal  wall  below  the  margin 
of  the  thorax  about  opposite  the  tip  of  the  tenth  costal  cartilage,  and 
the  bladder  rests  below  on  the  commencement  of  the  transverse  colon, 
and  behind  this  on  the  commencement  of  the  duodenum.  The  neck 
gradually  narrows  and  forms  an  abrupt  sigmoid  curvature,  and  turns 
downward  to  end  in  the  cystic  duct.  The  gall-bladder  is  three  or  four 
inches  long  by  about  an  inch  and  a  half  where  widest,  and  has  a 
capacity  of  an  ounce  to  an  ounce  and  a  half  or  more.  The  cystic 
duct 2  is  about  an  inch  and  a  half  long,  and  descends  to  the  left  back- 
ward and  unites  with  the  hepatic  duct  to  form  the  bile-duct. 

The  common  bile-duct,3  nearly  three  inches  long  and  two  or  three 
lines  wide,  continues  in  the  course  of  the  hepatic  duct,  descending  in 
the  small  omentum  in  front  of  the  portal  vein  and  to  the  right  of  the 
hepatic  artery.  Passing  downward  behind  the  transverse  portion  of 
the  duodenum  and  the  head  of  the  pancreas,  a  groove  or  canal  of 
which  it  occupies,  it  reaches  the  inner  side  of  the  descending  portion 
of  the  duodenum.  Here  it  is  joined  on  the  left  by  the  pancreatic  duct, 
and  the  two,  side  by  side,  pass  obliquely  downward  through  the  wall 
of  the  duodenum  and  open  by  a  common  orifice  on  its  inner  surface  at 
the  summit  of  a  low  papilla,  situated  near  the  lower  bend  of  the  gut, 
about  four  inches  from  the  pylorus.  In  passing  through  the  wall  of 
the  duodenum  the  hepatic  duct  is  somewhat  narrowed  and  its  orifice  is 
constricted,  and  not  unfrequently  opens  separately  from  that  of  the 
pancreatic  duct. 

The  gall-bladder,  besides  its  incomplete  serous  investment  of  the 
peritoneum,  is  provided  with  a  strong  fibrous  coat  lined  by  mucous 
membrane. 

The  fibrous  coat  is  composed  of  interlacing  fibro-connective  tissue 
bundles  with  elastic  fibres,  and  in  its  exterior  part  is  intermingled  with 

1  Vesicula  fellis  ;  cystis  fellea  or  choledochus.  2  Ductus  cysticus. 

3  Common  bile-duct ;  ductus  choledochus  or  communis  choledochus  ;  d.  hepatico- 
cysticus. 


452  THE   ALIMENTARY   APPARATUS. 

unstriped  muscular  fibres  mostly  pursuing  a  longitudinal  direction. 
The  larger  vessels  of  the  gall-bladder  ramify  and  form  plexuses  in  the 
fibrous  coat,  and  it  also  contains  a  gangliated  plexus  of  nerves. 

The  mucous  membrane,  colored  by  the  bile,  presents  a  minutely 
honey-combed  appearance,  due  to  intersecting  folds  of  the  membrane. 
It  has  a  columnar  epithelium,  and  is  furnished  with  glands  like  those 
of  the  hepatic  ducts,  but  smaller,  fewer,  and  more  scattered.  Its  mem- 
brana  propria  contains  a  fine  plexus  of  capillary  blood-vessels,  which 
extend  into  the  folds  on  the  surface  of  the  mucous  membrane  and 
communicate  with  the  vascular  plexuses  of  the  fibrous  coat. 

In  the  sigmoid  flexure  of  the  neck  of  the  gall-bladder  extending 
into  the  cystic  duct,  the  lining  membrane  is  thrown  into  a  series  of 
oblique  crescentic  folds,  partially  continuous,  and  together  presenting 
the  appearance  of  a  spiral  valve.1  In  the  structure  of  its  wall  the 
cystic  duct  resembles  that  of  the  gall-bladder,  but  has  a  greater  propor- 
tion of  muscular  fibres,  mainly  arranged  circularly. 

The  gall-bladder  is  supplied  by  the  cystic  artery  from  the  right 
branch  of  the  hepatic  artery.  The  cystic  vein  joins  the  portal  vein. 
The  lymphatics  follow  the  cystic  duct,  and  join  the  lumbar  lymphatics. 
The  nerves  are  derived  from  the  hepatic  plexus. 

The  common  bile-duct  has  the  same  construction  as  the  hepatic 
duct,  but  its  racemose  glands  are  few  and  small. 

BILE. 

The  bile  or  gall,1  the  secretion  of  the  liver,  is  a  clear,  yellow  liquid 
of  bitter  taste  and  alkaline  reaction.  In  the  gall-bladder  it  becomes 
mingled  with  mucus,  is  brown,  thicker,  and  more  alkaline.  It  is  readily 
decomposed,  and  on  exposure  to  air  becomes  green.  In  herbivorous 
animals  it  is  ordinarily  green,  and  in  carnivorous  animals  yellow. 

Bile  is  a  complex  material,  and  its  chief  essential  constituents  are 
the  glycocholate  and  taurocholate  of  sodium,  with  bilirubin,  dissolved  in 
water.  Besides  these,  it  contains  ordinary  fatty  acids  combined  with 
alkalies,  lecithin,  cholesterin,  and  mineral  matters,  mainly  sodium 
chloride,  etc.  Glycocholic  and  taurocholic  acids  are  compounds  of 
carbon,  hydrogen,  oxygen,  and  nitrogen,  and  the  latter  contains  in 
addition  sulphur.  To  the  pigment  bilirubin  the  yellow  color  of  the 
bile  is  due. 

The  quantity  of  the  bile  secreted  by  the  liver  is  very  large,  and  is 
estimated  to  approximate  the  weight  of  the  organ  itself  in  twenty-four 
hours. 

1  Valvulus  spiralis  Heisteri.  2  Bills  ;  fel ;  cholos. 


OHAPTEE    IX. 

THE   VASCULAR   SYSTEM. 

THE   BLOOD-VESSELS. 

The  blood-vessels  are  branching  membranous  tubes  by  which  the 
blood  is  conveyed  throughout  the  body.  They  consist  of  three  kinds, 
— the  arteries,  which  commence  in  the  heart  and  distribute  the  blood 
to  all  parts  of  the  body ;  the  veins,  by  which  the  blood  is  returned 
to  the  heart ;  and  the  capillaries,  intermediate  to  the  other  vessels, 
and  occupying  the  various  tissues  of  the  body,  which  they  supply  with 
nutritive  material. 

AKTERIES. 

The  arteries1  are  comparatively  thick-walled  vessels,  which  com- 
mence at  the  heart  in  two  great  trunks, — the  aorta,  by  which  the  blood 
is  distributed  to  all  the  organs  of  the  body,  and  the  pulmonary  artery, 
by  which  it  is  in  the  same  manner  distributed  to  the  lungs.  The  chief 
arterial  trunks  occupy  the  cavity  of  the  thorax  and  abdomen,  whence 
large  branches  proceed  to  the  head  and  limbs,  along  the  lines  of  flexure 
and  contiguous  to  the  bones,  in  which  position  they  are  least  liable  to 
extension  and  injury.  They  commonly  pursue  a  tolerably  direct  and 
straight  course,  continuing  in  the  line  of  the  trunk,  and  giving  off  suc- 
cessive branches  at  variable  distances  and  of  various  sizes,  or  they  fork 
into  two  or  more  branches  of  equal  or  unequal  sizes.  The  branches 
may  come  off  at  any  angle,  but  this  is  mostly  acute  at  their  origin.  The 
arteries  continue  of  uniform  size  until  they  branch,  when  they  are  in 
a  measure  reduced,  but  not  proportionately,  for  the  combined  capacity 
of  the  branches  is  commonly  greater  than  that  of  the  trunk  from 
which  they  spring,  except  in  the  case  of  the  origin  of  the  iliac  arteries 
from  the  aorta.  From  this  circumstance  it  follows  that  with  the 
division  of  the  arteries  there  is  a  successive  increase  in  the  capacity  of 
the  whole,  the  result  of  which  is  the  reduction  in  the  rapidity  of  the 
blood-current  as  it  proceeds  in  its  course.  Arteries  sometimes  pursue 
a  more  or  less  tortuous  course,  as  in  the  face  and  uterus,  the  condition 
being  favorable  in  permitting  the  vessels  to  follow  the  changes  of 
movement  in  the  parts  without  undue  stretching.  In  other  positions 
they  may  be  tortuous,  but  the  reason  is  not  so  obvious  as  in  the  case 
of  the  splenic  artery. 

1  Arteriae. 

453 


454 


THE    VASCULAR   SYSTEM. 


In  their  course  arteries  frequently  join  one  another,  inosculate,  or 
anastomose,  freely  communicating,  a  condition  which  becomes  more 
common  as  the  vessels  are  reduced  in  size,  though  frequently  occurring 
with  larger  arteries,  as  those  of  the  brain,  of  the  stomach  and  intestines, 
and  of  the  hand  and  foot.  The  arrangement  is  of  advantage  in  pre- 
venting an  interruption  in  the  flow  of  blood  from  accidental  pressure 
on  one  or  more  vessels. 

The  arteries  possess  considerable  tenacity,  and  are  highly  elastic, 
being  extensile  and  contractile  both  in  length  and  in  width.  During 
life  they  are  also  highly  contractile,  due  to  their  muscularity.  Their 
wall  is  thick  and  firm  enough  to  prevent  complete  collapse  when  empty, 
a  condition  the  reverse  of  that  of  the  veins. 

In  most  positions  the  arteries  are  enclosed  in  a  sheath  of  areolar 
tissue  loosely  attached  to  them,  and  usually  in  company  with  one  or 
two  veins  and  a  nerve.  Some  of  the  arteries,  as  those  of  the  brain 
and  of  the  bones,  are  devoid  of  a  sheath. 

The  inner  surface  of  the  arteries  is  smooth  and  shining,  but  when 
empty,  from  the  contracted  condition  of  the  vessels,  it  is  minutely 
wrinkled  longitudinally. 

Structure  of  the  arteries.  The  wall  of  the  arteries  consists  of 
three  chief  layers,  or  tunics,  of  different  constitution,  intimately  con- 
nected together,  and  named  the  external,  middle,  and  internal  tunics,  or 
the  tunica  adventitia,  media,  and  intima. 

The  external  tunic,  or  adventitia,1  on  which  the  strength  of 
the  arteries  mainly  depends,  is  mostly  thickest  in  the  larger  vessels, 
but  compared  with  the  other  tunics  is  relatively  thicker  in  the  smallest 

ones.     It  is  composed  of  in- 

FIG.  243.  terlacing    bundles   of  fibro- 

connective  tissue  associated 
with  reticular  longitudinal 
fibres  of  elastic  tissue.  The 
latter  are  more  conspicu- 
ous in  the  larger  arteries, 
and  are  most  numerous 
and  thickest  approaching 
the  middle  tunic,  but  are  ab- 
sent in  the  smallest  arteries. 
Generally  the  fibro-connec- 
tive-tissue  bundles  inter- 
sect one  another  diagonally 
around  the  vessels  in  closely- 
united  layers,  the  outer  of 
which  are  of  looser  texture 
the  sheath  of  the  blood- 


TRANSVERSE  SECTION  OF  THE  WALL  OF  AN  ARTERY.  1, 
internal  tunic ;  2,  endangium ;  3,  elastic  layer ;  4,  middle 
tunic  of  muscle-fibres  with  nuclei.  5 ;  6.  elastic  fibres ;  7, 
elastic  limiting  membrane ;  8,  external  tunic  of  fibro- 
connective  tissue  with  branching  corpuscles:  highly 
magnified. 

and   become   more   or  less   blended   with 


T.  externa  or  cellularis  ;  vagina  cellularis. 


THE   VASCULAR   SYSTEM. 


455 


FIG.  244. 


vessels.  In  the  meshes  of  the  connective-tissue  bundles  there  are 
numerous  branching  connective-tissue  corpuscles,  and  also  many  lym- 
phatic spaces. 

The  middle  tunic  or  media1  of  the  arteries  is  the  thickest  layer, 
and  in  the  larger  vessels  forms  the  main  portion  of  the  wall,  but  in 
the  smaller  ones  is  thicker  in  proportion  with  their  calibre.  It  is 
chiefly  composed  of  muscular  fibres,  whence  it  is  also  called  the  mus- 
cular coat,  and  in  it  resides  the  contractile  power  of  the  arteries.  It 
is  of  a  translucent,  pale  reddish-yellow  tint,  and  is  readily  broken. 
When  hardened  in  alcohol  it  assumes  an  opaque,  clay-yellow  color,  and 
is  easily  torn  into  transverse  annular  shreds.  It  consists  of  compara- 
tively short,  fusiform,  unstriped  muscle-fibres  transversely  arranged, 
and  forming  laminae  proportioned  in  number  with  the  thickness  of  the 
tunic,  and  in  the  smallest  arteries  is  reduced  to  a  single  lamina.  The  mus- 
cular lamin®  variably  alternate 
with  fenestrated  elastic  mem- 
branes and  nets  of  elastic  fibres, 
which  connect  the  latter  through 
the  former.  In  the  smaller  ar- 
teries the  proportion  of  the  elas- 
tic tissue  is  much  reduced,  while 
the  muscular  tissue  is  relatively 
greater  than  in  the  larger  arteries, 
and  hence  they  possess  propor- 
tionately greater  contractility. 
In  some  of  the  larger  vessels, 
as  the  carotid  and  mesenteric  ar- 
teries, the  elastic  tissue  is  in 
greater  quantity  than  usual,  and 
forms  a  considerable  portion  of 
the  media.  A  small  proportion 
of  fibro-connective  tissue  accom- 
panies the'  elastic  tissue  in  the 
larger  arteries,  and  increases  in 
the  largest  trunks.  .Mostly,  also, 
in  the  latter,  the  media  is  out- 
wardly defined  by  fenestrated 

elastic  membrane,2  as  in  the  carotid,  mesenteric,  renal,  hepatic,  and 
femoral  arteries.  Further,  the  media  of  the  larger  arteries  contains 
some  small  bundles  of  both  oblique  and  longitudinal  muscle-fibres. 

The  muscle-fibres  of  the  arteries  are  fusiform  cells,  rarely  exceeding 
one-twelfth  to  one-eighth  of  a  millimetre  in  length ;  and  they  are  most 
regular  and  uniform  in  the  small  vessels.  They  are  faintly  striated 
longitudinally,  and  contain  a  central,  elongated  elliptical  nucleus. 


A  SMALL  BRANCHING  ARTERY,  highly  magni- 
fied, a,  6,  elastic  layer  of  the  internal  tunic  or 
intima ;  c,  middle  tunic  or  media  of  transverse 
nucleated  muscle-fibres;  <2,  external  tunic  or 
adventitia  of  fibre-connective  tissue. 


1  Tunica  elastica. 


2  External  elastic  membrane  of  Henle. 


456 


THE   VASCULAR  SYSTEM. 


,The  internal  tunic  or  intima1  of  the  arteries  is  the  thinnest 
of  the  series.  It  is  quite  distinct  from  the  media,  and  in  transverse 
sections,  prepared  for  the  microscope,  appears  as  a  narrow,  bright  band, 


FIG.  245. 


FIG.  246. 


ELASTIC  TISSUE  FROM  THE  MIDDLE  COAT  OF  THE 
POPLITEAL  ARTERY,  highly  magnified.  The  dark 
reticular  lines  indicate  a  narrow  net  of  elastic 
tissue ;  the  other  part  of  the  figure  represents  a 
layer  of  fenestrated  membrane,  which  is  a  va- 
riety of  the  same  tissue. 


UNSTRIATED  MUSCULAR  FIBRES  FROM  THE  MID- 
DLE COAT  OF  THE  ARTERIES,  highly  magnified. 
1,  from  the  popliteal  artery :  a,  without,  and  6, 
treated  with  acetic  acid ;  2,  from  a  branch  of  the 
anterior  tibial  artery  :  a,  pointing  to  the  centre 
in  the  figures,  indicates  the  nucleus. 


with  waving  folds,  invested  with  a  delicate  endothelium.  In  the  large 
arteries  it  is  composed  of  thin  laminae  of  fenestrated  elastic  membrane, 
alternating  with  fibrous  nets  of  a  like  character.  In  the  smallest  arteries 
it  is  reduced  to  a  single  lamina  of  elastic  membrane,  outwardly  con- 
nected with  a  net  of  elastic  fibres.  The  intima  is  defined  inwardly  by 
a  delicate  transparent  membrane,  the  endangium,  which  in  constitu- 
tion resembles  the  serous  membranes,  and  consists  of  an  endothelium 
and  a  membrana  propria. 

The  endothelium  is  a  single  stratum  of  clear,  transparent  pave- 
ment cells,  for  the  most  part  elongated  lozenge-shaped,  or  fusiform, 
with  sinuous  margins,  and  a  central  nucleus,  and  arranged  with  the 
length  parallel  to  that  of  the  vessel.  In  the  larger  vessels  the  cells  ap- 
pear of  greater  proportionate  width,  but  being  elastic  they,  as  well  as 
the  more  elongated  forms  of  the  smaller  vessels,  are  variable  according 
to  the  contraction  or  expansion  of  the  arteries.  The  membrana 
propria  consists  of  longitudinal,  interlacing  fibro-connective  tissue, 
with  branching  corpuscles,  and  is  related  in  thickness  to  the  size  of 
the  vessels,  but  is  absent  in  the  smallest  ones. 

The  aorta  differs  slightly  in  some  respects  from  the  other  large 
arteries.  Its  external  tunic  is  relatively  thin.  The  middle  tunic  con- 


1  Tunica  glabra. 


THE   VASCULAR   SYSTEM. 


457 


FIG.  247. 


tains  between  the  muscular  laminae  elastic  layers,  in  horizontal  or  oblique 
patches,  consisting  of  laminae  of 
fenescrated  elastic  membrane  and 
nets  of  fine  elastic  fibres.  In  the 
arch  of  the  aorta  a  limited  interior 
portion  of  the  middle  tunic  differs 
from  the  rest  in  the  circumstance 
that  the  muscular  fibres  are  ar- 
ranged in  longitudinal  or  oblique 
bundles,  alternating  with  bundles 
of  longitudinal  elastic  fibres  and 
intervening  nets  of  finer  fibres  of 
the  same  kind.  The  fibres  of  the 
muscular  bundles  subsequently  as- 
sume the  usual  transverse  course, 
and  the  elastic  fibres  gradually 
merge  into  the  usual  fenestrated 
membranes.  The  outer  part  of 

the  middle  tunic  also  contains  groups  of  longitudinal  muscular  fibres, 
especially  near  the  external  tunic. 

The  muscle-cells  of  the  aorta  are  short,  flattened  prismatic,  fusi- 
form, and  vary  considerably  in  their  breadth. 

The  internal  tunic  of  the  aorta  is  thicker  than  in  other  arteries,  and 
is  reinforced  by  the  addition  of  an  appreciable  quantity  of  fibro-con- 


ENDOTHELIUM  OF  THE  BLOOD-VESSELS,  a,  from 
a  large  artery ;  6,  from  a  small  artery :  highly 
magnified. 


FIG.  248. 


TRANSVERSE  SECTION  OF  THE  WALLS  OF  THE  AORTA,  treated  with  acetic  acid,  and  magnified. 
1,  internal  tunic :  a,  endothelium  and  membrana  propria ;  6,  c,  layers  of  elastic  tissue.  2,  middle 
tunic :  d,  layers  of  elastic  tissue :  e,  muscular  tissue.  3,  external  tunic,  composed  of  fibrous  con- 
nective tissue  and  fine  nets  of  elastic  tissue. 


nective  tissue.  In  the  ascending  portion  and  arch  of  the  aorta  it  is 
distinctly  laminated,  the  laminas  consisting  of  elastic  fibres  with  inter- 
vening connective  tissue.  The  membrana  propria  of  fibro-connective 
tissue  is  well  produced,  and  in  the  ascending  portion  and  arch  of  the 
aorta  is  thicker  than  elsewhere. 


458  THE   VASCULAR   SYSTEM. 

VEINS. 

The  veins 1  are  comparatively  thin-walled  vessels,  which  return  the 
blood  to  the  heart  by  seven  trunks :  the  superior  cava  and  inferior  cava 
from  the  body  generally,  the  coronary  sinus  fr6m  the  walls  of  the  heart 
itself,  and  four  pulmonary  veins  from  the  lungs.  For  the  most  part 
the  veins  accompany  the  arteries,  whence  they  are  called  the  com- 
panion veins,2  but  there  are  many  others  which  pursue  an  indepen- 
dent course.  The  latter  chiefly  run  immediately  beneath  the  skin,  and 
are  distinguished  as  the  superficial  or  subcutaneous  veins,  while 
those  accompanying  the  arteries  are  distinguished  as  deep  veins. 

The  pulmonary  veins  accompany  the  corresponding  arteries,  and 
accord  with  them  both  in  number  and  capacity.  The  other  veins,  in- 
cluding those  accompanying  the  arteries,  are  of  greater  capacity  than 
the  latter.  The  largest  arteries  and  their  largest  branches  have  a  single 
companion  vein,  but  the  medium-sized  and  smaller  branches  commonly 
have  two  companion  veins,  though  there  are  exceptions  to  the  rule. 

The  veins  of  the  brain  and  those  of  the  spinal  canal  and  the  hepatic 
veins  pursue  a  different  course  from  the  arteries ;  and  the  veins  of  the 
head  and  face  in  most  instances  but  partially  accompany  the  corre- 
sponding arteries. 

The  inosculation  or  anastomosis  of  veins  is  much  more  frequent 
than  in  arteries,  even  among  those  of  large  size,  as  is  notably  the  case 
with  the  superficial  veins,  which  indeed  form  a  conspicuous  subcutane- 
ous net-work  over  the  whole  body.  The  smaller  ones  exhibit  the  same 
disposition  to  frequent  inosculation,  and  in  some  positions  form  close 
nets  of  comparatively  large  vessels  with  small  intervals,  named  venous 
plexuses. 

Structure  of  the  veins.  The  veins  have  a  thinner  wall  than 
the  arteries,  and  therefore  commonly  appear  collapsed  when  empty, 
while  the  arteries  in  the  same  condition  remain  more  open.  They, 
however,  possess  considerable  strength,  and  proportioned  to  the  thick- 
ness of  their  wall  are  more  tenacious  than  the  arteries.  In  general 
the  superficial  veins  have  a  thicker  wall  than  the  deep  ones,  and  those 
of  the  lower  limbs  than  of  the  upper  limbs. 

Many  veins  are  provided  with  valves,  which  usually  consist  of  a 
pair  of  crescentic  membranous  flaps  placed  opposite  each  other,  with 
their  convex  border  attached  to  the  sides  of  the  vein,  and  their  free 
concave  border  directed  in  the  course  of  the  flow  of  the  blood.  Oppo- 
site each  flap  the  vein  is  dilated,  forming  a  pouch,  with  the  mouth 
directed  forward,  so  that  in  a  reflux  of  the  blood  the  two  pouches  are 
distended  and  th'e  flaps  brought  into  contact  so  as  to  close  the  pas- 
sage. In  some  of  the  smaller  veins  valves  occur  of  a  single  flap,  and 
in  some  of  the  larger  veins  a  single  flap  is  placed  over  the  mouth  of 
some  of  the  smaller  branches. 

1  Vena ;  phlebs.  2  Venae  comites  or  satellites. 


THE   VASCULAR   SYSTEM. 


459 


J 


DIAGRAMS  EXHIBITING  THE  ARRANGEMENT  OF 
THE  VALVES  OF  VEINS.  A,  vein  laid  open,  show- 
ing the  valves  in  pairs ;  B,  longitudinal  section 
of  a  vein,  indicating  the  mode  in  which  the 
valves,  by  apposition  of  their  free  edges,  close 
its  passage.  The  dilated  condition  of  the  wall 
behind  the  valves  is  also  seen.  C,  vein  dis- 
tended, showing  how  it  is  expanded  opposite 
the  position  of  the  valves. 


Many  of  the  veins  have  no  valves,  nor  do  they  usually  occur  in 
those  under  a  line  in  diameter.  They  are  most  numerous  in  the 
veins  of  the  limbs,  especially  the 
lower  ones.  They  are  absent  in 
the  pulmonary  veins,  in  the  su- 
perior and  inferior  cava,  in  the 
veins  of  the  cavity  of  the  cranium 
and  spinal  canal,  in  the  hepatic, 
renal,  spermatic,  ovarian,  and  uter- 
ine veins,  in  those  of  the  bones, 
and  generally  in  those  of  the  portal 
system.  Except  in  the  jugular 
veins,  few  or  none  occur  in  those 
of  the  head  and  neck,  the  azygos, 
hemiazygos,  and  intercostal  veins. 

The  veins  in  general,  like  the 
arteries,  have  their  wall  composed 
of  three  tunics,  but  less  distinctly 
separable  than  in  the  latter. 

The  external  tunic1  of  the 
veins  is  often  thicker  than  the  me- 
dia, from  which  it  is  usually  not  distinctly  defined.  It  ordinarily  con- 
sists of  a  compact  interlacement  of  fibro-connective-tissue  bundles,  asso- 
ciated with  nets  of  longitudinal  elastic  fibres.  In  some  of  the  larger 
veins  it  contains  muscular  fibres,  as  in  the  inferior  cava,  in  which  they 
pursue  a  longitudinal  course,  and  form  a  net-work  at  the  inner  part 
of  the  tunic.  These  fibres  likewise  extend  into  the  renal,  spermatic, 
external  iliac,  and  azygos  veins.  They  also  occur  in  the  trunks  of  the 
hepatic  veins,  and  that  of  the  portal  vein,  whence  they  extend  into  the 
splenic  and  mesenteric  veins.  They  likewise  exist  in  the  axillary  vein. 

The  middle  tunic 2  of  the  veins  is  much  thinner  than  that  of  the 
arteries,  and  is  less  distinctly  separable  from  the  external.  It  pre- 
sents considerable  variability  in  the  different  veins.  Commonly  it  is 
mainly  composed  of  unstriped  muscular  tissue,  for  the  most  part  ar- 
ranged in  transverse  bands,  and  not  in  continuous  laminae,  as  in  the 
arteries.  The  bands  are  separated  by  a  notable  proportion  of  fibro- 
connective  tissue  with  nets  of  elastic  fibres.  In  many  veins  the  outer- 
most bands  pursue  a  longitudinal  course,  as  in  the  superior  and  inferior 
cavae,  the  azygos,  hepatic,  renal,  spermatic,  and  axillary  veins.  In 
others  the  outer  and,  inner  bands  are  longitudinal,  and  the  intermediate 
ones  transverse,  as  in  the  external  iliac,  femoral,  and  popliteal  veins, 
branches  of  the  mesenteric,  and  the  umbilical  veins.  In  the  veins  of 
the  gravid  uterus  the  muscular  tissue  is  well  developed,  with  the  fibres 
all  pursuing  a  longitudinal  course. 


Tunica  adventitia. 


*  Tunica  media. 


460  THE    VASCULAR   SYSTEM. 

In  many  of  the  larger  veins  the  middle  coat  is  less  produced  than 
usual,  especially  in  muscular  tissue,  but  this  is  compensated  in  increased 
muscularity  of  the  external  coat. 

In  the  internal  and  external  jugular  and  subclavian  veins,  and  the 
terminal  portion  of  the  innominate  veins,  the  muscular  tissue  is  de- 
ficient ;  and  it  is  entirely  absent  in  the  veins  of  the  bones  and  muscles, 
those  of  the  retina,  of  the  brain  and  spinal  cord,  the  sinuses  of  the 
dura,  and  of  the  erectile  tissue  of  the  penis.  In  these  veins  mostly  the 
wall  consists  of  a  variably-produced  stratum  of  fibro-connective  tissue 
lined  by  endothelium. 

The  internal  tunic 1  of  the  veins  is  a  thin,  elastic  membrane,  com- 
posed of  compact  lamelliform  net-works  of  longitudinal  elastic  fibres. 
In  some  veins,  as  those  of  the  gravid  uterus,  these  are  associated  with 
bundles  of  longitudinal  muscular  fibres.  The  endangium,  like  that 
of  the  arteries,  consists  of  the  endothelium,  and  commonly  a  subjacent 
stratum  of  fibro-connective  tissue.  The  latter,  usually  thinner  than  in 
the  arteries,  is  better  marked  in  some  of  the  medium-sized  veins  than 
in  the  larger  ones.  In  some  of  the  veins,  as  those  of  the  bones,  it  is 
altogether  absent.  The  endothelium  consists  of  short,  spindle-shaped 
plates  with  sinuous  margins. 

The  valves  of  the  veins  consist  of  an  extension  of  the  internal 
coat,  with  muscular  fibres  from  the  middle  coat  invested  with  the 
endangium. 

THE   CAPILLAKIES. 

The  capillaries,  as  expressed  by  the  name,  are  fine,  hair-like  blood- 
vessels, which  occupy  the  various  tissues  composing  the  organs  of  the 
body.  The  ultimate  branches  of  the  arteries  terminate  in  them,  and 
the  corresponding  branches  of  the  veins  commence  in  them.  They  in 
general  form  a  closed  reticular  system  of  tubes,  from  which  the  tissues 
imbibe  their  materials  of  growth,  repair  and  action,  and  to  which  they 
yield  their  waste  materials.  The  greater  the  vital  activity  of  a  tissue 
or  organ,  the  greater  is  its  supply  of  capillary  blood-vessels.  Commonly 
very  numerous,  they  vary  greatly  in  number  in  different  tissues,  and 
in  some,  as  the  cartilages,  epithelium,  and  epidermis,  do  not  exist  at 
all.  They  are  always  minute  vessels,  and  only  to  be  seen  and  studied 
by  the  microscope.  When  viewed  in  this  manner  in  any  transparent 
tissue  of  a  living  animal,  as  in  the  web  of  a  frog's  foot  or  the  mesen- 
tery of  a  salamander,  they  appear  as  a  net-work  of  transparent  tubes, 
through  which  the  blood  rapidly  flows,  its  clear  liquor  in  contact  with 
the  sides  of  the  vessels  and  the  corpuscles  aggregated  in  a  central 
column  and  moving  with  greater  rapidity  than  the  surrounding  blood- 
liquor.  The  capillaries  are  of  pretty  uniform  size  in  the  same  tissue,  and 
in  this  respect  differ  from  the  arteries,  which  undergo  constant  reduction 
as  they  divide.  In  different  tissues  they  vary  considerably  in  size,  but, 

1  Tunica  intima. 


THE   VASCULAR   SYSTEM. 


461 


as  the  capillaries  are  both  elastic  and  contractile,  the  same  vessels  may 
differ  under  different  conditions.  The  size  of  the  capillaries  when 
filled  with  blood  is  estimated  to  be  from  40100  to  20*00  of  an  inch  in 
diameter,  but  there  are  many  both  smaller  and  larger. 

The  capillary  nets  vary  greatly  in  the  size  of  their  meshes,  and 
hence  in  the  number  of  the  vessels  in  a  given  space.  The  net-work  is 
very  close  in  the  lungs  and  in  the  choroid  coat  of  the  eye.  It  is  also 
comparatively  close  in  the  muscular  and  adipose  tissues,  in  the  dermis, 
in  most  mucous  membranes,  in  glands,  and  in  the  gray  substance  of 
the  brain  and  spinal  cord.  On  the  other  hand,  it  has  wide  meshes,  and 
consequently  few  vessels,  in  tendons,  aponeuroses,  ligaments,  fasciae,  and 
similar  structures. 

The  arrangement  of  the  capillary  nets  is  accommodated  to  that  of 
the  tissues  to  which  they  pertain.  Thus,  in  the  muscles,  nerves,  ten- 
dons, and  aponeuroses  they  generally  conform  to  the  direction  of  the 


FIG.  250. 


FIG.  251. 


d.-- 


DIAGRAM  OF  THE  STRUCTURE  OF  A  CAPILLARY 
BLOOD-VESSEL  :  highly  magnified. 

bundles  and  fibres  of  those  tis- 
sues, running  in  greater  part  par- 
allel with  them  and  producing  long, 
narrow  meshes.  In  the  lungs 
they  form  little  bag-like  nets  with 
rounded  polygonal  meshes ;  in  adi- 
pose tissue  they  form  a  sponge 
with  polygonal  meshes  enclosing 

the  fat- vesicles ;   and  in  the  papillae  of  the  skin  or  the  villi  of  the 
intestine  they  form  loops  extending  from  the  subjacent  nets. 


A  SMALL  ARTERY  gradually  passing  into  the 
structure  of  the  capillary  vessels.  1,  artery  with 
transverse  muscular  fibres:  a,  hyaline  mem- 
brane; b,  nuclei  of  transverse  muscle-fibres; 
c,  nuclei  of  the  internal  tunic  or  intima;  2,  3, 
4,  capillaries  apparently  composed  of  struc- 
tureless membrane  (a)  with  scattered  nuclei 
(d) :  highly  magnified. 


462  THE   VASCULAR   SYSTEM. 

In  youth  the  tissues  contain  relatively  more  capillaries,  or  are  more 
vascular,  than  in  advanced  age. 

The  wall  of  the  capillaries  is  a  delicate,  elastic,  transparent,  and 
apparently  homogeneous  membrane,  which  by  treatment  with  silver 
nitrate  is  shown  to  have  a  cellular  constitution  like  the  endothelium  of 
the  arteries  and  veins,  with  which  it  is  continuous.  The  cells  form  a 
single  layer,  joined  at  their  margin  by  a  cement  which  is  stained  black 
by  the  silver  nitrate,  while  the  cells  remain  uncolored.  Thus  darkly  out- 
lined, the  cells  are  spindle-shaped  plates,  with  even  or  slightly  sinuous 
margins,  though  a  few  at  the  intersection  of  the  capillaries  are  radiate, 
with  two  or  three  points.  The  cells  are  arranged  longitudinally  in  the 
course  of  the  vessels,  and  there  are  commonly  two  or  three  to  the  cir- 
cumference of  each.  The  cells  contain  a  central  oval  nucleus,  which  is 
rendered  visible  by  staining  with  infusion  of  logwood  or  carmine. 

In  inflammation,  from  distention  of  the  capillaries,  the  cement  of 
the  cells  yields  at  certain  points,  leaving  small  openings,  the  so-called 
stomata,  through  which  blood-corpuscles  escape.  It  is  observed  that 
in  the  migration  of  the  colorless  blood-corpuscles  they  leave  the  capil- 
laries in  the  lines  of  the  cementing  substance. 

Branching  connective-tissue  corpuscles  of  the  adjacent  areolar  tissue 
are  intimately  connected  with  the  wall  of  the  capillary  vessels,  and  this 
is  most  conspicuously  seen  in  the  lymphatic  glands,  in  the  solitary 
and  agminated  glands,  and  in  the  adjacent  mucous  membrane  of  the 
intestine. 

Structure  of  the  smallest  arteries  and  veins.  The  smallest 
arteries  connected  with  the  capillaries  generally  exhibit  the  following 
characters : 

The  external  tunic  first  appears  as  a  layer  of  branching  connective- 
tissue  corpuscles,  or  of  unbranching  corpuscles  forming  a  continuous 
layer.  The  middle  tunic  appears  as  a  single  stratum  of  transverse 
muscle-fibres,  at  first  arranged  in  groups  on  alternate  sides  of  the 
vessel,  and  subsequently  forming  a  continuous  circular  layer.  The 
internal  tunic  appears  as  a  delicate,  hyaline  elastic  membrane.  The 
endothelium  consists  of  elongated  spindle-shaped  cells  continuous  with 
those  composing  the  capillaries. 

The  commencing  veins  communicating  with  the  capillaries  in  gen- 
eral proceed  to  accompany  the  corresponding  arteries,  than  which,  as 
usual  in  their  future  course,  they  are  wider  and  have  a  thinner  wall 
and  are  more  capacious.  Their  external  tunic  at  first  is  like  that  of 
the  terminal  arteries,  but  as  they  become  larger  it  becomes  thicker  by 
the  addition  of  bundles  of  fibro-connective  tissue.  A  thin  internal  tunic 
occurs  composed  of  a  net-work  of  fine  longitudinal  elastic  fibres.  The 
endothelium  is  composed  of  shorter  and  wider  spindle-shaped  cells  than 
in  either  the  capillaries  or  the  smallest  arteries.  At  first  there  is  no 
muscular  tunic,  but  as  the  vein  enlarges  this  makes  its  appearance  as 
a  single  stratum  of  transverse  muscle-fibres. 


THE   BLOOD.  463 

The  walls  of  arteries  and  veins  are  themselves  provided  with  blood- 
vessels, both  arteries  and  veins,  which  are  readily  visible  ramifying  in 
the  external  tunic  of  the  large  trunks,  but  require  the  aid  of  the  micro- 
scope to  see  them  in  the  smaller  ones.  The  vessel  arteries l  are  derived 
from  neighboring  arterial  branches,  and  the  vessel  veins  likewise 
end  in  neighboring  venous  branches.  A  net-work  of  capillaries  in  the 
external  tunic  occupies  the  usual  position  between  the  vessel  arteries 
and  veins.  The  middle  and  internal  tunics  of  the  arteries  and  veins  have 
generally  been  regarded  as  destitute  of  vessels,  but  some  recent  author- 
ities assert  the  existence  of  capillaries  in  the  middle  tunic.  In  some  of 
the  larger  animals  of  man's  class,  as  the  ox  and  the  whale,  the  capil- 
laries are  quite  evident  in  the  middle  tunic  of  the  aorta. 

Lymphatics  are  numerous  in  the  external  tunic  of  the  blood-vessels, 
appearing  as  lymphatic  spaces  in  the  smaller  trunks  and  as  plexuses 
of  vessels  in  the  larger  ones.  In  the  latter,  also,  lymphatics  occur  in 
the  middle  tunic. 

Arteries  and  veins  are  also  supplied  with  nerves,2  to  a  greater  extent 
in  the  former.  They  form  plexuses  in  the  external  tunic,  and  are  thence 
distributed  to  the  muscular  tissue,  chiefly  of  the  middle  tunic. 

THE   BLOOD. 

The  blood3  is  the  liquid  contents  of  the  heart,  the  arteries,  veins, 
and  capillary  vessels.  It  is  highly  complex  in  composition,  and  directly 
furnishes  the  nutritive  material  to  all  the  organs  and  tissues  of  the 
body.  It  is  thickish.  clammy,  and  somewhat  heavier  than  water,  hav- 
ing a  specific  gravity  of  about  1.055.  It  has  a  slightly  alkaline  reac- 
tion, a  saline  taste,  and  a  faint,  peculiar  odor.  To  the  naked  eye,  when 
fresh,  it  appears  homogeneous,  and  opaque  red  to  black,  according  to 
the  various  conditions  under  which  it  may  be  seen.  From  the  left  cavi- 
ties of  the  heart,  the  aorta  and  its  numerous  branches,  and  from  the 
pulmonary  veins  it  appears  deep  bright  red ;  from  the  right  side  of  the 
heart,  the  systemic  veins  and  their  branches,  and  from  the  pulmonary 
arteries  it  appears  of  the  color  of  claret  wine  or  of  the  ordinary  black- 
heart  cherry. 

The  amount  of  blood  in  the  body  is  ordinarily  about  equal  to  from 
one-twelfth  to  one-tenth  of  the  entire  weight  of  the  latter. 

When  the  blood  is  examined  by  means  of  the  microscope,  spread 
in  a  thin  layer  upon  a  plate  of  glass,  or  while  it  is  circulating  in  the 
capillary  vessels,  it  is  observed  to  consist  of  a  clear,  colorless  liquid, 
the  plasma,  or  blood-liquor,*  containing  a  great  number  of  minute, 
round  particles,  the  blood-corpuscles,5  which,  for  the  most  part,  are 
colored  and  give  to  the  blood  its  characteristic  red  color. 

1  Vasa  vasorum.  2  Vaso-motor  nerves.  3  Sanguis  ;  haema ;  cruor  ;  gore. 

4  Liquor  sanguinis  ;  haematoplasma  ;  plastic  or  coagulable  lymph. 

5  Blood-globules,  vesicles,  or  disks ;  corpuscula  or  globuli  sanguinis. 


464 


THE    BLOOD. 


FIG.  252. 


Ordinarily,  when  blood  is  drawn  from  the  vessels,  it  quickly  solidi- 
fies or  coagulates  into  a  mass,  the  blood-clot,1  which  subsequently  by 
contraction  squeezes  out  a  pale  yellow  liquid,  the  serum,  in  which  the 
clot,  reduced  in  size  and  retaining  the  original  color  of  the  blood, 
remains  floating.  The  coagulation  is  due  to  the  solidification  of  one 
of  the  constituents  of  the  blood,  the  fibrin,  which  in  the  change 
entangles  the  blood-corpuscles. 

The  blood-corpuscles  are  of  the  character  of  cells,  and  they  are  so 
minute  and  numerous  that  a  drop  of  blood,  about  a  line  in  diameter, 
may  contain  about  50,000,000.  They  are  of  two  kinds,  the  red  and 
the  white  or  colorless  corpuscles,  of  which  the  former  very  greatly  pre- 
dominate, while  the  latter  are  more  variable,  and  are  commonly  about 
one  to  five  hundred  or  more  of  the  red  corpuscles. 

The  red  corpuscles,  which  are  so  characteristic  of  the  blood,  are 

circular,  biconcave  disks,  with  a  thick, 
rounded  border,  and  resemble  in  shape 
the  common  biscuit,  with  us  known  as 
a  cracker.  They  appear  of  remarka- 
ble uniformity,  measuring  about  -g-^tf 
of  an  inch  in  breadth  with  about 
one-fourth  that  thickness ;  and  the  far 
greater  proportion  range  between  -g-^^ 
to  33*00  of  an  inch.  They  also  appear 
to  be  perfectly  homogeneous,  without 
evident  distinction  of  cell-wall  and 
contents,  and  have  no  nucleus.  Iso- 
lated, they  seem  of  a  pale  yellow  hue, 
and  it  is  only  in  mass  that  they  ex- 
hibit a  distinctly  red  color.  They  are 
quite  elastic,  and  readily  change  their 
shape  under  pressure  and  resume  their 
original  form  when  it  is  removed.  In  water  they  quickly  assume  a 
globular  form,  lose  their  color,  and  become  very  indistinct.  Through 
evaporation  and  inspissation  of  the  surrounding  plasma  the  corpuscles 
become  contracted,  tuberculate,  and  more  or  less  stellate ;  and  solutions 
of  salt,  sugar,  etc.,  produce  similar  effects.  When  a  fresh  portion  of 
blood  is  examined  beneath  the  microscope,  the  red  corpuscles  exhibit 
a  remarkable  tendency  to  arrange  themselves  together  in  piles,  like 
rolls  of  coin,  and  these  more  or  less  intersect  one  another. 

The  red  corpuscles  exhibit  no  difference  in  persons  of  different  age, 
sex,  or  race.  They  are  characteristic  of  the  blood  of  all  vertebrates, 
with  the  sole  exception  of  the. lowest  recognized  representative,  the 
headless  fish  or  lancelet,  in  which  they  are  absent.  In  all  mammals 
they  have  the  same  shape  and  composition  as  in  man,  with  the  remark  - 


RED  BLOOD-CORPUSCLES,  highly  magni- 
fied. 1,  corpuscles  seen  on  their  broad 
surface ;  2,  seen  on  their  edge ;  3,  rolls  of 
corpuscles,  indicating  the  manner  in 
which  they  are  frequently  observed  to 
arrange  themselves.  The  remaining 
figures  more  highly  magnified:  4,  cor- 
puscle seen  on  its  broad  surface ;  5,  seen 
on  its  edge ;  6,  a  series  of  corpuscles ;  7,  a 
corpuscle  in  section,  indicating  its  bi- 
concave discoidal  form. 


Crassamentum  ;  cruor ;  thrombus. 


THE    BLOOD. 


465 


able  exception  of  one  small  family,  that  of  the  camel,  in  which  they 
are  oval  disks  and  are  provided  with  a  nucleus.  In  all  other  classes 
of  vertebrates,  except  the  lowest  fishes,  exemplified  by  the  lampreys, 
they  are,  as  in  the  camel,  oval,  nucleated  disks. 

The  red  blood-corpuscles  are  not  proportioned  in  size  with  the  ani- 
mal. No  difference  is  observed  in  their  size  in  the  different  races  of 
man,  but  they  are  notably  smaller  in  monkeys.  Among  mammals  they 
are  largest  in  the  elephant,  but  in  all  our  large  domestic  animals  they 
are  smaller  than  in  man,  while  those  of  the  mouse  are  intermediate  in 
size.  They  are  remarkably  large  in  the  amphibia,  exemplified  by  the 
frog ;  but  especially  in  the  proteus  and  siren,  and  above  all  in  the  am- 
phiuma,  of  our  Southern  States,  in  which  the  corpuscles  are  visible  with 
the  naked  eye,  and  measure  ten  times  the  diameter  of  those  of  man. 

The  white  or  colorless  corpuscles l  are  comparatively  few,  and 
from  their  having  no  color  are  not  readily  recognized  among  the  mul- 
titude of  red  corpuscles  with  which  they  are  mingled.  They  are 
larger  than  the  latter,  about  27100  of  an  inch  in  diameter,  and  when  at 
rest  are  spherical.  They  are  composed  of  a  mass  of  finely  granular 
and  reticular  protoplasm,  mingled  with  a  few  coarser  granules,  and 
contain  from  one  to  three  nuclei,  usually  not  distinct,  but  brought 
more  clearly  into  view  by  certain  reagents,  as  acetic  acid.  They  often 
also  contain  one  or  more  conspicuous  vacuoles  or  clear  globules,  which 

FIG.  254. 


WHITE  OR  COLORLESS  CORPUSCLES  OF  THE  THE  SAME  CORPUSCLES,  more  highly  magni- 

BLOOD,  highly  magnified.    1,  corpuscle  at  rest;  fied,  and  observed  at  the  temperature  of  the 

2-10,  in  movement,  exhibiting  projections  of  body,    exhibiting   the   changes   of  shape    in 

the  protoplasm  called  pseudopods ;  6,  one  which  movement, 
has  assumed  a  stellate  shape. 

are  inconstant,  and  may  appear  and  disappear.  They  swell  up  in  water 
and  become  clearer,  and  in  this  condition,  under  high  power  of  the 
microscope,  granules  in  their  interior  may  be  observed  exhibiting  more 
or  less  lively  vibratory  motion. 

When  fresh  blood,  maintained  at  or  near  the  temperature  of  the 
body,  is  examined,  the  white  corpuscles  are  noticed  to  change  both 
their  shape  and  position.  The  movement  from  place  to  place  is  slow, 
and  the  change  of  shape  exceedingly  varied.  From  its  resemblance 

1  White  globules  ;  pale  or  lymph  corpuscles  ;  leucocytes. 
30 


466  THE    BLOOD. 

to  that  of  the  microscopic  animal,  amoeba,  which  is  as  simple  in 
structure  as  the  white  corpuscle,  it  is  called  amoeboid  movement. 
Through  this  the  corpuscle  projects  portions  of  its  protoplasm  in  any 
direction,  and  apparently  at  will  again  retracts  them.  In  its  move- 
ments it  is  also  observed  to  take  into  its  interior,  minute  particles  with 
which  it  may  meet,  as  fine  granules  of  carbon,  carmine,  milk-globules, 
starch,  etc.  Through  the  power  of  amoeboid  movement,  the  white  cor- 
puscles may  be  seen  wandering  from  the  blood-vessels,  passing  out 
between  the  tissue  elements  of  their  wall,  into  the  interstices  of 
neighboring  tissues.  Observed  in  this  way,  the  corpuscles  have  been 
distinguished  as  migratory  cells. 

The  white  corpuscles  of  the  blood,  which  are  identical  with  lymph- 
corpuscles,  are  derived  from  the  lymph,  which  is  incessantly  poured 
into  the  blood  by  the  trunks  of  the  lymphatics.  They  are  commonly 
regarded  as  the  source  of  the  red  corpuscles,  a  view  which  appears  to 
be  confirmed  by  many  observations,  but  is  considered  as  not  yet  satis- 
factorily demonstrated.  In  the  production  of  the  red  from  the  white 
corpuscle,  the  nucleus  of  the  latter  is  gradually  transformed  into  the 
former,  while  the  surrounding  protoplasm  disappears.  The  production 
of  the  earliest  red  corpuscles  in  the  embryo  occurs  in  the  same  manner. 

Besides  the  ordinary  solid  constituents  of  the  normal  blood,  as 
above  described,  others  have  been  indicated  of  an  obscure  character. 
They  appear  as  round,  colorless  disks.1  smaller  than  the  red  corpuscles, 
homogeneous  or  finely  granular,  and  without  a  distinct  nucleus. 

Blood  also  at  times,  especially  immediately  after  the  digestion  of 
much  fat  food,  contains  fine  oil-molecules,  which  have  been  absorbed  by 
the  intestine,  and  conveyed  into  the  blood  by  the  thoracic  duct. 

The  blood-liquor  or  plasma  consists  of  a  permanent  liquid,  the 
serurn,  and  of  certain  materials  distinguished  as  fibrin-factors,  which 
spontaneously  unite  when  blood  is  withdrawn  from  the  body,  and  by 
their  union  form  the  solid  substance  fibrin.  The  fibrin-factors  are 
fibrinogen  and  fibrino-plastin,  the  latter  of  which  is  probably  contained 
in  the  colorless  corpuscles  as  well  as  in  the  plasma.  The  union  of  the 
fibrin-factors  is  supposed  to  be  due  to  the  action  of  another  material, 
the  fibrin-ferment,  which  does  not  exist  in  the  circulating  blood,  but  is 
supposed  to  be  formed  after  the  blood  has  been  withdrawn  by  the 
breaking  down  of  some  of  the  colorless  corpuscles. 

Fibrin  freed  from  the  blood-corpuscles  is  a  yellowish-white  stringy 
substance,  which  under  the  microscope  presents  an  indistinct  fibrillar 
structure.  It  is  a  proteid  compound,  readily  dissolved  in  the  gastric 
and  pancreatic  juices. 

Serum  is  the  amber-colored  liquid  of  the  blood-plasma  after  the 
separation  of  the  fibrin.  It  has  an  alkaline  reaction  and  coagulates  by 
heat.  It  is  an  albuminous  solution  with  salts,  fatty  matters,  sugar,  etc. 

1  Hsematoblasts  ;  blood-plates  or  plaques. 


THE    HEART. 


467 


FIG.  255. 


11 


11 


The  blood  also  contains  gases,  which  are  readily  evolved  by  the  air- 
pump.  They  consist  of  carbonic  acid,  oxygen,  and  nitrogen.  The 
red  corpuscles  contain  a  coloring-matter  named  haemoglobin,  a  pro- 
teid  of  very  complex  character  and  having  a  strong  affinity  for  oxygen. 
It  is  readily  soluble  in  water,  and  under  certain  circumstances  may  be 
crystallized. 

THE    HEAKT. 

The  heart l  is  a  hollow,  muscular  organ,  in  whose  walls  resides  the 
power  which  produces  the  circulation  of  the  blood.  It  occupies  a 
nearly  central  position  in  the 
cavity  of  the  thorax,  placed 
behind  the  sternum,  between 
the  second  and  sixth  inter- 
costal spaces,  with  about  two- 
thirds  of  its  mass  to  the  left 
side  and  the  other  third  to 
the  right  of  the  median  line. 
Enclosed  in  a  pouch,  called 
the  pericardium,  it  rests  on 
the  diaphragm,  and  is  em- 
braced at  the  sides  by  the 
lungs  enclosed  in  the  pleurae. 
It  is  blunt  conical  in  shape, 
and  is  obliquely  inclined,  with 
its  base  directed  upward,  back- 
ward, and  to  the  right,  and  its 
apex  downward,  forward,  and 
to  the  left.  By  its  base  it  is 
attached,  through  means  of  its 
great  blood-vessels,  to  the  front 

of  the  spine,  in  the  space  be- 

„        ,1  j        •    j.1  FRONT  VIEW  OF  THE  HEART  AND  GREAT  BLOOD- 

tween  the  fourth  and  ninth  VESSELS.  1,  right  ventricle;  2,  left  ventricle;  3,  right 
thoracic  vertebrae.  Elsewhere  auricle:  4,  left  auricle;  5,  pulmonary  artery,  divid- 
ing into  the  right  and  left  branches ;  6,  arch  of  the 
aorta ;  7,  remains  of  the  ductus  arteriosus ;  8,  de- 
scending aorta ;  9,  innominate  artery ;  10,  common 
carotid  arteries ;  11,  subclavian  arteries  ;  12,  superior 
cava;  13,  right  innominate  vein,  formed  by  the 
union  of  the  right  internal  jugular  and  subcla- 
vian veins;  14,  left  innominate  or  transverse  vein, 
formed  like  the  preceding ;  15,  inferior  cava,  with 
the  hepatic  veins;  16,  left  coronary  artery;  17, 
branch  to  the  left  auriculo-ventricular  groove;  18, 
right  coronary  artery ;  19,  valvular  sinuses  of  the 
pulmonary  artery. 


it  is  entirely  free,  projecting 
forward  within  the  pericar- 
dium, with  its  apex  opposite 
the  interval  of  the  fourth  and 
fifth  costal  cartilages,  a  short 
distance  below  and  to  the  inner 
side  of  the  left  nipple,  where 
its  impulse  is  felt  during  life. 


The   posterior  surface   is  flat- 
tened, and  rests  on  the  central  tendon  of  the  diaphragm,  with  the  peri- 
cardium intervening,  and  tightly  attached  to  the  latter.     The  anterior 


1  Cor ;  cardia. 


468  THE    HEART. 

surface  is  convex,  and  looks  obliquely  forward  and  upward  towards  the 
sternum  and  costal  cartilages,  from  which  it  is  separated  by  the  peri- 
cardium and  pleurae.  The  lungs  also  project  over  it  in  front,  especially 
during  inspiration,  in  which  condition  there  remains  a  narrow,  uncov- 
ered interval,  widening  below  to  a  triangular  space  of  nearly  two 
square  inches,  to  the  right  of  the  apex.  The  right  border1  is  the 
longer  and  narrower,  is  rounded  angular,  and  directed  obliquely  down- 
ward. The  left  border'2  is  convex,  and  directed  obliquely  upward. 

The  exact  position  of  the  heart  is  affected  by  several  circumstances : 
thus,  when  a  person  is  lying  on  the  left  side  or  on  the  breast  it  comes 
more  into  contact  with  the  front  of  the  chest;  and  in  breathing  it 
alternately  recedes  and  approaches  the  latter. 

The  heart  is  divided  into  four  compartments  or  chambers,  named 
the  auricles  and  ventricles,  of  which  the  former  communicate  with 
the  latter.  The  division  is  indicated  on  the  exterior  by  grooves,  except 
where  these  are  interrupted  by  vessels.  The  auriculo-ventricular 
groove  encircles  the  heart  transversely,  and  separates  the  auricles, 
which  form  the  basal  portion  of  the  heart,  from  the  ventricles,  which 
form  the  apical  portion.  The  interventricular  groove  descends  from 
the  former  in  front  and  behind  to  the  right  of  the  apex,  and  separates 
the  right  from  the  left  ventricle.  The  fore  part  of  this  groove  is  nearer 
the  left  border  of  the  heart,  and  the  right  ventricle  forms  the  greater 
portion  of  the  front  surface  of  >the  latter;  the  back  part  of  the  groove 
is  nearer  the  right  border  of  the  heart,  and  the  left  ventricle  forms  the 
greater  portion  of  the  posterior  surface  of  the  heart.  The  interauric- 
ular  groove,  in  the  same  manner,  separates  the  right  and  left  auricles 
at  the  basal  portion  of  the  heart.  The  grooves  accommodate  the  chief 
nutritive  vessels,  the  coronary  arteries  and  veins,  the  lymphatics,  and 
the  nerves  of  the  heart,  usually  associated  with  more  or  less  fat,  which 
spreads  to  a  variable  extent  upon  the  adjacent  surfaces. 

The  auricles  are  cavities  with  thin,  fleshy  walls  adequate  to  their 
purpose,  that  of  sending  the  blood  into  the  adjoining  ventricles.  Each 
consists  of  a  more  capacious  portion,  the  atrium,3  and  of  a  prolonga- 
tion, the  auricular  appendix.  The  atria  are  separated  by  a  partition, 
the  auricular  septum,*  communicate  with  the  ventricles,  each  by  a 
large  aperture,  the  auriculo-ventricular  orifice,5  and  while  that  of 
the  right  auricle  receives  the  two  great  systemic  veins,  the  superior 
and  inferior  cava,  that  of  the  left  auricle  receives  the  four  pulmonary 
veins. 

The  right  auricle6  occupies  the  right  side  of  the  base  of  the  heart 
projecting  in  front,  in  contact  inwardly  with  its  fellow  behind,  and  with 
the  aorta  in  advance  of  this.  It  is  the  thinnest-walled  cavity  of  the 

1  Margo  acutus.  2  Margo  obtusus. 

3  Sinus  venosus.  *  Septum  auricularum. 

5  Ostium  atrio-ventriculare.  6  Auricula  dextra ;  atrium  dextrum. 


THE    HEART.  469 

heart,  being  scarcely  a  line  in  thickness.  The  atrium  is  quadrate,  and 
for  the  most  part  internally,  except  on  the  anterior  wall,  is  smooth. 
Communicating  with  it  are  the  superior  and  inferior  cava,  the  coronary 
sinus,  and  the  right  auriculo-ventricular  orifice. 

The  superior  cava  returns  the  blood  from  the  upper  part  of  the 
body  and  descends  to  open  into  the  upper  fore  part  of  the  atrium,  with 
its  orifice  directed  downward  and  forward,  so  that  the  entering  current 
of  blood  is  directed  to  the  auriculo-ventricular  orifice.  The  inferior 
cava,  larger  than  the  former,  returns  the  blood  from  the  lower  part  of 
the  body,  and  ascends  to  open  in  the  lowest  part  of  the  atrium,  with 
its  orifice  directed  upward  and  inward.  Between  the  openings  of  the 
two  veins  the  right  wall  of  the  atrium  is  produced  into  a  slightly  ob- 
tuse angle,1  more  evident  in  some  lower  animals  than  in  man.  In  front 
of  the  opening  of  the  inferior  cava  is  the  right  auriculo-ventricular 
orifice,  communicating  with  the  corresponding  ventricle,  oval  in  shape, 
and  about  an  inch  in  diameter.  Between  the  two  openings  at  the  inner 
side  is  the  smaller  orifice  of  the  coronary  sinus,  which  returns  the 
blood  from  the  coronary  veins  of  the  heart.  It  is  protected  by  a  semi- 
lunar  valve.2  which  is  formed  by  a  fold  of  the  lining  membrane  or 
endocardium. 

The  posterior  wall  of  the  atrium  to  the  left  forms  the  auricular 
septum.  Near  its  lower  part  to  the  left  of  the  orifice  of  the  inferior 
cava  is  a  depression,  the  oval  fossa,3  which  indicates  the  position 
during  foetal  life  of  the  oval  foramen,4  communicating  with  both 
auricles.  The  margin  of  the  fossa,  prominent  above  and  at  the  sides,  is 
the  oval  annulus.5  The  bottom  of  the  fossa  is  thin  and  translucent, 
and  is  formed  by  what  was  originally  a  valve6  to  the  oval  foramen. 
Not  unfrequently  a  little  cleft  is  found  beneath  the  annulus  above, 
remaining  as  part  of  the  latter  opening. 

In  front  of  the  orifice  of  the  inferior  cava,  and  partly  covering  it, 
is  the  eustachian  valve.7  This  is  a  thin,  crescentic  fold  of  the  endo- 
cardium, which  is  attached  along  the  anterior  margin  of  the  cava  and 
is  prolonged  at  the  left  extremity  to  the  fore  part  of  the  oval  annulus. 
It  is  variable  in  condition,  commonly  more  or  less  perforated  or  cribri- 
form, wide  or  narrow,  and  sometimes  nearly  or  quite  obsolete.  Before 
birth  it  is  well  produced,  and  then  serves  to  direct  the  entering  current 
of  blood  of  the  inferior  cava  through  the  oval  foramen  into  the  left 
auricle. 

A  variable  number  of  apertures8  of  little  veins9  of  the  heart  open 
on  different  portions  of  the  inner  surface  of  the  right  auricle. 

The  auricular  appendix,  prolonged  from  the   atrium   forward, 

1  Tuberculum  Loweri.  2  Valvula  Thebesii. 

3  Fossa  or  fovea  ovalis  ;  vestigium  foraminis  ovalis. 

4  F.  ovale  ;  f.  Botali.  5  Annulus  ovalis.  6  Valvula  foraminis  ovalis. 
T  Valvula  Eustachii ;  v.  foraminis  ovalis  anterior. 

8  Foramina  Thebesii.  9  Vense  minimse  cordis. 


470  THE    HEART. 

curves  to  the  left  around  the  right  side  of  the  commencement  of  the 
aorta.  It  is  pyramidal,  with  irregular  dentated  borders.  Internally, 
its  sides  are  provided  with  prominent  fleshy  fascicles,  mostly  vertical 
and  reticulated ;  while  others  extend  on  the  anterior  wall  of  the  atrium, 
parallel  with  one  another,  like  the  teeth  of  a  comb,  whence  the  name 
of  pectinate  muscles l  applied  to  them. 

The  left  auricle 2  occupies  the  left  of  the  base  of  the  heart  in  great 
part  behind,  is  somewhat  smaller  than  the  right  one,  and  has  slightly 
thicker  walls,  being  about  a  line  and  a  half  in  thickness.  The  atrium 
is  rounded  cuboidal  in  shape,  and  is  in  contact  with  its  fellow  behind 
on  the  right,  and  with  the  aorta  and  pulmonary  artery  in  advance.  In- 
ternally it  is  smooth  throughout,  and  on  the  auricular  septum  presents 
a  lunated  depression  defined  by  a  slight  ridge,  indicating  the  former 
position  of  the  oval  foramen.  At  its  back  part  it  receives  on  each  side 
a  pair  of  pulmonary  veins,  the  left  pair  sometimes  uniting  in  a  single 
vessel.  At  its  lower  fore  part  is  the  left  auriculo-ventricular  ori- 
fice, like  that  of  the  right  side,  but  slightly  smaller.  The  auricular 
appendix  extends  from  the  left  of  the  atrium  and  curves  forward 
to  the  right  around  the  commencement  of  the  pulmonary  artery.  It 
springs  more  abruptly  from  the  atrium  than  that  of  the  left  side,  is 
longer,  narrower,  and  more  dentated,  and  the  pectinate  muscles  are 
confined  to  its  interior  alone. 

The  ventricles3  form  the  more  massive  portion  of  the  heart 
towards  the  apex,  and  are  cavities  with  walls  of  a  thickness  propor- 
tioned to  the  distance  they  are  required  to  send  the  blood.  They  are 
separated  by  a  thick  partition,  the  ventricular  septum.4  They  com- 
municate with  the  auricles  by  the  auriculo-ventricular  orifices,  through 
which  they  receive  the  blood,  and  also  with  the  chief  arterial  trunks : 
the  right  ventricle  with  the  pulmonary  artery,  by  which  the  blood 
is  conveyed  to  the  lungs,  and  the  left  ventricle  with  the  aorta,  by 
which  the  blood  is  distributed  throughout  the  body.  The  auriculo- 
ventricular  orifices  are  provided  with  valves,  which  prevent  the  reflux 
of  the  blood  into  the  auricles,  and  the  arterial  orifices  are  provided 
with  others  of  different  construction,  which  prevent  the  reflux  of  the 
blood  from  the  vessels  into  the  heart. 

The  right  ventricle5  occupies  the  chief  portion  of  the  front  surface 
of  the  heart,  the  right  border,  and  a  smaller  portion  of  the  back  sur- 
face. It  is  pyramidal  in  shape,  convex  in  front,  flattened  behind,  and 
concave  to  the  inner  side,  where  it  embraces  the  left  ventricle.  With 
its  base  joined  to  the  corresponding  auricle,  its  apex  ceases  a  little 
short  of  that  of  the  left  ventricle,  which  forms  the  point  of  the  heart. 
The  upper  anterior  angle  is  prolonged  obliquely  upward  and  to  the 

1  Musculi  pectinati.  2  Auricula  sinistra. 

3  Ventriculi.  4  Septum  ventriculorum. 

5  Ventriculus  dexter,  anterior,  pulmonalis,  or  primus. 


THE   HEART. 


471 


FIG.  256. 


left  in  the  arterial  cone,1  from  which  springs  the  pulmonary  artery, 
continued  in  the  same  direction.  The  ventricular  septum  forms  the 
inner  wall,  and  bulges  into  the  cavity  with  a  convex  surface,  to  which 
the  outer  wall  presents  a 
concave  surface,  so  that  a 
cross-section  of  the  cavity 
is  crescentic  in  shape.  The 
outer  wall  is  about  the 
fourth  of  an  inch  in  thick- 
ness, but  is  not  uniform, 
being  thickest  at  the  base 
and  becoming  thinner  to- 
wards the  apex.  The  sur- 
face of  the  cavity,  for  the 
most  part,  is  broken  up 
by  a  multitude  of  carne- 
ous  columns,2  which  are 
of  various  sizes  and  inter- 
sect one  another  in  all 
directions;  many  partially 
projecting  in  their  length 
from  the  wall,  others  at- 
tached at  the  extremities 
and  free  at  the  middle, 
while  a  few  project  from 
their  base  into  the  ventri- 
cle as  the  papillary  mus- 
cles.3 These  are  directed 
upward  and  end  in  a  num- 
ber of  thread-like  tendi- 
nous cords,4  which  di- 
verge to  be  inserted  into 
the  tricuspid  valve.  Two 
of  the  muscles  conspicuous 
for  their  size  spring  from 

the  fore  and  back  part  of  the  ventricle,  and  are  called  from  their  position 
the  anterior  and  posterior  papillary  muscles.  The  others,  two  or 
three,  are  small,  and  proceed  from  the  septum.  The  inner  surface  of 
the  arterial  cone  is  devoid  of  the  fleshy  columns  and  is  smooth,  so  as 
to  facilitate  the  flow  of  blood  in  its  course  to  the  pulmonary  artery. 

At  the  base  of  the  ventricle  is  the  right  auriculo- ventricular 
orifice,  communicating  with  the  corresponding  auricle  and  bordered 


VIEW  OF  THE  HEART,  WITH  THE  ANTERIOR  PORTIONS  OF 

THE  VENTRICLES  REMOVED.  1,  interior  of  the  right  ventri- 
cle, exhibiting  its  carneous  columns;  2,  left  ventricle;  3, 
right  auricle;  4,  left  auricle;  5,  aorta;  6,  7,  8,  divisions 
of  the  tricuspid  valve ;  9,  papillary  muscles  attached  by 
tendinous  cords  to  the  tricuspid  valve ;  10,  mitral  valve ; 
11,  pulmonary  artery  laid  open ;  12,  one  of  the  semilunar 
valves ;  the  other  two  are  seen  in  section  on  each  side  of 
the  former ;  13,  sinus  or  dilatation  of  the  artery  behind 
one  of  the  semilunar  valves. 


1  Conus  arteriosus ;  infundibulum. 

2  Columnae  carneae ;  trabeculse  ;  fasciculi  teretes  ;  lacerti  or  lacertuli  cordis. 

3  Musculi  papillares.  4  Chordae  tendineae. 


472  THE   HEART. 

by  a  fibrous  ring,  which  gives  attachment  to  the  tricuspid  valve1 
guarding  the  aperture.  The  valve  is  a  thin,  fibrous  membrane  invested 
by  the  endocardium,  and  incompletely  divided  into  three  unequal  tri- 
angular flaps,  from  which  it  is  named.  As  commonly  seen,  the  flaps 
descend  from  around  the  orifice  into  the  ventricle,  and  are  attached 
by  their  free  border  and  ventricular  surface  to  the  tendinous  cords  of 
the  papillary  muscles.  The  flaps  are  thickest  centrally,  and  thinnest 
along  the  free  border,  where  the  edge  is  festooned  between  the  attach- 
ment of  the  tendinous  cords.  The  flaps  hold  the  relative  position  of 
posterior,  and  of  right  and  left  anterior.  The  tendinous  cords  attached 
to  the  adjacent  margins  of  the  anterior  flaps  proceed  from  the  anterior 
papillary  muscle ;  those  from  the  adjacent  margins  of  the  right  and 
posterior  flaps  proceed  from  the  posterior  papillary  muscle ;  and  those 
from  the  adjacent  margins  of  the  left  and  posterior  flaps  proceed  from 
the  smaller  papillary  muscles  or  directly  from  the  surface  of  the  ven- 
tricular septum.  In  the  attachment  of  the  cords  their  component  fibro- 
connective-tissue  bundles  diverge  and  interlace  with  one  another  in  the 
fibrous  layer  of  the  valve. 

The  left  ventricle2  occupies  the  left  border  of  the  heart,  appear- 
ing to  a  small  extent  in  the  front  view,  and  forming  a  greater  portion 
of  its  posterior  surface.  It  is  conical  in  shape,  and  is  longer  and  nar- 
rower than  the  right  ventricle,  beyond  which  it  extends  to  form  the 
rounded  apex  or  point  of  the  heart.  It  is  embraced  inwardly  by  the 
right  ventricle,  and  its  base  joins  the  left  auricle,  with  which  it  com- 
municates by  the  corresponding  auriculo-ventricular  orifice.  The  cross- 
section  of  its  cavity  is  fore  and  aft  oval,  so  that  the  ventricular  septum 
on  the  side  of  the  latter  is  concave. 

The  left  ventricle  is  constructed  on  nearly  the  same  plan  as  the 
right  one,  but  all  its  parts  display  a  greater  strength.  The  wall  is 
more  than  twice  the  thickness,  being  about  seven  lines ;  but  is  thickest 
where  it  is  broadest,  about  a  fourth  of  its  length  from  the  base,  towards 
which  it  becomes  thinner,  and  still  more  towards  the  apex,  where  it  is 
thinnest.  In  cross-section  it  forms  a  continuous  ring,  with  the  ventricu- 
lar septum  of  nearly  uniform  thickness ;  while  that  of  the  right  ven- 
tricle appears  as  a  thinner  half  ring  continuous  with  the  former  by 
its  extremities.  The  interior  surface  of  the  cavity  is  furnished  with 
carneous  columns  like  those  of  the  right  ventricle,  but  in  greater 
number,  generally  smaller  and  more  reticulated,  especially  near  the 
bottom  of  the  ventricle  and  on  its  posterior  wall.  On  the  upper  part 
of  the  anterior  wall  and  the  septum  they  disappear,  and  the  surface 
approaching  the  aortic  orifice  is  smooth.  From  among  the  fleshy 
columns  project  two  groups,  more  or  less  conjoined,  and  forming  the 
papillary  muscles,  of  more  robust  proportion  than  those  of  the  right 

1  Valvula  tricuspidalis  ;  valvulae  tricuspides. 

2  Ventriculus  sinister,  aorticus,  posterior,  or  secundus  ;  cor  aorticum  or  arteriosum. 


THE    HEAET.  473 

ventricle.     The  anterior  papillary  muscle  springs  from  the  left  wall- 
of  the  ventricle,  and  the  posterior  muscle  from  the  back  wall  on  the 
right.     They  terminate  in  tendinous  cords,  which  diverge  to  be 
inserted  into  the  mitral  valve. 

The  left  auriculo-ventricular  orifice  is  bordered  by  a  fibrous 
ring,  which  affords  attachment  to  the  bicuspid1  or  mitral  valve.2 
This  is  constructed  like  the  tricuspid  valve,  but  is  thicker  and  stronger, 
and  is  divided  into  two  unequal,  broad,  half-oval  flaps,  with  a  small 
offset  at  their  angles  of  conjunction.  The  flaps,  as  usually  seen, 
descend  into  the  ventricle,  and  receive  at  their  free  border  and  under 
surface  the  attachment  of  the  tendinous  cords  of  the  papillary  muscles 
and  adjacent  portion  of  the  wall  of  the  ventricle.  The  flaps  are  situ- 
ated obliquely  below  the  orifice,  the  larger  in  front  and  to  the  right, 
the  other  behind  and  to  the  left.  Their  tendinous  cords,  fewer  arid 
stronger  than  those  of  the  tricuspid  valve,  have  a  similar  arrangement, 
those  attached  to  the  adjacent  borders  of  the  flaps  to  the  right  pro- 
ceeding from  the  posterior  papillary  muscle  and  adjacent  part  of  the 
posterior  wall  of  the  ventricle ;  the  others  in  like  manner  on  the  left 
proceeding  from  the  anterior  papillary  muscle  and  adjacent  posterior 
wall  of  the  ventricle. 

The  aortic  orifice  lies  close  to  the  auriculo-ventricular  orifice,  in 
front  and  to  the  right,  and  is  separated  from  it  only  by  the  basis  of 
attachment  of  the  anterior  flap  of  the  mitral  valve. 

The  pulmonary  artery  and  the  aorta,  at  their  origin,  are  connected 
with  the  ventricles  by  fibrous  rings,  contiguous  to  those  which  encircle 
the  auriculo-ventricular  orifices.  The  two  vessels  are  alike  at  their 
commencement,  are  both  provided  with  the  same  kind  of  valves,  and 
differ  from  each  other  only  in  the  stronger  construction  of  the  aorta 
and  its  accessories.  In  each  artery  the  valve  consists  of  three  semi- 
circular, crescentic  flaps,  from  which  it  receives  the  name  of  the  semi- 
lunar  valve.3  The  flaps  are  arranged  in  a  circle,  immediately  above 
the  entrance  of  the  artery,  attached  to  this  by  their  convex  border, 
whence  they  project  upward  into  the  vessel,  and  terminate  in  a  free, 
loose,  concave  edge.  Opposite  each  flap  the  artery  is  dilated,  and  thus 
forms  with  it  a  pouch,4  the  mouth  of  which  is  directed  upward  into  the 
vessel.  The  three  pouches  outwardly  are  indicated  by  a  corresponding 
circle  of  convex  eminences  at  the  commencement  of  the  artery,  more 
conspicuous  in  the  aorta  from  their  being  larger.  "When  the  pouches 
are  distended  by  the  reflux  of  blood  in  the  arteries,  the  flaps  of  the 
valve  assume  a  trilateral  form,  and  the  angular,  free,  projecting  borders 
are  brought  into  contact  and  completely  close  the  orifice  of  the  vessels. 

1  Valvula  bicuspidalis  ;  valvulse  bicuspidatse. 

2  V.  mitralis  ;  valvulse  mitrales  or  episcopates. 

3  V.  semilunaris;  valvulae  semilunares  or  sigmoidese. 

4  Sinus  of  Valsalva ;  Valsalval  sinus. 


474  THE    HEART. 

The  semilunar  valves  are  composed  of  laminae  of  fibro-connective 
tissue  invested  by  the  endocardium  and  continuous  with  the  adjacent 
endangium.  The  segments  are  strongest  along  their  attached  border, 
and  the  free  marginal  portion  of  each  is  formed  by  two  thinner  cres- 
cents,1 which  join  at  the  middle  of  the  edge  in  a  little  fibrous  nodule.2 

The  heart  is  of  a  deep  reddish-brown  color,  due  to  its  fleshy  struc- 
ture. It  is  invested  with  a  delicate,  transparent  membrane,  the  epi- 
cardium,  beneath  which,  along  the  grooves  of  the  heart,  accompanying 
the  vessels,  are  yellowish-white  streaks,  due  to  adipose  tissue,  which 
often  accumulates  and  spreads  more  or  less  over  the  adjacent  surfaces. 

The  heart  is  variable  in  size  and  weight,  and  in  a  measure  is 
related  with  the  same  conditions  of  the  person.  In  the  adult  it  is 
commonly  about  five  inches  long,  three  and  a  half  inches  where  broad- 
est, and  two  and  a  half  inches  where  thickest.  Its  ordinary  weight  is 
about  nine  or  ten  ounces  in  the  male,  and  an  ounce  or  two  less  in  the 
female.  It  increases  with  the  advance  of  life,  and  proportionately  to 
a  greater  degree  before  thirty;  but  after  fifty  years  it  commonly 
undergoes  a  slight  decrease. 

The  capacity  of  the  cavities  is  about  three  ounces.  That  of  the 
auricles  is  commonly  regarded  as  smaller  than  that  of  the  ventricles, 
and  that  of  the  left  cavities  as  less  than  that  of  the  right  ones.  It  is 
probable  that  during  life  there  is  but  little  difference  in  the  capacity  of 
the  four  cavities.  Usually  after  death  the  left  ventricle  is  found  most 
contracted,  and  nearly  empty,  while  the  right  ventricle  is  of  greater 
capacity  and  filled  with  blood. 

Structure  of  the  heart.  The  chief  substance  of  the  heart  is 
the  muscular  tissue,  which  is  more  compact  than  that  of  the  muscles 
of  locomotion,  the  fascicles  being  more  closely  associated,  and  the 
interstices  occupied  with  a  comparatively  small  proportion  of  areolar 
connective  tissue.  With  the  muscular  tissue  is  the  usual  accompani- 
ment of  blood  and  lymphatic  vessels  and  nerves.  There  is  also  a 
variable  amount  of  adipose  tissue,  mainly  collected  along  the  base  of 
the  ventricles  and  the  grooves  of  the  heart.  The  auriculo-ventricular 
orifices  and  those  of  the  aorta  and  pulmonary  artery  are  bordered  by 
fibro-connective  tissue  rings,  which  afford  a  base  of  attachment  to  the 
valves,  and  serve  a  similar  purpose  to  many  of  the  fleshy  fibres  of  the 
walls  of  the  heart.  Fibro-cartilaginous  tissue  in  the  angle  between  the 
aortic  orifice  in  front  and  the  auriculo-ventricular  orifices  behind  gives 
additional  firmness  to  the  structure.  In  this  position  in  the  larger 
ruminating  animals,  as  the  ox  and  deer,  a  bone  partly  takes  the  place 
of  the  fibro-cartilage. 

The  muscular  portion  of  the  walls  of  the  auricles  is  composed  of  a 
superficial  layer  common  to  both,  and  a  deeper  layer  for  each.  The 
fascicles  of  the  superficial  layer  generally  run  transversely  across  the 

1  Lunulae.  2  Corpusculus  or  nodulus  Arantii  or  Morgagni. 


THE    HEART.  475 

atria,  and  are  more  numerous  in  front,  while  some  pass  into  the  auric- 
ular septum.  Of  the  deeper  layer  for  each  auricle,  some  of  the  fasci- 
cles pass  over  the  latter  from  the  fibrous  ring  of  the  auriculo-ventricular 
orifice,  and  others  encircle  the  auricular  appendix,  within  which  there 
are  also  some  longitudinal  fibres.  Annular  fibres  also  surround  the 
entrance  of  the  different  veins,  and  extend  some  distance  upon  them, 
especially  the  superior  cava  and  the  pulmonary  veins.  Others  likewise 
surround  the  oval  fossa  of  the  auricular  septum. 

The  muscular  portion  of  the  walls  of  the  ventricles  is  composed  of 
a  number  of  layers  intimately  associated,  and  only  more  or  less  sepa- 
rable after  the  heart  is  hardened  by  boiling,  or  by  other  means.  The 
fascicles  composing  the  layers  are  also  closely  connected,  and  have  a 
most  intricate  arrangement,  in  general  proceeding  from  the  fibrous 
rings  encircling  the  orifices  at  the  base  of  the  ventricles,  and  thence 
descending  obliquely  in  a  whorl  to  the  apex  of  the  heart.  Here  they 
become  closely  twisted  upon  one  another,  producing  the  vortex,  in 
which  they  enter  the  ventricles,  and  ascend  on  their  interior  to  the 
rings  from  which  they  started,  and  contribute  to  form  the  carneous 
columns  and  papillary  muscles.  In  front  of  the  heart  the  fascicles  of 
the  superficial  fleshy  layer  descend  from  right  to  left  across  the  ventri- 
cles ;  many  from  the  right  ventricle  turning  in  at  the  interventricular 
groove,  where  they  intersect  others  coming  out  from  the  ventricular 
septum,  while  those  towards  the  base  and  apex  proceed  uninterruptedly 
over  the  groove.  Behind  the  heart  the  fascicles  descend  from  left  to 
right,  and  pass  uninterruptedly  across  the  interventricular  groove.  At 
the  apex  of  the  heart  the  fascicles  ascend  the  vortex  and  enter  the  left 
ventricle,  whence  they  proceed  upward  in  its  inner  surface  to  the  base, 
and  mainly  form  the  papillary  muscles.  The  fascicles  of  the  deeper, 
fleshy  layers  of  the  ventricles  pursue  the  same  general  course  as  those 
of  the  superficial  layer,  but  in  the  outer  portion  of  the  former  they 
are  successively  less  inclined  in  their  descent.  From  the  vortex  many 
of  the  fascicles  ascend  in  the  ventricular  septum  to  the  fibro-cartilage 
and  fibrous  rings  at  the  base  of  the  ventricles,  while  others  proceed  for- 
ward through  the  septum,  emerge  at  the  fore  part  of  the  interventricu- 
lar groove,  and  become  continuous  with  those  in  front  of  the  left 
ventricle ;  and  a  third  set  pass  upward  and  backward,  and  diverge  in 
the  posterior  walls  of  the  ventricles,  those  to  the  right  ascending  to  the 
orifice  at  the  base  of  the  right  ventricle,  while  those  to  the  left  encircle 
the  cavity  of  the  left  ventricle  nearly  horizontally.  Additional  fasci- 
cles cross  the  ventricular  septum  fore  and  aft,  and  encircle  both  ventri- 
cles. The  fascicles  of  the  deeper  layers  of  the  ventricles  are  usually 
regarded  as  not  reaching  the  fibrous  rings  at  the  base  of  the  latter,  but 
as  commencing  and  terminating  below  them.  The  centre  of  the  vortex 
at  the  apex  of  the  heart  forms  a  narrow  passage  communicating  with 
the  cavity  of  the  left  ventricle,  but  closed  by  the  epicardium  and  the 
endocardium. 


476  THE    HEART. 

The  muscular  tissue  of  the  heart  consists  of  fibres  transversely 
striped  like  those  of  the  voluntary  muscles,  but  otherwise  quite  dif- 
ferent. They  are  smaller,  and  are  composed  of  rows  of  short  columnar 
cells  attached  end  to  end,  and  have  lateral  offsets  which  join  those 
of  contiguous  cells,  uniting  the  whole  in  a  sponge-like  intertexture. 
The  fibres  are  tolerably  uniform,  apparently  devoid  of  a  sarcolemma, 
and  with  the  transverse  stripes  less  distinctly  marked  than  in  the 
voluntary  muscles.  They  are  also  longitudinally  striated,  and  may  be 
resolved  into  fibrillae.  The  muscle-cells  are  provided  usually  with  a 
single  central  oval  nucleus. 

The  epicardium  is  a  serous  membrane  continuous  with  the  inner 
layer  of  the  pericardium.  It  consists  of  an  external  layer  of  irregular, 
polygonal  pavement  cells,  and  a  serosa  with  a  subserous  layer  of  areolar 
connective  tissue,  by  which  it  adheres  to  the  muscular  structure  of  the 
heart  and  is  continuous  with  the  interstitial  connective  tissue.  In  this 
layer  are  distributed  the  vessels  and  nerves  before  they  penetrate  the 
muscular  structure,  and  these  are  usually  associated  with  more  or  less 
fat,  which  is  chiefly  collected  along  the  grooves  of  the  heart,  but  often 
extends  more  or  less  over  the  surface  of  the  latter.  . 

The  endocardium,  similar  to  the  former  membrane,  lines  the  cav- 
ities of  the  heart,  invests  its  valves  and  other  parts,  and  is  continuous 
with  the  endangium  of  the  blood-vessels.  It  is  thicker  in  the  auricles 
than  in  the  ventricles,  and  is  thickest  in  those  of  the  left  side ;  and  is 
thinner  on  the  pectinate  muscles  and  carneous  columns  than  elsewhere. 
It  consists  of  a  superficial  layer  of  pavement  endothelium,  a  serosa,  and 
a  subjacent  layer  of  connective  tissue,  by  which  it  is  attached  to  the 
muscular  structure.  The  connective  tissue  is  associated  with  elastic 
tissue,  which  partially  assumes  the  condition  of  fenestrated  membrane, 
and  is  also  mingled  with  some  unstriped  muscular  fibres.  It  becomes 
more  or  less  pervaded  with  adipose  tissue  in  fat  persons. 

The  valves  and  their  tendinous  cords  of  the  heart  consist  of  a  basis 
of  fibro-connective  tissue  invested  with  the  endocardium.  They  are  non- 
vascular. 

VESSELS  AND   NEKVES   OF   THE   HEAKT. 

The  chief  blood-vessels  of  the  heart  are  the  coronary  arteries  and 
veins,  mainly  running  along  the  grooves  of  its  surface.  The  branches 
ramify  beneath  the  epicardium,  and  thence  penetrate  the  muscular  sub- 
stance, in  which  they  terminate  in  numerous  fine  capillaries,  which 
have  the  same  arrangement  as  in  the  voluntary  muscles.  The  lym- 
phatics of  the  heart  are  numerous,  and  the  larger  ones  mostly  accompany 
the  coronary  vessels  along  the  grooves.  They  generally  commence  in 
lymphatic  spaces  or  clefts  of  the  interstitial  fibro-connective  tissue  of 
the  muscular  structure. 

The  nerves  of  the  heart  are  also  numerous,  but  appear  of  small 
size  in  proportion  to  that  of  the  organ  when  compared  with  those  of 
voluntary  muscles.  They  come  from  the  cardiac  plexuses  formed  by 


THE   ARTERIES.  477 

the  sympathetic  and  vagus  nerves  at  the  base  of  the  heart,  and  mainly 
pursue  the  course  of  the  coronary  vessels.  The  nerves  to  the  auricles 
end  in  fine  plexuses  of  non-medullated  fibres  mingled  with  little  groups 
of  nerve-cells,  situated  for  the  most  part  beneath  the  epicardium,  and 
from  which  the  filaments  penetrate  the  muscular  structure.  The  nerves 
of  the  ventricles  proceed  from  the  coronary  plexuses,  which  extend 
along  the  corresponding  vessels  from  the  cardiac  plexuses.  They 
descend  for  the  most  part  beneath  the  epicardium,  where  they  are  asso- 
ciated with  minute  groups  of  nerve-cells,  and  are  thence  distributed  to 
the  muscular  structure. 

KELATIVE   POSITION  OF   IMPOKTANT   PARTS  OF  THE  HEAKT  TO 
THE   ANTEKIOK   WALL   OF   THE   CHEST. 

About  two-thirds  of  the  heart  lie  to  the  left  of  the  median  line  of 
the  sternum,  with  the  remaining  third  to  the  right,  extending  from  the 
second  intercostal  spaces  to  the  anterior  extremity  of  the  sixth  inter- 
costal space  on  the  left  side.  The  right  auricle  lies  behind  the  inner 
extremities  of  the  third,  fourth,  and  fifth  costal  cartilages  on  the  right 
side.  The  right  ventricle  extends  from  the  third  to  the  sixth  costal 
cartilage  on  the  left  side. 

The  apex  of  the  heart  is  opposite  the  fifth  intercostal  space,  about 
three  and  a  half  inches  to  the  left  of  the  median  line. 

The  auriculo-ventricular  groove  is  in  an  oblique  line  from  the  inner 
end  of  the  third  costal  cartilage  on  the  left  to  the  inner  end  of  the 
sixth  costal  cartilage  on  the  right.  The  auriculo-ventricular  orifices, 
with  the  mitral  valve  above  and  the  tricuspid  valve  below,  lie  a  little 
to  the  left  of  that  line. 

The  aortic  orifice  and  that  of  the  pulmonary  artery  lie  behind  the 
inner  end  of  the  third  costal  cartilage,  third  intercostal  space,  and  con- 
tiguous portion  of  the  sternum  on  the  left  side,  the  former  a  little 
lower  and  a  little  to  the  right  of  the  latter. 

THE   AOKTA. 

The  aorta l  is  the  principal  trunk  of  the  arteries  distributed  to  all 
the  organs  of  the  body,  and  is  contained  within  the  thorax  and  abdo- 
men. It  is  a  large  cylindrical  tube,  narrowing  somewhat  in  its  course, 
about  an  inch  in  diameter  in  the  thorax  or  larger  at  the  commence- 
ment, and  considerably  less  towards  its  termination  in  the  abdomen. 
It  springs,  near  the  centre  of  the  heart,  from  the  left  ventricle,  thence 
ascends  and  obliquely  arches  from  the  right  to  the  left  side  of  the  body, 
where  it  descends  on  the  vertebral  column,  usually  to  the  front  of  the 
fourth  lumbar  vertebra,  on  which  it  forks  into  the  common  iliac  arteries. 
Its  commencement  is  variably  somewhat  expanded  in  a  bulb-like  man- 

1  Arteria  maxima ;  haemal  axis. 


478 


THE   ARTERIES. 


ner,1  and  is  encircled  by  three  lesser  expansions,  the  valvular  sinuses,2 
which  are  due  to  dilatation  of  the  vessel  opposite  the  semilunar  valves, 

which  guard  the  orifice  of  the  ar- 
tery. The  first  portion  of  the  aorta, 
from  its  course,  is  named  the  arch, 
and  the  remainder  the  descending 
aorta,  which  follows  the  flexures 
of  the  spine,  and  is  further  divided 
into  the  thoracic  and  abdominal 
aorta,  from  the  cavities  through 
which  it  passes. 

The  aorta  varies  in  the  relative 
height  to  which  its  arch  rises ;  usu- 
ally ascending  to  within  an  inch  of 
the  upper  border  of  the  sternum,  it 
may  reach  a  level  with  it,  or  it  may 
recede  to  a  level  with  the  fifth 
thoracic  vertebra.  Its  termination 
may  also  vary  to  the  extent  of  a 
lumbar  vertebra,  and  from  the  usual 
position  may  extend  to  the  fifth  or 
may  only  reach  the  third  vertebra. 
Rarely,  cases  occur  of  transpo- 
sition of  the  aorta,  the  pulmonary 
artery,  and  the  heart,  either  with 
or  without  a  corresponding  change 
of  position  of  other  viscera.  A  speci- 
men in  the  museum  of  the  Univer- 
sity of  Pennsylvania  exhibits  a  com- 
plete transposition  from  left  to  right 
of  all  the  thoracic  and  abdominal 
viscera,  together  with  the  blood- 
vessels. 

Variations  in  the  arch  of  the 
aorta  are  related  with  the  course 
of  development  of  the  fourth  and 
fifth  branchial  arches  of  the  em- 
bryo. The  normal  aortic  arch  of 
man  and  his  class  is  to  the  left,  and 
is  dependent  on  the  persistence  and 
growth  of  the  fourth  left  branchial 
artery  of  the  embryo.  In  birds  it 
is  derived  from  the  right  fourth  branchial  artery ;  and  in  reptiles  both 
are  retained,  and  thus  produce  a  double  arch  to  the  aorta. 


THE  AORTA.  1,  arch  of  the  aorta ;  2,  thoracic 
aorta ;  3,  abdominal  aorta ;  4,  innominate 
artery ;  5,  right  common  carotid ;  6,  right  sub- 
clavian ;  7,  left  common  carotid ;  8,  left  sub- 
clavian ;  9,  bronchial  artery,  a  small  branch 
of  the  aorta ;  10,  oesophageal  arteries ;  11,  inter- 
costal arteries  of  the  right  side ;  12,  of  the  left 
side ;  13,  phrenic  arteries ;  14,  coaliac  axis ;  15, 
gastric  artery ;  16,  splenic  artery ;  17,  hepatic 
artery;  18,  superior  mesenteric  artery;  19, 
suprarenal  arteries;  20,  renal  arteries;  x20, 
spermatic  artery;  21,  inferior  mesenteric  ar- 
tery; 22,  lumbar  arteries;  23,  common  iliac 
arteries;  24,  middle  sacral  artery,  a,  aortic 
orifice  of  the  diaphragm ;  b,  articulation  of  the 
head  of  the  ribs ;  c,  anterior  scalene  muscle. 


Bulbus  aortae. 


2  Sinuses  of  Valsalva  or  of  the  aortic  valves. 


THE   ARTERIES.  479 

THE   AKCH   OF   THE   AORTA. 

The  arch  of  the  aorta,1  commencing  at  the  upper  part  of  the  left 
ventricle  of  the  heart,  ascends  with  a  slight  inclination  to  the  right, 
and  curves  to  the  left  obliquely  backward  over  the  right  pulmonary 
artery  and  left  bronchus  to  the  left  of  the  third  or  fourth  thoracic  ver- 
tebra, whence  the  vessel  descends  as  the  thoracic  aorta. 

The  ascending  portion2  of  the  arch,  little  over  two  inches  long, 
commonly  exhibits  to  the  right  a  variable  bulge,3  which  is  disposed  to 
increase  with  the  advance  of  age.  It  is  in  great  part  enclosed  in  the 
pericardium,  but  is  free  above,  and  in  this  position  is  covered  by  the 
edge  of  the  right  lung  with  the  pleura.  At  its  commencement  in  front 
it  is  covered  by  the  right  auricular  appendix  and  the  origin  of  the 
pulmonary  artery. 

The  transverse  portion  of  the  arch,  an  inch  and  a  half  or  more 
long,  crosses  fore  and  aft  from  right  to  left,  behind  the  upper  part  of 
the  sternum,  in  front  of  the  trachea,  and  above  the  bronchi.  In  front 
of  it  above  are  the  innominate  veins,  and  below  it  is  the  bifurcation  of 
the  pulmonary  artery.  From  its  convex  upper  part  spring,  in  near 
succession,  three  great  vessels,  the  innominate,  left  common  carotid, 
and  left  subclavian  arteries. 

The  descending  portion  of  the  arch,  less  than  two  inches  long,  is 
applied  to  the  left  side  of  the  centrum  of  the  fourth  thoracic  vertebra, 
below  which  it  becomes  the  thoracic  aorta.  To  its  left  and  in  front 
is  the  root  of  the  left  lung,  and  to  its  right  are  the  oesophagus  and 
thoracic  duct. 

BRANCHES   OF   THE   AORTA. 

These  consist  of  the  coronary  arteries,  which  supply  the  heart,  and 
the  innominate,  left  common  carotid,  and  left  subclavian  arteries,  which 
supply  the  head  and  neck,  the  upper  limbs,  and  part  of  the  walls  of  the 
thorax. 

The  coronary  arteries*  are  two  small  vessels  which  arise  from  the 
commencement  of  the  aortic  arch,  and  are  distributed  to  the  walls  of 
the  heart. 

The  right  coronary5  artery  arises  from  the  aortic  arch  above 
the  anterior  valvular  sinus,  passes  forward  between  the  right  auricular 
appendix  and  the  pulmonary  artery,  and  runs  outward  in  the  right 
auriculo-ventricular  groove  to  the  back  of  the  heart,  where  it  gives  a 
branch  to  the  left  auriculo-ventricular  groove,  and  then  descends  along 
the  interventricular  groove  to  the  apex  of  the  heart.  In  its  course  along 
the  grooves  of  the  heart  it  furnishes  branches  to  the  walls  of  the 

1  Arcus  aortse.  2  Aorta  adscendens. 

3  Sinus  maximus  or  quartus  ;  greater  sinus  of  the  aorta. 

4  Arterise  coronarise  cordis  ;  a.  cardiacae. 

6  Arteria  coronaria  dextra,  anterior  or  inferior. 


480  THE   ARTERIES. 

contiguous  cavities,  and  also  supplies  small  branches  to  the  aorta  and 
pulmonary  artery. 

The  left  coronary  artery,1  usually  the  larger,  arises  from  the  aorta 
above  the  left  posterior  valvular  sinus,  passes  forward  between  the 
pulmonary  artery  and  left  auricular  appendix,  and  divides  into  two 
branches,  of  which  the  larger2  descends  along  the  interventricular 
groove  in  front  of  the  heart  to  its  apex,  while  the  other  branch 3  runs 
outward  in  the  left  auriculo-ventricular  groove  to  the  back  of  the 
heart.  In  its  course,  like  the  former,  it  supplies  the  contiguous  cavities 
of  the  heart,  and  also  gives  small  branches  to  the  aorta  and  pulmonary 
artery.  The  two  coronary  arteries  together  form  fine  anastomoses 
at  the  surface  of  the  heart. 

The  remaining  branches  of  the  aortic  arch  spring  from  the  top  of 
the  transverse  portion  in  close  succession.  They  consist  of  three  large 
vessels,  the  innominate,  left  common  carotid,  and  left  subclavian  ar- 
teries, forming  a  row  inclining  from  right  to  left  and  backward  in  the 
direction  of  the  arch,  having  immediately  behind  them  the  trachea,  and 
in  front  of  them  the  innominate  veins.  In  their  ascent  the  innominate 
and  left  common  carotid  arteries  diverge  at  the  sides  of  the  trachea, 
while  the  left  subclavian  artery  is  placed  vertically  to  the  left  of  the 
latter.  They  arise  behind  the  sternum,  on  a  level  with  the  second  costal 
cartilages,  about  an  inch  below  the  upper  border  of  the  former,  from 
which  the  vessels  are  separated  by  the  atrophied  thymus  gland.  In 
youth  and  advanced  age  the  relative  position  is  lower,  usually  little 
more  than  half  the  distance  indicated  from  the  upper  border  of  the 
sternum. 

THE   INNOMINATE   ARTERY. 

The  innominate  artery,4  the  first  and  largest  of  the  three  great 
branches  from  the  top  of  the  aortic  arch,  ranges  from  one  to  two  inches, 
and  ascends  obliquely  to  the  position  behind  the  right  sterno-clavicular 
articulation,  where  it  divides  into  the  right  subclavian  and  right  com- 
mon carotid  arteries.  In  front  of  it  is  the  right  innominate  vein  joined 
by  the  left  one,  to  its  left  is  the  trachea,  and  to  its  right  below  and 
behind  is  the  apex  of  the  right  lung  with  the  pleura.  In  its  course 
ordinarily  it  gives  off  no  branches. 

THE   COMMON    CAROTID   ARTERIES. 

The  left  common  carotid  artery,6  immediately  succeeding  the 
innominate  artery,  diverges  from  this  to  the  left  of  the  trachea,  and 
ascends  the  neck  to  the  upper  border  of  the  larynx,  where  it  divides 
into  the  internal  and  external  carotid  arteries. 

1  A.  coronaria  sinistra,  posterior  or  superior. 

2  Ramus  anterior  or  descendens.  3  R.  posterior  or  circumflexus. 

4  A.  innominata,  anonyma,  or  brachio-cephalica. 

5  A.  carotis  communis  sinistra  or  primitiva. 


THE   ARTERIES. 


481 


The  right  common  carotid  artery,1  the  inner  branch  of  the  in- 
nominate artery,  ascends  the  neck  nearly  vertically  to  the  same-  point 
as  the  former,  and  divides  in  like  manner. 

As  the  left  common  carotid  artery  springs  directly  from  the  aorta, 
it  is  longer  than  the  right ;  and  as  it  comes  off  later  in  the  course  of 
the  latter,  it  is  somewhat  more  deeply  removed  from  the  front  of  the 
chest. 

Ascending  the  neck,  the  common  carotid  arteries  diverge  from  the 
sides  of  the  trachea  to  the  sides  of  the  larynx,  and,  after  the  obliquely 

TIG.  258. 


LEFT  COMMON  CAROTID  DIVIDING  INTO  THE  EXTERNAL  AND  INTERNAL  CAROTID  ARTERIES.  1, 
common  carotid  artery ;  2,  internal  carotid ;  3,  external  carotid ;  4,  superior  thyroid ;  5,  lingual ; 
6,  pharyngeal  artery ;  7,  facial ;  8,  inferior  palatine  and  tonsillar  arteries ;  9,  submaxillary ;  10, 
submental ;  11,  occipital ;  12,  posterior  auricular ;  13,  parotid  branches ;  14,  internal  maxillary ; 
15,  temporal  artery  ;  16,  subclavian  artery ;  17,  axillary  :  18,  vertebral  artery ;  19,  thyroid  axis ;  20, 
inferior  thyroid  giving  off  the  ascending  cervical;  21,  transverse  cervical;  22,  suprascapular ;  23, 
internal  mammary  artery. 

outward  course  of  the  first  portion  of  the  left  one,  they  ascend  nearly 
vertically  and  parallel  with  each  other,  though  from  the  projection  for- 
ward of  the  larynx  they  appear  to  incline  backward.  In  the  neck  the 
common  carotid  artery  rests  on  the  prevertebral  muscles,  enclosed  in 
a  sheath  of  the  cervical  fascia,  in  company  with  the  internal  jugular 
vein  and  vagus  nerve,  the  former  to  the  outer  side  of  the  artery,  and 
the  latter  between  the  two  vessels  behind.  At  the  lower  part  of  the 
neck  the  artery  and  its  companions  are  covered  by  the  sterno-mastoid, 

1  A.  c.  c.  dextra  or  primitiva. 
31 


482  THE   ARTERIES. 

sterno-hyoid,  and  sterno-thyroid  muscles,  besides  the  fascia,  platysma, 
and  skin ;  and  they  are  crossed  by  the  omo-hyoid  muscle.  Above  this 
the  artery  is  covered  by  the  skin,  platysma,  fascia,  and  edge  of  the 
sterno-mastoid  muscle.  To  its  inner  side  are  the  trachea  and  oesophagus, 
the  larynx,  thyroid  gland,  and  pharynx. 

The  sympathetic  nerve  descends  behind  the  sheath  of  the  common 
carotid  artery  and  its  companions,  while  the  recurrent  laryngeal  nerve 
ascends  inwardly  behind  the  lower  part  of  the  sheath.  The  cervical 
branch  of  the  hypoglossal  nerve  descends  in  front  of  the  sheath.  The 
common  carotids  are  of  uniform  diameter,  except  at  their  termination, 
where  they  are  somewhat  expanded,  and  they  commonly  give  off  no 
branches  until  they  end  in  the  internal  and  external  carotid  arteries. 

The  common  carotid  artery  not  unfrequently  divides  either  some- 
what higher  or  lower  than  the  usual  position. 

THE   SUBCLAVIAN   ARTERIES. 

The  left  subclavian  artery 1  arises  from  the  aortic  arch  immediately 
succeeding  the  left  common  carotid  artery,  than  which  it  is  larger.  It 
ascends  nearly  vertically  from  the  thorax  into  the  neck,  and  turns  rather 
abruptly  outward,  over  the  first  rib  between  the  insertion  of  the  ante- 
rior and  middle  scalene  muscles  to  the  outer  border  of  the  rib,  whence 
the  vessel  continues  as  the  axillary  artery.  In  its  ascent  to  the  rib  it 
has  the  trachea  and  oesophagus  to  the  right,  with  the  left  innominate, 
internal  jugular,  and  vertebral  veins  in  front,  covered  by  the  apex  of 
the  left  lung  and  pleura  extending  to  the  outer  side.  The  thoracic  duct 
arches  from  behind  forward  above  it,  to  terminate  in  the  junction  of 
the  left  subclavian  and  internal  jugular  veins. 

The  right  subclavian  artery,2  the  outer  branch  of  the  innominate, 
pursues  the  same  course  as  the  left  one  after  this  turns  outwardly  from 
behind  the  sterno-clavicular  articulation  over  the  first  rib.  In  front  of 
it  are  the  right  innominate,  internal  jugular,  and  vertebral  veins,  and 
below  it  is  in  contact  with  the  apex  of  the  right  lung  and  pleura. 

The  vagus  and  phrenic  nerves  descend  in  front  of  the  first  portion 
of  the  course  of  the  subclavian  artery,  and  the  brachial  plexus  accom- 
panies it  over  the  rib,  mostly  above  the  artery,  but  the  lower  cord, 
formed  by  the  last  cervical  and  the  first  thoracic  nerve,  is  behind  and 
in  close  contact  with  it. 

The  branches  of  the  subclavian  artery  arise  in  a  group  as  it  is 
about  to  pass  between  the  scalene  muscles,  and  usually  none  are  given 
off  near  the  commencement  of  the  artery,  nor  after  it  emerges  from 
the  muscles  over  the  outer  part  of  the  rib. 

Variations  in  the  branches  from  the  aortic  arch.  These  are 
numerous,  the  most  striking  of  which  affect  the  great  vessels  from  the 
top  of  the  arch.  They  may  arise  at  variable  distances,  all  separately 

1  A.  subclavia  sinistra.  2  A.  subclavia  dextra. 


THE   ARTERIES.  483 

or  variably  united,  or  they  may  be  multiplied.  Not  unfrequently  the 
left  common  carotid  arises  together  with  the  innominate  artery,  the 
normal  state  in  the  gibbon  and  cat,  less  commonly  there  are  two  in- 
nominate arteries,  as  in  the  dolphin,  and  more  rarely  the  subclavians 
are  separate  and  the  carotids  united,  or  all  may  arise  from  a  single 
trunk,  as  in  the  ox.  One  of  the  most  common  variations  in  the  dis- 
position of  these  vessels  is  that  in  which  the  right  subclavian  artery 
arises  after  the  others,  in  which  case  it  takes  its  course  from  the  left 
side  behind  the  trachea  and  oesophagus  to  its  ordinary  position  over 
the  rib  on  the  right  side. 

THE  INTERNAL  CAROTID  ARTEKY. 

The  internal  carotid  artery1  chiefly  supplies  the  brain  and  the 
eye  with  its  appendages.  One  of  the  terminal  branches  of  the  common 
carotid  artery,  it  ascends  directly  to  the  base  of  the  skull,  where  it 
enters  the  carotid  canal  of  the  temporal  bone  and  thence  the  cavity 
of  the  cranium.  Here  it  passes  along  the  carotid  groove  on  the  side 
of  the  sphenoidal  body,  and  turns  abruptly  upward  in  the  notch  at  the 
inner  side  of  the  anterior  clinoid  process,  pierces  the  dura,  and  at  the 
inner  extremity  of  the  sylvian  fissure  terminates  in  the  anterior  and 
middle  cerebral  arteries. 

In  the  neck  the  internal  carotid  lies  behind  the  external  carotid 
artery,  and  is  accompanied  by  the  internal  jugular  vein,  which  lies 
behind  and  to  its  outer  side,  enclosed  together  with  the  vagus  nerve 
in  the  same  sheath.  It  rests  behind  on  the  greater  pre-rectus  muscle, 
with  the  pharynx  and  tonsil  to  its  inner  side.  It  is  crossed  exter- 
nally by  the  digastric,  stylo-hyoid,  and  stylo-pharyngeal  muscles  and 
the  occipital  and  posterior  auricular  arteries,  and  is  covered  by  the 
parotid  gland.  The  first  cervical  ganglion  and  the  vagus  nerve  are 
behind  it,  and  the  superior  laryngeal  branch  of  the  latter  passes  in- 
ternally to  it.  The  hypoglossal  and  glosso-pharyngeal  nerves  and  the 
pharyngeal  branch  of  the  vagus  pass  forward  externally  to  it.  Near 
its  entrance  into  the  carotid  canal  the  glosso-pharyngeal,  vagus,  acces- 
sory, and  hypoglossal  nerves  pass  outwardly  between  it  and  the  internal 
jugular  vein. 

In  the  carotid  canal  the  artery  is  accompanied  by  the  sympathetic 
nerve,  and  is  separated  from  the  lining  periosteum  by  a  venous  plexus, 
which  communicates  with  the  cavernous  sinus  above,  and  by  one  or  two 
veins  joins  the  internal  jugular  vein  below  the  entrance  of  the  canal. 
"Within  the  cranium  it  lies  along  the  floor  of  the  cavernous  sinus, 
accompanied  by  the  sympathetic  nerve  and  having  the  abducent  nerve 
to  its  outer  side,  all  covered  by  the  lining  membrane  of  the  sinus. 

The  cervical  portion  of  the  internal  carotid  artery  gives  off  no 
branches.  Usually  straight,  it  is  sometimes  more  or  less  tortuous.  In 

1  A.  carotis  interim ;  a.  carotis  cerebralis. 


484 


THE   ARTERIES. 


FIG.  259. 


the  carotid  canal  the  artery  gives  off  a  little  tympanic  branch1  to 
the  tympanum.  In  the  cavernous  sinus  it  gives  off  little  branches  to 
the  dura,  the  pituitary  body,  and  the  trifacial  ganglion. 

After  perforating  the 
dura  at  the  notch  of  the 
anterior  clinoid  process,  the 
internal  carotid  artery 
gives  off  in  advance  the 
ophthalmic  artery,  and  as- 
cends to  the  inner  extrem- 
ity of  the  sylvian  fissure 
of  the  brain.  Here  it  is 
joined  by  the  posterior  com- 
municating artery,  gives 
off  the  choroid  artery,  and 
then  terminates  in  the  an- 
terior and  middle  cerebral 
arteries. 

The  posterior  com- 
municating artery2  is  a 
short,  slender  vessel,  di- 
rected backward  from  the 
internal  carotid  to  join  the 
posterior  cerebral  artery, 
derived  from  the  basilar, 

ARTERIES  OF  THE  INTERIOR  OF  THE  CRANIUM.  1,  internal      Wnicn  lormed     by    the 

carotid  arteries;  2,  ophthalmic  artery;  3,  posterior  com- 
municating arteries ;  4,  anterior  cerebral  arteries ;  5,  an- 
terior communicating  artery  ;  6,  middle  cerebral  arteries ; 
7,  lachrymal ;  8,  short  ciliary  arteries  piercing  the  back 
part  of  the  eyeball ;  9,  central  retinal  artery  piercing  the 
optic  nerve  to  reach  the  interior  of  the  eyeball ;  10,  mus- 
cular artery ;  11,  frontal  and  nasal  artery ;  12,  vertebral 
arteries;  13,  posterior  meningeal  artery;  14,  posterior 
spinal  artery ;  15,  anterior  spinal  arteries  conjoining  in  a 
single  one ;  16,  inferior  cerebellar  arteries ;  17,  basilar 
artery  formed  by  the  union  of  the  vertebrals;  18,  internal 
auditory ;  19,  superior  cerebellar ;  20,  posterior  cerebral 


confluence  of  the  vertebral 
arteries. 

The  choroid  artery,3  a 
small  branch  given  off  by 
the  internal  carotid  exter- 
nally to  the  posterior  com- 
municating artery,  ascends 
outwardly,  and  enters  the 

arteries.  descending  horn  of  the  lat- 

eral ventricle  through  the 

hippocampal  fissure  of  the  cerebrum,  to  be  distributed  to  the  choroid 
plexus. 

The  anterior  cerebral  artery,4  one  of  the  terminal  branches  of 
the  internal  carotid,  runs  forward  and  inward  to  the  great  longitudinal 
fissure,  within  which  it  proceeds  on  the  inner  surface  of  the  cerebral 
hemisphere  forward  and  upward  around  the  fore  part  of  the  callosum, 
and  backward.  In  the  longitudinal  fissure  it  lies  close  to  its  fellow  of 


1  A.  carotico-tympanica. 
3  A.  choroidea  anterior. 


2  A.  communicans  posterior. 

4  A.  cerebri  anterior ;  a.  corporis  callosi. 


THE    ARTERIES.  485 

the  opposite  side,  and  both  as  they  enter  the  fissure  are  joined  by  a 
vessel,  a  line  or  two  long,  the  anterior  communicating  artery.1  The 
branches  of  the  anterior  cerebral  artery  are  mainly  distributed  to  the 
under  part  of  the  frontal  lobe  and  the  inner  surface  of  the  cerebral 
hemisphere. 

The  middle  cerebral  artery,2  the  remaining  and  larger  terminal 
branch  of  the  internal  carotid,  ascends  outwardly  in  the  sylvian  fissure, 
distributing  its  branches  to  the  central  lobe  and  outer  surface  of  the 
cerebral  hemisphere.  At  its  commencement  it  gives  off  half  a  dozen 
or  more  fine  vessels,  which  ascend  in  the  anterior  perforated  space  of 
the  brain  to  the  striatum. 

Circle  of  Willis.3  In  the  union  of  the  anterior  cerebral  arteries 
through  the  anterior  communicating  artery,  and  the  union  of  the 
middle  cerebral  with  the  posterior  cerebral  arteries  through  the  pos- 
terior communicating  arteries,  a  continuous  vascular  circle  is  produced, 
by  which  the  four  great  vessels  that  supply  the  brain,  the  internal 
carotid  and  vertebral  arteries,  are  brought  into  free  communication. 
To  this  remarkable  anastomosis  is  given  the  name  of  the  circle  of 
Willis.  It  is  of  hexagonal  outline,  and  includes  within  its  area  the 
optic  commissure,  the  infundibulum  and  cinereous  tuber,  the  mammil- 
lary  eminences,  and  the  posterior  perforated  space. 

THE   OPHTHALMIC   ARTERY. 

The  ophthalmic  artery*  springs  from  the  internal  carotid  inter- 
nally to  the  position  of  the  anterior  clinoid  process,  and  is  directed 
forward  through  the  optic  foramen  in  company  with  the  optic  nerve 
into  the  orbit.  Entering  this  to  the  outer  side  and  below  the  nerve,  it 
proceeds  forward  and  commonly  over  the  latter  to  the  inner  wall  of 
the  orbit,  along  which  it  runs  below  the  trochlearis  muscle  to  the 
pulley,  and  terminates  in  the  frontal  and  nasal  branches.  In  its  course 
it  gives  off  a  number  of  branches,  more  or  less  variable,  as  follows : 

The  lachrymal  artery 5  arises  to  the  outer  side  of  the  optic  nerve, 
and  runs  along  the  external  rectus  muscle  to  the  lachrymal  gland,  to 
which  it  is  mainly  distributed.  It  gives  branches  to  the  eyelids  and 
conjunctiva  and  contiguous  muscles,  and  others  which  pass  through 
foramina  of  the  malar  bone  to  the  cheek  and  temple. 

The  central  retinal  artery,6  a  delicate  vessel,  enters  the  outer 
side  of  the  optic  nerve  a  short  distance  from  the  eyeball,  and  proceeds 
in  the  axis  of  the  nerve  to  the  retina,  to  which  it  is  distributed. 

The  supraorbital  artery7  springs  from  the  ophthalmic  as  it 
passes  over  the  optic  nerve,  and  proceeds  along  the  roof  of  the  orbit 

1  A.  communicans  anterior. 

2  A.  cerebri  media  or  transversa ;  a.  fossae  Sylvil. 

3  Circulus  arteriosus  Willisii.  *  A.  ophthalmica. 
5  A.  lachrymalis.                6  A.  centralis  retinas.  7  A.  supraorbitalis. 


486  THE   ARTEKIES. 

to  the  supraorbital  foramen,  through  which  it  passes,  and  thence 
ascends  to  the  forehead.  It  gives  branches  to  the  upper  eyelid,  and 
anastomoses  with  the  frontal  arteries. 

The  ciliary  arteries,  of  which  there  are  three  sets.  The  short 
ciliary  arteries,1  commonly  two  from  the  ophthalmic  artery,  or  some- 
times one  from  the  lachrymal  branch,  are  directed  forward,  and  divide 
into  ten  or  more  fine  vessels,  which  pierce  the  sclerotica  in  a  circle 
around  the  optic  nerve,  and  thence  proceed  to  be  distributed  to  the 
choroidea  and  ciliary  processes. 

The  long  ciliary  arteries,2  also  two,  but  larger  than  the  former, 
come  from  the  ophthalmic  artery  or  one  of  its  larger  branches,  pro- 
ceed along  the  optic  nerve,  and  pierce  the  back  of  the  sclerotica  on 
each  side.  Entering  the  eyeball,  they  continue  forward  between  the 
sclerotica  and  choroidea  to  the  ciliary  muscle,  to  which  and  the  iris 
they  are  distributed. 

The  anterior  ciliary  arteries,8  half  a  dozen  or  more  in  number, 
are  little  vessels  arising  from  the  contiguous  muscular  and  lachrymal 
arteries.  They  form  together  a  vascular  circle  beneath  the  conjunctiva 
around  the  cornea,  and  pierce  the  sclerotica  to  communicate  with  the 
long  and  short  ciliary  arteries. 

The  muscular  arteries.*  Commonly  two  larger  ones,  the  supe- 
rior5 and  the  inferior,6  from  the  ophthalmic  artery  or  some  of  its 
branches,  the  former  supplying  the  upper  and  inner  muscles,  the  latter 
the  lower  and  outer  muscles.  They  furnish  most  of  the  anterior  ciliary 
arteries,  and  often  other  branches. 

The  ethmoidal  arteries,7  of  which  there  are  two.  The  posterior  & 
enters  the  corresponding  canal,  and  supplies  the  posterior  ethmoidal 
sinuses  and  upper  part  of  the  nasal  fossa.  The  anterior,9  larger  than 
the  former,  passes  through  the  corresponding  canal  into  the  cranial 
cavity,  and  thence  into  the  nasal  cavity.  It  gives  a  meningeal  branch 
to  the  dura  of  the  anterior  cranial  fossa,  and  supplies  the  mucous  mem- 
brane at  the  fore  part  of  the  nasal  fossa,  and  of  the  frontal  sinus  and 
anterior  ethmoidal  sinuses. 

The  palpebral  arteries,10  two,  or  one  dividing  into  two,  coming 
from  the  fore  part  of  the  ophthalmic,  and  directed  outward  to  the 
eyelids,  near  the  edges  of  which  they  form  circles  by  anastomosing 
with  palpebral  branches  of  the  lachrymal  artery.  They  also  supply 
branches  to  the  lachrymal  sac  and  conjunctiva. 

The  nasal  artery,11  one  of  the  terminal  branches  of  the  ophthalmic, 
passes  from  the  orbit  above  the  internal  palpebral  ligament,  and  is 

I  A.  ciliares  posticse  breves.  2  A.  c.  p.  longse. 
3  A.  c.  anteriores.  *  A.  musculares. 
5  Ramus  muscularis  superior.  6  K.  m.  inferior. 

7  A.  ethmoidales.  8  A.  ethmoidalis  posterior. 

9  A.  ethmoidalis  anterior.  10  A.  palpebralis  superior  et  inferior. 

II  A.  nasalis  ;  a.  dorsalis  nasi. 


THE    ARTERIES.  487 

distributed  to  the  nose,  communicating  with  the  nasal  and  angular 
branches  of  the  facial  artery. 

The  frontal  artery,1  the  remaining  terminal  branch  of  the  oph- 
thalmic, passes  from  the  inner  upper  part  of  the  orbit  to  the  forehead, 
supplying  the  contiguous  structures  and  anastomosing  with  the  supra- 
orbital  artery. 

EXTERNAL  CAROTID  ARTERY. 

The  external  carotid  artery,2  nearly  as  large  as  the  internal 
carotid,  is  distributed  to  the  face,  except  the  orbit,  and  to  the  wall 
of  the  cranium.  It  ascends  from  the  common  carotid,  opposite  the 
upper  border  of  the  larynx,  to  the  neck  of  the  mandible,  where  it 
terminates  in  the  temporal  and  internal  maxillary  arteries.  At  first 
situated  in  advance  and  a  little  inwardly  of  the  internal  carotid,  it  is 
then  directed  slightly  outward,  so  as  to  become  more  superficial  than 
that  vessel,  and  ascends  in  the  interval  of  the  ramus  of  the  jaw  and 
the  mastoid  process,  enclosed  in  the  deeper  part  of  the  parotid  gland. 
Below,  it  rests  on  the  side  of  the  pharynx,  covered  by  the  fascia,  pla- 
tysma,  and  skin,  and  at  a  higher  point  by  the  stylo-hyoid  and  digastric 
muscles,  and  crossed  by  the  hypoglossal  nerve.  It  ordinarily  has  no 
companion  vein,  but  the  external  jugular  vein  lies  superficial  to  its 
upper  part,  and  it  is  crossed  below  by  the  facial  and  lingual  veins.  In 
the  parotid  gland  it  is  crossed  by  the  facial  nerve. 

The  branches  of  the  external  carotid  artery  are  as  follows :  three 
directed  forward,  the  superior  thyroid,  lingual,  and  facial  arteries ; 
from  the  inner  side,  the  pharyngeal  artery;  two  from  behind,  the 
occipital  and  posterior  auricular  arteries ;  and  the  terminal  ones,  the 
temporal  and  internal  maxillary  arteries.  Besides  these,  in  its  course 
it  gives  small  branches  to  the  parotid  gland,  and  twigs  to  the  masseter 
muscle. 

The  superior  thyroid  artery 3  arises  near  the  commencement  of 
the  external  carotid,  just  below  the  hyoid  bone,  and  curves  forward 
and  downward  to  the  upper  part  of  the  thyroid  gland,  to  which  it  is 
mainly  distributed.  It  gives  muscular  branches  to  the  omo-hyoid, 
thyro-hyoid,  and  sterno-thyroid  muscles,  under  which  it  lies,  and 
another  which  descends  in  front  of  the  carotid  sheath  to  the  sterno- 
mastoid  muscle,  the  platysma,  and  the  contiguous  skin.  It  also  supplies 
the  inferior  constrictor  of  the  pharynx,  and  gives  off  a  small  hyoid 
branch,  which  runs  forward  below  the  hyoid  bone.  A  laryngeal 
branch  pierces  the  thyro-hyoid  membrane  to  supply  the  interior  mus- 
cles, lining  membrane,  and  other  structures  of  the  larynx.  Sometimes 
it  enters  the  latter,  on  one  or  both  sides,  through  a  foramen  of  the 
thyroid  cartilage.  A  little  crico-thyroid' branch  runs  in  front  of 

1  A.  frontalis.  2  A.  carotis  externa  or  facialis. 

3  A.  thyroidea  superior. 


488 


THE   ARTERIES. 


the  crico-aryo-thyroid  membrane,  and  communicates  with  that  of  the 

opposite    side    of    the 
FIG.  260.  larynx. 

The  superior  thy- 
roid artery  sometimes 
arises  directly  from  the 
common  carotid,  and 
occasionally  it  arises  to- 
gether with  the  suc- 
ceeding branch. 

The  lingual  artery l 
arises  from  the  external 
carotid  above  the  pre- 
ceding, usually  opposite 
the  hyoid  bone.  Pur- 
suing a  flexuose  course 
forward  and  upward 
immediately  above  the 
greater  cornu  of  the  lat- 
ter, resting  inwardly  on 
the  middle  constrictor 
of  the  pharynx  under 
the  digastric  and  stylo- 
hyoid  muscles,  it  con- 
tinues forward  beneath 
the  tongue,  covered  by 
the  hyo-glossal  muscle. 
At  its  commencement  it 
is  crossed  externally  by 
the  hypoglossal  nerve, 
which  afterwards  lies  above  it  as  the  nerve  passes  forward  to  the  outer 
side  of  the  hyo-glossal  muscle.  From  it  are  derived  the  following- 
named  branches : 

The  hyoid  branch  is  a  small  vessel,  which  runs  forward  along  the 
upper  border  of  the  hyoid  bone,  supplies  the  contiguous  muscles  and 
skin,  and  anastomoses  with  that  of  the  opposite  side.  The  dorsal 
branch,2  a  little  longer  than  the  former  and  often  double,  ascends  from 
above  the  hyoid  cornu,  under  the  hyo-glossal  muscle,  to  the  root  of  the 
tongue,  to  which  it  is  distributed.  It  extends  to  the  mucous  membrane 
of  the  dorsum  of  the  tongue,  beneath  which  it  anastomoses  with  its 
fellow  of  the  opposite  side.  The  sublingual  branch  advances  between 
the  mylo-hyoid  muscle  and  the  mucous  membrane  of  the  floor  of  the 
mouth  to  the  inner  side  of  the  submaxillary  duct  and  sublingual  gland, 
which  it  mainly  supplies,  together  with  the  contiguous  muscles  and 


THE  EXTERNAL  CAROTID  ARTERY  AND  ITS  BRANCHES.    1,  right 

common  carotid;  2,  internal  carotid;  3,  external  carotid;  4, 
superior  thyroid;  5,  lingual;  6,  facial;  7,  submental;  8,  infe- 
rior labial ;  9,  superior  labial ;  10,  muscular  branches ;  11, 
lateral  nasal  artery ;  12,  angular  artery ;  13,  occipital  artery ; 
14,  descending  cervical ;  15,  muscular  branch ;  16,  posterior 
auricular  artery ;  17,  parotid  branches ;  18,  internal  maxil- 
lary ;  19,  temporal ;  20,  transverse  facial ;  21,  anterior  auric- 
ular; 22,  supraorbital ;  23,  middle  temporal;  24,  anterior 
temporal ;  25,  posterior  temporal  artery. 


1  A.  lingualis. 


3  A.  dorsalis  linguae. 


THE   ARTERIES.  489 

mucous  membrane.  The  ranine  artery1  proceeds  forward  as  a  con- 
tinuation of  the  trunk  in  a  more  tortuous  manner  between  the  genio- 
glossal  and  infralingual  muscles  to  the  tip  of  the  tongue,  where  it 
anastomoses  in  a  loop  with  that  of  the  opposite  side.  Beneath  the  tip 
of  the  tongue  at  the  side  of  the  frsenum  it  is  comparatively  superficial. 
In  its  course  it  gives  many  branches  to  the  tongue. 

The  lingual  artery  not  unfrequently  arises  in  common  with  the 
facial,  less  frequently  with  the  superior  thyroid,  and  rarely  all  arise 
together.  The  hyoid  branch  is  often  absent  and  compensated  by  a 
larger  hyoid  branch  of  the  superior  thyroid  artery.  The  sublingual 
branch  sometimes  comes  from  the  facial  artery. 

The  facial  artery2  arises  a  little  above  the  lingual  artery,  and 
.pursues  a  flexuose  course  upward  and  forward,  resting  on  the  mylo- 
hyoid  muscle  beneath  the  digastric  and  stylo-hyoid  muscles  towards 
the  angle  of  the  jaw,  then  runs  in  a  groove  of  the  submaxillary  gland 
along  the  base  of  the  jaw,  and  turns  outward  over  this,  in  advance 
of  the  insertion  of  the  masseter  muscle,  to  the  side  of  the  face.  In 
a  more  tortuous  condition,  which  increases  with  age,  it  ascends  ob- 
liquely to  near  the  oral  angle,  the  side  of  the  nose,  and  to  the  inner 
corner  of  the  eye,  where  it  anastomoses  with  the  nasal  branch  of  the 
ophthalmic  artery.  At  the  side  of  the  face  it  rests  on  the  bucci- 
nator and  supralabial  elevator,  and  near  its  termination  is  involved 
in  the  naso-labial  elevator;  and  is  covered  below  by  the  fascia  and 
platysma  and  the  zygomatic  muscles.  At  the  base  of  the  jaw,  where 
it  is  covered  by  the  platysma  and  skin,  from  the  resistance  of  the 
subjacent  bone,  during  life  its  pulsations  may  readily  be  felt.  The 
facial  vein  on  the  side  of  the  face  is  situated  some  distance  outwardly 
from  the  artery,  but  is  close  to  this  vessel  at  the  base  of  the  jaw ;  and 
in  the  neck  is  more  superficial  and  separated  from  the  artery  by  the 
submaxillary  gland. 

The  branches  of  the  facial  artery,  besides  small  muscular  and 
cutaneous  twigs,  are  as  follows:  in  the  neck,  the  inferior  palatine, 
tonsillar,  submaxillary,  and  submental  arteries;  and  in  the  face,  the 
inferior  and  superior  labial,  nasal,  and  angular  arteries. 

The  inferior  palatine  artery3  arises  near  the  commencement  of 
the  facial,  and  ascends  at  the  side  of  the  pharynx  between  the  stylo- 
pharyngeal  and  stylo-glossal  muscles,  and  then  between  the  former 
and  the  internal  pterygoid  muscle,  to  all  of  which  it  gives  branches, 
and  also  supplies  the  soft  palate,  the  tonsil,  and  opening  of  the  eusta- 
chian  tube ;  and  it  anastomoses  with  that  of  the  opposite  side.  The 
branches  to  the  palate  are  not  unfrequently  substituted  by  others  from 


1  A.  ranina  ;  a.  profunda  linguae. 

2  A.  facialis  ;  a.  maxillaris  externa ;  a.  labialis  or  angularis. 

3  Ascending  palatine  artery ;  a.  palatina  inferior  or  adscendens ;   a.  pharyngo- 
palatina. 


THE    ARTERIES. 

the  pharyngeal  artery,  when  the  inferior  palatine  is  proportionately 
reduced. 

The  tonsillar  artery,1  sometimes  a  branch  of  the  former,  comes 
from  the  facial  near  the  angle  of  the  jaw,  and  ascends  in  the  root  of 
the  tongue,  to  which  and  the  pharynx  it  gives  branches,  but  mainly  to 
the  tonsil. 

The  submaxillary  branches,2  a  variable  number  of  short  twigs, 
come  from  the  artery  in  its  course  through  the  submaxillary  gland, 
which  it  supplies. 

The  submental  artery,3  larger  than  any  of  the  preceding  branches, 
arises  from  the  facial,  at  the  base  of  the  jaw,  and  runs  forward  below 
the  mylo-hyoid  muscle  to  the  chin,  where  it  turns  over  the  base  of  the 
jaw  near  the  symphysis.  It  distributes  branches  to  the  mylo-hyoid 
and  genio-hyoid  muscles  and  the  contiguous  skin,  and  to  the  muscles 
and  skin  of  the  chin  and  lower  lip,  forming  anastomoses  with  the 
sublingual,  mental,  and  inferior  labial  arteries. 

The  inferior  labial  artery  *  arises  from  the  facial,  variably  between 
the  base  of  the  jaw  and  the  oral  angle,  and  passes  beneath  the  depressor 
of  the  latter  to  the  lower  lip,  along  the  border  of  which  it  runs  in  a 
tortuous  manner  between  the  oral  sphincter  and  mucous  membrane 
of  the  mouth,  and  inosculates  with  that  of  the  opposite  side.  It  dis- 
tributes branches  to  the  chin  and  lower  lip,  and  anastomoses  with  the 
mental  and  submental  arteries.  Frequently  a  larger  branch,5  some- 
times arising  separately  from  the  facial,  passes  beneath  the  oral  angle 
depressor  along  the  attachment  of  the  lower  lip. 

The  superior  labial  artery 6  arises  near  the  oral  angle,  and,  like  the 
inferior  one,  pursues  a  tortuous  course  in  the  upper  lip  and  inosculates 
with  its  fellow.  Besides  supplying  the  upper  lip,  it  gives  off  a  branch 
which  runs  along  the  nasal  column  to  the  tip  of  the  nose. 

Through  the  inosculation  of  the  inferior  and  superior  labial  arteries 
of  the  two  sides  a  complete  arterial  circle  is  formed  around  the  mouth, 
which  in  the  usual  condition  is  very  tortuous,  but  is  extended  in  the 
opening  of  the  mouth. 

The  nasal  artery,7  a  terminal  branch  of  the  facial,  often  replaced 
by  several  branches,8  turns  inward  to  be  distributed  to  the  side  and 
back  of  the  nose,  and  anastomoses  with  the  nasal  branch  of  the 
ophthalmic  artery. 

The  second  terminal  branch,  or  the  terminal  portion  of  the  facial 
artery  much  reduced,  is  named  the  angular  artery,9  and  inosculates 


1  A.  tonsillaris.  2  Kami  submaxillares  ;  glandular  branches. 

3  A.  submentalis.  4  Inf.  coronary  artery ;  a.  labialis  inf. ;  a.  coronaria  inf. 

5  Inferior  labial  artery. 

6  Superior  coronary  artery  ;  a.  labialis  sup. ;  a.  coronaria  sup. 

7  Lateral  nasal  artery  ;  a.  nasalis  lateralis  or  externa. 

8  Eami  pinnales  and  dorsales.  9  A.  angularia 


THE    ARTERIES.  491 

at  the  inner  side  of  the  orbit  with  the  nasal  branch  of  the  ophthalmic 
artery. 

The  pharyngeal  artery l  is  a  long,  slender  branch,  which  arises 
from  the  inner  side  of  the  external  carotid,  usually  near  the  lingual 
artery,  and  ascends  between  the  two  carotids  and  the  pharynx  to  the 
base  of  the  skull.  It  distributes  small  branches  to  the  prevertebral 
muscles,  to  the  constrictors  of  the  pharynx,  to  the  elevator  and  ten- 
sor muscles  of  the  palate,  to  the  tonsil,  and  to  the  eustachian  tube. 
From  it  a  small  meningeal  branch2  ascends  through  the  jugular 
foramen  to  the  dura,  and  in  its  course  gives  twigs  to  the  nerves  which 
pass  through  the  former,  and  others  to  the  superior  cervical  ganglion 
of  the  sympathetic  nerve. 

The  pharyngeal  artery  is  very  variable  in  its  origin.  It  sometimes 
springs  from  the  bifurcation  of  the  common  carotid  artery  or  from  the 
internal  carotid,  from  the  facial  directly  or  in  union  with  the  palatine 
artery,  or  it  may  be  derived  from  the  occipital  artery. 

The  occipital  artery3  springs  from  behind  the  external  carotid, 
usually  opposite  the  facial,  and  ascends  beneath  the  posterior  belly  of 
the  digastric  and  stylo-hyoid  muscles,  thence  passes  backward  through 
the  occipital  groove  of  the  mastoid  process,  resting  on  the  complexus 
and  supraoblique  muscles,  and,  covered  by  those  attached  to  the  mastoid 
process,  emerges  at  the  back  of  the  neck  between  the  insertion  of  the 
sterno-mastoid  and  trapezius,  and  ascends  to  be  distributed  over  the 
occipital  region  of  the  cranium.  In  the  early  part  of  its  course  it 
crosses  over  the  internal  carotid  artery  and  internal  jugular  vein,  and 
the  vagus  and  accessory  nerves  ;  and  is  crossed  from  behind  outwardly 
by  the  hypoglossal  nerve.  Near  its  commencement  it  gives  off  a  mus- 
cular branch/  which  descends  with  the  accessory  nerve  to  the  sterno- 
mastoid  muscle,  in  which  it  is  distributed.  It  also  supplies  branches  to 
the  digastric,  stylo-hyoid,  complexus,  trachelo-mastoid,  and  splenius 
muscles.  Commonly  a  large  but  variable  descending  branch5  divides 
into  two,  the  superficial  and  deep  cervical  arteries,6  of  which  the 
former  is  distributed  between  the  splenius  and  the  trapezius,  and  gives 
twigs  through  the  latter  to  the  skin,  while  the  deep  one  enters  the  space 
between  the  oblique  and  recti  muscles,  supplies  these  and  others  con- 
tiguous, and  anastomoses  with  branches  of  the  vertebral  and  ascend- 
ing cervical  arteries.  A  little  meningeal  branch 7  enters  the  mastoid 
foramen  to  the  neighboring  dura.  The  occipital  branches  8  pursue  a 
tortuous  course  over  the  occipital  region  of  the  cranium  between  the 


1  Ascending  pharyngeal  artery  ;  a.  pharyngea  adscendens  ov  inferior. 

2  A.  meningea  posterior.  s  A.  occipitalis. 

4  Sterno-mastoid  branch. 

5  Cervical  branch  ;  ramus  cervicalis  princeps,  or  a.  princeps  cervicis. 

6  Ramus  cervicalis  superficialis  superior  and  r.  c.  profundus  sup. 

7  Mastoid  branch.  8  Superficial  or  cranial  branches ;  rami  occipitales. 


492  THE   ARTERIES. 

skin  of  the  scalp  and  the  occipital  muscle  with  its  aponeurosis,  and 
freely  anastomose  with  one  another  and  with  the  posterior  auricular 
and  temporal  arteries.  Barely  the  occipital  artery  arises  from  the 
internal  carotid. 

The  posterior  auricular  artery,1  smaller  than  the  occipital,  arises 
above  it  from  the  external  carotid  artery  after  this  vessel  has  entered 
the  parotid  gland,  and  ascends  to  the  outer  side  of  the  styloid  process 
above  the  digastric  muscle  to  the  interval  between  the  mastoid  pro- 
cess and  the  auricle,  where  it  divides  into  the  auricular  and  mastoid 
branches.  In  its  course  it  is  crossed  by  the  facial  nerve.  It  gives  small 
branches  to  the  parotid  gland,  and  to  the  digastric  and  styloid  muscles. 
The  stylo-mastoid  artery,2  a  long,  slender  branch,  enters  the  corre- 
sponding foramen,  and  traverses  the  facial  canal  in  company  with  the 
facial  nerve.  It  gives  branches  to  the  mastoid  cells,  the  stapedial 
muscle,  and  the  tympanum.  A  branch  to  the  latter  anastomoses 
with  one  from  the  tympanic  branch  of  the  internal  maxillary  artery, 
forming  a  circle  around  the  tympanic  membrane.  The  stylo-mastoid 
artery  terminates  by  anastomosis  with  the  petrosal  branch  of  the 
great  meningeal  artery.  It  is  frequently  a  branch  of  the  occipital 
artery.  The  auricular  branch3  ascends  beneath  the  postauricular 
muscle,  which  is  supplied  by  it,  and  is  distributed  over  the  back  of 
the  auricle  beneath  the  skin.  The  mastoid  branch4  is  directed  back- 
ward, and  is  distributed  over  the  insertion  of  the  sterno-mastoid  muscle 
into  the  mastoid  process,  anastomosing  with  branches  of  the  occipital 
artery. 

The  posterior  auricular  is  frequently  a  branch  of  the  occipital  artery. 
It  may  be  smaller  or  larger  than  usual,  in  the  former  case  being  com- 
pensated through  branches  of  the  occipital  artery,  in  the  other  case 
partially  taking  the  place  of  the  latter. 

The  temporal  artery,5  the  more  superficial  and  smaller  terminal 
branch  of  the  external  carotid,  starting  from  the  neck  of  the  mandible, 
ascends  the  temple  in  a  flexuose  manner  for  about  an  inch,  more  or 
less,  and  divides  into  the  anterior  and  posterior  temporal  branches. 
At  first  enveloped  in  the  parotid  gland,  it  emerges  from  this  between 
the  auditory  meatus  and  the  articulation  of  the  jaw,  and  then,  passing 
over  the  root  of  the  zygoma,  rests  on  the  deep  temporal  fascia  covered 
by  the  skin.  In  its  course  it  gives  off  the  following  branches : 

The  transverse  facial  artery,6  a  variable  branch  and  sometimes 
absent,  runs  forward  beneath  the  parotid  gland,  resting  on  the  masseter 
muscle,  between  the  zygoma  and  the  parotid  duct,  to  the  cheek.  It  is 
distributed  to  the  parts  mentioned  and  to  the  contiguous  skin,  and 
anastomoses  with  branches  of  the  facial,  buccal,  and  infraorbital  ar- 


1  A.  auricularis  post.  2  A.  stylo-mastoidea 

3  Karaus  auricularis.  *  R.  occipitalis,  mastoideus,  or  posterior. 

5  A.  temporali-s  ;  superficial  temporal  artery.  8  A.  transversa  facei. 


THE    AETERIES.  493 

teries.  Occasionally  it  is  unusually  large,  and  may  substitute  the  upper 
portion  of  the  facial  artery. 

The  anterior  auricular  branches,1  two  or  three  small  vessels, 
come  from  the  adjacent  part  of  the  temporal  artery  and  are  distributed 
to  the  fore  part  of  the  auricle,  the  auditory  meatus,  and  the  pre-  and 
supra-auricular  muscles.  They  anastomose  with  branches  of  the  pos- 
terior auricular  artery. 

The  middle  temporal  branch 2  arises  above  the  zygoma,  pierces 
the  temporal  fascia,  and  ascends  beneath  the  temporal  muscle,  to  which 
it  is  distributed,  anastomosing  with  the  deep  temporal  branches  of  the 
internal  maxillary  artery.  It  usually  impresses  the  temporal  squama 
with  a  slight  groove. 

The  orbital  branch,3  small  and  inconstant,  runs  forward  above  the 
zygoma  to  the  eyelids,  to  which  it  is  distributed,  anastomosing  with  the 
lachrymal  and  anterior  temporal  arteries. 

The  anterior  temporal  branch4  diverges  from  the  bifurcation 
of  the  temporal  artery  forward  and  upward  to  the  fore  border  of 
the  temporal  fossa,  where  it  curves  backward  and  upward.  It  gives 
off  numerous  branches  to  the  forehead  and  temple,  which  anastomose 
with  one  another,  and  with  the  frontal,  orbital,  and  posterior  temporal 
arteries. 

The  posterior  temporal  branch 5  ascends  and  is  distributed  on 
the  side  of  the  cranium  to  the  vertex,  where  it  anastomoses  with 
branches  of  the  opposite  side,  in  front  with  the  anterior  temporal,  and 
behind  with  the  occipital  and  posterior  auricular  arteries. 

The  temporal  branches  supply  the  scalp.  Sometimes  one  and  some- 
times the  other  is  the  larger. 

The  internal  maxillary  artery,6  the  larger  of  the  terminal  branches 
of  the  external  carotid,  is  concealed  at  its  commencement  by  the  parotid 
gland.  It  turns  horizontally  inward  behind  the  neck  of  the  mandi- 
ble, from  the  inner  side  of  which  it  pursues  a  winding  course  through 
the  zygomatic  fossa  to  the  upper  part  of  the  spheno-maxillary  fossa, 
where  it  ends  in  the  nasal  branch.  In  its  course  it  first  passes  for- 
ward between  the  pterygoid  muscles,  then  abruptly  ascends  and  turns 
forward  between  the  internal  pterygoid  and  the  temporal  muscle,  and 
in  advance  of  this  ascends  to  its  termination.  The  branches  of  the 
internal  maxillary  artery  are  numerous,  and,  though  mostly  small,  are 
important. 

The  deep  auricular  branch,7  a  small  vessel  from  the  commence- 


1  A.  auriculares  anteriores ;  a.  auric,  ant.  inferior  and  a.  auric,  ant.  superior. 

2  A.  temporalis  media. 

3  A.  orbitalis  or  supraorbitalis  ;  a.  supraorbitalis  externa  ;  a.  zygomatico-orbitalis. 

4  A.  temporalis  superficialis  anterior  or  frontalis. 
6  A.  temp,  superf.  post,  or  occipitalis. 

6  A.  maxillaris  interna  ;  deep  facial  artery.  7  A.  auricularis  profunda. 


494 


THE    AETERIES. 


FIG.  261. 


ment  of  the  artery,  ascends  and  is  distributed  to  the  auditory  meatus, 
extending  to  the  bottom  and  supplying  the  tympanic  membrane  and 
anastomosing  with  the  tympanic  branch  of  the  stylo-mastoid  artery. 

The  tympanic  branch,1  fre- 
quently arising  in  common  with 
the  former,  ascends  through  the 
glenoid  foramen  into  the  tym- 
panum, in  which  it  is  distrib- 
uted. It  sometimes  arises  from 
the  great  meningeal,  the  inferior 
dental,  or  the  temporal  artery. 

The  great  meningeal  ar- 
tery,'2 the  largest  branch  of  the 
maxillary,  ascends  under  the 
external  pterygoid  muscle,  em- 
braced by  the  two  roots  of  the 
auriculo-temporal  nerve,  and  en- 
ters the  cranium  through  the 
sphenoidal  spinous  foramen. 
Within  the  cranium  it  ascends 
in  the  dura  and  divides  into  two 
principal  branches,  which  are 
distributed  in  the  course  of  the 
arborescent  channels  so  conspic- 
uous on  the  interior  of  the  cranial 
vault.  Before  entering  the  cra- 
nium it  usually  gives  off  the 
small  meningeal  artery,3 
sometimes  directly  derived  from 
the  internal  maxillary,  which 
enters  the  cranium  through  the 
sphenoidal  oval  foramen,  and 

after  giving  twigs  to  the  trifacial  semilunar  ganglion  is  distributed  to 
the  dura  in  the  vicinity  of  the  cavernous  sinus.  Within  the  cranium 
the  great  meningeal  artery  gives  off  a  little  petrosal  branch,4  which 
enters  the  hiatus  of  the  facial  canal  and  anastomoses  with  the  termina- 
tion of  the  stylo-mastoid  artery.  It  further  gives  fine  twigs  through 
the  petro-squamous  fissure  to  the  tympanum  and  mastoid  sinuses.  In 
its  course  it  gives  some  little  branches  of  communication  through 
foramina  of  the  great  sphenoidal  wing  to  the  deep  temporal  arteries. 

The  inferior  dental  artery5  arises  about  opposite  the  former,  and 
descends  to  the  dental  canal  of  the  mandible,  which  it  traverses  in 

1  A.  tympanica  ;  a.  cavi  tympani. 

2  A.  meningea  magna  or  media ;  a.  spheno-spinosa  ;  middle  menin.  art. 

3  A.  meningea  parva.  6  Kamus  petrosus. 
5  A.  dentalis,  maxillaris,  or  alveolaris  inferior. 


INTERNAL  MAXILLARY  ARTERY.  1,  right  com- 
mon carotid ;  2,  internal  carotid ;  3,  external 
carotid;  4,  superior  thyroid;  5,  lingual;  6,  facial; 
7,  occipital;  8,  posterior  auricular;  9,  parotid 
branch ;  10.  temporal  artery ;  11,  internal  max- 
illary ;  12,  tympanic ;  13,  great  meningeal  artery ; 
14,  inferior  dental  artery ;  15,  muscular  branches ; 
16,  superior  maxillary  artery  giving  off  the  poste- 
rior dental  arteries ;  17, 18,  infra-orbital  artery. 


THE   ARTERIES.  495 

company  with  the  corresponding  vein  and  nerve.  Before  entering  the 
canal  it  gives  off  a  mylo-hyoid  branch,1  which  runs  along  the  inner 
side  of  the  mandible  beneath  the  mylo-hyoid  muscle,  to  which  it  is 
distributed.  In  its  course  through  the  canal  it  gives  off  many  fine 
branches,  which  in  part  supply  the  marrow  of  the  bone  and  the  lower 
gum,  and  in  part  ascend  through  the  apertures  at  the  ends  of  the  fangs 
of  the  teeth  to  supply  the  dental  pulps.  At  the  fore  part  of  the  canal 
the  artery  divides  into  two  terminal  branches,  of  which  one  supplies 
the  incisor  teeth  and  the  other  emerges  at  the  mental  foramen  to  be 
distributed  to  the  chin,  where  it  anastomoses  with  the  inferior  labial 
and  submental  arteries. 

The  muscular  branches  usually  arise  from  the  middle  portion 
of  the  artery,  and  are  distributed  to  the  muscles  of  mastication,  in- 
cluding the  buccinator.  They  consist  of  the  posterior  and  anterior 
deep  temporals,2  which  ascend  beneath  the  temporal  muscle  supply- 
ing this  and  anastomosing  with  the  middle  temporal  artery ;  the  ptery- 
goids,3  short  and  variable  in  number,  size,  and  origin,  distributed  to 
the  pterygoid  muscles  ;  the  masseteric,4  which  passes  over  the  notch 
of  the  ramus  of  the  mandible  beneath  the  masseter,  which  it  supplies ; 
and  the  buccal  branch,5  which  passes  downward  and  forward  to  the 
buccinator  and  the  contiguous  mucous  membrane,  and  anastomoses 
with  branches  of  the  facial  artery. 

The  posterior  dental  artery6  arises  from  the  internal  maxillary 
separately  or  in  common  with  the  succeeding  branch,  near  the  back  of 
the  maxilla,  on  which  it  descends,  giving  small  branches  to  the  gum, 
and  others  which  traverse  the  posterior  dental  canals  to  supply  the 
molar  teeth  and  maxillary  antrum. 

The  infraorbital  artery7  runs  through  the  corresponding  canal  in 
company  with  the  superior  maxillary  nerve,  and  emerges  on  the  face 
to  end  in  branches  to  the  muscles  of  the  upper  lip  and  lower  eyelid, 
where  they  anastomose  with  branches  of  the  facial,  transverse  facial, 
buccal,  and  ophthalmic  arteries.  In  its  course  it  gives  a  branch  through 
the  spheno-maxillary  foramen  to  the  orbit,  where  it  anastomoses  with 
the  ophthalmic  artery,  and  is  distributed  to  the  inferior  muscles  and 
lachrymal  gland.  In  the  infraorbital  canal  it  gives  off  the  anterior 
dental  artery,  which  descends  through  the  corresponding  canal  and 
its  divisions  to  supply  the  front  teeth  and  the  maxillary  antrum. 

The  superior  palatine  artery8  descends  through  the  posterior 
palatine  canal  in  company  with  the  large  palatine  nerve  to  the  hard 
palate,  to  which  it  is  distributed,  including  the  mucous  membrane  with 

1  A.  mylo-hyoidea.  2  A   temporales  profundje. 

3  A.  pterygoideaj.  *  A.  masseterica.  «  A.  buccinatoria  or  buccalis. 

6  A.  dentalis  sup.  ;  a.  maxillaris  or  alveolaris  sup.  ;  a.  supramaxillaris. 

7  A.  infraorbitalis. 

8  Descending  palatine  artery ;   a.  palatina  superior  or  descendens ;   a.  pterygo- 
palatina. 


496  THE    ARTERIES. 

the  gum  and  the  palatine  glands.  In  its  course  it  gives  branches 
through  the  smaller  palatine  canals  to  the  soft  palate  and  tonsil, 
where  they  anastomose  with  branches  of  the  inferior  palatine  artery 

The  vidian  artery,1  a  small  vessel,  traverses  the  corresponding 
canal,  in  company  with  the  nerve,  to  the  top  of  the  pharynx  and  the 
eustachian  tube. 

The  pterygo-palatine  artery,2  another  little  vessel,  passes  through 
the  corresponding  canal  to  the  upper  back  part  of  the  nasal  fossa,  the 
top  of  the  pharynx,  and  the  sphenoidal  sinus. 

The  nasal  artery,3  the  termination  of  the  internal  maxillary, 
passes  through  the  spheno-palatine  foramen  into  the  nasal  fossa,  and 
divides  into  two  branches.  Of  these  the  external4  is  distributed  to 
the  outer  wall  of  the  nasal  fossa,  including  the  turbinals  and  the  eth- 
moidal  and  maxillary  sinuses.  The  internal  branch5  crosses  to  the 
nasal  septum,  on  which  it  descends  obliquely  forward  supplying  it 
with  branches,  and  ends  by  passing  through  the  naso-palatine  canal  to 
anastomose  with  the  superior  palatine  artery. 

THE   SUBCLAVIAN   AKTERY. 

The  subclavian  artery6  is  mainly  destined  to  supply  the  upper 
limb,  but  also  supplies  part  of  the  brain  and  spinal  cord,  and  part  of 
the  neck  and  wall  of  the  thorax.  Its  origin,  course,  and  mode  of  ter- 
mination are  described  on  page  482.  Its  branches  are  many,  and 
commonly  come  off  in  a  group  immediately  before  the  artery  passes 
between  the  scaleni  muscles,  and  usually  none  are  given  off  at  or  near 
its  commencement,  or  after  it  emerges  from  between  the  muscles  over 
the  first  rib. 

Four  or  five  principal  branches  emanate  from  the  subclavian  artery : 
the  vertebral  artery,  the  thyroid  axis,  and  the  internal  mammary, 
superior  intercostal,  and  deep  cervical  arteries. 

The  vertebral  artery,7  the  largest  and  most  important  branch  of 
the  subclavian,  comes  off  from  the  upper  back  part  of  this  vessel,  and 
passes  a  little  backward  and  outward  to  enter  the  foramen  of  the 
costo-transverse  process  of  the  sixth  cervical  vertebra.  Thence  ascend- 
ing through  the  corresponding  foramina  above,  in  that  of  the  axis  it 
turns  outward,  and  then  upward  through  that  of  the  atlas,  winds 
backward  and  inward  in  the  groove  behind  the  prearticular  process  of 
the  latter,  and  once  more  ascends,  perforates  the  dura,  and  enters  the 
cranium  through  the  occipital  foramen.  Finally  it  proceeds  forward 

1  A.  Vidiana  or  pterygoidea. 

2  A.  pterygo-palalina ;  a.  pharyngea  suprema  or  descendens. 

3  A.  nasalis  posterior;  spheno-palatine  artery ;  a.  spheno-palatina. 
*  A.  nasalis  posterior  externa  or  lateralis. 

5  A.  septi  narium  posterior. 

6  A.  subclavia ;  a.  brachio-cephalica.  7  A.  vertebralis. 


THE   ARTERIES.  497 

and  upward,  turning  from  the  side  to  the  front  of  the  medulla  oblon- 
gata,  and  converges  to  join  its  fellow  at  the  lower  border  of  the  pons, 
to  form  the  basilar  artery.  In  front  of  its  commencement  is  the  in- 
ternal jugular  vein,  and  also  the  vertebral  vein,  which  accompanies  it 
through  the  costo-trans verse  processes  of  the  vertebra  and  encloses  it 
in  a  plexus.  On  the  left  side  the  thoracic  duct  arches  in  front  of  it 
from  within  outwardly.  The  cervical  nerves,  as  they  issue  from  the 
intervertebral  foramina,  pass  behind  the  artery,  but  the  first  one  passes 
beneath  it  in  the  groove  of  the  atlas. 

Occasionally  the  vertebral  artery,  especially  that  of  the  left  side, 
arises  directly  from  the  aorta.  Sometimes  one  artery  is  considerably 
larger  than  the  other,  usually  the  left.  Within  the  cranium,  where  the 
arteries  converge,  they  are  sometimes  curved  towards  the  same  side. 

The  vertebral  artery,  in  its  course  through  the  neck,  gives  off  sev- 
eral small  muscular  and  spinal  branches,  the  former  distributed  to 
the  contiguous  muscles  and  anastomosing  with  the  ascending  and  deep 
cervical  and  occipital  arteries,  and  the  latter  passing  through  the  inter- 
vertebral  foramina,  to  be  distributed  to  the  spinal  canal  and  its  contents. 
Within  the  cranium,  besides  small  branches  to  the  medulla  oblongata, 
it  gives  off  the  posterior  meningeal,  posterior  and  anterior  spinal,  and 
posterior  inferior  cerebellar  arteries. 

The  posterior  meningeal  artery,1  a  small  branch,  is  given  from 
the  vertebral  as  this  pierces  the  dura,  and  is  distributed  to  this  mem- 
brane in  the  cerebellar  fossa. 

The  posterior  spinal  artery,2  a  small,  flexuose  vessel,  descends  on 
the  medulla  oblongata,  in  the  pia,  to  the  back  of  the  spinal  cord,  along 
which  it  continues  to  the  lower  end,  inosculating  in  its  course  with  the 
lateral  spinal  arteries,  which  ascend  on  the  roots  of  the  spinal  nerves  to 
the  cord. 

The  anterior  spinal  artery,3  larger  than  the  former,  is  given  from 
the  vertebral  near  its  termination,  descends,  converging  in  front  of  the 
medulla  oblongata,  and  near  the  occipital  foramen  unites  with  its  fellow 
in  a  common  trunk.  This  descends  in  a  tortuous  manner  in  front  and 
along  the  middle  of  the  spinal  cord  and  its  terminal  filum  to  the  end 
of  the  spinal  canal,  in  its  course  inosculating  with  the  lateral  spinal 
arteries. 

The  posterior  and  anterior  spinal  arteries  pursue  their  course,  inos- 
culate with  the  lateral  spinal  arteries,  and  together  form  a  plexus  in 
the  pia  of  the  cord  before  they  are  distributed  directly  to  the  cord 
itself. 

The  posterior  inferior  cerebellar  artery,4  the  largest  branch  of 
the  vertebral,  but  sometimes  arising  from  the  basilar  artery,  turns  out- 
ward and  backward  at  the  side  of  the  medulla  oblongata  and  the  fourth 

1  A.  meningea  post.  2  A.  spinalis  post. 

3  A.  spinalis  ant.  4  A.  cerebelli  inf.  post,  or  magna. 

32 


498 


THE   ARTERIES. 


FIG.  262. 


ventricle  to  the  valley  of  the  cerebellum,  in  which  it  divides  into  two 
branches.  Of  these,  the  internal  branch  is  mainly  distributed  to  the 
vermis,  anastomosing  with  its  fellow,  while  the  external  branch  is 
distributed  to  the  inferior  part  of  the  hemisphere  of  the  cerebellum. 
Before  division  the  artery  supplies  branches  to  the  choroid  plexuses  of 
the  fourth  ventricle. 

The  basilar  artery,1  a  single  vessel  formed  by  the  confluence  at  an 
acute  angle  of  the  vertebral  arteries,  lies  along  the  median  groove  be- 
neath the  pons,  sometimes 
curved  more  or  less  to  one 
side,  and  divides  at  the  an- 
terior border  of  the  latter 
into  the  posterior  cerebral 
arteries.  Besides  a  number 
of  small  branches  on  each 
side  distributed  to  the  pons, 
it  gives  off  the  auditory 
and  the  anterior  inferior 
and  superior  cerebellar  ar- 
teries. 

The  auditory  artery,2 
a  small  but  important  ves- 
sel, is  derived  from  the  bas- 
ilar or  from  the  anterior 
inferior  cerebellar  artery, 
and  accompanies  the  au- 
ditory nerve  through  the 
auditory  meatus  to  the 
labyrinth  of  the  ear,  to 
which  it  is  distributed. 

The  anterior  inferior 
cerebellar  artery,3  vary- 
ing proportionately  in  size 
with  its  fellow  and  with 
the  posterior  inferior  cere- 
bellar artery,  arises  from 
the  basilar  back  of  the  mid- 
dle, and  passes  outward  and 
backward  to  the  fore  part 
of  the  inferior  surface  of 
the  cerebellum,  to  which 

it  is  distributed,  anastomosing  with  the  posterior  inferior  cerebellar 
arteries. 


ARTERIES  OF  THE  INTERIOR  OF  THE  CRANIUM.  1,  internal 
carotid  arteries ;  2,  ophthalmic  artery ;  3,  posterior  com- 
municating arteries ;  4,  anterior  cerebral  arteries ;  5,  an- 
terior communicating  artery ;  6,  middle  cerebral  arteries; 
7,  lachrymal ;  8,  short  ciliary  arteries  piercing  the  back 
part  of  the  eyeball ;  9,  central  retinal  artery  piercing  the 
optic  nerve  to  reach  the  interior  of  the  eyeball ;  10,  mus- 
cular artery ;  11,  frontal  and  nasal  artery ;  12,  vertebral 
arteries;  13,  posterior  meningeal  artery;  14,  posterior 
spinal  artery ;  15,  anterior  spinal  arteries  conjoining  in  a 
single  one ;  16,  inferior  cerebellar  arteries ;  17,  basilar 
artery  formed  by  the  union  of  the  vertebrals ;  18,  internal 
auditory  artery ;  19,  superior  cerebellar  artery ;  20,  pos- 
terior cerebral  arteries. 


1  A.  basilaris  ;  a.  meso-cephalica. 

2  Internal  auditory  artery  ;  a.  auditoria  interna. 


3  A.  cerebelli  inf.  ant. 


THE   ARTERIES.  499 

The  superior  cerebellar  artery l  arises  near  the  termination  of 
the  basilar,  and  turns  outward  and  backward  in  the  groove  between 
the  pons  and  the  cerebral  crus  to  the  upper  surface  of  the  cerebellum, 
over  which  it  is  distributed. 

The  posterior  cerebral  artery,2  formed  on  each  side  by  the  di- 
vision of  the  basilar  artery,  curves  outward  and  backward  around  the 
cerebral  crus,  parallel  with  the  superior  cerebellar  artery,  and  proceeds 
on  the  under  part  behind  of  the  cerebral  hemisphere  to  the  temporo- 
sphenoidal  and  occipital  lobes,  to  which  it  is  mainly  distributed.  At 
its  commencement  it  gives  off  some  small  branches  to  the  posterior 
perforated  space.  As  it  turns  backward  it  i.3  joined  in  front  by  the 
posterior  communicating  artery,  by  which  it  is  connected  with  the 
internal  carotid  artery.  In  its  subsequent  course,  passing  near  the 
posterior  border  of  the  callosum,  it  gives  one  or  two  small  branches, 
the  posterior  choroid  arteries,  to  the  choroid  plexus  of  the  lateral 
ventricle. 

The  thyroid  axis3  is  a  short,  variable  trunk,  about  the  fourth 
of  an  inch  long,  arising  from  the  subclavian  artery  at  the  inner  bor- 
der of  the  anterior  scalenus  muscle,  and  dividing  into  branches, — the 
inferior  thyroid,  suprascapular,  and  transverse  cervical  arteries,  or 
in  place  of  the  latter  the  superficial  cervical  artery,  usually  one  of 
its  branches.  It  may  arise  together  with  any  other  branch  of  the 
subclavian  artery,  or  any  of  its  branches  may  arise  separately  from 
the  latter. 

The  inferior  thyroid  artery*  ascends  from  the  thyroid  axis  in 
front  of  the  vertebral  artery,  and  turns  inwardly  behind  the  sheath  of 
the  great  cervical  vessels  and  the  sympathetic  nerve  to  the  thyroid 
gland,  in  which  it  is  distributed,  anastomosing  with  the  superior  thy- 
roid artery  and  those  of  the  opposite  side.  As  it  turns  inward  behind 
the  sheath  of  the  cervical  vessels  it  gives  off  the  ascending  cervical 
branch,5  passing  up  along  the  origin  of  the  anterior  scalenus  and 
greater  pre-rectus  muscles,  supplying  them  with  branches,  and  giving 
off  several  spinal  branches,  which  enter  the  adjacent  intervertebral 
foramina.  Other  branches  from  the  inferior  thyroid  supply  the  anterior 
scalenus  and  infrahyoid  muscles,  the  contiguous  portions  of  the  pharynx 
and  oesophagus,  and  the  larynx  and  trachea. 

The  suprascapular  artery6  springs  from  the  thyroid  axis,  and 
runs  outwardly  and  deeply  in  the  supraclavicular  fossa,  behind  the 
clavicle,  to  the  upper  border  of  the  scapula,  over  which  it  descends  into 
the  supraspinous  fossa,  and  thence  back  of  the  neck  of  the  scapula  into 


1  A.  cerebelli  sup.  2  A.  cerebri  post,  or  profunda. 

3  Arteria  thyreo-cervicalis.  4  A.  thyroidea  inf. 

5  A.  cervicalis  adscendens  ;  a  dorsalis  suprema. 

6  A.  suprascapularis ;  a.  scapularis  superior ;  a.  transversa  scapulae ;  transverse 
scapular  or  transverse  humeral  artery. 


500  THE   ARTERIES. 

the  infraspinous  fossa,  where  it  terminates  by  anastomosing  with  the 
dorsal  and  posterior  scapular  arteries.  In  its  course  it  crosses  the  sca- 
leni  muscles  and  brachial  plexus  of  nerves,  or  sometimes  passes  through 
the  latter,  and  gives  branches  to  the  sterno-mastoid,  subclavian,  and 
other  contiguous  muscles.  Approaching  the  scapula  it  is  joined  by  the 
suprascapular  nerve,  which  passes  through  the  coracoid  foramen,  while 
the  artery  usually  passes  over  it.  It  also  gives  off  a  supra-acromial 
branch,  which  perforates  the  insertion  of  the  trapezius  muscle,  and  is 
distributed  on  the  surface  of  the  acromion,  anastomosing  with  the 
acromial  thoracic  artery.  In  the  supraspinous  fossa  it  distributes 
branches  beneath  the  supraspinatus  muscle,  and  supplies  the  latter, 
the  scapula,  and  the  shoulder-joint. 

The  suprascapular  artery  sometimes  arises  separately  from  the 
subclavian  in  any  lower  position,  and  sometimes  from  the  axillary 
artery  or  from  its  subscapular  branch.  It  is  sometimes  very  small, 
when  it  may  be  compensated  by  a  branch  of  the  posterior  scapular 
artery. 

The  transverse  cervical  artery1  springs  from  the  thyroid  axis, 
and  proceeds  in  a  tortuous  course  outward  beneath  the  sterno-mastoid 
muscle  in  the  supraclavicular  fossa,  a  short  distance  above  the  clavicle 
and  the  preceding  vessel.  Crossing  over  the  scaleni  muscles  and  the 
brachial  plexus  of  nerves,  behind  the  sterno-mastoid  muscle,  to  the 
edge  of  the  trapezius,  it  divides  into  two  branches,  the  superficial  cer- 
vical and  posterior  scapular  arteries.  Sometimes  it  is  very  small,  and 
is  compensated  by  a  considerable  branch  arising  from  the  lower  part 
of  the  subclavian  artery  and  passing  outward  to  near  the  edge  of  the 
trapezius,  where  it  divides  into  two  branches.  Of  these,  one  corre- 
sponds with  the  greater  portion  of  the  superficial  cervical  artery,  and 
the  other  is  the  posterior  scapular  artery. 

The  superficial  cervical  artery 2  ascends  beneath  the  trapezius, 
and  distributes  branches  to  this,  the  scapular  elevator,  and  splenius 
muscles,  and  to  the  skin,  platysma.  and  contiguous  lymphatic  glands 
of  the  neck. 

The  posterior  scapular  artery,3  larger  than  the  preceding,  passes 
backward  within  the  position  of  the  scapular  elevator  to  the  upper 
angle  of  the  scapula,  and  then  descends  within  the  position  of  the 
rhomboid  muscles  to  the  lower  angle  of  the  bone.  It  anastomoses 
with  the  branches  of  the  supra-  and  subscapular  arteries,  and  supplies 
branches  to  the  trapezius,  supraspinatus,  scapular  elevator,  rhomboid, 
serrati,  and  latissimus  muscles.  It  sometimes  arises  from  the  sub- 
clavian directly,  or  from  the  axillary  artery,  in  which  case  usually  the 
transverse  cervical  artery  is  small,  and  continues  as  the  superficial 
cervical  artery. 

1  A.  transversa  colli :  a.  cervico-scapularis.  2  A.  superficialis  cervicis. 

3  A.  scapularis  post.  ;  a.  dorsalis  scapulae  or  descendens. 


THE   ARTERIES.  501 

The  mammary  artery1  springs  from  the  subclavian  below  the 
thyroid  axis,  inclines  forward  and  inward,  and  descends  behind  the 
costal  cartilages,  about  half  an  inch  from  the  lateral  border  of  the 
sternum,  to  the  sixth  intercostal  space,  where  it  terminates  in  the 
musculo-phrenic  and  superior  epigastric  artery.  At  first  crossing  the 
innominate  vein,  with  the  phrenic  nerve  descending  to  its  inner  side, 
it  lies  on  the  pleura,  and  subsequently  in  its  descent  is  placed  between 
the  costal  cartilages  and  the  internal  intercostal  muscles  in  front  and 
the  sternal  triangular  muscle  behind.  Its  numerous  branches  are  as 
follows : 

The  mediastinal  arteries.2  Small  branches  to  the  thymus,  lym- 
phatic glands,  and  pericardium,  in  the  anterior  mediastinum. 

The  phrenic  artery,3  a  slender  vessel  accompanying  the  phrenic 
nerve  to  the  diaphragm.  In  its  descent  it  gives  twigs  to  the  pericardium 
and  pleura. 

The  sternal  branches  to  the  sternum  and  sternal  triangular  muscle. 

The  perforating  arteries,  which  pierce  the  intercostal  muscles 
near  the  sternum,  to  be  distributed  to  the  contiguous  portion  of  the 
greater  pectoral  muscle,  the  mammary  gland,  and  the  skin.  In  the  fe- 
male, during  lactation,  those  which  go  to  the  mammary  gland  become 
much  enlarged. 

The  anterior  intercostal  arteries/  a  pair,  or  one  dividing  into  a 
pair,  for  each  of  the  upper  six  intercostal  spaces,  in  which  they  run 
outwardly  along  the  costal  cartilages.  First  passing  between  the 
pleura  and  the  internal  intercostal  muscle,  and  then  between  the  latter 
and  the  external  intercostal  muscle,  they  anastomose  with  the  aortic 
intercostal  arteries.  They  supply  the  contiguous  portions  of  the 
intercostal  and  pectoral  muscles  and  the  skin. 

The  musculo-phrenic  artery,5  the  outer  terminal  branch  of  the 
mammary,  runs  downward  and  outward  behind  the  asternal  costal  car- 
tilages to  the  last  intercostal  space  along  the  attachment  of  the  dia- 
phragm. It  gives  branches  backward  to  the  latter,  and  furnishes  the 
anterior  intercostal  arteries  to  the  lower  intercostal  spaces,  in  which 
they  are  distributed  in  the  manner  of  the  upper  ones. 

The  superior  epigastric  artery,6  the  remaining  terminal  branch 
of  the  mammary,  descends  between  the  sternal  and  costal  portions  of 
the  diaphragm  into  the  sheath  of  the  abdominal  rectus  muscle.  Con- 
tinuing downward  behind  the  latter,  it  enters  the  muscle,  to  which  it  is 
mainly  distributed,  and  anastomoses  freely  with  the  epigastric  artery 
from  the  external  iliac.  It  supplies  branches  to  the  broad  abdominal 
muscles  and  their  tendons,  to  the  integument,  and  to  the  diaphragm. 

1  Internal  mammary  artery  ;  a.  mammaria  or  thoracica  interim. 

2  A.  mediastinales  anteriores,  thymicse,  etc. 

3  Superior  phrenic  artery  ;    a.  phrenica  sup.  ;    a.  pericardiaco-phrenica ;   comes 
nervi  phrenici. 

4  A.  intercostales  ant.  5  A.  musculo-phrenica.  •  6  A.  epigastrica  sup. 


502  THE   ARTERIES. 

The  superior  intercostal  artery1  springs  from  the  back  of  the 
subclavian  artery,  curves  upward,  backward,  and  outward,  and  de- 
scends in  front  of  the  neck  of  the  first  rib.  After  giving  off  a  branch 
to  the  first  intercostal  space  it  descends  in  front  of  the  second  rib,  to  be 
distributed  in  the  second  intercostal  space.  The  branches  to  the  inter- 
costal spaces  correspond  with  the  aortic  intercostal  arteries,  and  have 
the  same  manner  of  distribution.  The  branch  to  the  second  space 
is  frequently  joined  by  a  branch  from  the  first  of  the  latter,  and  is 
sometimes  replaced  by  it. 

The  deep  cervical  artery 2  arises  from  the  subclavian,  close  to  the 
former,  or  frequently  in  common  with  it,3  passes  backward  over  the 
neck  of  the  first  rib,  and  ascends  the  back  of  the  neck  between  the 
complexus  and  semispinalis  muscles.  It  is  distributed  to  the  latter 
and  other  contiguous  muscles,  gives  off  a  spinal  branch  or  two,  and 
anastomoses  with  branches  of  the  vertebral  and  occipital  arteries. 

Surgical  relation  of  the  subclavian  artery.  In  this  relation 
the  vessel  is  described  in  three  portions :  the  first,  extending  from  the 
origin  of  the  artery  to  the  inner  border  of  the  anterior  scalenus  muscle ; 
the  second,  that  portion  placed  behind  the  latter ;  and  the  third,  that 
extending  from  the  outer  border  of  the  muscle  to  the  outer  border  of 
the  first  rib.  The  branches  of  the  artery  come  off,  for  the  most  part, 
from  the  first  portion,  close  to  the  anterior  scalenus  muscle,  and  partly 
behind  the  latter  from  the  second  portion.  The  first  portion  of  the  left 
subclavian  artery  arising  from  the  aorta  is  much  longer  than  that  of 
the  right  artery  arising  from  the  innominate,  but  from  the  point  where 
the  left  artery  turns  outward  the  two  vessels  are  alike  in  all  respects. 
The  first  portion  of  the  artery,  from  its  comparative  depth  and  other 
circumstances,  is  difficult  of  access.  The  third  portion,  comparatively 
superficial  and  usually  free  from  branches,  is  most  favorably  situated 
for  the  application  of  a  ligature.  After  this  operation  the  circulation 
of  the  upper  limb  is  restored  through  anastomosis  of  the  suprascapular, 
posterior  scapular,  and  subscapular  arteries,  and  also  through  the  inter- 
costals  and  thoracic  branches  of  the  axillary  artery. 

THE  AXILLAEY  ARTEKY. 

The  axillary  artery 4  is  the  continuation  of  the  subclavian  through 
the  axilla,  after  passing  which  the  vessel  becomes  the  brachial  artery. 
Emerging  from  beneath  the  middle  of  the  clavicle,  from  which  it 
is  separated  by  the  subclavian  muscle,  it  lies  along  the  inner  side  of 
the  shoulder-joint  and  upper  extremity  of  the  humerus,  extending  from 
the  outer  border  of  the  first  rib  to  the  outer  border  of  the  axilla,  Its 
direction  varies  with  a  change  in  the  position  of  the  upper  limb,  curving 
outward  and  downward  in  the  usual  pendent  condition  of  the  latter, 

1  A.  intercostalis  suprema.  2  A.  cervicalis  profunda. 

3  A.  costo-cervicalis.  4  A.  axillaris. 


THE   ARTERIES. 


503 


FIG.  263. 


and  passing  directly  outward  when  the  limb  is  horizontally  extended. 
In  succession  it  rests  on  the  first  intercostal  space  and  great  serratus 
muscle,  then  the  subscapular  muscle,  and  finally  the  tendons  of  the 
latissimus  and  greater  teres  mus- 
cles. It  is  at  first  covered  by  the 
subclavian  and  then  by  the  pec- 
toral muscles.  The  axillary  vein 
lies  to  its  inner  side.  The  brachial 
plexus  of  nerves  is  first  situated 
above  and  partly  behind  it,  at 
the  middle  surrounds  it,  and  di- 
verges below. 

The  branches  of  the  axillary 
artery,  very  variable  in  number, 
origin,  and  size,  commonly  con- 
sist of  three  thoracic  arteries,1 
the  subscapular  artery,  and  two 
circumflex  arteries. 

The  superior  thoracic  ar- 
tery,2 usually  a  small  branch, 
comes  from  near  the  commence- 
ment of  the  axillary  and  descends 
forward  between  the  pectoral 
muscles,  to  which  it  is  distributed, 
giving  also  branches  to  the  con- 
tiguous portion  of  the  great  ser- 
ratus muscle,  the  mammary  gland,  and  the  skin. 

The  acromial  thoracic  artery,3  succeeding  the  former,  is  directed 
outwardly  between  the  pectoral  muscles,  to  which,  the  subclavian  mus- 
cle, and  the  contiguous  portions  of  the  great  serratus  and  deltoid  mus- 
cles, it  is  distributed.  A  slender  branch  descends  in  the  groove,  occu- 
pied by  the  cephalic  vein,  between  the  deltoid  and  pectoral  muscles,  to 
which  and  the  adjacent  skin  it  is  distributed.  The  acromial  branch 
ascends  outwardly  beneath  the  origin  of  the  deltoid  muscle,  supplying 
the  shoulder-joint  and  perforating  the  former  to  ramify  over  the  sur- 
face of  the  acromion  and  anastomose  with  the  acromial  branch  of  the 
suprascapular  artery.  , 

The  inferior  thoracic  artery4  descends  at  the  side  of  the  chest 
along  the  lower  border  of  the  small  pectoral  muscle  and  on  the  great 
serratus  muscle,  to  which  and  the  greater  pectoral  muscle  it  is  dis- 
tributed. It  anastomoses  with  branches  of  the  contiguous  intercostal 
arteries  and  of  the  subscapular  artery. 

1  A.  thoracicae  externae.  2  A.  thoracica  suprema,  prima,  or  minor. 

3  A.  thoracica  acromialis  or  humeraria. 

4  Long  thoracic  artery ;   a.  thoracica   inferior,  longa,  or  major ;   a.  mammaria 
externa. 


VIEW  OF  THE  AXILLARY  ARTERY  ;   portions  Of 

the  pectoral  and  deltoid  muscles  removed.  1, 
axillary  artery ;  2,  superior  thoracic ;  3,  acromial 
thoracic  ;  4,  inferior  thoracic ;  5,  subscapular ;  6, 
anterior  circumflex ;  7,  posterior  circumflex ;  8, 
brachial  artery ;  9,  superior  profunda  artery. 


504  THE    ARTERIES. 

The  inferior  thoracic  artery  sometimes  comes  off  in  common  with 
the  acromial  thoracic.  Sometimes  it  is  very  small  or  is  absent,  when 
it  may  be  substituted  by  a  branch  of  the  subscapular  artery. 

A  branch1  or  several  smaller  ones  from  the  axillary  artery,  or 
from  one  or  several  of  the  above-named  thoracic  arteries,  supply  the 
axillary  lymphatic  glands.  Not  unfrequently,  also,  one  or  two  sepa- 
rate muscular  branches  from  the  axillary  artery  go  to  the  pectoral 
muscles. 

The  subscapular  artery,2  the  largest  branch  of  the  axillary,  arises 
near  the  lower  border  of  the  subscapular  muscle,  on  which  it  descends 
in  a  flexuose  manner  and  divides  into  two  branches.  Of  these  the 
smaller  or  descending  branch,3  continuing  in  the  course  of  the  trunk 
towards  the  lower  angle  of  the  scapula,  proceeds  downward  between 
the  great  serratus  and  latissimus  muscles,  to  which  and  the  subscap- 
ular and  teres  muscles  it  is  distributed.  The  larger  dorsal  branch,4 
derived  about  an  inch  from  the  origin  of  the  trunk,  turns  backward 
around  the  outer  border  of  the  scapula,  between  the  greater  teres  and 
the  subscapular  muscle,  and  enters  the  infraspinous  fossa,  in  which  it 
ramifies  and  anastomoses  with  the  suprascapular  and  posterior  scapular 
arteries.  It  furnishes  branches  to  the  subscapular  and  teres  muscles, 
the  long  head  of  the  triceps,  and  the  infraspinatus  muscles. 

The  anterior  circumflex  artery,5  a  small  branch,  arises  just  below 
the  former,  and  passes  forward  between  the  common  head  of  the 
biceps  and  coraco-brachialis  muscles  and  the  humerus  to  the  bicipital 
groove,  where  it  divides  into  a  branch  ascending  the  latter  to  the 
shoulder-joint,  and  another  continuing  outward  to  anastomose  with  the 
succeeding  artery. 

The  posterior  circumflex  artery,6  second  in  size  to  the  subscap- 
ular artery,  arises  below  this  and  passes  backward  between  the  teres 
muscles.  Winding  around  the  humerus,  between  this  and  the  triceps 
muscle,  it  breaks  up  into  branches  distributed  to  the  deltoid  muscle. 
It  also  gives  branches  to  the  triceps  muscle  and  the  skin,  and  anasto- 
moses with  the  anterior  circumflex,  acromial  thoracic,  and  superior 
profunda  arteries. 

THE  BRACHIAL   AKTEKY. 

The  brachial  artery,7  the  continuation  of  the  axillary,  extends 
along  the  inner  part  of  the  arm  from  the  outer  border  of  the  axilla 
to  the  bend  of  the  elbow,  where  it  terminates  by  dividing  into  the 
radial  and  ulnar  arteries.  In  the  usual  position  of  the  upper  limb, 

1  Axillary  or  alar  thoracic  artery  ;  a.  thoracica  axillaris  or  alaris. 

2  A.  subscapularis  or  infrascapularis  ;  a.  scapularis  inferior  or  communis. 

3  Ram  us  descendens,  thoracica  longa,  or  thoracica  dorsalis. 

4  A.  dorsalis  scapulae  ;  a.  circumflexa  scapulas. 

5  A.  circumflexa  anterior.  6  A.  c.  posterior. 
7  A.  brachialis  ;  a.  humeraria. 


THE   ARTERIES. 


505 


Fio.  264. 


in  the  descent  of  the  vessel  it  gradually  inclines  from  the  inner  side 

forward  to  the  central  depression  in  front  of  the  elbow.     In  its  course 

it  lies  in  the  groove  along  the  inner  border  of  the  coraco-brachialis  and 

biceps  muscles,  resting  above  on  the  triceps  and  below  on  the  brachi- 

alis    muscle,   and    covered    by   the 

fasciae  and  skin.     Approaching  its 

termination,  it  sinks  in  the  interval 

between   the    terete   pronator  and 

long  supinator  muscles,  covered  by 

the  offset  of  the  biceps  tendon  to 

the  fascia  of  the  forearm. 

The  two  brachial  veins  and  the 
median  nerve  accompany  the  bra- 
chial artery,  included  in  the  same 
sheath.  The  veins  lie  at  the  inner 
and  outer  sides  of  the  artery,  united 
here  and  there  by  branches  crossing 
the  latter.  The  nerve  at  first  lies 
to  the  outer  side  of  the  artery,  in 
its  descent  gradually  crosses  the 
vessel,  and  then  lies  to  the  inner 
side.  The  basilic  vein  lies  along 
the  inner  side  of  the  artery,  sepa- 
rated from  it  below  by  the  deep 
fascia.  The  musculo-spiral  nerve 
is  behind  the  artery  for  a  short 
distance  above.  The  ulnar  nerve 
lies  at  the  inner  side  to  near  the 
middle  of  the  arm,  when  it  gradually 
diverges  to  the  internal  condyle ; 
and  the  internal  cutaneous  nerve 
runs  in  front  and  at  the  inner  side 
to  near  the  same  position,  when  it 
pierces  the  fascia  to  become  subcu- 
taneous. The  median  basilic  vein 
crosses  the  artery  at  the  bend  of 
the  elbow,  separated  by  the  offset  from  the  biceps  tendon  to  the  fascia 
of  the  forearm. 

In  the  extended  position  of  the  upper  limb  horizontally  outward 
from  the  body,  a  line  from  the  middle  of  the  clavicle  to  the  depression 
in  front  of  the  elbow  indicates  the  continued  course  of  the  axillary  and 
brachial  artery. 

Variations  of  the  brachial  artery.  Earely  it  divides  in  its 
course,  and  the  two  vessels  again  reunite  approaching  the  elbow.  Oc- 
casionally, a  long  slender  vessel  arises  from  the  brachial  or  from  the 
axillary,  and  descends  superficially  to  join  one  of  the  arteries  of  the 


1214 


VIEW  OF  THE  AXILLARY  AND  BEACHIAL  AR- 
TERY; portions  of  the  pectoral  and  deltoid 
muscles  removed.  1,  axillary  artery ;  2,  bra- 
chial artery ;  3,  superior  thoracic  artery ;  4, 
acromial  thoracic ;  5,  inferior  thoracic ;  6,  sub- 
scapular  ;  7,  anterior  circumflex ;  8,  posterior 
circumflex;  9,  superior  profunda,  the  first 
branch  of  the  brachial  artery ;  10,  inferior  pro- 
funda ;  11,  anastomotica ;  12,  radial ;  13,  ulnar; 
14,  interosseous ;  15,  radial  recurrent ;  16,  ulnar 
recurrent  artery. 


506  THE   ARTERIES. 

forearm,  usually  the  radial  artery.  Besides  the  variations  in  the  origin 
of  the  branches  arising  in  the  course  of  the  brachial  artery  above  indi- 
cated, variations  in  the  origin  of  the  terminal  branches  are  of  frequent 
occurrence.  The  radial  or  ulnar  artery,  or  the  interosseous  artery 
normally  a  branch  of  the  latter,  may  arise  at  any  position  of  the 
brachial  or  may  come  from  the  axillary  artery.  Either  arises  more 
frequently  from  the  upper  part  of  the  brachial  than  from  the  middle 
or  lower  part.  In  this  condition  there  appear  to  be  a  pair  of  brachial 
arteries,  as  the  two  vessels  commonly  lie  close  together,  and  usually 
the  additional  vessel  is  the  more  superficial.  The  radial  artery  is  most 
frequently  the  abnormal  vessel,  and  the  interosseous  artery  most  rarely. 
"When  the  radial  artery  is  the  abnormal  one,  it  usually  runs  along  the 
inner  side  of  the  larger  brachial  artery  to  the  front  of  the  elbow, 
where  it  crosses  over  or  occasionally  under  the  latter  vessel  to  its 
ordinary  position  at  the  outer  part  of  the  forearm.  When  the  ulnar 
artery  is  the  abnormal  one,  as  it  descends  the  arm  at  the  lower  part  it 
diverges  from  the  brachial  towards  the  inner  part  of  the  elbow,  and 
passes  over  the  origin  of  the  flexors  of  the  forearm,  beneath  but  some- 
times above  the  fascia,  to  the  inner  side.  The  abnormal  interosseous 
artery  usually  descends  behind  the  brachial  to  the  bend  of  the  elbow, 
where  it  dips  between  the  muscles  to  pursue  its  usual  course. 

In  addition  to  a  number  of  variable  small  branches  to  the  contiguous 
muscles,  and  integument,  the  brachial  artery  gives  off  the  following- 
named  branches : 

The  superior  profunda  artery,1  the  largest  branch,  springs  from 
behind  the  brachial  artery  below  the  border  of  the  latissimus  muscle, 
and  descends  outwardly  in  the  groove  at  the  back  of  the  humerus  in 
company  with  the  musculo-spiral  nerve,  covered  by  the  triceps  muscle. 
It  distributes  branches  to  the  heads  of  the  latter,  and  at  the  outer 
part  of  the  humerus,  below  the  insertion  of  the  deltoid  muscle,  divides 
into  two  terminal  branches.  Of  these  the  smaller  continues  in  company 
with  the  musculo-spiral  nerve,  and  descends  in  the  interval  of  the 
brachialis  and  long  supinator  muscles,  to  which  it  gives  branches,  and 
anastomoses  with  the  radial  recurrent  artery.  The  other  and  deeper 
branch  descends  behind  the  external  intermuscular  septum  and  epi- 
condyle  of  the  humerus,  and  anastomoses  with  the  posterior  inter- 
osseous recurrent  artery,  and  across  the  back  of  the  bone  with  the 
inferior  profunda  and  anastomotica. 

The  inferior  profunda  artery,2  a  very  variable  and  usually  much 
smaller  branch  than  the  preceding,  arises  from  near  the  middle  of  the 
brachial  artery,  and  descends  in  company  with  the  ulnar  nerve  behind 
the  intermuscular  septum  on  the  triceps  muscle  to  the  inner  epicondyle. 

1  A.  profunda  superior;  a.  p.  humeri ;  a.  brachialis  profunda;  a.  collaterals 
magna  or  externa. 

2  A.  p.  inferior;  a.  collateralis  ulnaris  superior  or  prima. 


THE   AETEEIES.  507 

It  gives  branches  to  the  triceps  muscle,  and  anastomoses  with  the  anas- 
tomotica  artery  in  front  and  with  the  superior  profunda  and  posterior 
interosseous  recurrent  arteries  across  the  back  of  the  humerus. 

The  medullary  nutritious  artery,1  a  small  vessel,  comes  from  the 
brachial,  or  from  one  of  its  muscular  branches  or  the  inferior  profunda, 
and  traverses  the  medullary  nutritious  canal  of  the  humerus  to  the 
interior  marrow. 

The  anastomotica  artery,2  a  constant  but  small  branch,  arises 
from  the  lower  part  of  the  brachial  artery,  and  descends  on  the  brachi- 
alis  muscle  to  the  internal  epicondyle,  where  it  anastomoses  in  front 
with  the  inferior  profunda  and  anterior  ulnar  recurrent  arteries,  and 
behind  with  the  superior  profunda  and  posterior  interosseous  recur- 
rent arteries.  It  gives  branches  to  the  brachialis  and  terete  pronator 
muscles  and  to  the  elbow-joint. 

The  superior  profunda  artery  sometimes  arises  directly  from  the 
axillary,  and  sometimes  it  is  derived  from  a  common  trunk,  together 
with  the  subscapular  and  circumflex  arteries.  The  inferior  profunda 
not  unfrequently  arises  from  the  superior  profunda ;  and  in  like  manner 
the  anastomotica  frequently  springs  from  the  former. 

KADIAL   ARTERY. 

The  radial  artery,3  somewhat  smaller  than  the  ulnar,  appears 
more  like  the  continuation  of  the  brachial  artery,  from  its  pursuing 
the  same  direction,  in  a  line  from  the  central  depression  in  front  of 
the  elbow  to  the  front  of  the  styloid  process  of  the  radius.  More 
superficial  than  the  ulnar  artery,  it  occupies  the  outer  side  of  the 
front  of  the  forearm,  in  a  straight  line  parallel  with  the  radius  to  the 
wrist,  where  it  turns  back  around  the  outer  part  of  the  carpus,  and 
descends  to  the  upper  angle  of  the  first  interosseous  space.  Here  it 
penetrates  to  the  palm  of  the  hand,  and  curves  inward  to  join  the 
deep  communicating  branch  of  the  ulnar  artery,  and  thus  form  the 
deep  palmar  arch.4  In  its  course  in  front  of  the  forearm,  with  its 
pair  of  companion  veins,  it  rests  in  succession  on  the  short  supinator, 
the  insertion  of  the  terete  pronator,  the  radial  origin  of  the  superficial 
digital  flexor,  the  long  pollical  flexor,  the  quadrate  pronator,  and  the 
lower  extremity  of  the  radius.  To  its  outer  side  is  the  long  supinator, 
the  inner  edge  of  which  covers  it  above,  while  it  is  covered  below  by 
the  fasciae  and  skin  only.  To  its  inner  side  are  the  terete  pronator 
and  long  palmar  muscles.  Along  the  middle  of  its  course  outwardly 
it  is  accompanied  by  the  radial  nerve.  Below  the  styloid  process  of 
the  radius  the  artery  passes  backward  around  the  carpus,  beneath  the 
extensor  tendons  of  the  thumb,  and,  reaching  the  first  interosseous 

1  A.  nutritia  humeri. 

2  A.  anastomotica ;  a.  collateralis  interna ;   a.  c.  ulnaris  inferior  or  secunda. 

3  A.  radialis.  4  Arcus  palmaris  profundus  ;  a.  volaris  prof. 


508 


THE   ARTERIES. 


FIG.  265. 


space,  penetrates  between  the  heads  of  the  interosseous  muscle  to 
the  palm  of  the  hand.  The  deep  palmar  arch  rests  on  the  metacarpal 
bones  and  interosseous  muscles,  beneath  the 
flexor  tendons  of  the  fingers;  it  is  situated 
nearer  the  carpus  than  the  superficial  arch, 
and  is  also  of  more  uniform  diameter. 

The  branches  of  the  radial  artery  and  its 
continuation  the  deep  palmar  arch,  in  addition 
to  small  and  variable  muscular  and  cutane- 
ous branches  to  the  contiguous  muscles  and 
skin,  are  as  described  below. 

The  radial  recurrent  artery,1  of  variable 
size,  arises  near  the  origin  of  the  radial  artery, 
and  is  directed  outward  and  upward  between 
the  long  supinator  and  brachialis  muscles,  to 
which  it  gives  branches,  and  anastomoses  with 
the  superior  profunda  artery.  It  also  gives 
branches  outward  and  downward  to  the  long 
supinator  and  radio-carpal  extensors,  and  be- 
neath them  anastomoses  with  the  interosseous 
recurrent  artery. 

The  radial  recurrent  artery  is  sometimes 
much  enlarged,  and  not  unfrequently  is  repre- 
sented by  several  branches.  It  is  sometimes 
derived  from  the  brachial,  especially  when  the 
radial  artery  rises  high  up  from  the  latter,  or 
less  commonly  it  comes  from  the  ulnar.  or 
rarely  from  the  interosseous  artery. 

The  anterior  carpal  artery,2  a  little 
branch  from  the  radial  below  the  quadrate 
pronator,  proceeds  inward  beneath  the  flexor 
tendons  to  the  front  of  the  carpus,  where  it 
anastomoses  with  a  similar  branch  of  the 
ulnar  artery  to  form  the  anterior  carpal 
arch.3  The  arch  also  anastomoses  with  the 
communicating  branch  of  the  anterior  inter- 
osseous artery  of  the  forearm  and  with  the 
recurrent  branches  of  the  deep  palmar  arch, 

and  forms  a  fine  net-work  of  vessels  supplying  the  contiguous  articu- 
lations. 

The  volar  artery,4  usually  a  small  branch,  arises  from  the  radial 


ARTERIES  OF  THE  FOREARM. 
2,  brachial  artery;  3,  anasto- 
motic  artery  ;  4,  radial  artery ; 
5,  ulnar  artery ;  6,  ulnar  recur- 
rent; 7,  interosseous;  8,  ante- 
rior carpal ;  9,  volar  artery ; 
10,  anterior  carpal  branch  of 
the  ulnar ;  11,  superficial  pal- 
mar arch ;  12,  digital  artery  of 
the  thumb;  13,  radial  digital 
artery  of  the  index  finger ;  14, 
digital  arteries;  15,  recurrent 
branches. 


1  A.  radialis  recurrens. 

2  A.  carpea  anterior ;  a.  radio-carpalis  ant. ;  a.  carpea  volaris  ;  a.  transversa  carpi 
anterior.  3  Kete  carpeum  anterius  or  volare. 

4  Eamus  volaris  ;  superficial  volar  artery  ;  a.  superficialis  volae  ;  a.  radio-palmaris. 


THE    ARTERIES. 


509 


near  where  this  turns  to  the  back  of  the  wrist,  and  descends  subcuta- 
neously  to  the  ball  of  the  thumb,  to  the  muscles  and  skin  of  which  it 
distributes  branches,  and 
in  the  palm  of  the  hand 
anastomoses  with  the  ter- 
mination of  the  ulnar  ar- 
tery to  form  the  super- 
ficial palmar  arch.1 

The  volar  artery  may 
be  distributed  to  the  ball 
of  the  thumb  alone,  and 
take  no  part  in  the  super- 
ficial palmar  arch.  Some- 
times it  rises  much 

I 

higher,  and  may  be 
much  enlarged,  so  as  to 
appear  like  one  of  the 
terminal  divisions  of  the 
radial  artery,  in  which 
case  it  usually  supplies 
the  digital  arteries  to 
the  thumb  and  contigu- 
ous side  of  the  index 
finger,  and  does  not  con- 
tribute to  form  the  super- 
ficial palmar  arch. 

The  posterior  carpal  artery,2  a  small  branch,  arises  from  the  radial, 
beneath  the  extensor  tendons  of  the  thumb,  and  proceeds  to  the  car- 
pus, where  it  anastomoses  with  the  corresponding  branch  of  the  ulnar 
artery  to  form  the  posterior  carpal  arch.  This  also  anastomoses 
above  with  the  termination  of  the  anterior  interosseous  artery  of  the 
forearm,  supplies  the  contiguous  articulations,  and  gives  off  below  two 
dorsal  metacarpal  arteries,3  the  second  and  third  of  the  series  of 
these  vessels.  Joined  each  at  their  commencement  by  a  short  com- 
municating branch4  from  the  deep  palmar  arch,  they  descend  on 
the  inner  two  dorsal  interosseous  muscles  to  the  cleft  of  the  fingers, 
whei'e  they  divide  each  into  a  pair  of  dorsal  digital  branches.  These 
run  along  the  adjoining  sides  of  the  middle,  ring,  and  little  fingers,  to 
the  first  phalangeal  articulation,  and  anastomose, with  branches  of  the 
adjacent  palmar  digital  arteries. 

1  Arcus  palmaris  superficialis. 

2  A.  carpea  posterior  or  dorsalis ;  a.  transversa  carpi  dorsalis ;  posterior  radio- 
carpal  artery. 

3  A.  metacarpa?  dorsales  ;  a.  interossese  dorsales  ;  second  and  third  dorsal  inter- 
osseous arteries. 

4  Ramus  interossea  perforans  ;  perforating  artery. 


ARTERIES  OF  THE  HAND;  PALMAR  SURFACE.  1,  radial  ar- 
tery; 2,  ulnar;  3,  communicating  branch  with  the  deep 
palmar  arch ;  4,  superficial  palmar  arch ;  5,  volar  artery ;  6, 
digital  arteries  of  the  thumb ;  7,  radial  digital  artery  of  the 
index  finger ;  8,  digital  artery  to  the  little  finger ;  9,  common 
digital  arteries ;  10,  digitals  to  the  fingers. 


510  THE   ARTERIES. 

Succeeding  the  posterior  carpal  artery,  but  often  arising  in  common 
with  it,  is  the  first  dorsal  metacarpal  artery,1  which  proceeds  on 
the  second  dorsal  interosseous  muscle,  and  ends  in  a  pair  of  dorsal 
digital  branches  to  the  adjacent  sides  of  the  middle  and  index  finger. 
It  is  connected  with  the  deep  palmar  arch  by  a  communicating 
branch,2  and  also  before  division  through  another  communicating 
branch3  with  the  contiguous  digital  artery.  Occasionally  the  other 
dorsal  metacarpal  arteries  in  like  manner  communicate  with  the 
adjacent  digitals. 

Sometimes  the  first  dorsal  metacarpal  artery  is  much  larger  than 
usual,  and  furnishes  the  palmar  digital  branches  of  the  middle  and 
index  fingers. 

Following  these  vessels  are  the  dorsal  digital  branches  *  of  the 
thumb,  arising  separately  or  together  from  the  radial  artery,  near  the , 
base  of  the  metacarpal  bone,  along  the  back  of  which  they  run  on  each 
side  of  the  last  phalanx.  Succeeding  these,  or  arising  together  with 
them,  is  a  dorsal  digital  branch,5  running  along  the  radial  side  of 
the  index  finger  to  the  first  phalangeal  articulation. 

Commonly,  as  the  radial  artery  enters  the  palm  of  the  hand,  be- 
tween the  heads  of  the  first  dorsal  interosseous  muscle,  it  gives  off  the 
palmar  digital  arteries  to  the  thumb  and  adjacent  side  of  the  index 
finger. 

The  digital  artery6  of  the  thumb  descends  in  front  of  the  first 
dorsal  interosseous  muscle,  between  the  metacarpal  bone  of  the  thumb 
and  the  muscles  covering  it,  to  the  interval  of  the  short  pollical  flexor, 
and  divides  under  the  tendon  of  the  long  pollical  flexor  into  two 
branches,  which  run  along  the  sides  of  the  thumb. 

The  digital  artery 7  of  the  index  finger  arises  from  the  radial,  close 
to  the  former,  or  in  common  with  it,  proceeds  between  the  first  dorsal 
interosseous  and  pollical  adductor  muscles,  and  continues  along  the 
radial  side  of  the  index  finger.  Frequently  it  arises  in  common  with 
the  inner  branch  of  the  digital  artery  of  the  thumb. 

Occasionally  the  digital  artery  of  the  thumb  arises  from  the  radial 
before  it  enters  the  palm  of  the  hand,  in  which  case  it  descends  behind 
the  first  dorsal  interosseous  muscle  to  the  interval  of  the  thumb  and 
index  finger,  where  it  may  end  in  the  two  branches  to  the  thumb,  or, 
in  addition,  give  off  the  contiguous  digital  artery  of  the  index  finger. 

Sometimes  the  radial  artery  appears  to  divide  at  the  back  of  the 
wrist  into  two  branches,  of  which  the  outer  passes  in  the  usual  manner 
between  the  heads  of  the  first  dorsal  interosseous  muscle  to  the  palm 

1  First  dorsal  interosseous  artery.  2  First  perforating  artery. 

8  Inferior  perforating  artery. 

4  Dorsal  arteries  of  the  thumb ;  a.  dorsales  pollicis. 

5  Dorsal  artery  of  the  index  finger  ;  a.  dorsalis  indicis. 

6  Principal  or  large  artery  ;  a.  pollicis  princeps  or  magna. 

7  Kadial  hranch  ;  a.  radialis  indicis  ;  a.  volaris  indicis  radialis. 


THE   ARTEEIES.  511 

of  the  hand,  and  terminates  in  the  digitals  of  the  thumb  and  contiguous 
side  of  the  index  finger,  while  the  other  branch  pursues  the  usual  course 
of  the  first  perforating  artery,  and  continues  as  the  deep  palmar  arch. 

The  recurrent  branches  of  the  latter,  four  or  five  little  arteries, 
ascend  from  the  deep  palmar  arch,  and  anastomose  with  the  anterior 
carpal  arch. 

The  communicating  arteries,1  usually  three,  pass  from  the  deep 
palmar  arch  backward  through  the  upper  extremity  of  the  inner  three 
interosseous  spaces,  to  join  the  dorsal  metacarpal  arteries. 

The  palmar  metacarpal  arteries,2  usually  three,  from  the  deep 
palmar  arch,  descend  on  the  interosseous  muscles  of  the  inner  three 
spaces,  which  they  supply,  and  at  the  clefts  of  the  fingers  anastomose 
with  the  digital  arteries.  Sometimes  they  are  unusually  enlarged,  and 
in  a  measure  substitute  the  digital  arteries  of  the  superficial  palmar 
arch,  which  are  then  proportionately  small. 

ULNAK  ARTERY. 

The  ulnar  artery,3  the  larger  of  the  two  terminal  branches  of  the 
brachial  artery,  runs  inward  and  downward  along  the  inner  side  of  the 
front  of  the  forearm  and  wrist  to  the  palm  of  the  hand,  where  it  ends 
in  the  superficial  palmar  arch.  From  its  commencement  it  passes  in- 
ward and  downward,  resting  on  the  insertion  of  the  brachialis  muscle, 
under  cover  of  the  muscles  arising  from  the  inner  epicondyle  of  the 
humerus,  and  then  descends  the  forearm,  resting  on  the  deep  digital 
flexor,  with  the  ulno-carpal  flexor  to  the  inner  side,  and  the  superficial 
digital  flexor  covering  it.  Near  the  wrist  it  rests  on  the  quadrate  pro- 
nator,  with  the  tendons  of  the  digital  flexors  to  the  radial  side,  and  the 
tendon  of  the  ulno-carpal  flexor  to  the  inner  side,  covered  by  the  fascia 
and  skin.  At  the  wrist  it  passes  over  the  anterior  annular  ligament, 
guarded  inwardly  by  the  pisiform  bone,  and  covered  by  the  superficial 
palmar  muscle.  Entering  the  palm  of  the  hand,  it  arches  outwardly, 
and  anastomoses  with  the  volar  branch  of  the  radial  artery  to  form  the 
superficial  palmar  arch,  which  rests  on  the  flexor  tendons,  just  below 
the  annular  ligament,  covered  by  the  palmar  fascia.  The  ulnar  artery 
is  accompanied  by  a  pair  of  veins,  and  in  the  lower  two-thirds  of  its 
course  by  the  ulnar  nerve,  which  at  the  wrist  intervenes  between  the 
vessels  and  the  pisiform  bone.  Near  its  commencement  the  artery  is 
crossed  by  the  median  nerve,  separated  from  it  by  a  slip  of  the  terete 
pronator  muscle. 

The  branches  of  the  ulnar  artery  including  the  superficial  palmar 
arch,  besides  a  variable  number  of  small  muscular  branches  to  the 

1  Perforating  arteries ;   a.  perforantes ;  r.  interosseae  perforantes ;  superior  per- 
forating branches. 

2  A.  metacarpeae  or  interosseae  volares  ;  palmar  interosseous  arteries. 

3  A.  ulnaris  or  cubitalis. 


512  THE    ARTERIES. 

contiguous  muscles,  give  off  the  ulnar  recurrent,  interosseous,  posterior 
and  anterior  carpal,  deep  communicating,  and  digital  arteries. 

The  ulnar  recurrent  artery,1  a  considerable  branch  from  near  the 
commencement  of  the  ulnar  artery,  turns  inward  beneath  the  muscles 
arising  from  the  inner  epicondyle  of  the  humerus,  and  divides  into  two 
branches.  Of  these,  the  anterior  branch 2  ascends  on  the  brachialis 
muscle,  and  anastomoses  with  the  anastomotica  artery.  The  posterior 
branch 3  turns  backward,  and  ascends  in  company  with  the  ulnar  nerve 
between  the  olecranon  and  inner  epicondyle,  and  the  two  heads  of  the 
ulno-carpal  flexor,  and  anastomoses  with  the  inferior  profunda,  anasto- 
motica, and  interosseous  recurrent  arteries.  The  branches  are  distrib- 
uted to  the  muscles  arising  from  the  internal  epicondyle.  the  brachialis, 
ulno-carpal  flexor,  insertion  of  the  triceps,  the  articulation  of  the  elbow, 
and  the  contiguous  skin.  Frequently  the  two  principal  branches  arise 
separately  from  the  ulnar  artery,  and  occasionally  one  or  both  together 
arise  from  the  brachial  artery,  or  from  the  succeeding  branch. 

The  interosseous  artery,4  the  largest  branch,  arises  from  the 
ulnar  artery,  below  the  bicipital  tuberosity  of  the  radius,  and  after  a 
short  course  backward  divides  into  two  nearly  equal  branches.  Of 
these,  the  anterior  interosseous  artery5  descends  in  front  of  the 
interosseous  membrane,  between  the  deep  digital  and  long  pollical 
flexors,  to  the  quadrate  pronator,  above  which  it  perforates  the  mem- 
brane, and  descends  behind  this  to  the  back  of  the  carpus,  where  it  an- 
astomoses with  the  posterior  carpal  arteries.  Near  its  commencement 
it  gives  off  the  median  artery,  usually  a  long,  slender  branch,  accom- 
panying the  median  nerve.  In  its  course  it  gives  muscular  branches 
to  the  contiguous  muscles  and  the  medullary  nutritious  arteries, 
which  enter  the  corresponding  canals  of  the  radius  and  ulna.  As  it  is 
about  to  perforate  the  interosseous  membrane  it  gives  off  the  commu- 
nicating branch,  which  descends  beneath  the  quadrate  pronator  to 
the  front  of  the  carpus,  where  it  anastomoses  with  the  anterior  carpal 
arteries. 

The  posterior  interosseous  artery6  passes  backward  through 
the  aperture  above  the  interosseous  membrane,  and,  appearing  behind 
and  between  the  short  supinator  and  first  pollical  extensor,  descends 
the  back  of  the  forearm,  between  the  superficial  digital  and  the  pollical 
and  indical  extensors,  to  the  back  of  the  carpus,  where  it  anastomoses 
with  the  anterior  interosseous  and  posterior  carpal  arteries.  Besides 
muscular  branches  to  the  contiguous  muscles  in  its  course,  near  its 
origin  it  gives  off  the  interosseous  recurrent  branch,7  which  as- 
cends beneath  the  anconeus,  between  the  olecranon  and  outer  epicon- 

1  A.  ulnaris  recurrens.  2  Anterior  ulnar  recurrent  artery. 

3  Posterior  ulnar  recurrent  artery.  4  A.  interossea. 

5  A.  interossea  anterior  or  interna. 

6  A.  interossea  posterior,  externa,  or  perforans  suprema. 

7  Posterior  interosseous  recurrent  artery  ;  a.  interossea  recurrens. 


THE  ARTERIES. 


513 


dyle,  where  it  anastomoses  with  the  superior  profunda  and  the  ulnar 
and  radial  recurrent  arteries. 

Sometimes  the  interosseous  artery  is  a  branch  of  the  brachial,  and 
rarely  of  the  radial.  When  the  ulnar  artery  arises  above  its  usual 
position  from  the  brachial,  this  then  divides  into  the  radial  and  inter- 
osseous  arteries.  The  anterior  and  posterior  interosseous  arteries  may 
arise  separately  from  the  ulnar  artery.  Occasionally  the  anterior  inter- 
osseous artery  is  of  larger  size,  and  through  its  enlarged  median  or  an- 
terior communicating  branch  may  join  the  superficial  arch,  and  in  a 
measure  substitute  the  ulnar  or  radial  artery  in  the  supply  of  the  hand. 
Sometimes  in  this  enlarged  condition  it  gives  off  a  transverse  branch, 
which  joins  the  radial,  or  more  rarely  the  ulnar  artery. 

The  posterior  carpal  artery,1  variable  in  size  and  exact  position, 
arises  from  the  ulnar  artery  above  the  wrist,  and  winds  around  the  ulna 
under  the  tendon  of  the 
ulno-carpal  flexor,  and 
proceeds  beneath  the  ex- 
tensor tendons  to  the 
back  of  the  carpus,  where 
it  anastomoses  with  the 
posterior  carpal  branch 
of  the  radial  artery  to 
form  the  posterior  carpal 
arch.  From  the  same 
artery,  or  sometimes  di- 
rectly from  the  ulnar, 
a  small  dorsal  digital 
branch2  runs  along  the 
inner  border  behind  of 
the  metacarpal  bone  and 
first  phalanx  of  the  little 
finger.  The  posterior 
carpal  arch  anastomoses 
with  terminal  branches 
of  the  anterior  interosse- 
ous artery,  and  gives  off 
below  two  dorsal  meta- 
carpal arteries,3  which 
are  joined  by  two  short  communicating  branches,4  proceeding  from 
the  deep  palmar  arch.  The  dorsal  metacarpal  arteries  then  descend 
on  the  inner  two  dorsal  interosseous  muscles  to  the  clefts  of  the 
corresponding  fingers,  and  divide  each  into  a  pair  of  dorsal  digital 


ARTERIES  OF  THE  HAND;  PALMAK  SURFACE.  1,  radial' ar- 
tery; 2,  ulnar;  3.  communicating  branch  with  the  deep 
palmar  arch ;  4,  superficial  palmar  arch ;  5,  volar  artery ;  6, 
digital  arteries  of  the  thumb ;  7,  radial  digital  artery  of  the 
index  finger ;  8,  digital  artery  to  the  little  finger ;  9,  common 
digital  arteries ;  10,  digitals  to  the  fingers. 


1  A.  carpea  dorsalis  ;  a.  dorsalis  ;  post,  ulno-carpal  artery. 

2  Metacarpal  branch  ;  a.  digitalis  dorsalis. 

3  Second  and  third  dorsal  interosseous  arteries.  4  Perforating  arteries. 

33 


514  THE   AKTERIES. 

branches,  which  run  along  the  contiguous  borders  of  the  first  pha- 
langes to  the  first  phalangeal  articulation,  where  they  anastomose  with 
branches  of  the  palmar  digital  arteries. 

Near  the  pisiform  bone  a  little  branch,  or  two,  the  anterior  carpal 
artery,1  proceeds  from  the  ulnar  artery  beneath  the  flexor  tendons  to 
the  front  of  the  carpus,  and  anastomoses  with  a  similar  branch  of  the 
radial  artery. 

The  deep  communicating  artery 2  comes  from  the  ulnar  artery 
below  the  pisiform  bone,  and  dips  between  the  abductor  and  short 
flexor  of  the  little  finger  into  the  palm  of  the  hand,  where  it  joins  the 
termination  of  the  radial  artery  to  form  the  deep  palmar  arch.  It 
distributes  branches  to  the  muscles  of  the  little  finger. 

The  digital  arteries,3  usually  four  from  the  superficial  palmar 
arch,  diverge  in  the  intervals  of  the  flexor  tendons,  resting  on  the 
lumbrical  muscles  and  digital  nerves.  The  innermost  digital  artery 
proceeds  to  the  inner  side  of  the  palrn,  and  continues  to  the  end  of 
the  little  finger.  The  other  digitals  reaching  the  ends  of  the  interos- 
seous  spaces  are  there  joined  by  the  palmar  metacarpal  arteries  from 
the  deep  palmar  arch,  and  then  divide  each  into  two  digital  branches, 
which,  with  their  companion  veins  and  the  digital  nerves,  run  along 
the  adjacent  sides  of  the  fingers  to  their  tips.  In  all  the  fingers,  in- 
cluding the  thumb,  the  digital  arteries  pursue  the  same  course,  have 
the  same  relations,  and  the  same  distribution.  In  their  course  they 
anastomose  with  the  dorsal  digital  branches,  and  about  the  middle 
of  the  last  phalanx  they  converge  and  unite  in  an  arch  from  which 
numerous  branches  are  distributed  to  the  tip  of  the  finger,  while  many 
others  proceed  to  the  matrix  of  the  nail. 

THE  DESCENDING  THOKACIC  AOKTA. 

The  descending  thoracic  aorta*  extends  from  the  arch  at  the 
lower  part  of  the  fourth  thoracic  vertebra  on  the  left,  gradually  in- 
clining inward  to  the  front  of  the  last  thoracic  vertebra,  where  it 
passes  through  an  opening  of  the  diaphragm,  subsequently  to  continue 
as  the  abdominal  aorta.  It  lies  in  the  posterior  mediastinum,  covered 
in  front  by  the  pericardium  and  the  pleura  of  the  root  of  the  left  lung. 
To  its  right  above  is  the  oesophagus,  which  gradually  obtains  a  position 
in  front  below,  and  then  to  the  left  at  its  termination.  The  thoracic 
duct  and  azygos  vein  are  also  situated  to  the  right.  In  its  course  it 
gives  off  numerous  but  small  branches,  so  that  its  diameter  is  nearly 
uniform. 

1  Anterior  ulno-carpal  artery. 

2  Deep  branch  of  the  ulnar  artery  ;  ramus  communicans  profundus. 

3  A.  digitales  communes  or  volares. 

4  A.  thoracica  descendens  ;  a.  thoracica. 


THE    ARTERIES. 


515 


BRANCHES   OF   THE   DESCENDING   THOKACIC   AORTA. 


FIG.  268. 


These  consist  of  small  vessels, 
the  bronchial,  ossophageal,  and  me- 
diastinal  arteries;  and  larger  ones 
to  the  walls  of  the  thorax,  the  in- 
tercostal arteries. 

The  bronchial  arteries,1  very 
variable  in  number  and  mode  of 
origin,  commonly  consist  of  one  for 
each  side,  though  frequently  there 
are  three,  of  which  usually  one  is 
to  the  right  and  the  others  are  to 
the  left ;  and  they  may  arise  sepa- 
rately or  together.  The  right  bron- 
chial artery  arises  from  the  aorta 
or  from  the  first  aortic  intercostal 
artery,  and  proceeds  along  the  back 
of  the  right  bronchus  to  the  root 
of  the  lung.  The  left  bronchial 
artery  also  arises  from  the  aorta 
directly  or  in  common  with  the 
right,  and  proceeds  in  the  same 
manner  to  the  left  lung.  When 
there  is  a  second  left  bronchial  ar- 
tery it  usually  arises  lower  and  sep- 
arately from  the  aorta.  Entering 
the  lungs,  the  bronchial  arteries 
ramify  in  company  with  the  bron- 
chial tubes,  to  the  tissues  of  which 
they  are  chiefly  distributed.  Be- 
fore entering  the  lungs  they  give 
branches  to  the  bronchial  lymphatic 
glands,  the  oesophagus,  the  pericar- 
dium, and  the  pleura. 

The  oesophageal  arteries,2  also 
variable,  commonly  consist  of  three 
or  four  little  branches,  which  arise 
from  the  fore  part  of  the  aorta  and 
proceed  to  be  distributed  to  the 
O3sophagus. 

The  mediastinal  arteries3  are 
the  smallest  branches  from  the  aorta,  to  the  lymphatic  glands,  peri- 


THE  AORTA.  1,  arch  of  the  aorta ;  2,  thoracic 
aorta ;  3,  abdominal  aorta ;  4,  innominate 
artery ;  5,  right  common  carotid ;  6,  right  sub- 
clavian ;.  7,  left  common  carotid ;  8,  left  sub- 
clavian ;  9,  bronchial  artery,  a  small  branch 
of  the  aorta ;  10,  cesophageal  arteries ;  11,  inter- 
costal arteries  of  the  right  side ;  12,  of  the  left 
side ;  13,  phrenic  arteries ;  14,  coaliac  axis ;  15, 
gastric  artery ;  16,  splenic  artery ;  17,  hepatic 
artery;  18,  superior  mesenteric  artery;  19, 
suprarenal  arteries;  20,  renal  arteries;  x20, 
spermatic  artery ;  21,  inferior  mesenteric  ar- 
tery ;  22,  lumbar  arteries ;  23,  common  iliac 
arteries;  24,  middle  sacral  artery,  a,  aortic 
orifice  of  the  diaphragm ;  b,  articulation  of  the 
head  of  the  ribs ;  c,  anterior  scalene  muscle. 


1  A.  bronchiales  or  bronchicse.  2  A. 

3  A.  mediastinales  posteriores,  a.  pericardiaei,  and  a.  phrenicae  superiores. 


516  THE   ARTERIES. 

cardium,  and  pleura,  the  wall  of  the  aorta  itself,  and  the  crura  of  the 
diaphragm. 

The  intercostal  arteries,1  of  which  there  are  nine  pairs,  arise 
from  the  back  of  the  aorta  directed  a  little  upward  and  outward  on 
the  centra  of  the  vertebrae,  and  then  run  outward  in  the  lower  nine 
intercostal  spaces,  the  upper  two  of  these  being  supplied  in  the  same 
manner'  by  the  superior  intercostal  branch  of  the  subclavian  artery. 
From  the  position  of  the  aorta  on  the  left  of  the  spine  the  right  inter- 
costals  are  longer  than  the  left,  and  cross  in  front  of  the  vertebras  be- 
hind the  oesophagus,  thoracic  duct,  and  azygos  vein.  On  both  sides 
the  intercostal  arteries  in  their  course  are  crossed  by  the  sympathetic 
nerve,  and  are  covered  by  the  pleura.  In  the  intercostal  spaces  they 
ascend  obliquely  to  the  lower  border  of  the  rib  above  near  the  angle, 
resting  on  the  external  intercostal  muscle  covered  by  the  pleura,  and 
divide  into  two  branches,  which  continue  forward  between  the  external 
and  internal  intercostal  muscles.  The  superior  branch,  a  continua- 
tion of  the  main  trunk,  runs  along  the  subcostal  groove,  while  the 
inferior  branch  descends  and  runs  along  the  upper  border  of  the  rib 
below ;  both  branches  terminating  by  anastomosis  with  the  anterior 
intercostal  branches  of  the  mammary  and  musculo-phrenic  arteries. 
Each  aortic  intercostal  artery,  besides  the  companion  vein,  is  accom- 
panied by  the  corresponding  nerve,  which  is  placed  below  the  artery, 
while  the  vein  is  above  it. 

The  first  aortic  intercostal  artery  anastomoses  with  the  superior 
intercostal  of  the  subclavian  artery,  and  the  lower  two  intercostal 
arteries  run  into  the  abdominal  wall  and  anastomose  with  the  epi- 
gastric artery. 

The  intercostal  arteries  in  their  course  distribute  branches  to  the 
intercostal  muscles  and  others  contiguous  to  them,  to  the  pleura,  to  the 
skin,  and  the  mammary  gland,  and  anastomose  with  thoracic  branches 
of  the  axillary  artery.  From  each  intercostal  artery,  before  turning 
outward  in  the  intercostal  space,  a  dorsal  branch2  runs  backward 
between  the  transverse  processes  of  the  vertebrae  to  the  muscles  of 
the  back,  and  divides  into  two  branches.  Of  these  the  internal 
branch  passes  towards  the  spinous  processes  between  the  multifidus 
and  semispinalis,  to  which  and  other  contiguous  muscles  and  the  skin 
it  is  distributed.  The  external  branch  passes  between  the  longissi- 
mus  and  ilio-costalis,  to  which  and  other  muscles  and  the  skin  it  is 
likewise  distributed. 

From  the  dorsal  branch  of  the  intercostal  arteries  emanates  a 
spinal  branch,3  which  enters  the  adjacent  intervertebral  foramen  to 
be  distributed  to  the  spinal  canal  and  cord. 

Besides  the  anterior  and  posterior  spinal  branches  given  off 

1  A.  intercostales  aorticse  or  inferiores.  2  Eamus  dorsalis  or  posterior. 

3  K.  spinalis  or  vertebralis. 


THE   ARTERIES.  517 

within  the  cranium  by  the  vertebral  arteries,  the  spinal  cord  and  its 
membranes,  together  with  the  spinal  canal,  are  supplied  with  spinal 
branches,  along  the  vertebral  column,  derived  from  the  neighboring 
arteries  of  the  different  regions ;  in  the  neck  from  the  vertebral  and 
the  ascending  and  deep  cervical  arteries,  in  the  thorax  from  the  dorsal 
branches  of  the  intercostal  arteries,  in  the  loin  from  the  dorsal  branches 
of  the  lumbar  and  ilio-lumbar  arteries,  and  in  the  pelvis  from  the  lat- 
eral sacral  arteries.  These  spinal  branches  have  the  same  mode  of 
distribution,  and  generally  each  consists  of  a  short  stem,  which  divides 
into  two  or  three  branches,  the  entovertebral,  meningeal,  and  lateral 
spinal. 

The  entovertebral  branch1  is  distributed  to  the  parietes  of  the 
spinal  canal,  the  vertebrae,  and  ligaments,  and  anastomoses  with  the 
corresponding  branches  above,  below,  and  laterally,  forming  together, 
around  the  canal,  a  plexus  of  fine  vessels. 

The  meningeal  branch,2  the  smallest  and  usually  arising  with 
the  former,  is  distributed  to  the  dural  sheath  of  the  cord  and  the 
surrounding  areolar  and  adipose  tissue. 

The  lateral  spinal  branch,3  arising  separately  or  with  one  of  the 
preceding  branches,  enters  the  dural  sheath  of  the  cord  on  the  roots 
of  the  spinal  nerves,  and  ascends  with  them  to  the  pia  of  the  spinal 
cord,  in  which  it  is  distributed.  Like  the  roots  of  the  spinal  nerves,  the 
lateral  spinal  arteries  become  successively  longer,  and  on  the  cauda 
equina  they  appear  as  slender,  thread-like  vessels  ascending  vertically 
on  the  nerves  of  the  latter.  In  the  pia  of  the  cord  they  inosculate, 
in  front  and  behind  the  latter,  with  the  anterior  and  posterior  spinal 
branches  of  the  vertebral  arteries,  and  incessantly  reinforce  them  in 
their  course. 

THE   ABDOMINAL   AOKTA. 

The  abdominal  aorta  *  is  situated  in  the  abdomen  on  the  centra 
of  the  lumbar  vertebra}  to  the  left  of  the  median  line,  extending  from 
the  thoracic  aorta  at  the  opening  of  the  diaphragm  in  front  of  the 
last  thoracic  vertebra  to  the  middle  or  lower  part  of  the  fourth  lum- 
bar vertebra,  where.it  forks  into  the  common  iliac  arteries.  It  is 
covered  in  front  by  the  pancreas,  duodenum,  and  root  of  the  mesentery, 
and  to  its  right  is  the  inferior  cava,  with  the  right  crus  of  the  diaphragm 
intervening  above.  It  gives  off  many  branches,  of  which  the  largest 
arise  near  together  at  the  commencement,  after  which  the  vessel  ex- 
hibits a  marked  reduction  in  diameter. 

1  Eamus  vertebralis.  2  E.  meningeus. 

3  K.  spinalis  lateralis.  *  A.  abdominalis. 


518  THE   AKTERIES. 


BRANCHES   OF   THE   ABDOMINAL  AORTA. 

Of  the  branches  of  the  abdominal  aorta  three  are  single  vessels 
arising  from  its  fore  part,  the  coeliac,  and  the  superior  and  inferior  mes- 
enteric  arteries,  distributed  to  the  stomach,  intestines,  liver,  pancreas, 
and  spleen ;  others  in  pairs  are  the  suprarenal,  renal,  and  spermatic 
or  ovarian  arteries,  to  the  suprarenal  bodies,  kidneys,  and  testicles  or 
ovaries,  and  the  phrenic  and  lumbar  arteries,  to  the  diaphragm  and 
lateral  walls  of  the  abdomen.  A  single  terminal  branch,  the  middle 
sacral  artery,1  is  a  small  vessel  which  springs  from  behind  the  aorta 
immediately  above  the  bifurcation  into  the  common  iliac  arteries.  It 
descends  in  front  of  the  last  lumbar  vertebra,  and  alono-  the  middle 

'  O 

of  the  sacrum  and  coccyx  to  the  end.  In  its  course  it  gives  oif  small 
lateral  branches,  which  anastomose  with  the  lateral  sacral  arteries  and 
others  which  proceed  to  the  rectum,  where  they  anastomose  with  the 
hemorrhoidal  arteries. 

The  middle  sacral  artery  is  actually  the  continuation  of  the  aorta, 
and  in  all  vertebrate  animals  is  proportioned  in  volume  to  the  degree 
of  development  of  the  tail.  In  fishes,  shakes,  and  cetaceans  the  aorta 
gradually  tapers  to  the  end  of  the  tail,  with  no  appearance  of  division 
into  iliac  arteries.  In  animals  with  hind  limbs  the  iliacs  are  developed 
proportionately  to  their  size,  and  if  the  limbs  are  large  and  the  tail 
small  or  rudimental,  as  in  man  and  the  higher  apes,  the  iliacs  appear 
as  the  bifurcation  of  the  aorta,  with  the  rudimental  remainder  as  a 
middle  sacral  artery. 

The  coeliac  artery,  or  axis,2  is  a  short  trunk,  commonly  not  over 
half  an  inch  long,  arising  from  the  front  of  the  aorta  opposite  the  last 
thoracic  vertebra,  directed  forward  and  dividing  into  three  divergent 
branches,  the  gastric,  hepatic,  and  splenic  arteries.  It  is  immediately 
above  the  pancreas,  and  has  the  semilunar  ganglion  of  the  sympa- 
thetic nerve  on  each  side.  It  is  sometimes  longer  than  usual,  in  which 
case  commonly  one  of  the  branches  has  a  separate  origin. 

The  gastric  artery,3  ordinarily  the  smallest  branch  of  the  cceliac 
axis,  ascends  to  the  left  to  reach  the  right  of  the  cardiac  orifice  of  the 
stomach,  whence  it  turns  to  the  right  along  the  small  curvature,  in  the 
small  omentum,  and  inosculates  with  the  pyloric  branch  of  the  hepatic 
artery.  It  gives  oif  cesophageal  branches,4  which  are  distributed 
to  the  oesophagus,  and  anastomose  with  those  from  the  aorta :  and  in 
its  further  course  is  distributed  in  branches  to  the  fundus,  anterior  and 
posterior  surfaces  of  the  stomach,  where  they  anastomose  with  those 
from  the  arterial  arch  along  the  greater  curvature.  The  gastric  artery 


1  A.  sacralis  ;  a.  sacra  media  or  anterior. 

2  A.  coeliaca ;  a.  opisto-gastrica ;  tripod  of  Haller  ;  tripus  Halleri. 

8  Coronary   artery  ;  a.   gastrica   or  coronaria,  a.  g.  major,  superior,  or  sinistra 
superior ;  a.  coronaria  ventriculi.  *  Kami  oasophagei  inferiores. 


THE   ARTERIES.  519 

sometimes  arises  directly  from  the  aorta.  Occasionally  it  gives  a 
branch  to  the  left  lobe  of  the  liver,  which  is  sometimes  large  enough 
to  replace  the  usual  branch  from  the  hepatic  artery. 

FIG.  269. 


DISTRIBUTION  OF  THE  CCELIAC  ARTERY.  1,  liver  turned  upward,  and  showing  its  lower  surface ; 
2,  transverse  fissure ;  3,  gall-bladder ;  4,  stomach ;  5,  oesophagus ;  6,  7,  8,  duodenum ;  9,  pancreas ; 
10,  spleen ;  11,  aorta ;  12,  co3liac  artery ;  13,  gastric  artery ;  14,  hepatic  artery ;  15,  pyloric  artery ; 
16,  gastro-duodenal  artery;  17,  right  gastro-epiploic  artery;  18,  pancreatico-duodenal  artery; 
19,  hepatic  artery  dividing  into  the  right  and  left  branches  for  the  liver ;  20,  splenic  artery ; 
its  course  indicated  behind  the  stomach  by  dotted  lines;  21,  left  gastro-epiploic  artery  ;  22,  pan- 
creatic branch ;  23,  gastric  branches ;  24,  superior  mesenteric  artery,  emerging  from  between  the 
pancreas  and  the  duodenum. 

The  hepatic  artery l  in  the  infant  is  the  largest  branch  of  the 
coeliac  axis,  but  is  the  second  in  size  at  maturity.  Directed  transversely 
to  the  right,  it  passes  over  the  pancreas  to  the  pylorus,  and  divides  into 
the  gastro-duodenal  and  hepatic  branches,  nearly  equal  in  size.  The 
gastro-duodenal  branch2  descends  behind  the  pylorus  between  the 
duodenum  and  head  of  the  pancreas,  gives  off  the  superior  pancre- 
atico-duodenal artery,3  and  then  continues  as  the  right  gastro-epip- 
loic artery.  The  former  is  a  small  branch  which  descends  between 
the  head  of  the  pancreas  and  the  duodenum,  supplying  them  both,  and 
anastomosing  with  the  inferior  pancreatico-duodenal  branch  of  the 
superior  mesenteric  artery.  The  right  gastro-epiploic  artery4  runs 
from  right  to  left  in  the  great  omentum  along  the  greater  curvature 
of  the  stomach,  and  joins  the  left  gastro-epiploic  artery,  with  which  it 
forms  a  continuous  arch.  It  distributes  branches  to  the  anterior  and 
posterior  walls  of  the  stomach,  where  they  anastomose  with  the 
branches  of  the  gastric  artery,  and  also  sends  long,  slender  branches 

1  A.  hepatica.  2  Kamus  gastro-duodenalis.  3  A.  pancreatico-duodenalis. 

4  A.  gastro-epiploica  dextra ;  a.  coronaria  ventriculi ;  a.  gastrica  dextra  inferior. 


520  THE   ARTERIES. 

downward  to  the  omentum.  The  hepatic  branch1  of  the  hepatic 
artery  is  directed  forward  in  the  small  omentum,  in  which  it  ascends 
in  front  of  the  foramen  of  Winslow,  and  divides  into  the  right  and  left 
hepatic  branches.  In  its  course  it  lies  in  front  of  the  portal  vein,  with 
the  common  bile-duct  to  its  right.  It  gives  oif  a  small  pyloric  branch,2 
which  supplies  the  pylorus,  and  turning  to  the  left  anastomoses  with 
the  termination  of  the  gastric  artery.  Sometimes  it  is  unusually  large, 
and  replaces  the  latter.  Occasionally  it  arises  from  the  gastro-duodenal 
artery. 

The  right  hepatic  artery3  gives  off  the  cystic  artery,4  which  is 
directed  forward,  and  extends  from  the  neck  to  the  fundus  of  the  gall- 
bladder, dividing  into  two  main  branches,  of  which  one  is  distributed 
in  the  upper  wall,  and  the  other  in  the  lower  wall.  The  terminal 
branches  enter  the  right  side  of  the  transverse  fissure  of  the  liver,  and 
are  distributed  to  the  right  lobe  and  its  accessory  quadrate  lobe. 

The  left  hepatic  artery,5  smaller  than  the  former,  enters  the  left 
side  of  the  transverse  fissure,  and  is  distributed  to  the  left  lobe  and 
caudate  lobe  of  the  liver. 

The  trunk  of  the  hepatic  artery  occasionally  arises  separately  from 
the  aorta,  or  together  with  the  superior  mesenteric  artery.  The  two 
chief  terminal  branches  may  arise  from  the  coeliac  axis  or  from  the 
aorta,  or,  more  frequently,  the  right  one  comes  from  the  former  and 
the  left  one  from  the  latter. 

The  splenic  artery,6  at  maturity  the  largest  branch  of  the  coeliac 
axis,  proceeds  transversely,  in  a  more  or  less  tortuous  course,  to  the 
left  and  backward,  along  the  upper  border  of  the  pancreas  to  the  hilus 
of  the  spleen.  In  its  course  it  gives  off  from  three  to  six  pancreatic 
branches,7  which  are  distributed  to  the  pancreas.  On  the  left  it 
gives  off  the  left  gastro-epiploic  artery,8  which  proceeds  in  the 
great  omentum  to  the  right,  along  the  great  curvature  of  the  stomach, 
to  join  the  right  gastro-epiploic  branch,  in  like  manner  with  which  it 
is  distributed. 

The  terminal  or  splenic  branches 9  of  the  splenic  artery,  four  or 
five,  and  subdividing  into  more,  diverge  and  enter  the  hilus  of  the 
spleen,  to  which  they  are  distributed. 

The  short  gastric  branches,10  usually  four  or  five,  come  from  the 
splenic  artery  and  its  terminal  branches,  and  proceed  to  the  fundus 
of  the  stomach,  to  which  they  are  distributed,  anastomosing  with  the 
gastric  and  left  gastro-epiploic  arteries. 


1  Kamus  hepaticus.  2  R.  pyloricus. 

3  A.  hepatica  dextra.  *  A.  cystica. 

5  A.  hepatica  sinistra.  6  A.  splenica ;  a.  lienalis. 

7  A.  pancreatici. 

8  A.  gastro-epiploica  sinistra ;  a.  coronaria  ventriculi ;  a.  gastrica  sinistra  inferior. 

9  Kami  splenici  or  lienales.  10  A.  gastricae  breves  ;  vasa  brevia. 


THE   ARTERIES. 


521 


FIG.  270. 


The  superior  mesenteric  artery  is  smaller  than  the  cceliac  axis, 
just  beneath  which  it  arises  from  the  aorta,  and  curves  forward  and 
downward  behind  the  pan- 
creas and  over  the  duode- 
num to  the  root  of  the 
mesentery,  in  which  it  de- 
scends with  a  curvature 
towards  the  right  iliac 
fossa,  and  terminates  by 
joining  its  own  ileo-colic 
branch.  Its  branches  are 
as  follows  : 

The  inferior  pancre- 
atico-duodenal  artery, 
a  small  branch  from  the 
superior  mesenteric  at  the 
lower  border  of  the  pan- 
creas, to  which  and  the 
duodenum  it  is  distributed, 
anastomosing  with  the 
superior  branch,  derived 
from  the  gastro-duodenal 
artery. 

The  intestinal  branch- 
es, commonly  a  dozen  or 
more,  spring  in  close  suc- 
cession from  the  left  or 
convex  side  of  the  supe- 
rior mesenteric,  and  proceed  downward  and  forward  in  the  mesentery, 
to  supply  the  jejunum  and  ileum.  They  run  parallel  with  one  another, 
and  after  some  distance  divide  each  into  two  branches,  of  which  the 
contiguous  ones  unite  in  loops.  From  the  first  series  of  these  loops  a 
greater  number  of  branches  proceed,  divide,  and  unite  to  form  a  second 
series  of  smaller  and  more  numerous  loops.  In  the  same  manner  is 
formed  a  third  series  of  the  smallest  and  most  numerous  loops,  and 
from  these  proceed  a  multitude  of  nearly  uniform  branches  to  the  in- 
testine, to  the  right  and  left  of  which  they  are  distributed,  freely  anas- 
tomosing with  one  another.  In  the  mesentery  numerous  fine  branches 
are  distributed  to  the  lymphatic  glands  and  other  contiguous  structures. 

From  the  right  side  of  the  superior  mesenteric  artery  there  usually 
proceed  two  or  three  branches,  named  successively  from  below  upward 
the  ileo-colic,  right  colic,  and  middle  colic  arteries. 

The  ileo-colic  artery  arises  from  near  the  middle  of  the  superior 
mesenteric,  descends  obliquely  beneath  the  peritoneum  towards  the 
caecum,  and  divides  into  two  widely-diverging  branches.  Of  these  the 
lower  one  joins  the  termination  of  the  superior  mesenteric,  forming 


DISTRIBUTION  OF  THE  SUPERIOR  MESENTERIC  ARTERY.  1, 
superior  mesenteric  artery;  2,  intestinal  branches;  3, 
ileo-colic  artery ;  4,  right  colic ;  5,  middle  colic  artery ;  6, 
inferior  pancreatico-duodenal  artery,  a,  small  intestine 
turned  to  the  left;  6,  large  intestine;  c,  pancreas. 


522  THE   AETERIES. 

with  it  a  large  loop,  while  the  other  ascends  and  inosculates  with  the 
middle  colic  artery,  forming  another  loop.  From  the  loops  proceed 
many  branches,  the  longer  of  which,  by  division  and  union  of  the  con- 
tiguous branches,  form  a  series  of  smaller,  irregular  loops,  from  which 
branches  proceed,  all  being  finally  distributed  to  the  termination  of  the 
ileum,  the  csecum  with  its  vermiform  appendix,  and  the  commence- 
ment of  the  ascending  colon. 

The  right  colic  artery  arises  above  the  former,  or  in  common  with 
it,  proceeds  to  the  right  beneath  the  peritoneum,  and  divides  into  two 
widely-divergent  branches,  of  which  the  lower  one  joins  the  contiguous 
branch  of  the  ileo-colic  artery,  and  the  other  one  ascends  and  joins  the 
middle  colic  artery,  forming  with  it  one  of  the  largest  loops.  The  ter- 
minal branches  form  here  and  there  a  few  secondary  loops  in  the  usual 
manner,  and  are  distributed  to  the  ascending  colon. 

The  middle  colic  artery  arises  on  the  right  of  the  upper  part  of 
the  superior  mesenteric,  runs  forward  and  downward  in  the  transverse 
mesocolon,  and  divides  in  two  widely-diverging  branches,  of  which  the 
right  one  inosculates  with  the  right  colic  artery,  and  the  left  one  joins 
the  left  colic  branch  of  the  inferior  mesenteric  artery,  forming  with  it 
the  largest  of  the  mesenteric  loops.  Branches  from  the  two  principal 
ones  produce  a  second  and  third  series  of  loops  in  the  usual  manner,  from 
which  the  terminal  branches  proceed  to  supply  the  transverse  colon. 

The  superior  mesenteric  artery  sometimes  arises  in  common  with 
the  cceliac  artery,  and  occasionally  in  two  separate  trunks  from  the 
aorta.  The  number  and  arrangement  of  its  branches  are  variable, 
and  sometimes  it  furnishes  branches  to  other  organs.  It  sometimes 
gives  off  the  right  hepatic  artery  to  the  liver.  Occasionally,  with 
unusual  enlargement  of  the  inferior  pancreatico-duodenal  branch,  it 
gives  off  the  right  gastro-epiploic  artery.  The  ileo-colic  artery  is 
not  always  distinct  from  the  termination  of  the  main  artery,  nor  the 
right  colic  from  the  former;  and  sometimes  there  are  two  middle 
colic  arteries. 

The  inferior  mesenteric  artery,1  much  smaller  than  the  pre- 
ceding, arises  an  inch  or  two  below  it,  from  the  front  of  the  aorta,  and 
descends  in  advance  of  this,  inclining  to  the  left,  gives  off  the  left  colic 
and  sigmoid  arteries,  and  continues  downward  as  the  superior  hemor- 
rhoidal  artery. 

The  left  colic  artery 2  is  directed  to  the  left  side  behind  the  peri- 
toneum, in  front  of  the  kidney,  and  divides  into  two  branches,  of  which 
the  upper  one  inosculates  with  the  left  branch  of  the  middle  colic  of 
the  superior  mesenteric  artery,  while  the  other  one  descends  to  join  the 
sigmoid  artery.  It  forms  a  series  of  large  and  small  loops,  as  in  the 
other  colic  arteries,  from  which  proceed  branches  to  be  distributed  to 
the  descending  colon. 

1  A.  mesenterica  inf.  2  A.  colica  sinistra  superior. 


THE   ARTERIES. 


523 


The  sigmoid  artery l  enters  the  mesocolon  in  the  left  iliac  fossa, 
and  divides  into  two  or  three  or  more  branches,  of  which  the  upper 
and  lower  inosculate  with 

the  left  colic  and  superior  FIG.  271. 

hemorrhoidal  arteries,  and 
in  the  usual  manner  form 
one  or  two  series  of  loops, 
from  which  the  terminal 
branches  proceed,  to  be 
distributed  to  the  sigmoid 
flexure  of  the  colon.  Sev- 
eral separate  branches  may 
substitute  the  single  sig- 
moid artery. 

The  superior  hemor- 
rhoidal artery,2  the  con- 
tinuation of  the  inferior 
mesenteric,  descends  to  the 
pelvis,  in  its  course  cross- 
ing the  left  common  iliac 
vessels  and  entering  the 
mesorectum,  and  divides 
into  two  branches,  which 
are  distributed  to  the  sides 
of  the  rectum,  extending  to 
the  lower  part,  where  they 
anastomose  with  the  mid- 
dle and  inferior  hemorrhoi- 
dal arteries,  derived  from 
the  internal  iliac  artery. 

The  inferior  mesenteric  artery  may  be  absent,  and  its  place  supplied 
by  branches  from  the  superior  mesenteric  artery.  Sometimes  it  gives 
off  the  middle  colic  artery. 

The  suprarenal  arteries 3  are  little  vessels  which  arise  from  the 
aorta,  one  on  each  side  of  the  superior  mesenteric  artery.  They  pass 
outwardly  over  the  crura  of  the  diaphragm  to  the  suprarenal  bodies, 
to  which  they  are  distributed,  anastomosing  with  other  branches  from 
the  phrenic  and  renal  arteries.  They  are  sometimes  very  small,  and 
substituted  by  the  latter  branches. 

The  renal  arteries,4  large  vessels,  whether  compared  with  the 
preceding  or  in  proportion  with  the  organs  they  supply,  come  from 


DISTRIBUTION  OF  THE  INFERIOR  MESENTERIC  ARTERY.  1, 
aorta ;  2,  inferior  mesenteric  artery ;  3,  left  colic  artery ;  4, 
sigmoid  artery ;  5,  superior  hemorrhoidal  artery ;  6,  supe- 
rior mesenteric  artery  ;  7,  middle  colic  artery  anastomos- 
ing with  the  left  and  right  (8)  colic  arteries ;  9,  branches 
to  the  small  intestine ;  10,  left  renal  artery,  a,  small  intes- 
tine turned  to  the  right  side ;  b.  large  intestine ;  c,  pancreas. 


1  A.  sigmoidea ;  a.  col.  sin.  inferior. 

2  A.  haemorrhoidalis  superior  or  interna. 

3  A.  suprarenales  mediae  or  aorticae ;  a.  capsulares  ;  a.  atrabilariae. 

4  A.  renales ;  emulgent  arteries ;  a.  emulgentes. 


524  THE   ARTERIES. 

the  sides  of  the  aorta,  a  short  distance  below  the  superior  mesenteric 
artery,  the  right  one  usually  being  situated  a  little  lower  than  the  left 
one.  They  proceed  outward,  with  a  curve  backward  on  the  sides  of 
the  spine,  and  divide  each  usually  into  two,  and  then  four  or  five 
branches,  which  enter  the  hilus  and  pass  into  the  sinus  of  the  kidney, 
partly  in  front  and  partly  behind  the  pelvis,  subdivide,  and  penetrate 
the  substance  of  the  organ.  From  the  position  of  the  aorta  on  the  left 
of  the  spine  the  right  artery  is  longer,  and  proceeds  across  the  spine  be- 
hind the  inferior  cava.  Both  arteries  have  the  accompanying  vein  in 
front,  with  the  renal  pelvis  and  ureter  behind.  Before  entering  the 
kidney  the  renal  artery  gives  off  one  or  two  little  branches  to  the 
suprarenal  body,  and  others  yet  smaller  to  the  pelvis  and  ureter,  the 
contiguous  lymphatic  glands,  and  investing  tissues. 

The  renal  arteries  exhibit  many  variations,  especially  in  number, 
there  frequently  being  two  on  one  or  both  sides,  and  occasionally  three 
or  four.  When  there  are  two  the  vessels  commonly  pursue  the  usual 
course  together,  but  when  there  are  more  the  additional  vessel  is  apt 
to  arise  higher  or  lower  and  enter  the  upper  or  lower  extremity  of  the 
kidney.  An  upper  additional  branch  may  arise  from  the  aorta  or  from 
the  superior  mesenteric  artery ;  a  lower  branch  from  any  part  of  the 
aorta  below  the  usual  position  or  from  any  of  its  branches. 

The  spermatic  arteries,1  of  the  male,  are  two  long,  slender  vessels, 
which  arise  near  together  from  the  fore  part  of  the  aorta  a  short  but 
variable  distance  below  the  renal  arteries.  They  descend  obliquely,  the 
right  one  across  the  inferior  cava,  each  resting  on  the  psoas  muscle,  and 
crossing  the  ureter  and  the  external  iliac  vessels,  covered  by  the  perito- 
neum, to  the  internal  abdominal  ring.  Here  it  joins  the  vas  deferens, 
and  as  a  constituent  of  the  spermatic  cord  traverses  the  inguinal  canal, 
from  which  it  issues  and  descends  to  the  scrotum,  where,  after  giving 
a  branch  to  the  epididymis,  it  enters  the  back  of  the  testicle,  to  which 
it  is  distributed.  In  its  course  it  gives  a  delicate  branch  to  the  ureter, 
and  in  the  spermatic  cord  anastomoses  with  the  cremasteric  and  def- 
erential arteries. 

The  spermatic  artery  sometimes  arises  from  the  renal  artery,  espe- 
cially on  the  left  side.  Sometimes  it  arises  in  common  with  the  supra- 
renal artery,  and  occasionally  the  right  and  left  arteries  arise  together. 

In  the  female  the  ovarian  arteries  correspond  with  the  former,  and 
have  the  same  mode  of  origin  and  course  to  the  entrance  of  the  pelvis, 
whence  they  proceed  in  a  tortuous  manner  in  the  broad  ligaments  of 
the  uterus  to  the  attached  border  of  the  ovaries,  to  which  they  are 
mainly  distributed,  a  considerable  branch  running  inward  towards  the 
uterus  to  anastomose  with  the  uterine  artery.  Small  branches  also 
supply  the  oviduct,  the  broad  and  round  ligaments.  In  pregnancy  the 
ovarian  arteries  become  much  enlarged. 

1  A.  spermaticae  interne. 


THE   ARTERIES.  525 

The  phrenic  arteries1  are  two  small  vessels,  which  usually  arise 
together  at  the  upper  border  of  the  aortic  orifice  of  the  diaphragm 
from  the  fore  part  of  the  aorta  or  the  root  of  the  coeliac  axis.  They 
diverge  and  ascend  beneath  the  peritoneum  on  the  crura  and  under 
surface  of  the  diaphragm,  to  which  they  are  distributed.  Before 
reaching  the  central  tendon  each  gives  off  an  external  branch,  which 
is  directed  outwardly  towards  the  side  of  the  thorax,  and  anastomoses 
with  the  aortic  intercostal  arteries.  The  internal  branch  is  directed 
towards  the  fore  part  of  the  chest,  and  anastomoses  with  that  of  the 
opposite  side.  The  phrenic  arteries  give  small  branches  to  the  supra- 
renal bodies ;  and  the  left  one  gives  small  branches  to  the  oesophagus, 
which  anastomose  with  the  other  contiguous  cesophageal  arteries. 

The  lumbar  arteries,2  of  which  there  are  usually  five  pairs,  cor- 
respond with  the  intercostal  arteries.  They  arise  from  the  back  of  the 
aorta  and  run  outwardly  on  the  spine,  the  first  pair  across  the  last  tho- 
racic vertebra,  the  others  on  the  upper  four  lumbar  vertebrae.  The  right 
ones  pass  beneath  the  inferior  cava,  and  the  upper  ones  on  both  sides 
beneath  the  origin  of  the  crura  of  the  diaphragm.  Turning  backward 
on  each  side  beneath  the  psoas  muscle  opposite  the  interval  of  the 
transverse  processes,  they  divide  into  an  abdominal  and  a  dorsal  branch. 
The  abdominal  branch  runs  outward,  mostly  behind  the  quadrate 
lumbar  muscle,  and  then  divides  into  branches  which  run  forward  be- 
tween the  abdominal  muscles,  to  which  and  to  the  contiguous  skin  they 
are  distributed,  anastomosing  with  one  another,  and  with  the  epigas- 
trics  in  front,  the  intercostals  above,  and  the  ilio-lumbar  and  circumflex 
arteries  below.  They  also  furnish  branches  to  the  diaphragm,  the  psoas 
and  quadrate  muscles.  The  first  branch  runs  along  the  lower  border 
of  the  last  rib  in  company  with  the  last  thoracic  nerve ;  the  fifth  branch 
runs  along  the  crest  of  the  ilium  and  gives  branches  to  the  iliac  and 
gluteal  muscles.  The  dorsal  branch  passes  backward  between  the 
transverse  processes  to  be  distributed  to  the  muscles  and  skin  of  the 
back  in  the  same  manner  as  the  corresponding  branch  of  the  inter- 
costal arteries.  It  likewise  gives  off  a  spinal  branch,  which  enters  the 
adjacent  intervertebral  foramen,  to  be  distributed  as  already  described. 
See  page  516. 

THE   COMMON   ILIAC  AETEEIES. 

The  common  iliac  arteries3  are  forks  of  the  abdominal  aorta, 
which  descend  obliquely  at  the  sides  of  the  last  lumbar  vertebra 
towards  the  sacro-iliac  articulation,  above  which  each  divides  into  the 
internal  and  external  iliac  arteries.  The  right  one,  slightly  the  longer, 
crosses  over  the  termination  of  the  inferior  cava,  upon  which  it  rests  in 
contact  below  with  the  inner  border  of  the  psoas  muscle.  The  left 

1  A.  phrenicae  ;  a.  p.  inferiores  or  magnse  ;  a.  diaphragmaticae. 

2  A.  lumbales  or  lumbares. 

3  Primitive  iliac  arteries  ;  a.  iliaca  communis  or  primitiva. 


526  THE   ARTERIES. 

one  rests  on  the  bodies  of  the  fourth  and  fifth  lumbar  vertebrae  to  the 
inner  side  of  the  corresponding  psoas  muscle.  Both  are  covered  by 
the  peritoneum,  behind  the  small  intestine,  and  are  crossed  by  the 
descending  branches  of  the  sympathetic  from  the  aortic  to  the  hypo- 
gastric  plexus,  and  near  their  termination  by  the  ureters.  The  accom- 
panying veins  lie  partly  behind  and  to  their  inner  side.  They  usually 
give  off  no  branches  of  importance,  other  than  little  vessels  to  the 
contiguous  lymphatic  glands,  the  psoas  muscle,  and  the  ureter.  Com- 
monly about  three  inches  in  length,  they  frequently  range  to  one-half 
the  extent,  and  when  longer  are  more  or  less  curved  or  tortuous.  The 
point  at  which  they  divide  often  varies  from  about  the  middle  of  the 
last  lumbar  vertebra  to  the  upper  border  of  the  sacrum. 

THE   IKTEKNAL   ILIAC   AKTEKY. 

The  internal  iliac  artery l  descends  from  the  bifurcation  of  the 
common  iliac  artery  in  front  of  the  sacro-iliac  articulation  to  near  the 
upper  border  of  the  great  sciatic  foramen,  where  it  commonly  divides 
into  two  principal  branches,  though  frequently  more,  or  gives  them  off 
in  succession.  Besides  being  much  shorter,  it  is  smaller  in  the  adult, 
but  is  larger  in  the  foetus,  when  it  is  continuous  with  the  umbilical 
artery.  It  rests  against  the  sacrum  and  the  sacro-lumbar  nerve,  with 
its  companion  vein  behind  and  to  the  inner  side  covered  by  the  perito- 
neum, beneath  which  it  is  crossed  by  the  ureter. 

The  position  at  which  the  internal  iliac  artery  divides  is  often  vari- 
able, and  occurs  at  any  point  between  the  upper  border  of  the  sacrum 
and  the  great  sciatic  foramen.  Sometimes  the  greater  part  or  all  of 
its  branches  are  given  off  before  the  ultimate  division.  Though  very 
variable  in  their  origin,  the  branches  are  quite  constant  and  regular  in 
their  distribution. 

Continuous  with  the  trunk  of  the  internal  iliac  artery  or  with  its 
usual  anterior  division  is  a  fibrous  cord,  the  obliterated  umbilical  artery 
of  the  foetus,  which  proceeds  to  the  side  and  summit  of  the  bladder, 
and  thence  to  the  umbilicus.  At  maturity  the  commencement  of  the 
cord  for  an  inch  or  two  encloses  a  narrow  channel  and  constitutes  the 
superior  vesical  artery,2  which  gives  off  two  or  three  branches  to  be 
distributed  to  the  sides  and  summit  of  the  bladder,  anastomosing  with 
those  of  the  opposite  side  and  of  the  inferior  vesical  artery. 

Besides  the  foregoing  branch,  the  anterior  division  of  the  internal 
iliac  artery  usually  gives  off  the  inferior  vesical,  obturator,  internal 
pudic,  and  ischiatic  branches  ;  and  the  posterior  division  the  ilio-lumbar 
and  lateral  sacral  branches,  and  continues  as  the  gluteal  artery. 

The  inferior  vesical  artery3  commonly  springs  from  below  the 
superior  and  descends  to  the  base  of  the  bladder,  to  which  and  to 

1  Hypogastric  artery  ;  a.  iliaca  interna  ;  a.  hypogastrica. 

2  A.  vesicalis  sup. ;  a.  umbilicalis.  3  A.  vesicalis  inf. 


THE   ARTERIES. 


527 


the  prostate  and  seminal  vesicle  it  is  distributed,  anastomosing  with 
that  of  the  opposite  side.  From  this  or  the  superior  vesical  artery  is 
given  off  the  deferential  artery,1  a  slender  vessel  which  accompanies 
the  vas  deferens,  giving  a  branch  to  the  commencement  and  running 
upward  to  the  inguinal  canal  and  sometimes  to  the  epididymis.  The 


VIEW  OF  THE  LEFT  SIDE  OF  THE  PELVIS,  THE  BLADDER,  UTERUS,  VAGINA,  AND  RECTUM,  turned 

downward  so  as  to  exhibit  the  distribution  of  the  internal  iliac  artery.  1,  aorta ;  2,  right  common 
iliac  artery ;  3,  left  common  iliac ;  4,  middle  sacral ;  5,  external  iliac ;  6,  circumflex  iliac ;  7,  epi- 
gastric; 8,  internal  iliac;  9,  ilio- lumbar;  10,  lateral  sacral  arteries;  11,  gluteal  artery  passing  from 
the  pelvis,  above  the  pyriform  muscle,  at  the  upper  part  of  the  great  sciatic  foramen ;  12, 
superior  vesical  artery ;  the  branch  cut  off  is  extended  into  the  remains  of  the  umbilical  artery ; 
13,  obturator  artery ;  14,  inferior  vesical  artery  giving  off  the  uterine  artery  to  the  vagina  and 
uterus;  15,  middle  hemorrhoidal  artery ;  16,  internal  pudic  artery,  seen  emerging  from  and  again 
entering  the  pelvis;  17,  ischiatic  artery,  a,  iliac  muscle;  b,  psoas  muscle;  c,  pubic  symphysis; 
d,  sacrum ;  e,  pyriform  muscle ;  /,  internal  obturator  muscle ;  g,  sacro-sciatic  ligaments ;  h,  rec- 
tum ;  i,  uterus  and  vagina ;  j,  fallopian  tube ;  k,  bladder. 

inferior  vesical  artery  is  sometimes  double,  or  it  may  arise  from  the 
internal  pudic,  the  ischiatic,  or  the  obturator  artery. 

The  obturator  artery,2  usually  from  the  anterior  division  of  the 
internal  iliac,  frequently  springs  from  the  posterior  division  or  the 
trunk,  and  runs  forward  below  the  brim  of  the  pelvis  to  the  aperture 


1  A.  deferentialis. 


2  A.  obturatoria. 


528  THE   ARTERIES. 

at  the  upper  part  of  the  obturator  membrane,  through  which  it  passes, 
and  divides  into  two  branches.  In  its  course  it  rests  on  the  pelvic 
fascia,  accompanied  by  the  obturator  vein  and  nerve,  and  covered  by 
the  peritoneum.  Besides  small  branches  to  the  internal  obturator  and 
anal  elevator  muscles,  the  contiguous  lymphatics  and  inner  surface  of 
the  pubis,  it  gives  off  a  larger  iliac  branch,  which  ascends  to  the  iliac 
fossa,  where  it  is  distributed  to  the  psoas  and  iliac  muscles,  and  anas- 
tomoses with  the  ilio-lumbar  artery.  Of  the  terminal  divisions  the  in- 
ternal branch 1  descends  along  the  inner  border  of  the  obturator  fora- 
men, and  anastomoses  with  the  external  branch ;  is  distributed  to  the 
obturator  muscles,  the  heads  of  the  adductors,  and  the  contiguous  skin 
of  the  thigh,  and  anastomoses  with  the  internal  circumflex  artery. 
The  external  branch 2  descends  at  the  outer  border  of  the  obturator 
foramen,  and  is  distributed  to  the  obturator  and  femoral  quadrate  mus- 
cles, the  heads  of  the  flexors  arising  from  the  ischial  tuberosity,  and  to 
the  hip-joint,  a  branch  entering  the  cotyloid  foramen  to  supply  the 
interior ;  and  it  anastomoses  with  the  ischiatic  and  external  circumflex 
arteries. 

The  obturator  artery  is  very  variable  in  its  origin.  Besides  the 
sources  mentioned,  it  may  arise  in  common  with  the  superior  vesical, 
the  internal  pudic,  the  ischiatic,  or  the  ilio-lumbar  artery.  Frequently 
it  arises  from  the  termination  of  the  external  iliac  artery,  usually  in 
common  with  the  epigastric  artery,  or  sometimes  from  the  commence- 
ment of  the  femoral  artery.  In  the  latter  cases  the  obturator  descends 
to  the  inner  or  outer  side  of  the  femoral  ring  behind  the  pubis  to  the 
obturator  foramen. 

The  internal  pudic  artery,3  the  smaller  terminal  branch  of  the 
anterior  division  of  the  internal  iliac,  or  otherwise  directly  from  the 
trunk  of  this  vessel,  descends  in  front  of  the  sacral  plexus  of  nerves 
and  the  pyriform  muscle  at  the  side  of  the  rectum  to  the  lower  part 
of  the  great  sciatic  foramen,  through  which  it  passes  out  of  the  pelvis. 
Thence  it  curves  behind  the  ischial  spine  and  re-enters  the  pelvis,  in 
company  with  the  internal  pudic  nerve,  through  the  small  sciatic  fora- 
men, and  proceeds  forward  above  the  ischial  tuberosity  and  upward 
along  the  inner  side  of  the  pubic  arch  to  the  union  of  the  crura  of 
the  cavernous  bodies  of  the  penis,  where  it  divides  into  two  terminal 
branches. 

Before  leaving  the  pelvis  the  internal  pudic  artery  usually  gives  off 
the  middle  hemorrhoidal  artery,4  which  often,  however,  proceeds 
directly  from  the  anterior  division  of  the  internal  iliac.  It  descends 
to  the  side  of  the  rectum,  to  the  lower  part  of  which  it  is  mainly  dis- 
tributed, anastomosing  with  the  superior  and  inferior  hemorrhoidal 

1  Kamus  interims  or  anterior.  2  R.  externus  or  posterior. 

3  A.  pudenda ;  a.  p.  interna,  communis,  or  circumflexa  ;  a.  haemorrhoidea  externa. 

4  A.  haemorrhoidalis  media. 


THE   ARTERIES. 


529 


FIG.  273. 


and  inferior  vesical  arteries.  It  gives  branches  to  the  prostate  and 
seminal  vesicle,  or  in  the  female  to  the  vagina.  It  sometimes  arises, 
in  common  with  the  superior  vesical  artery,  from  the  ischiatic  or 
lateral  sacral  artery,  and  at  times  it  is  absent. 

The  inferior  hem- 
orrhoidal  artery,1  often 
replaced  by  two  or  three 
branches,  comes  from  the 
internal  pudic  in  the  is- 
chio-rectal  fossa,  and  de- 
scends inwardly  through 
the  areolar  tissue  and  fat 
of  the  latter  to  the  end 
of  the  rectum,  to  which  it 
is  distributed,  including 
the  sphincter  and  anal 
elevator  muscles,  and 
anastomosing  with  the 
other  hemorrhoidal  and 
the  superficial  perineal 
arteries. 

The  superficial  per- 
ineal artery 2  arises  from 
the  pudic  at  the  fore  part 
of  the  ischio-rectal  fossa, 
descends  from  behind  the 
transverse  perineal  mus- 
cle, and  runs  forward  be- 
neath the  superficial  fas- 
cia of  the  perineum  to 
the  scrotum,  or  in  the 
female  to  the  labium.  It 
is  distributed  to  the  muscles  and  other  structures  and  skin  of  the 
perineum.  A  branch,  the  transverse  perineal  artery,3  important 
in  its  surgical  relations,  runs  inward  to  the  perineal  centre,  and  anas- 
tomoses with  that  of  the  opposite  side. 

The  bulbar  artery*  arises  from  the  pudic  between  the  layers  of 
the  triangular  ligament,  passes  inward,  and  penetrates  the  side  of  the 
bulb  of  the  spongy  body  of  the  penis,  to  which  it  is  distributed,  ex- 
tending to  the  glans.  In  the  female  it  enters  the  semi-bulb  of  the 
spongy  body  of  the  clitoris,  and  is  distributed  as  in  the  preceding. 

The  cavernous  artery,5  one  of  the  terminal  branches  of  the  in- 


VlEW  OF  THE  PERINEUM,  EXHIBITING  THE  DISTRIBUTION  OF 

THE  INTERNAL  PUDIC  ARTERY.  1,  the  internal  pudic  issuing 
from  the  pelvis  at  the  lower  part  of  the  great  sciatic  fora- 
men ;  2,  the  same  vessel  after  it  has  returned  into  the  pelvis 
through  the  small  sciatic  foramen  ;  3,  inferior  hemorrhoidal 
artery ;  4,  5,  superficial  perineal  branches  to  the  perineum ; 
6,  transverse  perineal ;  7,  perineal  branch  to  the  scrotum 
and  skin  of  the  penis;  8,  bulbar  artery ;  9,  cavernous  ar- 
tery ;  10,  dorsal  artery  of  the  penis,  a,  tuberosity  of  the 
ischium;  b,  greater  sacro-sciatic  ligament;  c,  sphincter  of 
the  anus;  d,  perineal  fascia,  which  is  removed  on  the  oppo- 
site side  so  as  to  expose  the  anal  elevator  muscle ;  e,  ischio- 
cavernous  muscle ;  /,  bulbo-urethral  muscle. 


1  A.  h.  inf.  or  externa.  2  A.  perinea.  3  A.  transversa  perinei. 

4  A.  bulbo-urethralis  ;  artery  of  the  bulb. 

5  Artery  of  the  corpus  cavernosum  ;  a.  cavernosa ;  a.  profunda  penis  or  clitoridis. 

34 


530  THE    ARTERIES. 

ternal  pudic,  penetrates  the  inner  side  of  the  crus  of  the  cavernous 
body  of  the  penis,  and  proceeds  forward  to  the  anterior  extremity,  and 
is  distributed  to  the  erectile  tissue.  In  the  female  it  in  the  same 
manner  supplies  the  cavernous  body  of  the  clitoris. 

The  dorsal  artery  of  the  penis,1  the  smaller  terminal  branch  of 
the  internal  pudic,  ascends  between  the  crus  of  the  cavernous  body 
and  pubic  symphysis  to  the  dorsum  of  the  penis,  along  which  it  runs 
to  the  neck,  and  ends  in  branches  to  the  glans  and  prepuce.  It  per- 
forates the  suspensory  ligament,  and  lies  at  the  side  of  the  dorsal  vein, 
in  company  with •  the  corresponding  nerve.  It  distributes  branches 
to  the  wall  of  the  cavernous  body  and  the  skin  of  the  penis.  In 
the  female,  as  the  dorsal  artery  of  the  clitoris,  it  has  a  similar 
distribution. 

In  the  female  the  internal  pudic  artery  is  considerably  smaller 
than  in  the  male.  The  superficial  perineal  artery  is  larger,  and  is  dis- 
tributed to  the  labium.  The  bulbar  and  cavernous  arteries  and  the 
dorsal  artery  of  the  clitoris  are  much  smaller  than  the  corresponding 
ones  of  the  male,  but  have  a  similar  distribution. 

The  vesico-vaginal  artery'2  substitutes  the  inferior  vesical  artery 
of  the  male.  Arising  as  in  the  latter,  it  descends  to  the  side  of  the 
vagina,  to  the  wall  of  which  and  the  lower  part  of  the  bladder  it  is 
distributed. 

The  uterine  artery3  arises  from  the  anterior  division  of  the  in- 
ternal iliac,  separately  or  in  common  with  the  preceding,  passes  in  the 
broad  ligament  towards  the  neck  of  the  uterus,  and  then  ascends  in 
a  tortuous  manner  on  the  side  of  that  organ,  to  which  it  is  distributed. 
Anastomosing  with  the  ovarian  artery  it  forms  a  continuous  arch,  from 
which  branches  are  distributed  to  the  oviduct.  During  pregnancy  the 
uterine  artery  and  its  branches  become  greatly  enlarged  and  very 
tortuous. 

The  internal  pudic  artery  sometimes  arises  higher  and  sometimes 
lower  than  usual,  and  not  unfrequently  it  divides  into  two  branches, 
of  which  one  pursues  the  usual  course  and  gives  off  the  hemorrhoidal, 
superficial  perineal,  and  bulbar  arteries,  while  the  other  descends  in 
the  pelvis  beneath  the  bladder  to  the  arch  of  the  pubis,  and  ends  in 
the  cavernous  and  dorsal  arteries  of  the  penis,  sometimes  including  the 
bulbar  artery. 

The  ischiatic  artery,*  the  larger  terminal  branch  of  the  anterior 
division  of  the  internal  iliac,  and  appearing  as  its  continuation,  de- 
scends in  front  of  the  sacral  plexus  of  nerves  and  the  pyriform  muscle 
to  the  lower  part  of  the  great  sciatic  foramen,  through  which  it  leaves 
the  pelvis  in  company  with  the  internal  pudic  artery  and  the  sciatic 
nerves.  It  thence  continues  to  descend  beneath  the  great  gluteal  mus- 

1  A.  dorsalis  penis  or  clitoridis.  2  A.  vesico-vaginalis.  3  A.  uterina. 

4  Sciatic  artery  ;  a.  ischiadica  ;  a.  glutsea  inferior. 


THE   ARTERIES.  531 

cle,  resting  on  the  internal  obturator  and  geminus  muscles,  and  termi- 
nates in  a  descending  branch,  which  accompanies  the  small  sciatic 
nerve  down  the  back  of  the  thigh,  to  the  fasciae  and  skin  of  which  it 
is  distributed,  anastomosing  with  branches  of  the  femoral  perforating 
arteries.  Beneath  the  great  gluteal  it  gives  off  branches  to  that  mus- 
cle, in  which  they  anastomose  with  the  gluteal  artery,  others  to  the 
small  rotator  muscles  and  those  arising  from  the  ischial  tuberosity, 
anastomosing  with  the  obturator  and  internal  circumflex  arteries.  Sev- 
eral cutaneous  branches  proceed  to  the  skin  of  the  buttock.  A 
coccygeal  branch,1  which  penetrates  the  great  sacro-sciatic  ligament, 
is  distributed  to  the  great  gluteal  muscle  and  the  adjacent  connective 
tissue  and  fat  over  the  sacrum  and  coccyx  and  in  the  perineum.  An 
anastomotic  branch,  directed  to  the  trochanteric  fossa,  supplies  the 
rotator  muscles  and  hip-joint,  and  anastomoses  with  the  gluteal  and 
internal  circumflex  arteries.  A  sciatic  branch,2  long  and  slender, 
penetrates  among  the  fascicles  of  the  great  sciatic  nerve,  and  descends 
with  it  to  about  the  middle  of  the  thigh. 

The  ischiatic  artery  sometimes  arises  much  higher  than  usual,  and 
sometimes  much  lower,  even  to  the  point  at  which  it  leaves  the  pelvis. 

The  ilio-lumbar  artery,3  usually  derived  from  the  posterior  di- 
vision of  the  internal  iliac,  or  from  the  trunk  before  division,  ascends 
outward  behind  the  obturator  nerve  and  between  the  base  of  the 
sacrum  and  the  psoas  muscle,  and  divides  into  two  branches.  Of  these 
the  lumbar  branch 4  ascends  beneath  the  psoas  to  the  quadrate  lumbar 
muscle,  to  both  of  which  it  is  distributed,  anastomosing  with  the  last 
lumbar  artery.  It  gives  off  a  spinal  branch,  which  passes  through 
the  adjacent  intervertebral  foramen  to  the  spinal  canal.  The  iliac 
branch 5  is  directed  outward  in  the  iliac  fossa,  and  is  distributed  below 
and  above  the  iliac  muscle,  and  anastomoses  with  the  last  lumbar,  ob- 
turator, and  circumflex  iliac  arteries.  The  ilio-lumbar  artery  sometimes 
arises  from  the  external  iliac  or  from  the  common  iliac  artery,  and 
sometimes  its  branches  arise  separately. 

The  lateral  sacral  arteries,6  usually  two,  sometimes  arising  to- 
gether as  one  from  the  posterior  division  of  the  internal  iliac  or  the 
trunk  of  this  vessel,  descends  at  the  side  of  the  sacrum  internally  to  the 
anterior  sacral  foramina.  They  distribute  small  branches  to  the  pyri- 
form,  coccygeal,  and  anal  elevator  muscles,  anastomosing  with  the 
ilio-lumbar,  lateral  sacral,  and  hemorrhoidal  arteries.  The  terminal 
branches  enter  the  anterior  sacral  foramina,  and  give  spinal  branches 
to  the  sacral  canal  and  its  contents,  and  dorsal  branches 7  through 
the  posterior  sacral  foramina  to  the  muscles  and  skin  on  the  back  of 


1  A.  coccygea.  2  Comes  nervi  ischiadici. 

3  A.  ilio-lurnbaris  or  lombalis  ;  a.  iliaca  parva. 

4  Kamus  lumbaris  or  adscendens.  6  K.  iliacus  or  transversalis. 
6  A.  sacrales  laterales.  T  R.  dorsales  or  posteriores. 


532  THE   ARTERIES. 

the  sacrum,  anastomosing  with  the  gluteal  and  ischiatic  arteries.  The 
lateral  sacral  arteries  sometimes  arise  in  three  or  four  separate  branches. 
The  upper  one  sometimes  arises  in  common  with  the  ilio-lumbar  artery, 
or  it  may  arise  from  the  external  iliac  or  the  common  iliac  artery. 

The  gluteal  artery,1  the  largest  branch  of  the  internal  iliac,  ordi- 
narily appears  as  a  continuation  of  its  posterior  division  or  of  the 
trunk  itself.  It  turns  backward  between  the  lumbo-sacral  and  first 
sacral  nerves,  and  passes  from  the  pelvis  at  the  upper  border  of  the 
great  sciatic  foramen,  and  under  cover  of  the  great  gluteal  muscle 
divides  into  a  superficial  and  a  deep  branch.  Before  leaving  the  pelvis 
it  supplies  several  small  variable  branches  to  the  pyriform,  internal  ob- 
turator, and  anal  elevator  muscles,  and  a  nutritious  branch  to  the  ilium. 
The  superficial  branch  runs  backward  between  the  great  and  middle 
gluteal  muscles,  distributed  to  these,  the  pyriform  muscle,  and  contigu- 
ous skin,  and  anastomoses  with  branches  of  the  ilio-lumbar  and  dorsal 
branches  of  the  lateral  sacral  arteries.  The  deep  branch,  directed 
forward  between  the  middle  and  small  gluteal  muscles,  usually  divides 
into  an  upper  and  a  lower  branch,  distributed  to  these,  the  pyriform 
muscle,  and  the  hip-joint,  giving  nutritious  branches  to  the  ilium,  and 
anastomosing  behind  with  the  ischiatic  artery  and  in  front  with  the 
external  circumflex  and  epigastric  arteries. 

When  the  internal  iliac  artery  does  not  divide  as  usual,  the  gluteal 
appears  as  a  continuation  of  the  trunk,  or  it  may  arise  higher  up  from 
the  latter. 

THE   EXTERNAL   ILIAC   AKTEKY. 

The  external  iliac  artery,2  the  anterior  terminal  branch  of  the 
common  iliac,  continues  in  the  line  of  the  latter  within  the  abdomen,  and 
runs  above  the  brim  of  the  pelvis  to  the  middle  of  the  groin,  where  it 
passes  through  the  femoral  arch  into  the  thigh,  and  subsequently  con- 
tinues under  the  name  of  the  femoral  artery.  A  line  on  the  outside 
of  the  abdomen,  from  the  left  side  of  the  umbilicus  to  the  middle  of 
the  groin,  indicates  the  course  of  the  common  iliac  and  external  iliac 
arteries  on  either  side.  The  external  iliac  artery  rests  against  the  inner 
side  of  the  psoas,  but  approaching  the  femoral  arch  lies  in  front  of  that 
muscle.  It  is  enclosed  in  a  sheath,  with  the  accompanying  vein  tightly 
adherent  to  the  iliac  fascia  investing  the  psoas  muscle,  and  is  covered 
by  the  peritoneum  and  a  number  of  lymphatic  glands.  The  external 
iliac  vein  at  first  is  behind  and  then  to  the  inner  side  of  the  artery, 
and  at  the  femoral  arch  is  on  the  same  plane.  It  is  larger  and  longer 
than  the  internal  iliac,  usually  about  three  and  a  half  to  four  inches, 
and  is  of  uniform  diameter.  Except  small  twigs  to  the  psoas  and  con- 
tiguous lymphatics,  it  gives  off  no  branches  until  near  its  termination. 

1  A.  glutsea  ;  a.  g.  superior  ;  a.  iliaca  posterior. 

2  A  iliaca  externa  or  anterior ;  a.  cruralis  or  c.  iliaca. 


THE   ARTERIES.  533 

The  epigastric  artery *  arises  near  the  termination  of  the  external 
iliac  from  its  inner  fore  part,  and  ascends  inwardly  involved  in  the 
transversalis  fascia  of  the  abdomen,  covered  by  the  peritoneum,  to  the 
sheath  of  the  abdominal  rectus  muscle.  Entering  the  sheath  it  continues 
upward  behind  the  rectus,  which  it  penetrates,  and  is  mainly  distributed 
to  that  muscle,  giving  twigs  through  the  fore  part  of  the  sheath  to  the 
adjacent  fascia  and  skin,  and  anastomosing  with  the  epigastric  branch 
of  the  internal  mammary  artery.  It  is  accompanied  by  a  pair  of  veins, 
and  near  its  commencement  crosses  the  course  of  the  inguinal  canal, 
through  which  it  gives  a  small  spermatic  branch  2  to  the  cremaster 
muscle  and  tunics  of  the  spermatic  cord,  anastomosing  with  the  sper- 
matic artery.  It  also  gives  off  a  small  pubic  branch  to  the  back  of 
the  pubis,  anastomosing  with  that  of  the  obturator  artery.  Lateral 
branches  are  also  given  to  the  broad  muscles  of  the  abdomen,  anasto- 
mosing with  the  circumflex  iliac,  lumbar,  and  lower  intercostal  arteries. 

The  epigastric  artery  sometimes  arises  higher  or  lower  than  the 
usual  position,  and  not  unfrequently  it  arises  together  with  the  obtu- 
rator artery  from  the  external  iliac. 

The  circumflex  iliac  artery 3  arises  from  the  external  iliac  near  the 
preceding,  and  runs  upward  and  outward  behind  Poupart's  ligament, 
in  the  conjunction  of  the  transversalis  and  iliac  fascia,  to  the  iliac  crest, 
along  which  it  runs  backward  and  anastomoses  with  the  iliac  branch 
of  the  ilio-lumbar  artery.  It  gives  branches  to  the  psoas  and  iliac 
muscles,  the  origin  of  the  sartorius  and  fascial  tensor,  and  the  trans- 
versalis and  internal  oblique  muscles,  and  anastomoses  with  the  epi- 
gastric and  lumbar  arteries. 

THE   FEMORAL   AKTEEY. 

The  femoral  artery,*  the  continuation  of  the  external  iliac,  runs 
along  the  upper  two-thirds  of  the  inner  fore  part  of  the  thigh,  and 
then  passes  through  an  opening  of  the  tendon  of  the  great  adductor 
to  the  back  of  the  thigh,  where  it  receives  the  name  of  the  popliteal 
artery.  Commencing  beneath  the  femoral  arch  at  the  middle  of  the 
groin,  its  course  is  indicated  by  a  line  drawn  from  the  latter  position 
to  the  inside  of  the  knee.  It  extends  along  the  middle  of  a  wide  de- 
pressed space,  named  Scarpa's  triangle,  of  which  the  base  is  formed 
by  Poupart's  ligament,  the  inner  lateral  boundary  by  the  adductors, 
and  the  outer  by  the  extensors  in  front  of  the  thigh.  At  first  it  rests 
on  the  psoas  muscle,  which  separates  it  from  the  ilio-pubic  eminence 
and  the  hip-joint,  next  upon  the  pectineus  and  short  adductor,  and  then 
the  long  adductor,  after  which  it  passes  through  the  opening  of  the 

1  A.  epigastrica  ;  a.  e.  inferior  or  inf.  interna. 

2  A.  spermatica  externa  ;  a.  cremasterica. 

3  A.  circumflexa  iliaca  ;  a.  epigastrica  externa  ;  a.  abdominalis. 

4  A.  femoralis  ;  crural  artery  ;  a.  cruralis. 


534 


THE    ARTERIES. 


great  adductor.     It  is  enclosed  in  a  sheath  accompanied  by  the  femoral 

vein,  which  is  at  first  situated 
FIG.  274. 

along  its  inner  side,  but  gradu- 
ally inclines  backward,  and  is 
placed  behind  the  artery  as  it 
passes  through  the  opening  of 
the  adductor  tendon.  Above,  it 
is  covered  by  the  fasciae  and 
skin,  and  subsequently  in  ad- 
dition by  the  sartorius  and  an 
aponeurotic  offset  from  the  in- 
ner side  of  the  long  and  great 
adductor  tendons  to  that  of  the 
internal  vastus  muscle.  At  the 
commencement,  the  artery  is 
most  advanced  in  position,  situ- 
ated in  front  of  the  border  of 
the  pelvis  and  the  inner  part  of 
the  head  of  the  femur,  in  its  de- 
scent gradually  acquires  a  more 
posterior  position,  and  at  the 
lower  part  of  the  thigh  lies  close 
to  the  shaft  of  the  femur,  sepa- 
rated from  it  by  the  internal 
vastus.  At  the  groin  the  crural 
nerve  lies  a  little  way  to  the 
outer  side  of  the  artery,  and 
about  the  middle  of  the  thigh 
it  is  accompanied  by  the  long 
saphenous  nerve  until  the  ves- 
sel passes  through  the  opening 
of  the  adductor  tendon.  Usu- 
ally, about  an  inch  and  a  half 
below  its  commencement  the 
femoral  artery  gives  off  a 
branch,  the  profunda,  nearly 
as  large  as  the  main  trunk, 
which  is  subsequently  consid- 
erably reduced  in  size.  Other 
branches  of  the  femoral  artery 
are  mostly  small. 

In  addition  to  several  lit- 
tle branches  to  the  lymphatic 
glands  and  skin  of  the  groin, 
the  femoral  artery  in  its  course  gives  off  a  half-dozen  or  more  variable 
muscular  branches,  to  the  sartorius,  gracilis,  adductors,  and  extensors. 


ARTERIES  OF  THE  FRONT  OF  THE  THIGH.  1,  femoral 
artery ;  2,  popliteal  artery ;  3,  posterior  tibial  artery  ; 
4,  superficial  epigastric  artery ;  5,  superficial  circum- 
flex iliac ;  6,  external  pudics ;  7,  femoral  profunda ; 
8,  9,  external  and  internal  circumflex  arteries ;  10, 
perforating  arteries;  11,  muscular  branches;  12, 
anastomotic  artery ;  13, 14,  internal  articular  ar- 
teries; 15,  small  branch  from  the  epigastric;  16, 
dorsal  arteries  of  the  penis,  a,  rectus  muscle ;  b, 
internal  vastus ;  c,  d,  e,  adductor  muscles ;  /,  semi- 
tendinosus  muscle ;  g,  sartorius  muscle. 


THE   ARTERIES.  535 

The  superficial  epigastric  artery,1  usually  a  small  and  constant 
branch,  comes  from  the  femoral  just  below  the  groin,  pierces  the  fem- 
oral fascia,  and  ascends  in  the  superficial  abdominal  fascia  towards  the 
umbilicus.  It  is  distributed  to  the  fascia  and  skin,  and  anastomoses 
with  branches  of  the  deep  epigastric  artery. 

The  superficial  circumflex  iliac  artery,2  another  small  branch, 
often  arising  together  with  the  former,  ascends  outwardly  in  the  super- 
ficial fascia  of  the  groin  to  the  iliac  crest.  It  supplies  branches  to  the 
contiguous  glands  and  skin,  and  gives  others  through  the  deep  fascia  to 
the  iliac  and  sartorius  and  other  contiguous  muscles,  and  anastomoses 
with  the  corresponding  deep  artery. 

The  external  pudic  arteries,3  usually  a  couple  of  branches,  come 
from  the  front  and  inner  part  of  the  femoral,  within  an  inch  or  two 
below  the  groin.  The  superior,  more  superficial  branch  passes  inward 
through  the  cribriform  fascia  of  the  saphenous  opening,  to  be  dis- 
tributed in  front  of  the  pubis.  The  inferior,  deeper  branch,  often  di- 
vided into  two,  is  directed  inwardly  on  the  pectineus  and  small  ad- 
ductor muscles,  and  pierces  the  femoral  fascia  to  be  distributed  to 
the  skin  of  the  scrotum,  or  in  the  female  to  the  labium.  The  external 
pudic  arteries  anastomose  with  one  another  and  with  the  superficial 
epigastric  and  external  spermatic  arteries. 

The  femoral  profunda  artery  *  arises  from  the  outer  back  part  of 
the  femoral,  usually  about  an  inch  and  a  half  below  the  groin,  is  di- 
rected backward  and  a  little  outward,  and  descends  behind  the  femoral 
artery  close  to  the  inner  side  of  the  femur.  In  its  course  it  first  rests 
on  the  iliac,  then  the  pectineus  and  small  adductor  muscles,  and  finally 
the  great  adductor,  continuing  on  this  beneath  the  long  adductor.  It 
sometimes  arises  higher  or  lower  than  the  usual  point;  sometimes  from 
the  inner  side  of  the  parent  trunk,  or  occasionally  directly  from  the 
back  part.  It  is  the  chief  nutrient  vessel  of  the  thigh,  and  breaks  up 
into  the  circumflex  and  perforating  arteries,  besides  giving  off  smaller 
and  less  regular  branches  to  the  internal  vastus  and  adductor  muscles. 

The  internal  circumflex  artery5  arises  from  the  inner  side  of  the 
profunda  near  its  commencement,  and  passes  backward  between  the 
psoas  and  pectineus  muscles  over  the  short  adductor  towards  the  small 
trochanter,  and  divides  into  an  ascending  and  a  transverse  branch. 
It  supplies  the  external  obturator  and  adductor  muscles,  and  anasto- 
moses with  the  obturator  artery.  It  also  furnishes  an  articular 
branch 6  to  the  hip-joint,  which  enters  through  the  cotyloid  foramen, 
and  varies  proportionately  with  the  corresponding  branch  of  the  latter. 


1  A.  epigastrica  superficialis ;  a.  abdominalis  subcutanea;  a.  ad  cutis  abdominis. 

2  A.  circumflexa  superficialis  or  externa  ;  ramus  iliacus  of  the  a.  epig.  superf. 

3  A.  pudendae  externse. 

4  Deep  femoral  artery ;  a.  profunda ;  a.  p.  femoris  ;  a.  femoralis  profunda. 

5  A.  circumflexa  femoris  interna.  6  K.  articularis  ;  a.  acetabuli. 


536  THE    ARTERIES. 

The  ascending  branch1  proceeds  to  the  trochanteric  fossa,  supplies 
the  small  rotator  muscles,  and  anastomoses  with  branches  of  the  gluteal, 
ischiatic,  and  first  perforating  arteries.  The  transverse  branch,  larger 
than  the  former,  passes  back  between  the  femoral  quadrate  and  great 
adductor  muscles,  and  is  distributed  to  the  heads  of  the  flexors,  anasto- 
mosing with  the  sciatic  and  first  perforating  arteries. 

The  internal  circumflex  artery  frequently  arises  directly  from  the 
femoral,  and  occasionally  from  the  external  iliac,  separately  or  in 
common  with  the  epigastric  or  circumflex  iliac  artery. 

The  external  circumflex  artery,2  larger  than  the  preceding, 
sometimes  arises  together  with  it,  but  usually  separately,  and  opposite, 
or  a  little  lower  from  the  profunda  artery.  Directed  outward  between 
the  sartorius  and  femoral  rectus,  and  between  the  divisions  of  the  crural 
nerve,  after  giving  branches  to  the  contiguous  muscles  it  commonly 
terminates  in  a  pair  of  widely-divergent  branches.  Of  these,  the 
ascending  branch 3  is  distributed  to  the  upper  part  of  the  sartorius, 
rectus,  and  external  vastus,  and  the  fore  part  of  the  middle  and  small 
gluteal  muscles,  gives  a  branch 4  to  the  hip-joint,  and  anastomoses  with 
branches  of  the  gluteal  and  circumflex  iliac  arteries.  The  descending 
branch,6  larger  than  the  former,  supplies  the  extensors  and  the  fasciae 
and  skin  at  the  outer  part  of  the  thigh,  the  terminal  branch  descending 
at  the  outer  border  of  the  rectus  to  the  knee. 

The  external  circumflex  artery  sometimes  arises  from  the  femoral 
above  the  profunda,  and  sometimes  its  ascending  branch  arises  from 
either  of  the  former,  independent  of  the  descending  branch. 

The  perforating  arteries,6  variable  in  number  and  arrangement, 
usually  three  or  four,  including  the  terminal  branch  of  the  profunda, 
come  off  in  succession,  and  pass  backward  close  to  the  femur  through 
apertures  in  the  tendinous  insertion  of  the  short  and  great  adductors 
to  the  back  of  the  thigh.  Here  they  are  chiefly  distributed  to  the 
femoral  flexors,  the  fasciae,  and  skin ;  give  twigs  to  the  sciatic  nerve, 
and  anastomose  with  branches  of  the  ischiatic,  gluteal,  circumflex,  and 
popliteal  nerves.  Terminal  branches  directed  outwardly  pierce  the 
attachments  of  the  external  gluteal  muscle,  short  head  of  the  biceps, 
and  external  intermuscular  septum,  and  end  in  the  external  vastus  and 
crureus,  in  which  they  anastomose  with  branches  of  the  external 
circumflex  artery.  The  first  perforating  artery,  commonly  the 
largest,  passing  through  the  short  and  great  adductors,  furnishes 
branches  to  these,  and  then  mainly  supplies  the  flexors.  An  ascending 
branch  beneath  the  insertion  of  the  external  gluteal  muscle  to  the 
back  of  the  neck  of  the  femur  supplies  the  former  and  the  femoral 
quadrate  muscle,  and  anastomoses  with  the  gluteal,  ischiatic,  and  cir- 

1  K.  adscendens ;  r.  trochantericus.  2  A.  circ.  fern,  externa. 

3  A.  adscendens  or  circumflexa.  *  R.  trochantericus  anterior. 

8  E.  descendens.  6  A.  perforantes. 


THE   ARTERIES.  537 

cumflex  arteries.  The  second  perforating  artery,  passing  thi-ough 
the  great  adductor,  is  mainly  distributed  to  this,  the  external  vastus, 
and  crureus.  The  third  perforating  artery,  the  terminal  branch  of 
the  profunda,  pierces  the  great  adductor  a  short  distance  above  the  aper- 
ture for  the  femoral  artery,  and  is  mainly  distributed  to  that  muscle, 
the  short  head  of  the  biceps,  and  the  semimembranosus. 

The  medullary  nutritious  artery  of  the  femur,  when  single, 
usually  comes  from  the  first  or  second  perforating  artery,  and  when  a 
second  exists,  this  comes  from  the  third  perforating  artery. 

The  anastomotic  artery,1  a  slender  vessel,  arises  from  the  femoral 
as  this  is  about  to  pass  through  the  aperture  of  the  great  adductor,  and 
quickly  divides  into  a  superficial  and  a  deep  branch,  which  frequently 
also  come  directly  from  the  femoral  artery.  The  superficial  branch2 
accompanies  the  long,  saphenous  nerve-  to  the  knee,  and  is  distributed 
to  the  sartorius  and  gracilis  and  the  skin  of  the  region,  and  anasto- 
moses with  the  lower  internal  articular  branch  of  the  popliteal  artery. 
The  deep  branch3  penetrates  the  internal  vastus  muscle,  descends  to 
the  inner  condyle  of  the  femur,  and  anastomoses  with  the  internal 
articular  arteries.  It  supplies  the  lower  part  of  the  internal  vastus  and 
crureus,  and  sends  branches  across  the  knee  to  anastomose  with  the 
upper  external  articular  branch  of  the  popliteal  artery. 

POPLITEAL   AKTEKY. 

The  popliteal  artery,4  continuous  with  the  femoral,  occupies  the 
bottom  of  the  depressed  space  at  the  back  of  the  knee,  extending  from 
the  perforation  of  the  great  adductor  at  the  lower  third  of  the  inner 
side  of  the  thigh  to  the  perforation  of  the  interosseous  membrane  at 
the  upper  part  of  the  leg,  where  it  divides  into  the  anterior  and  pos- 
terior tibial  arteries.  In  the  early  part  of  its  course  the  artery  inclines 
from  the  front  on  the  inner  side  of  the  femur  downward  and  outward 
to  the  back  part,  where  it  descends  vertically  behind  the  middle  of  the 
knee-joint  to  its  termination.  It  first  rests  on  the  inner  side  of  the 
femur,  and  then  behind  this  on  a  layer  of  areolar  and  adipose  tissue, 
subsequently  on  the  capsular  ligament  of  the  knee-joint,  and  finally  on 
the  popliteal  muscle.  Its  upper  end  is  covered  by  the  semimembrano- 
sus ;  its  lower  end  by  the  heads  of  the  gastrocnemius  and  soleus  mus- 
cles. In  the  intermediate  position,  in  company  with  the  popliteal  vein 
and  nerve,  it  is  enveloped  in  areolar  and  adipose  tissue,  invested  super- 
ficially by  the  fasciae  and  skin  of  the  popliteal  space.  The  companion 
vein  lies  more  superficially  in  close  contact  with  the  artery,,  at  first 
behind  and  a  little  to  the  outer  side,  gradually  inclining  below  to 
the  inner  side.  The  internal  popliteal  nerve,  more  superficial  behind 

1  A.  anastomotica  magna. 

2  A.  articularis  genu  superficialis ;  a.  a.  g.  superior  interna  superficial  or  prima. 

3  Eamus  musculo-articularis.  *  A.  poplitea. 


538 


THE   AETERIES. 


than  the  corresponding  vessels,  lies  first  to  the  outer  side,  gradually 

gaining  the  inner  side  below. 

ARTERIES  OF  THE  BACK  OF  THE  THIGH.    1,  glu- 

FlG.  275.  teal  artery ;  2,  3,  its  superficial  and  deep  branch ; 

4,  internal  pudic  artery;  5,  ischiatic  artery;  6, 
branch  of  the  external  circumflex ;  7,  8,  terminal 
branches  of  the  perforating  arteries ;  9,  popliteal 
artery;  10, 11,  superior  internal  and  external  ar- 
ticular arteries ;  12,  13,  inferior  internal  and  ex- 
ternal articular  arteries:  14,  middle  articular 
artery;  15,  gastrocnemial  branches,  a,  origin 
and  insertion  of  the  great  gluteal  muscle ;  6, 
origin  of  the  middle  gluteal  muscle;  c,  small 
gluteal  muscle ;  d,  great  trochanter ;  e,  pyriform 
muscle ;  /,  sacro-sciatic  ligaments ;  g,  internal  ob- 
turator muscle;  h,  femoral  quadrate  muscle;  i, 
sciatic  nerve :  j,  tuberosity  of  the  ischium ;  k,  ex- 
ternal vastus  muscle ;  I,  great  adductor ;  m,  short 
head  of  the  femoral  biceps ;  n,  long  head ;  o,  p, 
semimembranosus  and  semitendinosus  muscles; 
q,  gracilis ;  r,  gastrocnemius. 

The  branches  given  off  in  the 
course  of  the  popliteal  artery  are 
small,  and  consist  of  muscular  and 
articular. 

Of  the  muscular  arteries,  three 
or  four *  are  distributed  in  the  thigh 
to  the  lower  part  of  the  flexors, 
great  adductor,  internal  vastus,  and 
crureus,  and  also  give  branches  to 
the  popliteal  nerves,  the  fasciae,  and 
skin  of  the  popliteal  space.  Others, 
the  gastrocnemial  arteries,2  usu- 
ally two,  though  sometimes  arising 
together,  spring  from  the  back  of 
the  popliteal  just  above  the  knee- 
joint,  and  descend,  one  on  each  side, 
to  the  heads  of  the  gastrocnemius, 
which  they  enter  and  supply,  besides 
giving  branches  to  the  plantaris 
and  soleus.  A  superficial  branch3 
from  each,  or  from  the  popliteal 
directly,  descends  on  the  surface  of 

the  gastrocnemius  to  be  distributed  to  -the  skin  of  the  calf. 

Of  the  articular  arteries  *  there  are  commonly  five,  named  from 

their  relative  position.     Four  are  in  pairs,  one  on  each  side,  passing 

above  and  below,  around  the  knee-joint,  the  fifth  one  proceeding  directly 

forward  to  the  centre  of  the  joint  behind. 


1  Superior  muscular  arteries. 
3  A.  suralis  superficialis. 


2  A.  surales  ;  a.  gemellse. 
*  A.  articulares  genu. 


THE   ARTERIES.  539 

The  superior  internal  articular  artery1  passes  from  the  popliteal 
inward  above  the  internal  condyle  of  the  femur  beneath  the  attachment 
of  the  contiguous  muscles,  and  is  distributed  on  the  condyle  and  among 
the  adjacent  tendons  at  the  inner  side  of  the  knee  to  the  patella.  It 
anastomoses  with  the  anastomotica  and  other  articular  arteries.  It 
varies  in  size  proportionately  with  the  anastomotica. 

The  superior  external  articular  artery,2  larger  than  the  former, 
passes  outward  above  the  external  condyle  of  the  femur  beneath  the 
contiguous  muscular  attachments,  and  is  distributed  on  the  condyle 
and  among  the  adjacent  tendons  extending  on  the  outer  side  of  the 
knee-joint.  It  anastomoses  with  the  descending  branch  of  the  external 
circumflex  artery,  the  deep  branch  of  the  anastomotica,  and  the 
articular  arteries. 

The  inferior  internal  articular  artery3  passes  downward  and  in- 
ward along  the  upper  border  of  the  popliteal  muscle,  and  then  forward 
below  the  inner  tuberosity  of  the  tibia  beneath  the  internal  lateral  liga- 
ment, to  be  distributed  at  the  inner  side  of  the  knee-joint.  It  gives 
branches  to  the  popliteal  muscle,  and  anastomoses  with  the  anasto- 
motica and  other  articular  arteries. 

The  inferior  external  articular  artery,4  smaller  than  the  former, 
passes  outward  along  the  border  of  the  external  semilunar  cartilage, 
above  the  head  of  the  fibula,  beneath  the  external  lateral  ligament  to 
the  outer  side  of  the  knee-joint,  where  it  anastomoses  with  the  recurrent 
tibial  and  other  articular  arteries. 

The  middle  articular  artery5  is  a  small  branch,  which  proceeds 
from  the  popliteal  artery  directly  forward,  and  perforates  the  centre 
of  the  capsular  ligament  to  be  distributed  to  the  crucial  ligaments  and 
other  structures  within  the  joint. 

All  the  articular  arteries,  together  with  the  anastomotica  and  re- 
current tibial  arteries,  anastomose  freely,  forming  a  superficial  wide- 
meshed  net-work  between  the  fascia  and  skin,  and  a  deeper,  closer  one 
of  larger  vessels  on  the  bones  and  the  ligaments  enclosing  the  knee- 
joint. 

Deviations  of  the  popliteal  artery  from  the  usual  condition  are 
unfrequent.  Earely,  it  divides  at  a  higher  point  into  its  terminal 
branches. 

ANTEKIOK    TIBIAL    AKTEKY. 

The  anterior  tibial  artery,6  the  smaller  terminal  branch  of  the 
popliteal,  occupies  the  outer  fore  part  of  the  leg,  extending  to  the  back 
of  the  foot,  on  which  the  vessel  is  continued  forward  as  the  dorsal 

1  A.  articularis  genu  superior  interim  or  interna  secunda  or  profunda. 

2  A.  articularis  genu  superior  externa. 

3  A.  articularis  genu  inferior  interna. 

4  A.  articularis  genu  inferior  externa. 

5  A.  articularis  genu  media  ;  a.  azygos  inferior.  6  A.  tibialis  antica. 


540 


THE   ARTERIES. 


pedal  artery.   Passing  from  the  lower  end  of  the  popliteal  space,  through 

the  opening  of  the  interos- 

FIQ.  276.  seous   membrane,  close   to 

the  neck  of  the  fibula,  it 
descends  in  front  of  that 
membrane,  and  gradually 
inclines  inward  and  for- 
ward, and  continues  down- 
ward on  the  lower  part  of 
the  tibia  to  the  middle  of 
the  bend  in  front  of  the 
ankle.  In  company  with 
a  pair  of  veins  and  the 
corresponding  nerve  it  is 
closely  adherent  to  the  con- 
tiguous structures.  In  the 
upper  two-thirds  of  its 
course  it  is  deeply  placed 
between  the  anterior  tibi- 
alis  muscle  on  the  inner 
side  and  the  long  digital 
and  hallucal  extensors  on 
the  outer  side.  In  the  lower 
third,  inclining  forward,  it 
becomes  more  superficial, 
and  is  crossed  from  the 
outer  to  the  inner  side  by 
the  tendon  of  the  hallucal 
extensor,  and  above  the 
ankle  is  covered  by  the 
upper  band  of  the  anterior 
annular  ligament.  A  line 
drawn  from  a  point  mid- 
way between  the  head  of 
the  fibula  and  the  outer 
tuberosity  of  the  tibia  to 
the  middle  of  the  ankle- 
joint  in  front  indicates  the 
direction  of  the  artery.  The 
following  branches  are  de- 
rived from  the  anterior 
tibial  artery : 

The  posterior  recur- 
rent branch,1  a  small  ves- 


AETERIES  OF  THE  FRONT  OF  THE  LEG.  1,  anterior  tibial 
artery ;  2,  recurrent  tibial ;  3,  dorsal  pedal ;  4,  5,  external 
and  internal  malleolar  arteries ;  6,  metatarsal  artery  ;  7, 
dorsal  artery  of  the  great  toe ;  8,  terminal  branches  of  the 
articular  arteries,  a,  tibia;  b,  anterior  tibialis  muscle ;  c, 
hallucal  extensor ;  d,  long  digital  extensor :  the  short  ex- 
tensor occupies  the  back  of  the  foot ;  e,  peroneal  muscles : 
on  each  side  of  the  leg  the  bellies  of  the  gastrocnemius 
are  visible. 


1  A.  t.  recurrens  post. 


THE   AETEEIES.  541 

sel,  ascends  beneath  the  popliteal  muscle  to  the  knee-joint,  to  both  of 
which  it  is  distributed. 

The  anterior  recurrent  artery,1  larger  than  the  former,  comes  from 
the  tibial  after  passing  the  interosseous  aperture,  ascends  through 
the  upper  extremity  of  the  anterior  tibialis  muscle,  and  ramifies  over 
the  outer  tuberosity  of  the  tibia,  anastomosing  with  the  contiguous 
articular  arteries. 

Numerous  small  muscular  branches  arise  in  the  course  of  the 
anterior  tibial  artery,  and  supply  the  contiguous  muscles. 

The  malleolar  arteries  are  variable  in  their  origin  and  number; 
usually  an  external  and  an  internal,  they  arise  near  the  ankle,  the 
former  being  commonly  the  higher.  Not  unfrequently  two  branches 
or  more  substitute  either  or  both,  especially  the  internal  smaller  one. 
The  external  malleolar  artery 2  descends  obliquely  outward  beneath 
the  extensor  tendons  to  be  distributed  over  the  external  malleolus, 
where  it  supplies  the  contiguous  articulations  and  anastomoses  with 
the  anterior  peroneal  and  tarsal  arteries.  The  internal  malleolar 
artery3  passes  inward  beneath  the  tendon  of  the  anterior  tibialis,  and 
is  distributed  over  the  internal  malleolus,  supplying  the  contiguous 
parts  and  anastomosing  with  the  internal  tarsal  arteries  and  branches 
of  the  posterior  tibial  artery. 

DOKSAL   PEDAL   AETEKY. 

The  dorsal  pedal  artery,4  the  continuation  of  the  anterior  tibial, 
runs  forward  on  the  back  of  the  foot  from  the  middle  of  the  front  of 
the  ankle-joint  to  the  first  metatarsal  interval,  where  it  descends  be- 
tween the  heads  of  the  interosseous  muscle  to  the  sole,  in  which  it 
joins  the  external  plantar  artery  to  complete  the  plantar  arch.  It 
rests  on  the  tarsus  between  the  tendons  of  the  hallucal  and  long  digi- 
tal extensors,  covered  by  the  lower  band  of  the  anterior  annular  liga- 
ment. It  is  accompanied  by  a  pair  of  veins  and  the  anterior  tibial 
nerve,  and  gives  off  the  following  branches : 

The  internal  tarsal  arteries,5  two  or  three  small  and  variable 
branches,  descending  on  the  inner  side  of  the  tarsus,  to  the  articula- 
tions of  which  they  are  distributed,  anastomosing  with  the  internal 
malleolar  and  branches  of  the  posterior  tibial  arteries. 

The  external  tarsal  artery,6  usually  arising  near  the  head  of  the 
astragalus,  passes  outwardly  beneath  the  short  digital  extensor,  to 
which  and  the  contiguous  articulations  it  is  distributed,  and  anasto- 
moses with  the  external  malleolar,  peroneal,  external  plantar,  and 
metatarsal  arteries. 

The  metatarsal  artery7  arises  near  the  bases  of  the  metatarsal 

1  A.  t.  recurrens  ant.  2  A.  malleolaris  externa.          3  A.  mal.interna. 

4  Dorsal  artery  of  the  foot.  5  Kami  tarsei  interni. 

6  Tarsal  artery  ;  a.  tarsea  externa ;  a.  t.  ext.  posterior. 

7  A.  metatarsea ;  a.  tarsea  externa  anterior. 


542  THE   AETERIES. 

bones,  runs  outwardly  beneath  the  short  digital  extensor,  to  which  and 
the  contiguous  articulations  it  is  distributed,  and  anastomoses  with  the 
external  plantar  and  tarsal  arteries.  With  the  latter  it  forms  an  arch,1 
from  which  proceed  three  interosseous  arteries 2  to  the  outer  three 
metatarsal  spaces,  resting  on  the  corresponding  interosseous  muscles 
and  supplying  them  with  twigs.  At  the  fore  part  of  the  metatarsal 
intervals  each  interosseous  artery  bifurcates  into  a  pair  of  dorsal 
digital  branches,  which  proceed  along  the  adjacent  sides  of  the 
corresponding  toes.  At  the  back  of  the  metatarsal  intervals  each 
interosseous  artery  is  connected  with  the  plantar  arch  by  a  commu- 
nicating branch  ;3  and  likewise  less  constantly  at  its  bifurcation  in 
front  it  is  united  by  an  anterior  communicating  branch 4  with  the 
contiguous  plantar  digital  artery.  From  the  outermost  of  the  inter- 
osseous arteries  a  dorsal  digital  branch  proceeds  along  the  inner 
border  of  the  little  toe. 

The  first  interosseous  artery,5  larger  than  the  others,  proceeds 
from  the  fore  part  of  the  dorsal  pedal  artery  on  the  interosseous  mus- 
cle of  the  first  metatarsal  interval,  and,  after  giving  a  dorsal  digital 
branch  to  the  outer  side  of  the  great  toe,  bifurcates  into  dorsal 
digital  branches  for  the  adjacent  sides  of  the  latter  and  the  second 
toe ;  and  at  the  bifurcation,  by  a  communicating  branch  joins  the 
contiguous  plantar  digital  artery. 

The  external  tarsal  and  metatarsal  arteries  are  not  unfrequently 
represented  by  three  or  four  branches,  and  sometimes  they  are  replaced 
by  branches  from  an  enlarged  anterior  peroneal  artery. 

POSTEEIOK   TIBIAL   AKTEKY. 

The  posterior  tibial  artery,6  the -larger  terminal  branch  of  the 
popliteal  and  appearing  as  its  continuation,  descends  the  leg  behind  the 
tibia  between  the  muscles  of  the  calf  and  the  deep  muscles,  enclosed 
with  the  latter  by  the  deeper  layer  of  the  deep  fascia.  It  extends 
from  the  lower  border  of  the  popliteal  muscle  to  that  of  the  inter- 
nal annular  ligament,  which  encloses  it  behind  the  internal  malleolus, 
where  it  divides  into  the  internal  and  external  plantar  arteries.  In 
its  course  it  rests  successively  on  the  posterior  tibialis  and  the  long 
digital  flexor,  and  at  its  termination  directly  on  the  tibia  and  the  ankle- 
joint.  Above,  it  is  covered  by  the  bellies  of  the  gastrocnemius  and 
soleus,  and  below  these  by  two  layers  of  the  deep  fascia,  the  superficial 
fascia,  and  skin.  It  is  accompanied  as  usual  by  two  veins,  and  with 

1  Arcus  tarseus  ;  a.  dorsalis  pedis. 

2  Dorsal  interosseous  arteries ;  a.  interossese  dorsales. 

3  Posterior  perforating  artery  ;  ramus  perforans  post. 

4  Anterior  perforating  artery  ;  ramus  perforans  ant. 

5  A.  metatarsea  or  interossea  dorsalis  prima ;  first  dorsal  interosseous  artery. 

6  A.  tibialis  postica. 


THE    AETERIES. 


543 


the  posterior  tibial  nerve  at  the  start  on  its  outer  side,  and  afterwards 

running  along  its  inner  side.     At  the 

ankle   it   lies   about   midway  between  FIG.  277. 

the  prominences  of  the  heel  and  the 

inner  malleolus,  and   in   this   position 

ends  in  its  terminal  branches. 

In  its  course  the  posterior  tibial  ar- 
tery gives  off  the  medullary  artery  of 
the  tibia,  muscular  branches,  the  pero- 
neal  artery,  and  the  communicating 
and  malleolar  branches. 

The  medullary  nutritious  artery,1 
the  largest  of  its  kind,  arises  near  the 
commencement  of  the  posterior  tibial, 
and  descends  on  the  surface  of  the  tibia 
to  the  medullary  nutritious  canal.  It 
usually  gives  some  muscular  branches 
.to  the  contiguous  muscles. 

The  muscular  branches  are  nu- 
merous, several  of  the  largest  being 
distributed  to  the  soleus,  while  the 
others  supply  the  posterior  tibialis  and 
flexor  muscles,  and  give  cutaneous 
branches  to  the  adjacent  fasciae  and 
skin. 

The  peroneal  artery,2  the  largest 
branch  of  the  posterior  tibial,  springs 
from  the  outer  side  of  this  vessel  an 
inch  or  two  below  its  commencement. 
It  descends  deeply  close  along  the  inner 
side  of  the  fibula  to  the  lower  end  of 
the  interosseous  space,  where  it  divides 
into  the  anterior  and  posterior  peroneal 
arteries.  Accompanied  by  the  usual 
pair  of  veins,  it  rests  on  the  posterior 
tibialis  muscle,  covered  above  by  the 
soleus  and  below  by  the  long  hallucal 
flexor.  In  its  course  it  gives  many 
small  muscular  branches  to  the  so- 
leus, posterior  tibialis,  long  hallucal 
flexor,  and  the  peroneal  muscles,  with 
cutaneous  branches  to  the  skin  and 
a  medullary  nutritious  branch  to 
the  fibula.  The  lower  part  of  the  artery 


ARTERIES  OF  THE  BACK  OF  THE  LEG.  1. 
popliteal  artery;  2,  2,  superior  internal 
and  external  articular  arteries ;  3,  3,  in- 
ferior internal  and  external  articular  ar- 
teries ;  4,  middle  articular  artery  ;  5,  gas- 
trocnemial  arteries;  6,  peroneal  artery; 
7,  posterior  peroneal  branch ;  8,  posterior 
tibial  artery ;  9,  calcanean  branches,  a, 
popliteal  muscle ;  6,  c,  origin  of  the  gas- 
trocnemius ;  d,  peroneal  muscles  ;  e,  long 
hallucal  flexor;  /,  long  digital  flexor; 
that  between  the  two  latter  is  the  pos- 
terior tibialis  muscle. 


1  A.  nutritia  tibiae. 


2  A.  peronaea  ;  a.  fibularis. 


544  THE   ARTERIES. 

is  commonly  joined  by  a  communicating  branch,1  which  crosses  the 
tibia  from  the  adjacent  part  of  the  posterior  tibial  artery. 

The  anterior  peroneal  artery,2  one  of  the  terminal  divisions  of 
the  peroneal,  passes  through  an  aperture  at  the  lower  end  of  the  inter- 
osseous  space,  and  descends  in  front  of  the  articulation  of  the  tibia  and 
fibula,  to  be  distributed  over  the  external  malleolus  and  the  outer  part 
of  the  ankle-joint,  where  it  anastomoses  with  the  external  malleolar 
branch  of  the  anterior  tibial,  and  with  branches  of  the  posterior  pero- 
neal and  external  tarsal  arteries.  It  supplies  the  third  peroneal 
muscle,  the  contiguous  articulations,  the  fascia,  and  skin. 

The  posterior  peroneal  artery,3  the  remaining  terminal  division 
and  continuation  of  the  peroneal,  descends  behind  the  articulation  of 
the  tibia  and  fibula  and  the  external  malleolus,  and  is  distributed  over 
the  outer  side  of  the  calcaneum.  It  supplies  the  contiguous  articula- 
tions, and  anastomoses  with  the  external  malleolar,  tarsal,  and  calcanean 
arteries. 

The  peroneal  artery  sometimes  arises  either  higher  or  lower  than 
the  usual  position.  It  occasionally  comes  from  the  end  of  the  popliteal 
or  from  the  anterior  tibial  artery.  Rarely  it  is  absent.  The  anterior 
peroneal  artery  is  sometimes  enlarged  to  compensate  for  deficiency  in 
the  terminal  portion  of  the  anterior  tibial  artery ;  and  sometimes  it  is 
very  small  or  absent,  and  is  replaced  by  an  enlarged  external  malleolar 
artery. 

The  communicating  branch 4  of  the  posterior  tibial  artery,  usu- 
ally a  considerable  vessel,  springs  from  behind  the  internal  malleolus, 
and  passes  transversely  across  the  tibia,  to  join  the  termination  of  the 
peroneal  artery.  Sometimes  it  is  represented  by  a  smaller  pair ;  and 
sometimes  it  is  absent,  and  then  may  ,be  represented  by  a  branch  from 
the  peroneal  artery,  which  proceeds  to  the  internal  malleolus,  and 
substitutes  the  following. 

The  malleolar  branch,5  small  and  often  double,  from  near  the 
termination  of  the  posterior  tibial  artery,  passes  inward  beneath  the 
tendons  of  the  posterior  tibialis  and  long  digital  flexor,  to  be  distrib- 
uted on  the  internal  malleolus,  where  it  anastomoses  with  the  internal 
malleolar  branch  of  the  anterior  tibial  artery. 

PLANTAR   ARTERIES. 

The  plantar  arteries,  the  terminal  branches  of  the  posterior  tibial, 
proceed  from  this  vessel  at  the  lower  border  of  the  internal  annular 
ligament,  covered  by  the  origin  of  the  hallucal  abductor.  The  in- 
ternal plantar  artery,6  the  smaller  branch,  runs  forward  along  the 

1  Eamus  anastomoticus  transversus.  2  A.  peronsea  antica  or  perforans. 

3  A.  p.  post. ;  rami  calcanei  extern!. 

4  Ramus  anastomoticus  transversus  or  superior. 

5  A.  malleolaris  interna  posterior.  6  A.  plantaris  interna. 


THE   ARTERIES. 


545 


FIG.  278. 


inner  side  of  the  sole  of  the  foot  between  the  hallucal  abductor  and 
short  flexor  to  the  fore  part  of  the  first  metatarsal  interval,  where  it 
usually  ends  by  joining  the  internal 
branch  of  the  first  plantar  digital 
artery.  In  its  course  it  gives  off 
numerous  branches,  of  which  the 
deeper  ones  are  distributed  to  the 
articulations  of  the  inner  side  of  the 
foot,  anastomosing  with  branches 
of  the  external  plantar  artery ;  and 
the  superficial  branches  supply  the 
muscles,  fascia,  and  skin  on  the 
inner  side  of  the  foot,  anastomos- 
ing with  branches  of  the  dorsal 
pedal  artery. 

The  external  plantar  artery,1 
.appearing  as  the  continuation  of 
the  posterior  tibial,  runs  through 
the  arch  of  the  calcaneum,  out- 
ward and  forward  into  the  sole  of 
the  foot,  passing  along  the  outer 
part  to  the  base  of  the  last  metatar- 
sal bone,  where  it  turns  obliquely 
inward  to  the  first  metatarsal  in- 
terval and  joins  the  dorsal  pedal 
artery,  to  form  the  plantar  arch.2 
At  first  the  artery,  with  its  accom- 
panying veins  and  nerve,  is  placed 
between  the  calcaneum  and  hallucal 
abductor,  afterwards  between  the 

accessory  and  short  digital  flexors,  and  then  in  the  interval  of  the  latter 
and  the  minimal  abductor.  The  plantar  arch,  with  its  convexity 
•directed  forward,  rests  on  the  interosseous  muscles,  covered  by  the 
digital  flexors  and  lumbrical  muscles.  In  its  course  the  external  plantar 
artery  gives  off  numerous  branches,  as  follows : 

Two  or  three  calcanean  branches,3  often  partly  derived  from  the 
termination  of  the  posterior  tibial.  They  pierce  the  origin  of  the 
hallucal  abductor,  which  they  supply,  and  are  distributed  over  the  heel, 
anastomosing  with  corresponding  branches  of  the  posterior  peroneal 
artery. 

Many  muscular  branches  supply  the  contiguous  muscles  in  the 
outer  part  of  the  sole  of  the  foot,  and  other  branches  are  devoted  to 
the  adjacent  articulations  and  skin,  and  anastomose  with  the  internal 
tarsal  and  metatarsal  arteries. 


ARTERIES  OF  THE  SOLE  OF  THE  FOOT.  1,  pos- 
terior tibial  artery  dividing  into,  2,  the  internal, 
and,  3,  external,  plantar  arteries;  4,  branch 
to  the  inner  side  of  the  foot ;  5,  branch  to  the 
great  toe ;  6,  plantar  arch ;  7.  perforating  ar- 
teries; 8,  common  digitals;  9,  digitals  to  the 
contiguous  sides  of  the  toes;  10,  calcanean 
branches  of  the  peroneal  and  posterior  tibial 
arteries. 


A',  plantaris  externa. 


2  Arcus  plantaris. 
35 


3  Kami  calcanei  interni. 


546  THE   ARTERIES. 

From  the  plantar  arch  small  branches  proceed  backward  to  supply 
the  contiguous  articulations,  and  anastomose  with  branches  of  the 
internal  plantar  artery.  Three  posterior  communicating  branches1 
proceed  from  the  arch  through  the  back  ends  of  the  corresponding 
metatarsal  intervals  to  join  the  interosseous  arteries  on  the  back  of 
the  foot. 

From  the  fore  part  of  the  plantar  arch  proceed  five  digital  ar- 
teries.2 The  first8  of  these,  usually  regarded  as  the  last  branch  of 
the  dorsal  pedal  artery,  runs  forward  in  the  first  metatarsal  interval 
to  its  fore  part,  and  divides  into  a  pair  of  digital  branches,4  which 
run  along  the  adjacent  borders  of  the  great  and  adjoining  toes  to  the 
tips.  In  its  course  it  gives  off  a  digital  branch,  which  crosses  the 
first  metatarsal  bone  and  runs  along  the  inner  border  of  the  great  toe. 
The  succeeding  three  digital  arteries5  proceed  forward  in  the  corre- 
sponding metatarsal  intervals,  and  divide  like  the  former,  each  into  a 
pair  of  digital  branches,  which  run  along  the  adjacent  borders  of 
the  toes.  The  fifth  digital  artery 6  proceeds  from  the  outer  part  of 
the  arch  obliquely  across  the  last  metatarsal  bone,  and  runs  along  the 
outer  border  of  the  little  toe.  At  their  bifurcation  the  digital  arteries, 
for  the  most  part,  are  joined  by  a  communicating  branch 7  from  the 
adjacent  interosseous  arteries  of  the  back  of  the  foot;  often  failing 
in  the  outer  one  or  two  metatarsal  intervals.  The  distribution  of  the 
plantar  digital  arteries  in  all  respects  accords  with  that  of  the  palmar 
digitals. 

The  arteries  of  the  foot  deviate  from  the  ordinary  condition  much 
less  frequently  than  those  of  the  hand.  The  internal  plantar  is  some- 
times larger,  and  may  play  a  more  important  part  in  the  formation 
of  the  plantar  arch ;  and  sometimes  it  continues  forward  as  the 
first  plantar  digital  artery.  Sometimes  it  is  small,  and  ends  in  the 
short  hallucal  flexor.  The  external  plantar  is  observed  to  vary  pro- 
portionately with  the  dorsal  pedal  artery,  so  that  one  or  the  other  may 
contribute  more  or  less  to  the  plantar  arch.  The  posterior  communi- 
cating arteries,  Tisually  small,  may  be  larger  and  form  the  interosseou& 
arteries,  in  which  case  the  metatarsal  branch  of  the  dorsal  pedal  artery 
is  smaller  than  normally. 

VEINS  OF   THE   HEAKT. 

The  principal  veins  of  the  heart,  for  the  most  part,  accompany  the 
arteries  along  the  grooves  and  unite  in  a  trunk,  the  terminal  portion  of 

1  Posterior  perforating  branches  ;  rami  perforantes  posteriores. 

2  A.  interossese  plantares. 

8  Plantar  digital  branch  of  the  dorsal  artery  of  the  foot. 

4  Collateral  digital  arteries  ;  a.  digitales  plantares. 

5  A.  interossese  plantares. 

6  A.  plantaris  externa  digit!  minimi. 

7  Anterior  perforating  artery  ;  a.  perforans  ant. 


THE    VEINS. 


547 


FIG.  279. 


.16 


which,  for  about  an  inch,  is  slightly  dilated,  and  is  named  the  coronary 
sinus.  They  are  the  great  and  small,  the  middle,  and  the  posterior 
coronary  veins.  In  addition  to  these 
are  the  anterior  cardiac  veins  and 
some  still  smaller  ones,  which  open 
separately  into  the  right  auricle. 

The  great  coronary  vein 1  com- 
mences at  the  apex  of  the  heart, 
ascends  along  the  anterior  interven- 
tricular  groove  in  company  with 
the  anterior  branch  of  the  left  cor- 
onary artery,  and  turns  to  the  left 
along  the  left  auriculo-ventricular 
groove  backward  to  end  in  the  com- 
mencement of  the  coronary  sinus. 
As  it  ascends  in  its  course  it  receives 
branches  from  the  front  of  the  ven- 
tricles and  the  interventricular  sep- 
tum, and  as  it  turns  to  the  left 
backward  it  receives  descending 
branches  from  the  left  auricle  and 
ascending  branches  from  the  left 
ventricle.  At  its  termination  its 
orifice  is  protected  by  a  valve,  usu- 
ally consisting  of  a  pair  of  folds. 

The  small  coronary  vein 2  runs  backward  along  the  right  auriculo- 
ventricular  groove,  receiving  branches  from  the  back  of  the  right  auricle 
and  ventricle,  and  ends  in  the  coronary  sinus  near  its  termination. 

The  middle  coronary  vein 3  commences  at  the  apex  of  the  heart, 
and  ascends  along  the  posterior  interventricular  groove,  receiving 
branches  from  the  back  of  both  ventricles  and  the  interventricular 
septum,  and  terminates  in  the  coronary  sinus  near  its  termination  and 
behind  the  former  vein. 

The  posterior  coronary  veins  are  several  small  branches,  of 
which  one  is  sometimes  considerably  the  largest,  ascending  from  the 
back  of  the  left  ventricle  to  end  in  the  coronary  sinus. 

The  coronary  sinus,4  about  an  inch  long,  occupies  the  back  part 
of  the  left  auriculo-ventricular  groove,  continued  from  the  great  cardiac 
vein  to  the  inner  lower  back  corner  of  the  right  auricle,  into  which  it 
opens  between  the  auriculo-ventricular  orifice  and  the  aperture  of  the 
inferior  cava.  The  sinus  is  enclosed  by  muscular  fibres  extending  from 
the  wall  of  the  right  auricle.  Its  orifice  communicating  with  the  latter 


POSTERIOR  VIEW  OF  THE  VEINS  OF  THE  HEART. 
1,  2,  right  and  left  auricles  ;  3,  4,  right  and  left 
ventricles ;  5,  aorta ;  6,  7,  superior  and  inferior 
cavse ;  8,  pulmonary  veins ;  9,  right  coronary 
artery;  10,  coronary  sinus;  11,  great  coronary 
vein ;  12,  middle  coronary  vein ;  13,  posterior 
coronary  veins ;  14,  small  coronary  vein  ;  15, 
oblique  vein ;  16,  anterior  coronary  vein. 


1  Great  cardiac  vein ;  v.  cardiaca,  coronaria,  or  cordis  magna. 

2  Small  or  right  cardiac  vein. 

3  V.  cordis  media ;  posterior  cardiac  vein.  4  Valve  of  Thebesius. 


548  THE    VEINS. 

is  protected  by  the  coronary  valve,  a  semilunar  fold  of  the  endocar- 
dium. All  the  chief  veins,  at  their  communication  with  the  coronary 
sinus,  are  protected  by  valves  more  or  less  complete. 

A  small  oblique  vein  descending  obliquely  from  left  to  right  at  the 
back  of  the  left  auricle,  sometimes  obliterated,  and  connected  with  the 
coronary  sinus,  is  with  the  latter  the  representative  of  the  left  superior 
cava  of  the  embryo. 

The  anterior  cardiac  veins 1  are  several  small  vessels,  which  as- 
cend on  the  front  and  right  border  of  the  right  ventricle  and  open  into 
the  right  auricle  above  the  auriculo-ventricular  groove.  They  are 
devoid  of  valves. 

Many  of  the  smallest  cardiac  veins,2  from  the  walls  of  the  heart, 
open  into  its  cavities,  but  especially  into  the  right  auricle  about  the 
interauricular  septum. 

THE   SUPERIOR   CAVA. 

The  superior  cava 3  is  the  principal  vein  which  returns  the  blood 
to  the  heart  from  the  head  and  neck,  the  upper  limbs,  and  the  walls 
of  the  thorax.  It  is  a  short  trunk,  about  three  inches  long,  and  is 
of  less  diameter  than  the  aorta,  to  the  right  of  which  it  lies.  It  is 
formed  by  the  conjunction  of  the  two  innominate  veins,  behind  the 
right  costo-sternal  articulation,  descends  vertically  with  a  slight  curve 
to  the  right,  and  terminates  in  the  upper  back  part  of  the  right  auricle 
of  the  heart.  It  is  unprovided  with  valves.  About  the  middle  of  its 
course  it  is  joined  by  the  azygos  vein,  and  immediately  below  enters  the 
pericardium. 

THE   INNOMINATE   VEINS. 

The  innominate  vein,4  on  each  side  of  the  body  behind  the  inner 
end  of  the  clavicle,  is  formed  by  the  union  of  the  internal  jugular  and 
subclavian  veins,  and  terminates  on  the  right  side,  behind  the  first 
costo-sternal  articulation,  by  joining  its  fellow  to  form  the  superior 
cava.  The  right  innominate  vein,  about  an  inch  long,  descends 
to  the  right  of  the  corresponding  artery ;  the  left  innominate  vein, 
nearly  three  times  as  long,  passes  from  right  to  left  with  a  slight 
downward  inclination  to  join  its  fellow.  Crossing  in  front  of  the  three 
large  arteries  springing  from  the  arch  of  the  aorta,  behind  the  upper 
border  of  the  sternum,  the  left  vein,  from  its  course,  has  also  been 
called  the  transverse  vein. 

The  innominate  veins  are  destitute  of  valves.  Each  is  joined  by 
the  corresponding  vertebral,  inferior  thyroid,  and  mammary  veins. 

1  Venae  Galeni.  2  Venae  Thebesii ;  v.  cordis  minimae. 

;  Vena  cava  superior,  descendens,  or  thoracica. 

4  Vena  innominata  or  anonyma ;  brachio-cephalic  vein ;  v.  brachio-cephalica ; 
v.  jugularis  communis. 


THE   VEINS. 


549 


The  vertebral  vein,1  with  a  plexiform  arrangement,  pursues  the 
course  of  the  vertebral  artery 
through  the  foramina  in  the  costo- 
transverse  processes  of  the  cervi- 
cal vertebrae,  but  does  not  accom- 
pany it  within  the  cranium.  It 
commences  in  branches  which 
proceed  from  the  pericranium 
and  the  muscles  contiguous  to 
the  occipital  foramen,  and  in  its 
course  receives  branches  from  the 
spinal  canal  through  the  interver- 
tebral  foramina,  and  communicates 
with  the  neighboring  superficial 
vertebral  veins.  Emerging  from 
the  sixth  cervical  vertebra  it  passes 
forward  over  the  subclavian  artery, 
and  ends  in  the  commencement  of 
the  innominate  vein.  Near  its  ter- 
mination it  receives  the  anterior 
vertebral,  deep  cervical,  and  su- 
perior intercostal  veins.  Occasion- 
ally it  continues  its  course  by  en- 
tering the  costo-transverse  process 
of  the  last  cervical  vertebra. 

The  anterior  vertebral  vein2 
commences  in  a  plexus  in  front  of 
the  cervical  vertebrae,  descends  in 
company  of  the  ascending  cervical 
artery,  receiving  branches  from 
the  contiguous  muscles,  and  joins 
the  vertebral  vein  near  its  termina- 
tion. 

The  deep  cervical  vein3  de- 
scends at  the  back  of  the  neck, 
between  the  complexus  and  semi- 
spinalis  muscles,  receiving  in  its 
course  the  occipital  vein,  and 
branches  from  the  dorsi-spinal  plexus  and  contiguous  muscles.  Turn- 
ing forward  beneath  the  costo-transverse  process  of  the  last  cervical 
vertebra,  it  ends  in  the  termination  of  the  vertebral  vein. 

The  inferior  thyroid  vein,4  of  large  proportionate  size,  proceeds 


VEINS  OF  THE  THORAX  AND  ABDOMEN.  1,  in- 
ferior cava ;  2,  right,  3,  left,  renal  veins ;  4,  supe- 
rior cava ;  5,  right,  6,  left,  innominate  veins ; 
7,  internal,  8,  external,  jugular  veins ;  9,  sub- 
clavian vein ;  10,  azygos  vein ;  11,  inferior, 
12,  superior,  hemi-azygos  veins. 


1  V.  vertebralis.  2  Y.  vertebralis  ant. 

3  V.  cervicalis  profunda ;  v.  vertebralis  externa  or  superficialis. 
*  V.  thyroidea  inf.  or  ima. 


550  THE    VEINS. 

from  the  lateral  lobe  of  the  thyroid  body,  in  which  its  many  branches 
freely  anastomose  with  the  middle  and  superior  thyroid  veins.  It 
anastomoses  with  its  fellow,  forming  a  plexus  below  the  thyroid 
isthmus,  in  front  of  the  trachea.  In  its  descent  it  receives  branches 
from  the  larynx,  trachea,  and  oesophagus.  The  left  inferior  thyroid 
joins  the  left  innominate  vein ;  and  the  right  inferior  thyroid,  the  right 
innominate  vein,  or  its  conjunction  with  the  left  innominate.  Some- 
times the  inferior  thyroids  unite  in  a  common  trunk,1  which  usually 
terminates  in  the  left  innominate  vein ;  and  occasionally  an  interme- 
diate vein  descends  from  the  thyroid  isthmus,  or  a  venous  plexus  below 
this,  to  end  in  the  left  innominate  vein. 

The  internal  mammary  vein,2  a  short  trunk  joining  the  innomi- 
nate vein,  is  formed  by  the  union  of  the  pair  of  companions  of  the 
corresponding  artery,  derived  from  similar  branches  in  the  walls  of  the 
thorax  and  abdomen. 

The  superior  intercostal  vein,3  subsequently  to  be  again  noticed, 
opens  into  the  innominate  vein. 

Small  veins  from  the  thymus  gland,  the  pericardium,  and  other 
structures  of  the  mediastinum  join  the  innominate  vein. 

VEINS   OF   THE   HEAD  AND  NECK. 

The  principal  venous  trunks  of  the  head  and  neck  are  the  jugulars, 
of  which  there  are  two  on  each  side,  a  larger  and  deeper,  the  internal 
jugular  vein,  and  an  external  jugular  vein.  Besides  these  are  the  ver- 
tebral and  inferior  thyroid  veins,  already  described.  All  the  veins  of 
the  head,  and  those  of  the  neck,  are  without  valves,  except  the  internal 
and  external  jugulars. 

THE    INTEENAL   JUGULAE  VEIN. 

The  internal  jugular  vein,*  much  the  larger  of  the  principal 
trunks,  and  usually  about  the  size  of  a  finger,  receives  the  blood  of 
the  cranial  cavity  and  the  orbit,  and  portions  of  that  of  the  face  and 
neck,  and  terminates  in  the  innominate  vein.  It  commences  with  the 
termination  of  the  lateral  sinus  of  the  dura  in  the  jugular  foramen  of 
the  skull,  where  it  forms  a  variable  dilatation,  the  jugular  gulf.5  From 
the  foramen  the  vein  descends  the  neck  at  the  outer  side  of  the  internal 
carotid  and  then  the  common  carotid  artery,  enclosed  in  the  same 
sheath,  and  behind  the  inner  end  of  the  clavicle  joins  the  subclavian 
vein  to  form  with  it  the  innominate  vein.  Its  termination  is  guarded 
by  a  pair  of  valves. 

1  V.  thyroidea  ima  impar.  2  V.  mammaria  interna. 

s  V.  intercostalis  sup. 

4  V.  jugularis  interna,  magna,  or  cerebralis  ;  v.  cephalica  interna  and  communis  ; 
v.  cerebralis. 

5  Bulb  or  sinus  of  the  jugular  vein  ;  bulbus  venae  jugularis. 


THE   VEINS. 


551 


The  internal  jugular  vein  is  very  variable  in  size  in  different  per- 
sons and  on  the  two  sides  of  the  neck,  the  right  one  usually  being 
the  longer,  but  it  maintains  a  reciprocal  proportion  with  its  fellow, 
and  also  in  a  measure  with  the  external  jugular  vein. 


FIG.  281. 


VEINS  OF  THE  HEAD  AND  NECK.  1,  frontal  vein ;  2,  nasal  vein ;  3,  4,  labial  veins ;  5,  facial  vein ; 
>6,  lingual  vein  ;  7,  internal  jugular  vein ;  8,  9,  posterior  and  anterior  temporal  veins ;  10,  trans- 
verse facial  vein;  11,  internal  maxillary  vein  ;  12,  posterior  auricular  vein;  13,  external  jugular 
vein;  14,  posterior,  15,  anterior,  jugular  veins,  a,  external  carotid  artery;  6,  sterno-mastoid 
muscle ;  c,  trapezius ;  d,  pectoral  muscle ;  e,  deltoid  muscle. 

In   its   course   the   internal  jugular   vein   receives    the    following 
tributaries : 

The  inferior  petrosal  sinus,1  which  issues  from  the  cranium  at 


1  S.  petrosus  inf. 


552  THE    VEINS. 

the  inner  division  of  the  jugular  foramen,  and  thence  opens  into  the 
internal  jugular  vein. 

The  pharyngeal  vein *  descends  from  the  pharyngeal  plexus,  a 
net-work  of  veins  in  the  walls  of  the  pharynx,  and  joins  the  internal 
jugular  vein  near  the  hyoid  bone.  Several  branches  may  substitute  it, 
partly  joining  the  latter  and  partly  the  facial  vein,  alone  or  together 
with  the  lingual  or  superior  thyroid  vein.  The  pharyngeal  plexus 
communicates  with  the  maxillary  plexus,  receives  the  vidian  and 
pterygo-palatine  veins,  and  branches  from  the  soft  palate,  the  eusta- 
chian  tube,  and  the  prevertebral  muscles. 

The  lingual  veins.  These  consist  of  several  branches  which 
emerge  from  the  tongue,  and  either  separately  or  after  uniting  in  a 
short  trunk  terminate  in  the  internal  jugular  or  the  facial  vein.  The 
longest  branch,  the  ranine  vein,2  commences  beneath  the  tongue,  where 
it  is  conspicuously  seen  through  the  mucous  membrane  at  the  side  of 
the  frsenum.  It  runs  backward  between  the  genio-glossal  and  hyo- 
glossal  muscles,  in  company  with  the  hypoglossal  nerve,  and  ends  in 
the  internal  jugular  or  facial  vein.  In  its  course  it  receives  branches 
from  the  tongue,  sublingual  gland,  and  adjacent  mucous  membrane. 
Two  small  companion  veins  3  pursue  the  course  of  the  lingual  artery, 
and  join  the  ranine  or  either  of  the  other  veins.  The  dorsal  lingual 
vein,4  accompanying  the  corresponding  arterial  branch,  issues  from  a 
plexus  beneath  the  mucous  membrane  at  the  root  of  the  tongue,  com- 
municating with  the  veins  of  the  tonsil  and  epiglottis,  and  descends  to 
terminate  in  the  internal  jugular  vein. 

The  facial  vein 5  is  subsequently  described. 

The  superior  thyroid  vein 6  is  derived  from  numerous  branches  ' 
of  the  thyroid  body.     It  accompanies  the  corresponding  artery,  and 
usually  joins  the  internal  jugular  vein  or  sometimes  the  facial  vein. 

The  middle  thyroid  vein,7  freely  anastomosing  with  the  branches 
of  the  superior  and  inferior  thyroid  veins,  passes  outwardly  from  the 
thyroid  body  over  the  carotid  artery,  and  joins  the  internal  jugular  vein. 

The  top  of  the  head  is  covered  with  a  subcutaneous  net-work  or 
plexus  of  veins,  from  which  branches  converge  and  descend  on  the 
forehead  as  the  frontal  vein,  on  the  temple  as  the  temporal  vein,  and 
from  the  occiput  as  the  posterior  auricular  and  occipital  veins. 

The  chief  superficial  vein  of  the  face  is  the  facial  vein;  the  chief 
deep  ones  are  the  internal  maxillary  and  ophthalmic  veins.  The  first 
commonly  terminates  in  the  internal  jugular  vein,  the  second  by  join- 
ing the  temporal  vein,  and  the  last  by  passing  backward  from  the  orbit 
and  opening  into  the  cavernous  sinus. 

The  facial  vein 8  pursues  nearly  the  course  of  the  facial  artery, 

1  V.  pharyngea.  2  V.  ranina.  3  V.  linguales. 

*  V.  dorsalis  linguae.  5  V.  facialis.  6  V.  thyroidea  sup. 

7  V.  thyroidea  media.  8  V.  facialis;  v.  f.  anterior  or  interna. 


THE   VEINS.  553 

but  is  less  tortuous  and  placed  more  back.  Commencing  at  the  inner 
border  of  the  orbit  as  the  angular  vein,  it  descends  obliquely  to  the 
base  of  the  mandible  in  advance  of  the  masseter  muscle.  Below  the 
jaw,  covered  by  the  platysma  muscle  and  cervical  fascia,  it  is  com- 
monly joined  by  the  anterior  fork  of  the  external  jugular  vein,  and 
near  the  hyoid  bone  terminates  in  the  internal  jugular  vein.  Occa- 
sionally it  turns  backward  on  the  sterno-mastoid  muscle,  and  joins  the 
external  jugular  vein. 

Its  tributaries  are  as  follows  : 

The  frontal  vein.1  This  descends  from  the  cranial  plexus  near  the 
median  line  of  the  forehead,  parallel  with  and  joining  its  fellow  by 
one  or  two  cross  branches,  and  at  the  root  of  the  nose  terminates  in 
the  angular  vein. 

The  supraorbital  vein.2  Smaller  than  the  former,  it  receives  its 
branches  from  the  brow  and  upper  eyelid,  and  is  directed  inward  to 
join  the  former  in  the  angular  vein.  It  anastomoses  with  the  oph- 
thalmic vein. 

The  angular  vein  3  is  the  commencement  of  the  facial  vein,  and  is 
commonly  visible  through  the  skin  near  the  inner  angle  of  the  eye  at 
the  side  of  the  root  of  the  nose.  Formed  by  the  union  of  the  two  pre- 
ceding veins,  it  receives  small  branches  from  the  eyelids,  the  palpebral 
veins,*  and  others  ascending  from  the  nose,  the  nasal  veins.5  It 
freely  communicates  with  the  ophthalmic  vein.  In  its  further  course 
as  the  facial  vein  it  receives  the  following  : 

The  supralabial  vein,6  arising  in  a  plexus  of  the  upper  lip. 

The  deep  facial  vein,7  from  the  maxillary  plexus  within  the  posi- 
tion of  the  ramus  of  the  jaw,  and  communicating  with  the  facial  vein 
from  below  the  malar  bone. 

Branches  from  the  parotid  gland  and  from  the  masseter  and 
buccinator  muscles. 

The  submental  vein,8  below  the  base  of  the  jaw,  and  receiving 
branches  from  a  plexus  of  the  lower  lip  and  from  the  chin. 

Branches  from  the  submaxillary  gland. 

The  inferior  palatine  vein,9  derived  from  a  plexus  of  the  tonsil 
and  soft  palate,  and  descending  at  the  side  of  the  pharynx. 

The  external  jugular  vein 10  is  variable  in  size  and  manner  of 
origin :  it  is  commonly  a  very  small  vessel  compared  with  the  in- 
ternal jugular  vein,  and  is  mostly  formed  by  the  conjunction  of  the 

1  V.  frontalis  ;  v.  preparata.  2  Y.  supraorbitalis. 

3  V.  angularis.  *  Y.  palpebrales. 

5  V.  nasales  dorsales  et  laterales,  pinnales,  or  alares.  6  V.  supralabialis. 

7  V.  facialis  profunda,  maxillaris  interna   anterior,  ramus  anastomoticus   pro- 
fundus. 

8  Y.  submentalis.  9  Y.  palatina ;  inferior  palatine  vein. 

10  V.  jugularis  externa  or  externa  posterior;  v.  cutanea colli posterior ;  v.  trachelo- 
subcutanea. 


554  THE    VEINS. 

temporal  and  maxillary  veins.  Commencing  behind  the  neck  of  the 
mandible,  it  descends  nearly  vertically  at  the  side  of  the  neck,  behind 
the  angle  of  the  jaw,  and  across  the  sterno-mastoid  muscle  to  the  supra- 
clavicular  fossa,  about  the  middle  of  the  position  of  the  clavicle.1  It 
is  covered  by  the  platysma  muscle,  and  perforates  the  cervical  fascia  of 
the  supraclavicular  fossa  to  terminate  in  the  subclavian  vein,  or  some- 
times in  the  end  of  the  internal  jugular  vein.  In  the  vicinity  of  the 
angle  of  the  jaw  it  commonly  gives  off  a  considerable  branch,  which 
descends  obliquely  forward  to  join  the  termination  of  the  facial  vein 
or  the  contiguous  portion  of  the  internal  jugular  vein.  In  its  course 
it  commonly  receives  the  posterior  auricular  vein,  the  anterior  and 
posterior  jugular  veins,  and  the  transverse  cervical  and  suprascapular 
veins.  Sometimes  it  also  receives  the  facial  vein,  in  whole  or  part,  and 
sometimes  it  does  not  receive  the  posterior  auricular  vein.  Rarely  it 
does  not  commence  in  the  temporal  and  internal  maxillary  veins  to- 
gether, and  then  appears  to  commence  in  the  latter  alone,  or  in  con- 
junction with  a  branch  of  the  occipital  vein.  It  has  an  imperfect  valve 
at  its  termination,  and  another  more  complete  a  short  distance  above. 

The  temporal  vein 2  arises  in  the  cranial  plexus  of  veins  by  two 
main  branches,  the  anterior  and  posterior  temporal  veins,3  corre- 
sponding with  but  not  closely  accompanying  the  arteries  of  the  same 
name,  and  lying  more  superficially.  Descending  the  temple  the  two 
branches  unite  in  front  of  the  ear,  whence  the  temporal  vein  passes 
over  the  zygoma  and  beneath  the  parotid  gland  to  the  neck  of  the 
mandible,  where  it  joins  the  internal  maxillary  vein  to  form  the  external 
jugular.  Other  tributaries  of  the  temporal  vein  are  as  follows  : 

The  middle  temporal  vein,4  derived  from  a  plexus  in  the  temporal 
fossa  communicating  with  the  deep  temporal  veins  and  with  the  ptery- 
goid  plexus  of  veins.  It  pierces  the  temporal  fascia,  and  receives  an 
orbital  branch  proceeding  from  the  palpebral  veins. 

The  anterior  auricular  veins,  small  branches  from  a  fine  plexus 
of  the  pinna. 

Branches5  from  an  articular  plexus  surrounding  the  articu- 
lation of  the  mandible. 

Branches  from  the  parotid  gland. 

One  or  two  transverse  facial  veins  from  the  cheek. 

The  internal  maxillary  vein 6  is  a  short  trunk,  sometimes  double, 

1  Many  authorities  name  the  trunk  formed  by  the  union  of  the  temporal  and 
internal  maxillary  veins  the  temporo-maxillary  vein,  which  is  then  described  as  de- 
scending to  the  vicinity  of  the  angle  of  the  jaw  and  dividing  into  two  branches, 
of  which  one  joins  the  facial  vein,  and  the  other  joins  with  the  posterior  auricular 
vein  to  form  the  external  jugular  vein. 

2  V.  temporalis.  3  V.  t.  superficialis  ant.  et  post. 
4  V.  t.  media.                                                       5  V.  articulares. 

6  V.  maxillaris  interna  or  interna  posterior ;  deep  branch  of  the  posterior  facial 


THE   VEINS.  555 

proceeding  in  company  with  the  internal  maxillary  artery,  behind  the 
neck  of  the  mandible,  from  the  pterygoid  plexus,  to  join  the  temporal 
vein  in  the  formation  of  the  external  jugular  vein.  Occasionally  a 
division  of  it  descends  within  the  ramus  of  the  jaw  and  joins  the 
internal  jugular  vein.  The  pterygoid  plexus l  is  a  close  net-work  of 
veins  accompanying  the  internal  maxillary  artery  between  the  ptery- 
goid muscles.  It  communicates  with  the  temporal,  pharyngeal,  and 
alveolar  venous  plexuses,  and  receives  the  following  tributaries  : 

Two  or  three  deep  temporal  veins  issuing  from  the  temporal 
muscle  and  plexus  of  veins  on  its  surface. 

Pterygoid,  masseter,  and  buccinator  branches,  issuing  from  the 
corresponding  muscles. 

An  alveolar  branch  from  the  alveolar  plexus,  on  the  surface  of  the 
maxilla. 

An  inferior  dental  vein  from  the  dental  canal  of  the  mandible. 

A  pair  of  great  meningeal  veins,2  companions  of  the  correspond- 
ing artery,  descending  through  the  spinous  or  oval  foramen. 

The  superior  palatine,  infraorbital,  and  nasal  veins,  accom- 
panying the  corresponding  arteries. 

The  posterior  auricular  vein,3  much  larger  than  the  correspond- 
ing artery,  issues  from  the  cranial  venous  plexus  back  of  the  ear,  de- 
scends on  the  mastoid  process  and  contiguous  portion  of  the  sterno- 
mastoid  muscle,  and  commonly  joins  the  external  jugular  vein,  but 
sometimes  turns  inwardly  and  ends  in  the  internal  jugular  vein.  It 
receives  the  stylo-mastoid  vein. 

The  occipital  vein4  issues  from  the  occipital  portion  of  the  cranial 
venous  plexus,  and  mainly  pursues  the  course  of  the  corresponding 
artery  between  the  muscles  at  the  back  of  the  neck,  descending  to 
terminate  in  the  deep  cervical  vein  or  the  internal  jugular  vein.  An 
outer  branch  communicates  with  the  mastoid  vein  and  the  lateral 
sinus.  Superficially,  it  may  communicate  with  the  posterior  auricular 
vein  or  with  the  external  jugular  vein. 

The  anterior  jugular  vein5  springs  from  superficial  branches  in 
the  submaxillary  region,  and  descends  in  front  of  the  neck  to  near  the 
inner  end  of  the  clavicle,  where  it  pierces  the  fascia  and  proceeds  out- 
wardly within  the  insertion  of  the  sterno-mastoid  muscle  to  join  the 
termination  of  the  external  jugular  vein.  In  descending  the  neck  it 
commonly  communicates  with  its  fellow  by  cross-branches,  and  some- 
times joins  it  part  way  in  a  single  median  vessel. 

The  posterior  jugular  vein,6  at  the  back  of  the  neck,  issues  from 
branches  of  the  integument  in  the  suboccipital  region,  and  descends  to 

1  P.  pterygoideus.  2  Venae  meningese  mediae. 

3  V.  auricularis  posterior.  4  V.  occipitalis. 

5  V.  jugularis  anterior  or  externus  anterior;  v.  mediani  colli ;  v.  cutanea  colli. 

6  V.  jugularis  posterior. 


556 


THE    VEINS. 


join  the  external  jugular  vein  about  the  middle  of  the  course  of  the 
latter. 

The  transverse  cervical1  and  suprascapular  veins2  accompany 
the  corresponding  arteries,  and  run  forward  in  the  supraclavicular  fossa 
to  join  the  external  jugular  vein,  but  not  unfrequently  end  in  the  sub- 
clavian  vein. 

VEINS  OF  THE   CEANIUM. 

The  veins  of  the  cranial  cavity  consist  of  the  sinuses  of  the  dura 
mater  and  the  veins  of  the  brain,  the  sinuses  being  intermediate  chan- 
nels of  the  circulation  between  the  latter  and  the  internal  jugular  veins. 

SINUSES   OF   THE   DUKA.3 

These  are  venous  channels  of  the  dura,  or  dura  mater,  which  in 

their  course  are  joined  by 

FIG.  282.  the  veins  of  the  brain  and 

the  ophthalmic  vein  from 
the  orbit,  and  terminate  at 
the  jugular  foramen  in  the 
internal  jugular  vein.  The 
sinuses  are  formed  between 
the  layers  of  the  dura,  and 
are  lined  by  a  delicate  mem- 
brane like  that  of  veins 
generally.  They  possess 
no  muscular  coat,  are  free 
from  valves,  and  do  not 
accompany  corresponding 
arteries. 

The  lateral  sinuses* 
are  the  main  channels  to 
which  the  other  sinuses 
converge.  They  commence 
at  the  internal  occipital 
protuberance,  turn  outward 
in  the  lateral  groove  of  the 
occipital  bone,  in  the  at- 
tachment of  the  tentorium, 
to  the  posterior  inferior 
angle  of  the  parietal  bone, 
curve  downward  in  the 
groove  of  the  mastoid  por- 
tion of  the  temporal  bone, 
and  forward  over  the  occip- 


SlNUSES  AT  THE  BASE  OF  THE  CRANIUM,  with  the  right 

orbit  exposed,  a,  eyeball ;  b,  optic  nerve ;  c,  occipital 
foramen  ;  d,  e,  f,  anterior,  middle,  and  posterior  cranial 
fossae.  1,  confluence  of  the  sinuses  from  which  the  lateral 
sinus  on  each  side  passes  off  to  terminate  at  the  jugular 
foramen ;  2,  ophthalmic  vein  ;  3,  cavernous  sinus ;  4,  cir- 
cular sinus  surrounding  the  sella;  5,  anterior  occipital 
sinus ;  6, 7,  superior  and  inferior  petrosal  sinuses ;  8,  poste- 
rior occipital  sinus;  9,  commencement  of  the  internal 
jugular  vein. 


1  V.  transversa  colli.  2  V.  transversa  scapulae. 

3  Sinus  durae  matris  ;  fistulse,  tubuli,  or  sanguiductus  durae  matris. 

4  S.  laterales  or  trans versi. 


THE   VEINS. 


557 


FIG.  283. 


ital  jugular  process,  and  terminate  at  the  jugular  foramen  in  the  gulf  of 
the  internal  jugular  vein.  They  commonly  differ  more  or  less  in  size, 
usually  the  right  one  being  the  larger.  Occasionally  one  sinus  exhibits 
a  great  reduction  in  size  when  the  other  is  proportionately  enlarged.1 

In  its  course  the  lateral  sinus  is  joined  by  the  superior  petrosal 
sinus,  and  receives  veins  from  the  back  of  the  cerebrum  and  from  the 
cerebellum.  It  also  receives  the  occipital  diploic  vein,  and  communi- 
cates with  veins  of  the  scalp  by  emissary  veins  through  the  mastoid 
and  posterior  condylar  foramina. 

The  longitudinal  sinus,2  a  single  median  channel,  commences  at 
the  anterior  extremity  of 
the  falx,  and  extends  back 
along  its  attached  border, 
occupying  the  median 
groove  of  the  cranial 
vault  and  gradually  en- 
larging in  its  course.  It 
is  trilateral,  and  has  the 
lower  angle  of  its  passage 
bridged  here  and  there  by 
fibrous  bands.3  It  usually 
communicates  with  the 
veins  of  the  scalp  by  em- 
issary veins  through  the 
parietal  foramina,  and  in 
its  course  receives  the 
superior  cerebral  veins  of 
the  brain.  Descending  on 
the  occipital  bone,  the  si- 
nus usually  deviates  a 
little  from  the  median  line 

to  one  side  of  the  occipital  protuberance,  mostly  the  right,  where 
it  becomes  somewhat  dilated,  and  then  abruptly  turns  into  the  corre- 
sponding lateral  sinus.  The  dilatation,  named  the  torcular,*  or  con- 
fluence of  the  sinuses,5  is  variable,  and  occupies  a  usually  well- 
marked  depression  of  the  occipital  bone.  From  it  a  branch  of  variable 
size  passes  over  the  occipital  protuberance  to  the  straight  sinus,  as  this 
curves  to  the  opposite  lateral  sinus.  Sometimes  the  longitudinal  sinus 
approaching  its  termination  retains  the  median  position,  and  the 

1  In  a  specimen  in  the  University  museum,  one  lateral  sinus  is  reduced  to  the 
condition  of  a  small  vein,  which  empties  itself  at  the  mastoid  foramen,  while  the 
venous  portion  of  the  jugular  foramen  of  that  side  is  almost  closed,  and  on  the  oppo- 
site side  the  lateral  sinus  and  jugular  foramen  are  very  large. 

2  Superior  longitudinal  sinus ;   s.  longitudinalis   sup. ;  s.  triangularis  ;  s.  falci- 
formis.  3  Chordae  Willisii. 

*  T.  Herophili  ;  wine-press  of  Herophilus.  5  Confluens  sinuum. 


VERTICAL  SECTION  OF  THE  SKULL,  exhibiting  the  sinuses 
of  the  dura.  1,  superior  longitudinal  sinus ;  2,  termination 
of  the  superior  cerebral  veins;  3,  inferior  longitudinal 
sinus ;  4,  internal  cerebral  veins ;  5,  straight  sinus  ;  6,  7, 
superior  and  inferior  petrosal  sinuses  of  the  right  side ; 
8,  right  lateral  sinus;  9,  commencement  of  the  left  lateral 
sinus;  10,  internal  jugular  vein,  a,  cerebral  falx ;  b,  ten- 
torium;  c,  cerebellar  fossa;  d,  partition  of  the  nose;  c, 
frontal  sinus ;  /,  sphenoidal  sinus. 


558  THE    VEINS. 

straight  sinus  opens  into  it  directly  in  front,  at  the  torcular,  from  the 
sides  of  which  issue  the  lateral  sinuses.  Sometimes,  also,  the  branch 
from  the  torcular  to  the  straight  sinus  is  as  large  as  that  to  the 
opposite  lateral  sinus,  in  which  case  the  lateral  sinuses  may  be  nearly 
or  quite  equal  in  size. 

The  straight  sinus :  inclines  backward  along  the  union  of  the  falx 
and  tentorium  to  the  occipital  protuberance,  where  it  is  commonly  con- 
tinued into  the  lateral  sinus  opposite  that  into  which  the  longitudinal 
sinus  is  prolonged,  and  is  connected  by  a  smaller  diverging  channel 
with  the  torcular.  It  receives  at  its  commencement  in  front  the  in- 
ferior longitudinal  sinus  and  the  vein  of  Galen,  and  along  its  course 
some  of  the  superior  cerebellar  veins,  and  several  small  branches  from 
the  tentorium. 

The  inferior  longitudinal  sinus2  is  a  narrow  channel  running 
along  the  lower  border  of  the  falx,  and  ending  behind  in  the  straight 
sinus.  It  receives  branches  from  the  falx,  and  occasionally  from  the 
inner  surfaces  of  the  cerebrum. 

The  occipital  sinus,3  a  small  channel,  sometimes  double,  ascends 
in  the  cerebellar  falx  and  opens  into  the  torcular.  It  forks  below,  and 
continues  around  the  occipital  foramen  to  join  the  termination  of  the 
lateral  sinuses.  Occasionally  it  is  much  reduced,  or  is  even  absent; 
and  sometimes  it  is  greatly  enlarged,  and  produces  a  conspicuous  ring 
around  the  occipital  foramen.  It  receives  several  small  veins  from  the 
cerebellum,  and  communicates  by  others  with  the  posterior  spinal 
veins. 

The  cavernous  sinus*  is  situated  at  the  side  of  the  sphenoidal 
body,  and  is  a  venous  plexus  extending  from  the  inner  extremity  of 
the  sphenoidal  foramen  to  the  apex  of  the  temporal  pyramid..  The 
two  sinuses  communicate  with  each  other  by  a  pair  of  transverse 
sinuses  crossing  through  the  sella,  thus  forming  together  a  circular 
sinus 5  around  the  pituitary  body.  Either  of  the  transverse  sinuses 
may  be  absent,  and  occasionally  there  is  a  third.  The  cavernous  sinus 
in  front  receives  the  ophthalmic  vein  through  the  sphenoidal  foramen, 
and  behind  it  communicates  with  the  petrosal  sinuses.  It  also  receives 
several  small  veins  from  the  cerebrum. 

The  venous  plexus  of  the  cavernous  sinus  is  continued  along  the 
carotid  canal,  around  the  internal  carotid  artery,  and  ends  below  in 
one  or  two  branches,  w^hich  join  the  internal  jugular  vein. 

Lying  along  the  floor  of  the  cavernous  sinus  inwardly,  covered  by 
the  lining  membrane,  is  the  internal  carotid  artery,  with  the  cavernous 
plexus  of  the  sympathetic  nerve  and  the  abducent  nerve,  and  passing 

1  S.  rectus,  quartus,  obliquus,  perpendicularis,  or  tentorii  medius. 

2  S.  longitudinalis  inf.,  or  minor;  s.  falciformis. 

3  S.  occipitalis  posterior.  4  S.  cavernosus ;  receptaculum  cavernosum. 
5  S.  circularis  Ridleyi ;  s.  coronarius  or  ellipticus. 


THE  VEINS.  559 

through  the  outer  wall  of  the  sinus  are  the  oculo-motor,  pathetic,  and 
ophthalmic  nerves. 

The  superior  petrosal  sinus *  is  a  narrow  channel  running  from 
the  cavernous  sinus  along  the  upper  border  of  the  temporal  pyramid, 
within  the  attachment  of  the  tentorium,  to  the  lateral  sinus  as  it  curves 
downward  into  the  groove  of  the  mastoid  portion  of  the  temporal  bone. 
It  receives  small  veins  from  the  cerebrum  and  cerebellum,  and  others 
from  the  tympanum  through  the  petro-squamous  fissure. 

The  inferior  petrosal  sinus,2  much  shorter  than  the  former,  runs 
from  the  cavernous  sinus  along  the  course  of  the  petro-occipital  suture 
to  the  inner  compartment  of  the  jugular  foramen,  through  which  it 
descends  to  end  in  the  jugular  vein.  It  receives  some  small  veins  from 
the  cerebellum  and  the  auditory  veins  from  the  internal  ear. 

The  sphenoidal  sinus3  is  a  small  channel  beneath  the  small  sphe- 
noidal  wing,  terminating  in  the  cavernous  sinus.  It  receives  small 
veins  of  the  dura,  and  communicates  with  the  anterior  temporal 
diploic  veins  and  the  great  meningeal  veins. 

The  basilar  sinus  *  is  a  transverse  venous  plexus  of  the  dura  on 
the  basilar  process  of  the  occipital  bone,  communicating  laterally  with 
the  inferior  petrosal  sinuses,  and  below  with  the  anterior  spinal  veins. 

OPHTHALMIC  VEIN. 

The  ophthalmic  vein5  returns  the  blood  from  the  parts  within  the 
orbit,  and  in  general  accords  with  the  distribution  of  the  corresponding 
artery.  It  commences  at  the  inner  angle  of  the  eye,  where  it  freely 
communicates  with  the  angular  vein ;  thence  passes  backward  in  com- 
pany with  the  ophthalmic  artery,  above  the  optic  nerve  to  its  outer 
side,  and  proceeds  through  the  inner  end  of  the  sphenoidal  foramen  to 
terminate  in  the  cavernous  sinus.  Its  branches,  which  mainly  cor- 
respond with  those  of  the  artery,  are  the  ethmoidal,6  muscular, 
anterior  and  long  ciliary,  central  retinal,  and  lachrymal  veins. 
The  short  ciliary  veins,7  usually  four,  issue  at  equidistant  points  from 
the  sides  of  the  eyeball,  and  join  the  ophthalmic  or  contiguous  muscu- 
lar veins.  The  lower  ciliary  and  muscular  veins  commonly  unite  in  a 
considerable  branch,8  which  communicates  by  an  anastomotic  branch 
through  the  spheno-maxillary  foramen  with  the  deep  facial  vein,  and 
joins  the  trunk9  of  the  ophthalmic  vein  or  ends  directly  in  the  cavern- 
ous sinus. 

1  S.  petrosus  sup. ;  s.  tentorii  laterals.  2  S.  petrosus  inf. 

3  Spheno-parietal  sinus  ;  s.  spheno-parietalis  ;  s.  alse  parvae. 

4  S.  basilaris  ;  s.  transversus ;  s.  occipitalis  ant.  ;  plexus  basilaris. 

5  V.  ophthalmica  ;  superior  ophthalmic  vein. 

6  V.  ethmoidalis  ant.  et  post. 

7  Posterior  ciliary  veins. 

8  Inferior  ophthalmic  vein  ;  v.  ophthalmica  inferior,  externa,  or  facialis. 

9  Sinus  ophthalmicus. 


560  THE    VEINS. 

VEINS   OF   THE  BKAIN. 

The  more  conspicuous  veins  of  the  brain  occupy  the  pia,  which 
closely  invests  the  surface  of  the  organ  and  penetrates  its  many  fis- 
sures, and  generally  only  the  finest  hair-like  veins  pervade  and  issue 
from  the  substance  of  the  brain  to  join  those  of  the  pia.  They  do  not 
accompany  the  arteries,  but  are  closely  associated  with  them  in  the 
pia,  and  freely  anastomose  with  one  another,  everywhere  forming  a 
continuous  net-work  or  plexus,  from  which  the  larger  veins  emerge  and 
terminate  in  the  nearest  sinus  of  the  dura. 

The  superior  cerebral  veins,1  six  to  ten  or  more  on  each  side 
of  the  cerebrum,  ascend  from  the  outer  surface  of  the  hemispheres 
inwardly,  mostly  along  the  fissures  between  the  convolutions,  to  the 
longitudinal  fissure,  where  they  are  joined  by  branches  from  the  mesial 
surface  of  the  hemispheres,  and  then  terminate  in  the  longitudinal 
sinus.  With  the  exception  of  the  most  anterior  smaller  ones  they 
run  obliquely  forward,  and  open  into  the  sinus  in  a  direction  opposite 
to  that  of  the  current  of  the  blood  in  the  latter. 

The  inferior  cerebral  veins 2  run  from  the  outer  and  lower  sur- 
faces of  the  cerebral  hemispheres  to  the  cavernous,  superior  petrosal, 
and  lateral  sinuses. 

A  large  branch,  the  middle  cerebral  vein,3  derived  from  the 
lower  surface  of  the  frontal  and  temporo-sphenoidal  lobes,  passes  from 
the  sylvian  fissure  and  terminates  in  the  cavernous  sinus.  Another 
branch,  the  anastomotic  vein,4  derived  from  the  outer  surface  of  the 
parietal  lobe,  where  it  communicates  with  the  superior  cerebral  veins, 
runs  along  the  posterior  fork  of  the  sylvian  fissure,  perforates  the 
dura  near  the  apex  of  the  small  sphenoidal  wing,  and  then  passes  back 
through  the  middle  cranial  fossa  to  the  superior  petrosal  sinus ;  in  its 
course  communicating  with  the  great  meningeal  veins. 

The  veins  in  the  central  part  of  the  cerebrum  collect  finally  in  a 
short  trunk,  the  vein  of  Galen,5  which  is  formed  by  the  union  of  two 
chief  branches,  the  internal  cerebral  veins,  and  terminates  immedi- 
ately behind  in  the  commencement  of  the  straight  sinus.  It  also  re- 
ceives small  branches  from  the  contiguous  part  of  the  callosum,  from 
the  posterior  cornu  of  the  lateral  ventricle  and  the  quadrigeminal  and 
pineal  bodies.  In  addition  it  receives  the  basilar  vein,6  which  ascends 
from  the  base  of  the  cerebrum,  where  it  derives  tributaries  from  the 
anterior  perforated  space,  the  cinereous  tuber,  the  mammillary  emi- 
nences, and  the  cerebral  crus. 

The  internal  cerebral  veins 7  commence  at  the  foramen  of  JVf  onro, 


1  Venae  cerebri  superiores.  2  V.  cerebri  inferiores. 

3  Vena  fossae  Sylvii.  *  Great  anastomotic  vein. 

5  V.  magna  Galeni.  6  V.  basilaris  ;  v.  adscendens. 

7  V.  cerebri  internae  or  magnae  ;  venae  Galeni ;  v.  choroidese  mediae. 


THE   VEINS.  561 

each  by  the  conjunction  of  the  striatum  and  choroid  veins,  run  back- 
ward near  together  along  the  middle  of  the  choroid  tela,  and  unite  to 
form  the  vein  of  Galen.  In  their  course  they  receive  branches  from 
the  thalami  and  choroid  plexuses  beneath  of  the  third  ventricle. 

The  striatum  vein 1  runs  forward  in  the  groove  between  the  stri- 
atum and  the  thalamus,  receiving  branches  from  both,  and  from  the 
ventricular  septum,  the  callosum,  and  the  fornix,  and  unites  with  the 
choroid  vein. 

The  choroid  vein 2  starts  from  the  bottom  of  the  descending  cornu 
of  the  lateral  ventricle,  where  it  communicates  with  veins  in  the  syl- 
vian  fissure,  and  ascends  along  the  course  of  the  choroid  plexus  to  the 
foramen  of  Monro,  where  it  joins  the  striatum  vein  to  form  the  in- 
ternal cerebral  vein.  It  receives  branches  from  the  choroid  plexus  and 
the  hippocampus. 

The  veins  of  the  cerebellum  are  disposed  in  two  series.  The  supe- 
rior cerebellar  veins3  are  partly  directed  inward  and  upward  to  the 
straight  sinus  and  the  vein  of  Galen,  and  partly  outward  to  the  supe- 
rior petrosal  and  lateral  sinuses.  The  inferior  cerebellar  veins,*  and 
veins  of  the  pons  and  oblongata,  join  the  inferior  petrosal,  lateral,  and 
occipital  sinuses. 

THE   DIPLOIC   VEINS. 

The  diploic  veins5  form  an  irregular  net- work  or  plexus  in  the 
diploe  of  the  cranial  vault,  and  may  be  exposed  by  removal  of  the 
external  table  of  the  bones.  They  enlarge  and  become  more  conspicu- 
ous in  the  advance  of  life,  and  in  old  age  communicate  more  or  less 
across  the  sutures.  Lodged  in  canals  of  the  diploe,  they  have  a  deli- 
cate membranous  wall,  corresponding  with  the  internal  tunic  of  veins, 
and  are  devoid  of  a  muscular  tunic.  They  are,  for  the  most  part, 
directed  downward,  and  communicate  with  the  superficial  veins,  and 
with  the  sinuses  and  veins  of  the  dura.  Four  principal  veins  are 
commonly  evident  on  each  side  of  the  cranium,  and  are  named  from 
their  position. 

The  frontal  diploic  vein 6  arises  from  the  plexus  of  the  frontal 
diploe,  and  commonly  issues  at  the  supraorbital  foramen  to  join  the 
supraorbital  vein.  This  outlet  being  sometimes  absent,  the  frontal 
diploic  vein  may  terminate  in  the  succeeding  vein. 

The  anterior  temporal  diploic  vein 7  arises  in  the  frontal  diploe. 
and  often  also  in  the  contiguous  parietal  diploe,  passes  through  a 
foramen  of  the  great  sphenoidal  wing,  and  thence  proceeds  in  the 
dura  to  end  in  the  cavernous  sinus.  It  also  communicates  externally 


1  Vena  corporis  striati ;  v.  reflexa ;  v.  velata. 

2  V.  choroidea ;  v.  c.  lateralis.  3  Venae  cerebelli  superiores. 
4  V.  cerebelli  inferiores.  5  V.  diploicae  or  diploeticse. 
6  Vena  diploica  frontalis.  T  V.  d.  temporalis  anterior. 

36 


562  THE    VEINS. 

with  the  deep  temporal  veins,  and  internally  with  the  great  meningeal 
veins. 

The  posterior  temporal  diploic  vein  l  arises  in  the  plexus  of  the 
parietal  diploe,  and  emerges  through  a  foramen  at  the  lower  posterior 
angle  of  the  parietal  bone,  or  through  the  mastoid  foramen,  to  open  in 
the  lateral  sinus. 

The  occipital  diploic  vein'2  descends  from  the  plexus  of  the  oc- 
cipital diploe,  and  opens  into  the  occipital  vein,  the  torcular,  or  the 
lateral  sinus. 

THE   EMISSAKY   VEINS. 

The  emissary  veins 3  are  those  which  pass  through  foramina  of 
the  cranium  and  communicate  between  the  sinuses  of  the  dura  and  the 
superficial  veins.  They  are  inconstant,  and  vary  much  in  size. 

The  mastoid  vein,4  the  most  constant  and  the  largest  of  the  emis- 
saries, communicates  through  the  mastoid  foramen,  between  the  lateral 
sinus  and  a  branch  of  the  occipital,  or  of  the  posterior  auricular  vein. 

The  parietal  vein,5  usually  small  and  often  absent,  communicates 
through  the  parietal  foramen,  between  the  longitudinal  sinus  and  the 
contiguous  veins  ef  the  scalp. 

The  condylar  vein,6  also  inconstant  and  variable  in  size,  communi- 
cates through  the  posterior  condylar  foramen,  between  the  lateral  sinus 
and  the  dorsi-spinal  plexus  of  veins  of  the  cervical  vertebra. 

VEINS   OF   THE   UPPER   LIMBS. 

The  deep  veins  of  the  upper  limb  retrace  the  course  of  the  arteries, 
closely  accompanying  them  in  their  distribution,  all,  except  the  prin- 
cipal trunk,  the  subclavian  and  its  continuation  the  axillary  artery, 
having  two  companion  veins,  which  lie  on  each  side  of  the  arteries 
and  communicate  here  and  there  by  branches  crossing  the  latter.  In 
their  course  the  deep  veins  frequently  communicate  with  the  superficial 
veins  by  branches  which  ascend  from  the  former  through  the  deep 
fascia. 

The  subclavian  vein 7  is  the  continuation  of  the  axillary  vein  over 
the  first  rib,  and  is  separated  from  the  subclavian  artery  by  the  inser- 
tion of  the  anterior  scalenus  muscle.  It  receives  the  external  jugular 
vein  in  front  of  the  latter,  and  terminates  at  the  inner  border  of  the 
muscle  by  joining  the  internal  jugular  in  the  formation  of  the  innomi- 
nate vein. 

The  axillary  vein 8  extends  along  the  inner  side  of  the  axillary 
artery  to  the  outer  border  of  the  first  rib,  whence  it  continues  as 

1  Vena  diploica  t.  posterior.  2  V.  d.  occipitalis. 

3  Venae  emissariae  Santorini.  4  Vena  emissaria  mastoidea. 

5  V.  e.  parietalia.  6  V.  e.  condyloidea.    . 

7  V.  subclavia.  8  V.  axillaris. 


THE    VEINS. 


563 


the  subclavian  vein.  It  com- 
mences at  the  outer  border  of 
the  axilla  by  the  union  of  the 
brachial  veins,  and  the  inner 
of  these  with  the  basilic  vein. 
In  its  course  it  receives  the 
circumflex,  subscapular, 
and  thoracic  veins  accom- 
panying the  corresponding  ar- 
teries, and  near  its  termination 
the  cephalic  vein. 

The  brachial  veins,1  com- 
panions to  the  brachial  artery, 
lie  closely  applied  to  the  outer 
and  inner  side,  communicating 
by  short  branches  crossing  the 
artery.  The  inner  vein,  com- 
monly the  larger,  is  usually 
joined  at  some  part  of  its 
course  above  the  middle  of  the 
arm  by  the  basilic  vein,  and 
the  vessel  is  thus  continued 
into  the  axillary  vein,  joined 
at  the  axilla  by  the  outer  bra- 
chial vein.  In  other  instances 
the  brachial  veins  continue  to 
the  axilla,  unite,  and  then  join 
with  the  basilic  vein,  or  they 
successively  unite  with  the 
latter  to  form  the  axillary 
vein. 

The  subcutaneous  veins  of 
the  upper  limb  form  a  net- 
work or  plexus  in  the  super- 
ficial fascia  and  adipose  tissue 
between  the  skin  and  the  deep 
fascia.  Commencing  in  plex- 
uses of  the  fingers,  those  of 
the  hand,  forearm,  and  arm 
successively  enlarge  and  com- 
municate with  the  plexus  of 
the  shoulder  and  thorax.  As 
constituents  of  the  plexuses, 
larger  and  continuous  veins, 


FIG.  284. 


L._6 


-.1 


SUPEKFICIAL  VEINS  OF  THE  UPPER  LIMB.  1,  me- 
dian vein ;  2,  3,  radial  cutaneous  veins ;  4,  5,  ul- 
nar  cutaneous  veins;  6,  median  cephalic  vein;  7, 
median  basilic  vein ;  8,  anastomosis  with  the  deep 
veins;  9,  cephalic  vein;  10,  its  further  course  seen 
through  the  brachial  fascia;  11, 12,  basilic  vein. 


1  Venae  brachiales. 


564  THE    VEINS. 

more  or  less  variable,  form  the  chief  branches,  which  ordinarily  unite  in 
the  two  superficial  trunks  of  the  arm,  the  cephalic  and  basilic  veins, 
finally  terminating  in  the  axillary  vein. 

The  dorsal  veins  of  the  hand  are,  for  the  most  part,  larger  than  the 
palmar  veins.  From  the  dorsal  plexuses  of  the  digits  ascend  at  the  sides 
digital  veins,1  of  which  the  collateral  ones  unite  between  the  knuckles 
in  interosseous  veins.2  The  dorsal  veins  of  the  thumb,  contiguous 
side  of  the  index  finger,  and  outer  part  of  the  hand  unite  in  a  lai'ge 
branch,3  while  those  from  the  other  fingers  and  back  of  the  hand  unite 
in  a  second  large  branch,*  which  ascends  to  join  the  former  at  the 
outer  part  of  the  forearm,  and  produces  with  it  the  radial  vein.  Veins 
from  the  little  finger  and  the  inner  part  of  the  dorsal  plexus  of  the  hand 
unite  to  form  the  commencement  of  the  ulnar  vein  ascending  behind 
the  inner  border  of  the  forearm. 

The  principal  veins  of  the  forearm  issuing  from  its  plexus  and  that 
of  the  hand  are  the  radial,  ulnar,  and  median  veins. 

The  radial  vein,5  arising  in  the  manner  above  indicated  in  the 
dorsal  plexus  of  the  hand,  ascends  outwardly  on  the  back  of  the  fore- 
arm, and  turns  forward  to  the  outer  groove  in  front  at  the  bend  of 
the  elbow,  where  it  unites  with  the  median  cephalic  vein  to  form  the 
cephalic  vein. 

The  ulnar  vein6  arises  from  the  inner  part  of  the  plexus  of  the 
hand,  ascends  along  the  back  inner  border  of  the  forearm,  and  turns 
forward  below  the  inner  condyle  to  unite  with  the  median  basilic  vein 
in  the  formation  of  the  basilic  vein.  Besides  smaller  branches  in  its 
course,  it  commonly  receives  a  large  one  near  its  termination,  the 
anterior  ulnar  vein,  which  arises  from  the  palmar  plexus,  at  the 
inner  fore  part  of  the  forearm. 

The  median  vein,7  very  variable,  sometimes  arises  in  several 
branches  from  the  outer  part  of  the  palmar  plexus,  and  sometimes 
from  the  plexus  of  the  thumb  and  the  outer  part  of  the  dorsal  plexus 
of  the  hand.  Commonly  small,  it  may  be  large  and  form  the  chief 
vein  from  the  dorsal  plexus  of  the  hand,  in  which  case  the  radial  vein 
is  proportionately  reduced.  Ascending  in  front  of  the  forearm  to  the 
depression  in  the  bend  of  the  elbow,  it  forks  into  the  median  cephalic 
and  median  basilic  veins.  Near  its  bifurcation  it  receives  the  deep 
median  vein,  a  communicating  branch  ascending  from  one  of  the 
contiguous  deep  veins. 

The  median  cephalic  vein8  ascends  outwardly  in  the  groove  of 
the  biceps  and  long  supinator  muscles,  and  joins  the  radial  vein  to 


1  Venae  digitales.  2  V.  interossese  superflciales  ;  v.  metacarpeae. 

3  Vena  cephalica  pollicis.  4  V.  salvatella. 

5  V.  radialis  ;  v.  r.  cutanea  or  cephalica. 

6  V.  ulnaris ;  v.  u.  cutanea  ;  v.  basilica ;  posterior  ulnar  vein. 
1 V.  mediana.  8  V.  m.  cephalica. 


THE    VEINS.  565 

form  the  commencement  of  the  cephalic  vein.  The  musculo-cutaneous 
nerve,  in  its  course,  passes  beneath  it. 

The  median  basilic  vein,1  usually  larger  than  the  former,  ascends 
inwardly  over  the  position  of  the  brachial  artery,  from  which  it  is  sepa- 
rated by  an  offset  of  the  biceps  tendon  to  the  fascia,  and  joins  the  ulnar 
vein  to  form  the  commencement  of  the  basilic  vein.  In  its  course  it 
may  receive  the  anterior  ulnar  vein  and  other  branches  from  the  plexus 
of  the  forearm.  Branches  of  the  internal  cutaneous  nerve  cross  above 
and  beneath  the  vein. 

The  median  vein  is  liable  to  much  variation  in  its  termination.  The 
median  cephalic  vein  may  be  very  small  or  absent,  and  the  median  ba- 
silic vein  proportionately  large.  In  such  instances  the  radial  vein  may 
fork,  and  one  branch  continue  as  the  cephalic  vein,  while  the  other 
branch  may  join  the  median  vein,  and  together  with  the  median  basilic 
vein  form  an  oblique  trunk,  which  crosses  the  forearm  from  without 
inward,  and  receives  in  its  course  branches  from  the  plexus  below. 

The  cephalic  vein2  ascends  along  the  arm  in  the  groove  at  the 
outer  border  of  the  biceps  muscle,  thence  between  the  pectoral  and 
deltoid  muscles  to  the  clavicle,  below  which  it  dips  to  join  the  ax- 
illary vein.  In  its  course  it  receives  branches  from  the  subcutaneous 
plexus  of  the  arm,  shoulder,  and  breast.  It  is  sometimes  much  re- 
duced, and  may  be  absent.  Occasionally  it  passes  over  the  clavicle 
and  joins  the  external  jugular  vein,  or  it  may  be  united  with  this  by 
a  communicating  branch. 

The  basilic  vein,3  much  larger  than  the  former  or  either  of  the 
brachial  veins,  ascends  the  arm  along  the  inner  border  of  the  biceps 
muscle,  and  inwardly  to  the  position  of  the  brachial  vessels.  Perfo- 
rating the  fascia  near  the  middle  of  the  arm,  it  joins  the  inner  of  the 
brachial  veins,  or  continues  upward  into  the  axillary  vein.  Its  lower 
part  receives  branches  communicating  with  the  cephalic  vein. 

THE   INFEKIOK   CAVA. 

The  inferior  cava 4  is  the  main  trunk  which  returns  the  blood  to 
the  heart  from  the  lower  limbs  and  abdomen.  It  commences  in  the 
latter  cavity,  by  the  union  of  the  iliac  veins  in  front  of  the  last  lumbar 
vertebra,  ascends  to  the  right  of  the  aorta,  and  passes  through  an 
opening  in  the  central  tendon  of  the  diaphragm  into  the  thorax, 
where  it  enters  the  pericardium,  and  terminates  in  the  lower  part 
of  the  right  auricle  of  the  heart.  In  its  course  it  is  .covered  by  the 
mesentery,  the  duodenum,  and  the  pancreas,  and  is  then  lodged  in  a 
deep  groove  of  the  liver ;  and  rests  behind  upon  the  lumbar  vertebra 
and  the  right  cms  of  the  diaphragm.  It  is  a  larger  trunk  than 

1  Vena  mediana  basilica.  2  V.  cephalica. 

3  V.  basilica.  4  V.  cava  inferior  or  adscendens. 


566 


THE    VEINS. 


the  superior  cava  or  the  aorta,  and  contains  no  valves.     Besides  the 

common  iliac  veins  it  receives  the  following : 

The  lumbar  veins,1  accom- 
panying the  corresponding  ar- 
teries. They  arise  in  an  ante- 
rior branch  from  the  wall  of 
the  abdomen,  where  it  anasto- 
moses with  the  epigastric  -and 
other  contiguous  veins,  and  a 
posterior  branch,  larger  than 
the  former,  derived  from  the 
intraspinal  and  dorsi -spinal  plex- 
uses and  from  the  muscles  of  the 
back.  Passing  forward  on  the 
lumbar  centra,  behind  the  psoas 
muscle,  and  on  the  left  behind  the 
aorta,  they  terminate  in  the  back 
part  of  the  inferior  cava.  In  front 
of  the  transverse  process  they  are 
united  by  longitudinal  branches, 
together  forming,  on  each  side, 
the  ascending  lumbar  vein,2 
which  anastomoses  variably  with 
the  lateral  sacral,  ilio-lumbar,  and 
common  iliac  veins,  and  terminates 
in  the  azygos  vein  on  the  right 
and  the  inferior  hemi-azygos  on 
the  left  side. 

AZYGOS  AND   HEMI-AZYGOS 

VEINS. 

I 

The  azygos  and  hemi-azygos 
veins  ascend  along  the  back  of 
the  thoracic  cavity,  and  arise  from 
the  veins  which  accompany  most 
of  the  intercostal  and  partly  the 
lumbar  arteries. 

The  azygos  vein 3  commences 
in  the  abdomen  in  the  right  ascend- 
ing lumbar  vein,  whence  it  ascends  on  the  right  side  of  the  lumbar 
centra,  enters  the  thorax  through  the  right  crus  of  the  diaphragm  or 
the  aortic  orifice,  and  continues  upward  on  the  thoracic  centra  to  the 
fourth  one,  where  it  arches  forward  over  the  root  of  the  right  lung, 


VEINS  OF  THE  THORAX  AND  ABDOMEN.  1,  in- 
ferior cava;  2,  right,  3,  left,  renal  veins ;  4,  supe- 
rior cava ;  5,  right,  6,  left,  innominate  veins :  7, 
internal,  [8,  external,  jugular  veins :  9,  subcla- 
vian  vein ;  10,  azygos  vein ;  11,  inferior,  12, 
superior  hemi-azygos  veins. 


1  Venae  lumbares.  2  Vena  lumbaris  adscendens. 

3  Eight  or  large  azygos  vein ;  v.  azygos  major  or  dextra  ;  v.  sine  pari. 


THE    VEINS.  567 

and  ends  in  the  superior  cava  as  this  vessel  enters  the  pericardium.  In 
its  course  it  is  situated  close  to  the  right  of  the  thoracic  duct  and  the 
aorta,  crosses  over  the  right  intercostal  arteries,  and  lies  behind  the 
pleura.  Besides  the  ascending  lumbar  vein,  it  commonly  receives  the 
right  intercostal  veins,  except  the  upper  one  or  two,  the  hemi-azygos 
veins  separately  or  in  common,  the  right  bronchial  vein,  and  small 
branches  from  the  oesophagus,  pericardium,  and  other  structures  con- 
tiguous. There  is  ordinarily  a  valve  in  the  arch  of  the  azygos  vein. 

The  hemi-azygos  veins  commonly  appear  as  two  trunks,  which  relate 
with  the  left  intercostal  veins  as  the  azygos  does  with  the  right  ones, 
and  they  open  separately  or  in  conjunction  with  each  other  into  the 
azygos  vein.  They  usually  receive  the  lower  nine  or  ten  left  inter- 
costal veins  variably  divided  between  them,  but  sometimes  one  to 
three  of  the  intermediate  intercostals  open  alone  or  in  conjunction 
directly  into  the  azygos  vein. 

The  superior  hemi-azygos  vein,1  formed  by  the  union  of  the 
upper  four  to  six  intercostal  veins,  excepting  the  first  one  or  two  with 
which  it  anastomoses,  descends  on  the  left  side  of  the  vertebra?  to  near 
the  middle  of  the  thorax,  where  it  crosses  behind  the  aorta  and  thoracic 
duct,  and  ends  in  the  azygos  vein,  or  it  unites  below  with  the  inferior 
hemi-azygos  vein.  It  receives  the  left  bronchial  vein,  some  of  the  larger 
oesophageal  veins,  and  other  small  ones  from  the  mediastinum. 

The  inferior  hemi-azygos  vein2  commences  on  the  left  side  in 
the  manner  of  the  azygos,  ascends  through  the  left  crus  of  the  dia- 
phragm, and  on  the  left  side  of  the  thoracic  vertebra?  to  the  ninth, 
eighth,  or  seventh,  and  crosses  behind  the  aorta  and  thoracic  duct  to 
join  the  azygos  vein.  It  usually  receives  the  lower  three  or  four  left 
intercostal  veins,  some  of  the  larger  oesophageal  veins,  and  other  small 
ones  from  the  mediastinum. 

The  intercostal  veins 3  accompany  the  corresponding  arteries  in  the 
intercostal  spaces  lying  above  the  latter.  They  are  single  vessels,  and 
are  ioined  by  dorsal  branches  derived  from  the  veins  of  the  back  of 
the  thorax,  from  the  dorsi-spinal  plexus,  and  those  of  the  spinal  canal 
through  the  intervertebral  foramina.  Those  of  the  lower  ten  or  nine 
intercostal  spaces  usually  terminate  in  the  azygos  and  inferior  hemi- 
azygos  veins,  as  already  described.  The  first  one,  alone  or  conjoined 
with  the  second,  forms  the  superior  intercostal  vein,4  which  usually 
terminates  in  the  corresponding  innominate  vein,  or  may  join  the  ver- 
tebral vein.  Sometimes  by  an  enlargement  the  left  superior  intercostal 
vein  substitutes  the  superior  hemi-azygos  vein,  and  occasionally  all  the 
left  intercostal  veins  unite  in  a  common  trunk  opening  into  the  left 


1  Left  upper  azygos  vein ;  v.  hemi-azygos  superior  or  accessoria. 

2  Left  lower  or  small  azygos  vein  ;  v.  hemi-azygos  ;    v.  hemi-azyga  ;   v.  azygos 
sinistra  or  parva. 

3  Venae  intercostales.  *  Vena  intercostalis  superior. 


568  THE    VEINS. 

innominate  vein.  Earely,  the  azygos  vein  receives  directly  the  inter- 
costal veins  of  both  sides. 

Commonly  the  upper  intercostal  veins  have  valves  at  their  com- 
munication with  the  azygos  and  hemi-azygos  veins. 

The  bronchial  veins  are  small  vessels  accompanying  the  corre- 
sponding arteries  and  emerging  from  the  roots  of  the  lungs,  where 
they  receive  branches  from  the  lower  part  of  the  trachea.  The  right 
bronchial  vein  opens  into  the  azygos  vein  near  its  termination,  and  the 
left  one  ends  in  the  superior  hemi-azygos  vein. 

Besides  the  usual  manner  of  commencement  of  the  azygos  and 
inferior  hemi-azygos  veins,  they  often  communicate  with  other  veins 
of  the  region,  with  the  inferior  cava,  or  with  the  renal,  suprarenal, 
spermatic,  or  phrenic  veins. 

VEINS   OP   THE   SPINE. 

These  form  plexuses  which  extend  the  length  of  the  vertebral  col- 
umn, and  freely  communicate  with  one  another.  They  consist  of  the 
dorsi-spinal  plexus,  the  intraspinal  plexus,  the  central  veins,  and  the 
veins  of  the  spinal  cord. 

The  dorsi-spinal  plexus1  is  a  net-work  of  veins  investing  the 
arches  of  the  vertebrae  and  receiving  branches  from  the  contiguous 
muscles  and  skin  of  the  back.  The  largest  branches  pass  inward  be- 
tween the  spinous  processes,  after  proceeding  from  a  median  vein  pass- 
ing over  the  ends  of  the  latter.  It  communicates  by  branches  perfo- 
rating the  yellow  ligaments  with  the  posterior  veins  of  the  intraspinal 
plexus.  From  it  pass  off  branches  between  the  transverse  processes, 
which  terminate  in  the  dorsal  branches  of  the  intercostal  and  lumbar 
veins,  or  in  the  neck  in  the  vertebral  vein. 

The  intraspinal  plexus 2  is  an  irregular  net-work  of  veins  invest- 
ing the  spinal  canal  and  discharging  itself  through  branches  which 
emerge  at  the  intervertebral  foramina  into  the  dorsal  branches  of  the 
intercostal  and  lumbar  veins,  and  into  the  vertebral  and  lateral  sacral 
veins.  It  is  composed  of  a  pair  of  plexiform  anterior  longitudinal 
veins,  situated  at  the  sides  of  the  centra  in  front  of  the  canal,  and  a 
smaller  pair  of  posterior  longitudinal  veins  at  the  sides  of  the  arches 
behind  the  canal,  all  freely  communicating  with  one  another  by  cross 
branches.  The  anterior  longitudinal  veins  are  more  expanded  at  the 
centra  and  narrowed  at  the  intervertebral  disks,  and  are  joined  by 
transverse  veins,  which  receive  the  central  veins  and  emerge  from 
between  the  centra  and  the  posterior  vertebral  ligament. 

The  central  veins 3  occupy  the  interior  canals  of  the  centra,  anas- 
tomosing with  veins  in  front  of  the  vertebrae,  and  communicating  be- 

1  Dorsal  spinal  veins. 

2  Anterior  and  posterior  internal  plexus  of  the  spinal  canal. 

3  Veins  of  the  bodies  of  the  vertebrae. 


THE    VEINS.  569 

hind  through  the  single  or  double  foramen  with  the  transverse  veins 
of  the  intraspinal  plexus. 

The  veins  of  the  spinal  cord  are  small  and  tortuous,  and  form 
a  plexus  with  elongated  meshes  in  the  pia.  They  are  larger  below,  and 
one  exceeding  the  others  ascends  along  the  anterior  median  fissure  be- 
hind the  anterior  spinal  artery.  They  open  into  the  intraspinal  plexus 
by  branches  which  follow  the  nerves  to  the  intervertebral  foramina, 
and  above  they  communicate  by  several  small  branches  with  the 
inferior  cerebellar  veins  or  open  into  the  inferior  petrosal  sinus. 

BKANCHES   OF   THE   INFERIOE  CAVA. 

The  spermatic  veins.1  The  veins  issuing  from  the  testicle  and 
epididymis  form  the  spermatic  plexus,2  which  is  composed  of  tor- 
tuous vessels  ascending  in  the  spermatic  cord  and  passing  through  the 
inguinal  canal.  From  the  plexus  two  or  three  veins  continue  and  unite 
in  a  single  trunk,  the  spermatic  vein,  which  ascends  in  company 
with  the  spermatic  artery  in  front  of  the  psoas  muscle  under  the  peri- 
toneum, and  terminates  on  the  right  in  the  inferior  cava  and  on  the 
left  in  the  renal  vein.  Occasionally  it  divides  near  its  termination, 
when  one  branch  may  end  in  the  inferior  cava  and  the  other  in  the 
renal  vein. 

Incomplete  valves  are  found  in  the  spermatic  plexus,  and  generally 
there  is  a  valve  at  the  termination  of  each  spermatic  vein.  Some- 
times the  valve  is  absent  in  the  left  vein,  and  it  is  then  usually  substi- 
tuted by  one  in  the  renal  vein. 

The  ovarian  veins 3  have  the  same  general  course  as  the  corre- 
sponding arteries,  and  they  are  derived  from  the  ovarian  plexus 
enclosed  in  the  broad  ligament. 

The  renal  veins  consist  of  a  short,  thick  trunk  on  each  side,  formed 
by  branches  emerging  from  the  sinus  of  the  kidney,  and  passing  inward 
and  forward  in  front  of  the  corresponding  arteries  to  join  the  inferior 
cava.  The  left  renal  vein,  longer  and  usually  a  little  higher  than  the 
right,  passes  in  front  of  the  aorta.  Occasionally  the  veins  are  multi- 
plied, though  not  so  frequently  as  the  arteries.  They  receive  small 
branches  from  the  suprarenal  bodies,  and  the  left  one  is  also  joined  by 
the  left  spermatic  or  ovarian  vein.  Occasionally  they  contain  valves. 

The  suprarenal  veins,4  large  in  relation  to  the  size  of  the  supra- 
renal body,  terminate  the  one  on  the  right  in  the  inferior  cava,  the 
other  in  the  left  renal  vein. 

The  hepatic  veins 5  are  two  or  three  large  trunks,  which  return 
the  blood  from  the  liver,  converging  to  the  posterior  notch,  where  they 
emerge,  and  open  immediately  in  an  oblique  direction  upward  into  the 

1  Venae  spermaticae.  2  P.  spermaticus  or  pampiniformis. 

8  V.  renales  or  emulgentes.  *  V.  suprarenales,  eapsulares,  or  atrabilariae. 

5  V.  hepaticae. 


570  THE    VEINS. 

inferior  cava.  Besides  the  chief  trunks  there  are  some  small  branches 
from  the  liver,  directly  opening  into  the  inferior  cava.  The  hepatic 
veins  are  destitute  of  valves. 

The  phrenic  veins 1  consist  of  a  pair  of  companions  to  each  corre- 
sponding artery,  terminating  in  the  inferior  cava,  though  those  of  the 
left  side  frequently  end  together  with  the  corresponding  suprarenal  vein. 

VEINS   OF   THE   PELVIS   AND   LOWER   LIMBS. 

The  common  iliac  vein,2  on  each  side,  is  formed  by  the  union  of 
the  external  and  internal  iliac  veins.  Ascending  from  near  the  sacro- 
iliac  articulation  to  near  that  of  the  fourth  and  fifth  lumbar  vertebrae  to 
the  right  of  the  median  line,  it  joins  its  fellow  at  an  acute  angle  to  form 
the  commencement  of  the  inferior  cava.  The  right  vein  is  less  inclined 
and  shorter  than  the  left,  and  ascends  behind  the  right  iliac  artery, 
and  then  to  its  outer  side,  while  the  left  vein  is  placed  at  the  inner 
side  of  the  left  iliac  artery,  and  then  ascends  behind  the  right  artery. 
Usually  the  common  iliac  veins  are  destitute  of  valves.  They  receive 
the  following  tributaries  : 

The  ilio-lumbar  vein3  arises  in  branches  from  the  back  of  the 
abdominal  wall,  the  dorsal  muscles,  and  the  spinal  plexuses,  and  issues 
from  behind  the  psoas  muscle  to  end  in  the  lower  part  of  the  iliac 
vein.  It  communicates  with  the  lumbar  and  lateral  sacral  veins. 

The  middle  sacral  vein 4  is  formed  by  the  union  of  a  pair  of  com- 
panion veins  of  the  middle  sacral  artery,  and  terminates  in  the  left  iliac 
vein  or  the  conjunction  of  both  iliac  veins.  The  two  branches  anasto- 
mose with  the  lateral  sacral  veins,  and  communicate  with  the  veins  of 
the  rectum. 

The  veins  of  the  lower  limb,  like  those  of  the  upper  limb,  consist 
of  a  deep  set  accompanying  the  arteries  and  a  superficial  set  forming 
a  subcutaneous  plexus.  All  are  provided  with  valves,  more  numerous 
than  in  those  of  the  upper  limb,  and  also  in  greater  number  in  the 
deep  veins. 

The  deep  veins  of  the  lower  limb  closely  follow  the  course  of  the 
arteries,  and  for  the  most  part  form  a  pair  of  companions  for  each  of 
the  latter,  as  in  the  upper  limb.  The  companion  veins  of  the  chief 
arteries  of  the  leg,  the  anterior  and  posterior  tibial  veins,  unite 
near  the  lower  boi'der  of  the  popliteal  muscle  to  form  the  popliteal 
vein.5  This  is  placed  behind  the  popliteal  artery,  ascending  gradually 
from  the  inner  to  the  outer  side,  and  passes  with  the  artery  through 
the  aperture  in  the  great  adductor  muscle  to  become  continuous  with 
the  femoral  vein.  In  its  course  it  receives  the  articular  and  mus- 
cular veins,  accompanying  the  corresponding  arteries,  and  is  joined 
also  by  the  external  saphenous  vein. 

1  V.  phrenicae  ;  p.  inferiores  or  diaphragmatic*.  2  Vena  iliaca  communis. 

3  V.  ilio-lumbalis.  *  V.  sacralis  media.  5  V.  poplitea. 


THE    VEINS.  571 

The  femoral  vein l  accompanies  the  femoral  artery ;  placed  first 
behind  and  somewhat  to  the  outer  side,  it  gradually  inclines  to  the 
inner  side  and  at  the  groin  passes  under  Poupart's  ligament,  where  it 
becomes  the  external  iliac  vein.  It  receives  branches  which  accompany 
those  of  the  femoral  artery,  the  femoral  profunda  vein,  formed  by 
the  companions  of  the  profunda  artery,  and  near  its  termination  by 
the  internal  saphenous  vein.  It  contains  several  valves,  of  which  one 
is  situated  at  the  entrance  of  the  profunda  vein. 

The  external  iliac  vein,2  the  continuation  of  the  femoral  vein, 
ascends  from  the  groin  at  the  inner  side  of  the  external  iliac  artery, 
gradually  inclining  behind  this  vessel  to  join  the  internal  iliac  in  the 
formation  of  the  common  iliac  vein.  It  is  usually  provided  with  a 
valve.  Near  its  commencement  it  receives  the  circumflex  iliac  and 
epigastric  veins,  accompanying  the  corresponding  arteries,  and  a 
pubic  vein,  which  ascends  from  the  obturator  vein,  and  sometimes 
forms  the  chief  termination  of  the  latter. 

The  subcutaneous  venous  plexus  of  the  toes  and  foot  commonly 
gives  rise  to  the  production  of  a  more  or  less  regular  transverse  arch 3 
on  the  dorsum,  from  which  the  emerging  branches  unite  in  two  super- 
ficial trunks,  the  external  and  internal  saphenous  veins. 

The  external  or  short  saphenous  vein*  springs  from  the  outer 
side  of  the  dorsal  plexus  of  the  foot,  ascends  the  leg  behind  the 
outer  ankle  and  Achilles  tendon  and  over  the  interval  of  the  two  heads 
of  the  gastrocnemius  muscle  to  the  popliteal  space,  where  it  perforates 
the  deep  fascia,  and  ends  in  the  popliteal  vein.  In  its  course  it  receives 
branches  from  the  outer  part  of  the  leg,  and  from  the  back  of  the 
thigh.  At  the  ankle  it  communicates  with  the  contiguous  deep  veins, 
and  near  its  termination  by  a  branch  with  the  internal  saphenous  vein, 
which  occasionally  becomes  the  chief  termination  of  the  latter.  It  is 
accompanied  in  its  course  by  the  external  saphenous  nerve. 

The  internal  or  long  saphenous  vein 5  rises  in  the  inner  part  of 
the  dorsal  plexus  and  arch  of  the  foot,  ascends  the  leg  in  front  of  the 
inner  ankle  and  behind  the  inner  border  of  the  tibia,  up  the  thigh, 
over  the  inner  condyle  of  the  femur  and  the  course  of  the  sartorius 
muscle  to  the  groin,  where  it  enters  the  saphenous  opening  of  the 
femoral  fascia,  and  terminates  in  the  femoral  vein.  In  its  course  it 
receives  numerous  branches  from  the  subcutaneous  plexus  of  the  leg 
and  thigh,  among  which  there  is  usually  a  large  anterior  branch  as- 
cending from  the  fore  part  of  the  thigh,  and  frequently  a  posterior 
branch  from  the  back  of  the  same.  At.  the  saphenous  opening  it 
receives  the  superficial  epigastric  and  circumflex  iliac  and  the 


1  Vena  femoralis  or  cruralis.  2  V.  iliaca  externa. 

3  Arcus  dorsalis  superficialis. 

4  Small  saphenous  vein  ;  v.  saphena  breva,  parva,  or  externa. 

5  Great  saphenous  vein ;  v.  saphena  longa,  magna,  or  interna. 


572 


THE    VEINS. 


FIG.  286. 


FIG.  287. 


Fig.  286.  SUPERFICIAL  VEINS  OF  THE  BACK 
OF  THE  LEG.  1,  short  saphenous  vein  ;  2,  po- 
sition at  which  it  terminates  in  the  popliteal 
vein ;  3,  long  saphenous  vein. 


Fig.  287.  SUPERFICIAL  VEINS  OF  THE  INNER 

PART    OF    THE    LOWER    EXTREMITY.     1,  long 

saphenous  vein ;  2,  its  termination  at  the 
saphenous  opening  into  the  femoral  vein. 


external   pudic   veins,1  accompanying   the   corresponding   arteries. 
Below  the  knee  it  is  accompanied  by  the  internal  saphenous  nerve. 


Venae  pudendse  externse. 


THE   VEINS.  573 

The  internal  iliac  vein 1  is  formed  by  branches  which,  for  the  most 
part,  accord  with  those  of  the  internal  iliac  artery.  It  lies  behind  and 
somewhat  to  the  inner  side  of  the  latter,  ascending  from  near  the  great 
sciatic  foramen  to  join  the  external  iliac  in  the  formation  of  the  com- 
mon iliac  vein.  The  veins  of  the  pelvic  viscera  contributing  to  form 
the  internal  iliac  vein  are  remarkable  for  their  size  and  frequent  union 
into  conspicuous  plexuses,  which  are  named  from  their  position. 

The  gluteal,  sciatic,  and  obturator  veins,  commonly  single, 
accompany  closely  the  corresponding  arteries. 

The  lateral  sacral  veins,  two,  three,  or  more,  anastomose  freely 
with  the  middle  sacral  veins,  and  form  a  plexus  in  front  of  the  sacrum. 
They  receive  branches  from  the  intraspinal  plexus  through  the  anterior 
sacral  foramina. 

The  pudic  vein2  is  formed  by  tributaries  mostly  corresponding 
with  the  branches  of  the  pudic  artery,  and  also  receives  a  communi- 
cating branch  from  the  dorsal  vein  of  the  penis. 

The  dorsal  vein  of  the  penis,3  a  proportionately  large  vessel 
furnished  with  valves,  is  common  to  the  dorsal  arteries  of  the  two  sides 
of  the  organ  between  which  it  lies.  It  arises  in  numerous  tributaries 
issuing  from  the  glans  and  prepuce  around  the  neck  of  the  penis,  where 
they  unite  in  two  branches,  which  converge  behind  and  run  backward 
close  together  in  the  dorsal  groove  of  the  penis.  Often  of  unequal  size, 
after  a  short  or  variably  longer  distance,  they  unite  in  a  single  median 
trunk,  which  continues  to  the  root  of  the  penis,  where  it  perforates 
the  triangular  ligament  and  then  forks  to  open  on  each  side  in  the 
pudendal  plexus.  In  its  course  the  dorsal  vein  receives  branches  from 
the  cavernous  bodies  along  the  dorsal  groove  of  the  penis,  others  which 
issue  between  the  spongy  and  cavernous  bodies  and  run  around  the 
sides  of  these  to  the  trunk  of  the  vein,  and  superficial  branches  from 
the  skin  of  the  penis.  At  the  root  of  the  latter  a  communicating  branch 
on  each  side  joins  the  pudic  vein. 

The  dorsal  vein  of  the  clitoris,4  of  the  female,  accords  with  the 
former. 

The  pudendal  plexus 8  is  a  close  net  of  large  veins  occupying  the 
upper  part  of  the  pubic  arch  between  the  layers  of  the  triangular  lig- 
ament, and  mainly  derived  from  the  dorsal  vein  of  the  penis  or  of  the 
clitoris.  In  the  male  it  closely  embraces  the  upper  part  of  the  mem- 
branous portion  of  the  urethra,  and  communicates  above  and  behind, 
extending  laterally,  with  the  prostatic  and  vesical  plexuses  and  with  the 
pudic  veins.  In  the  female  it  embraces  the  fore  part  of  the  urethra,  and 
communicates  with  the  vaginal  and  vesical  plexuses  and  the  pudic  veins. 

1  Vena  iliaca  interna ;  hypogastric  vein  ;  v.  hypogastrica. 

2  V.  pudenda  interna  ;  v.  pudica. 

3  V.  dorsalis  penis  ;  v.  profunda  penis.  4  V.  dorsalis  clitoridis. 

5  P.  pudendalis  ;  p.  pudendo-vesicalis ;  p.  prostaticus  ;  p.  prostatico-vesicalis  ;  p. 
pudicus  impar ;  p.  Santorini ;  labyrinthus  venosus  Santorini. 


574  THE    VEINS. 

The  prostatic  plexus  mainly  occupies  the  sides  of  the  prostate, 
and  is  continuous  below  and  in  front  with  the  pudendal  plexus,  and 
above  and  behind  with  the  vesical  plexus  and  the  pudic  veins. 

The  vesical  plexus  occupies  the  wall  of  the  bladder  exterior  to 
its  muscular  coat,  with  the  veins  mainly  descending  from  the  summit 
to  the  base  of  the  bladder,  where  the  plexus  is  closest  and  most  con- 
spicuous, and  the  large  veins  proceed  from  the  fore  part  of  the  neck 
backward  and  upward  around  the  sides  of  the  base,  including  the 
seminal  vesicles.  At  the  neck  of  the  bladder  the  plexus  freely  com- 
municates with  the  pudendal,  prostatic,  or  vaginal,  and  hemorrhoidal 
plexuses,  and  the  efferent  branches  proceeding  from  the  sides  of  the 
base  join  the  internal  iliac  veins. 

The  vaginal  plexus  of  the  female,  occupying  the  walls  of  the 
vagina,  is  best  produced  and  closest  around  the  entrance  of  the  canal, 
where  it  communicates  with  the  pudendal,  vesical,  and  hemorrhoidal 
plexuses. 

The  uterine  plexus,  in  the  walls  of  the  uterus,  extends  into  the 
broad  ligaments,  where  it  communicates  with  the  ovarian  plexus,  and 
is  mainly  discharged  by  the  ovarian  veins. 

The  hemorrhoidal  plexus  is  formed  by  numerous  freely  anasto- 
mosing veins  in  the  walls  of  the  rectum,  commencing  beneath  the 
mucous  membrane.  Its  efferent  branches  form  the  inferior,  middle, 
and  superior  hemorrhoidal  veins,  which  accompany  the  corresponding 
arteries.  As  the  superior  hemorrhoidal  vein  joins  the  portal  system, 
the  hemorrhoidal  plexus  freely  communicates  between  the  latter  and 
the  internal  iliac  vein. 

POKTAL  SYSTEM  OF  VEINS. 

The  portal  vein1  is  peculiar  in  the  fact  that  it  forms  an  interme- 
diate trunk  derived  from  branches  in  the  usual  way,  arising  from  the 
abdominal  alimentary  canal,  the  pancreas,  and  the  spleen,  and  is  dis- 
tributed in  branches  like  an  artery  throughout  the  liver,  whence  the 
blood  is  conveyed  to  the  inferior  cava  by  the  hepatic  veins.  All  the 
veins  of  the  system  are  single,  or  never  occur  in  pairs  accompanying 
arteries,  and  they  are  for  the  most  part  unprovided  with  valves.2  The 
trunk  of  the  portal  vein  is  about  three  inches  long  and  over  half  an 
inch  in  diameter.  It  commences  behind  the  head  of  the  pancreas  by 
the  union  of  the  splenic  and  superior  mesenteric  veins,  and  ascends 
behind  the  duodenum  in  front  of  the  inferior  cava  to  the  transverse 
fissure  of  the  liver.  It  is  enclosed  in  the  small  omentum,  with  the 


1  Vena  portse  or  portarum. 

2  Valves  have  been  recently  reported  to  exist  in  infancy  in  the  gastric  and  intes- 
tinal branches  of  the  portal  system,  but  are  said  to  become  inefficient  or  obliterated 
approaching  maturity.     (HOCHSTETTER,  Archiv  f.  Anat.  u.  Phys.,  1887,  p.   137; 
BRYANT,  Boston  Med.  and  Surg.  Jour.,  1888,  p.  400.) 


THE   VEINS. 


575 


hepatic  artery  and  bile-duct  in  front,  accompanied  by  lymphatics  and 
nerves  invested  with  a  con- 
nective-tissue sheath.1  At  FlG-  288- 
the  transverse  fissure  the 
vein  is  somewhat  enlarged, 
as  the  portal  sinus,2  and 
divides  in  widely-diver- 
gent branches.  The  right 
branch,  much  the  larger, 
enters  the  right  portion 
of  the  transverse  fissure 
and  immediately  pene- 
trates the  liver,  in  which  it 
ramifies  in  a  dichotomous 
manner.  Usually  it  re- 
ceives the  cystic  vein,3 
which  accompanies  the 
corresponding  artery  of 
the  gall-bladder,  but  some- 
times ends  in  the  trunk 
of  the  portal  vein.  The 
left  branch,  longer  and 
smaller  than  the  right 
one,  divides  into  several 
branches,  which  enter  the 
left  part  of  the  transverse 
fissure  and  penetrate  the 
liver,  to  be  distributed  like 
the  former. 

At  the  fore  part  of  the 
longitudinal  fissure  the 
portal  vein  is  continuous 
with  a  fibrous  cord,  the 
round  ligament  of  the 
liver,  which  is  the  remains 
of  the  obliterated  umbil- 
ical vein  of  the  foetus. 
A  similar  cord,  connected 
with  the  vessel  behind 
and  passing  through  the 
back  part  of  the  longi- 
tudinal fissure  to  the  in- 
ferior cava,  is  in  like  man- 
ner the  remains  of  the  ductus  venosus  of  the  foetus. 


DIAGRAM  OF  THE  PORTAL  SYSTEM  OF  VEINS.  1,  trunk  of 
the  portal  vein  ;  2,  3,  right  and  left  branches  to  the  liver ; 
4,  round  ligament,  the  remains  of  the  umbilical  vein ;  5, 
remains  of  the  ductus  venosus ;  6,  splenic  vein  ;  7,  branches 
from  the  spleen  ;  8,  left  gastro-epiploic  vein :  9,  pancreatic 
branches ;  10,  inferior  mesenteric  vein ;  11,  left  colic  vein ; 
12,  branch  joining  the  middle  colic  vein  ;  13.  sigmoid  vein ; 
14,  superior  hemorrhoidal  vein ;  15,  superior  mesenteric 
vein ;  16,  17,  18,  middle  and  right'  colic  and  ileo-colic 
branches ;  19,  branches  from  small  intestine ;  20,  pancre- 
atico-duodenal  vein ;  21,  right  gastro-epiploic  vein;  22,  gas- 
tric vein ;  23,  hepatic  artery  dividing  into  right  and  left 
branches ;  24,  common  bile-duct  formed  by  union  of  the 
hepatic  and  cystic  ducts. 


Capsule  of  Glisson. 


2  Sinus  venas  portarum. 


3  Vena  cystica. 


576  THE   VASCULAR   SYSTEM    OP   THE    FCETUS. 

The  principal  tributaries  of  the  portal  vein  are  the  superior  mesen- 
teric  and  splenic  veins,  besides  which  it  separately  receives  the  gastric 
and  pyloric  veins  from  the  small  curvature  of  the  stomach. 

The  gastric  vein,1  the  companion  of  the  corresponding  artery, 
proceeds  along  the  small  curvature  of  the  stomach  to  the  cardiac  ori- 
fice, where  it  receives  branches  from  the  oesophagas  and  diaphragm, 
and  then  turns  to  the  right  above  the  coaliac  axis  to  join  the  portal 
vein  above  its  commencement. 

The  pyloric  vein,2  a  small  branch,  accompanies  the  corresponding 
artery,  and  ends  in  the  portal  vein  below  the  former,  or  sometimes  joins  it. 

The  superior  mesenteric  vein3  corresponds  in  its  distribution 
with  the  superior  mesenteric  artery,  and  returns  the  blood  from  the 
small  intestine  and  the  ascending  and  transverse  colon.  The  trunk  as- 
cends along  the  right  side  of  the  artery,  with  the  intestinal  branches 
crossing  in  front  of  the  latter  vessel.  The  chief  tributaries  are  the 
intestinal,  ileo-colic,  right  colic,  and  middle  colic  veins.  Near 
its  termination  it  is  also  joined  by  several  small  pancreatico-duo- 
denal  branches,  and,  from  the  great  curvature  of  the  stomach,  by  the 
right  gastro-epiploic  vein,  which  sometimes  also  joins  the  right  colic 
vein. 

The  inferior  mesenteric  vein4  accompanies  the  corresponding 
artery,  and  is  derived  from  similar  branches,  the  superior  hemor- 
rhoidal,  sigmoid,  and  left  colic  veins.  It  ascends  beneath  the 
peritoneum  to  the  left  of  the  aorta,  and  passes  behind  the  pancreas, 
where  it  joins  the  splenic  vein  at  a  right  angle,  or,  inclining  to  the  right, 
opens  into  the  junction  of  the  latter  with  the  superior  mesenteric  vein 
or  into  this  vessel  directly. 

The  splenic  vein,5  the  second  largest  tributary  of  the  portal  vein, 
corresponds  in  distribution  with  the  splenic  artery,  its  principal  branches 
being  the  splenic,  short  gastric,  left  gastro-epiploic,  and  pancre- 
atic veins.  It  runs  from  left  to  right  along  the  upper  border  of  the 
pancreas,  below  and  behind  the  splenic  artery,  pursuing  a  straight 
course  instead  of  the  tortuous  course  of  the  latter. 

THE   VASCULAE   SYSTEM   OF   THE   FCETUS. 

In  the  child  before  birth,  in  accordance  with  its  peculiar  circum- 
stances, the  vascular  system  exhibits  important  differences  from  its 
subsequent  condition.  In  the  early  part  of  foetal  life  the  heart  is  ver- 
tical in  position ;  its  auricles  are  proportionately  larger,  the  right  being 
the  more  capacious ;  and  the  ventricles  are  nearly  of  equal  thickness. 
These  conditions  gradually  change ;  but  at  the  time  of  birth  the  heart 
is  proportionately  larger  and  more  vertical  than  later. 

1  Coronary  vein ;  vena  gastrica ;  v.  g.  superior ;  v.  coronaria. 

2  V.  pylorica.  3  V-  mesenterica  superior  or  magna. 
4  V.  mesenterica  inferior  or  minor.          5  V.  splenica  ;  v.  lienalis. 


THE   VASCULAE   SYSTEM   OF   THE   FCETOS. 


577 


The  auricles  communicate  by  a  large  aperture,  the  oval  foramen,1 
situated  at  the  lower  back  part  of  the  auricular  septum,  and  protected  by 
a  valve,  which  is  next  the  left  auricle,  and  extends  from  behind  upward. 
The  arrangement  permits  the  flow  of  blood  from  the  right  into  the  left 


FIG.  289. 


DIAGRAM  OF  THE  FCETAL  CIRCULATION.  The  arrows  indicate  the  course  of  the  flow  of 
blood.  1,  right  auricle  laid  open ;  2,  oval  foramen,  with  its  valve,  opening  into  the  left  auricle, 
3 ;  4,  5,  right  and  left  ventricles ;  6,  superior  cava ;  7,  inferior  cava ;  8,  pulmonary  artery  dividing 
into  the  right  and  the  left  branch,  and  giving  off  the  ductus  arteriosus,  9 ;  10,  arch  of  the  aorta ;  11, 
abdominal  aorta ;  12,  common  iliac  artery ;  13,  internal  iliac  or  hypogastric  artery ;  14,  umbilical 
arteries ;  15,  umbilical  vein ;  16,  ductus  venosus ;  17, 18,  right  and  left  hepatic  veins ;  19,  20,  right 
and  left  lobes  of  the  liver ;  21,  portal  vein  ;  22,  gall-bladder. 

auricle,  but  not  in  the  opposite  direction.  At  the  bottom  of  the  right 
auricle  is  the  eustachian  valve,  which  extends  from  the  anterior  border 
of  the  inferior  cava  to  the  oval  foramen,  and  serves  to  direct  the  flow 
of  blood  from  the  former  through  the  latter  into  the  left  auricle. 

1  F.  ovale  ;  f.  Botale. 
37 


578  THE   VASCULAR   SYSTEM   OF   THE   FCETUS. 

From  the  pulmonary  artery,  at  its  fork,  proceeds  a  vessel,  named 
the  ductus  arteriosus,  which  is  larger  than  the  right  and  left 
branches  of  the  former,  and  opens  into  the  aorta  after  this  gives  off 
the  left  subclavian  artery.  It  is  about  half  an  inch  long,  and  as  thick 
as  a  goose-quill,  and  serves  to  conduct  the  main  portion  of  the  blood 
of  the  right  ventricle  into  the  descending  aorta. 

The  umbilical  cord,  which  connects  the  foetus  with  the  placenta 
of  the  mother,  consists  of  three  large  vessels.  Of  these  the  largest  is 
the  umbilical  vein,  which  conveys  the  blood  from  the  placenta  to  the 
foetus,  while  the  others,  which  return  the  blood  from  the  latter  to  the 
former,  are  the  umbilical  arteries. 

The  umbilical  vein,  from  the  cord,  ascends  from  the  umbilicus, 
or  navel,  to  the  liver,  where  it  enters  the  longitudinal  fissure.  After 
giving  off  branches  to  the  left,  quadrate  and  caudate  lobes,  at  the 
transverse  fissure  it  joins  the  portal  vein,  and  through  a  smaller  divis- 
ion, named  the  ductus  venosus,  continues  in  the  posterior  portion 
of  the  longitudinal  fissure,  and  joins  the  left  hepatic  vein  at  its 
termination  in  the  inferior  cava. 

The  umbilical  arteries  appear  as  the  continuation  of  the  internal 
iliac  arteries,  from  which  they  ascend  at  the  sides  to  the  summit  of  the 
bladder,  and  converge  to  the  navel,  whence  they  proceed  along  the  cord, 
coiled  together  around  the  umbilical  vein,  to  the  placenta. 

In  the  circulation  of  the  blood  of  the  foetus,  the  right  auricle  of  the 
heart  receives  the  blood  of  both  cavse  and  the  coronary  sinus.  The 
blood  of  the  superior  cava  is  that  returned  from  the  head,  upper  limbs, 
and  walls  of  the  chest ;  while  that  of  the  inferior  cava,  a  considerably 
larger  vessel,  is  not  only  the  blood  from  the  abdomen,  pelvis,  and  lower 
limbs,  but  also  all  that  from  the  placenta.  The  latter  blood,  through 
the  umbilical  vein,  reaches  the  inferior  cava  most  directly  through  the 
ductus  venosus,  but  in  greater  measure  through  the  hepatic  veins, 
which  convey  to  the  cava  all  the  blood  of  the  liver,  derived  from  the 
umbilical  and  portal  veins  and  hepatic  artery. 

The  blood  of  the  superior  cava,  passing  from  the  right  auricle  into 
the  right  ventricle,  is  thence  propelled  into  the  pulmonary  artery.  The 
smaller  portion  is  sent  to  the  lungs  through  the  right  and  left  branches, 
but,  as  these  remain  contracted  until  afterbirth,  the  larger  portion  passes 
through  the  ductus  arteriosus  to  the  descending  aorta,  by  which  it  is 
distributed  to  the  lower  division  of  the  body,  and  in  part  is  sent  to  the 
placenta. 

Of  the  blood  which  enters  the  right  auricle  from  the  inferior  cava 
but  a  small  portion  is  mingled  with  that  of  the  superior  cava  to  pass 
into  the  right  ventricle,  while  the  much  larger  portion,  directed  by  the 
eustachian  valve  through  the  oval  foramen,  passes  into  the  left  auricle. 
Here,  mingled  with  a  smaller  quantity  of  blood  from  the  pulmonary 
veins,  it  is  forced  into  the  left  ventricle,  whence  it  is  propelled  into  the 
arch  of  the  aorta,  and  is  almost  entirely  distributed  to  the  head,  upper 


THE    LYMPHATIC   SYSTEM.  579 


limbs,  and  walls  of  the  chest.  T°  *ne  fact  that  these  parts  of  the 
body  receive  a  purer  supply  of  the  placental  blood  than  the  lower 
parts  is  probably  due  their  comparatively  more  advanced  development 
at  the  time  of  birth. 

The  placental  circulation  is  at  once  stopped  at  birth  by  the  closure 
of  the  umbilical  vessels  at  the  navel.  With  the  first  act  of  inspiration 
the  lungs  expand,  and  the  pulmonary  vessels  rapidly  dilate  and  give 
passage  to  a  greater  flow  of  blood.  The  ductus  arteriosus  and  the 
umbilical  arteries  from  the  internal  iliacs  to  the  navel  rapidly  contract 
and  cease  to  give  passage  to  the  blood.  The  flow  also  ceases  through 
the  oval  foramen,  through  the  umbilical  vein  from  the  navel  to  the 
liver,  and  through  the  ductus  venosus. 

The  ductus  arteriosus  is  completely  closed  in  from  four  to  ten  days, 
and  is  ultimately  converted  into  a  fibrous  cord,  which  extends  from  the 
commencement  of  the  left  pulmonary  artery  to  the  under  part  of  the 
arch  of  the  aorta  after  this  gives  oif  the  left  subclavian  artery. 

The  umbilical  arteries  become  much  shrunken  and  for  the  most 
part  completely  closed  in  three  or  four  days,  and  are  ultimately  con- 
verted into  fibrous  cords,  which  form  the  basis  of  the  superior  and 
lateral  false  ligaments  of  the  bladder.  From  the  internal  iliac  arteries 
to  the  side  of  the  bladder  they  remain  partially  pervious,  and  contin- 
uous on  the  latter  with  the  superior  vesical  artery. 

The  umbilical  vein  and  ductus  venosus  become  closed  in  about  a 
week,  and  are  finally  converted  into  fibrous  cords,  of  which  one  forms 
the  round  ligament  of  the  liver,  and  the  other  occupies  the  back  part 
of  the  longitudinal  fissure  of  the  latter  and  connects  the  left  branch 
of  the  portal  vein  with  the  inferior  cava. 

The  oval  foramen,  though  ceasing  at  once  to  permit  the  passage  of 
blood  after  birth,  does  not  become  actually  closed  until  a  considerable 
time  afterwards.  The  closure  takes  place  gradually,  in  the  course  of 
ten  days  or  more,  by  the  union  of  the  fore  part  of  the  valve  with  the 
contiguous  annulus  of  the  foramen,  but  not  unfrequently  the  latter,  at 
its  upper  part,  remains  as  a  permanent  cleft  communicating  between 
the  auricles.  Sometimes  in  the  first  year  of  infancy  a  wider  aperture 
continues,  and  permits  the  flow  of  blood  from  the  right  into  the  left 
auricle,  giving  rise  to  the  condition  known  as  the  blue  disease,  or 
morbus  cseruleus. 

THE   LYMPHATIC   SYSTEM. 

The  lymphatic  system,  also  called  from  its  habitual  function  the 
absorbent  system,  consists  of  numerous  tubular  and  branching  lym- 
phatic vessels  and  certain  nodular  bodies,  the  lymphatic  glands, 
which  are  situated  in  the  course  of  the  chief  vessels.  The  lymphatics 
are  generally  associated  with  the  blood-vessels,  and  the  larger  ones  pursue 
nearly  the  same  course,  and  often  accompany  them.  The  principal  lym- 
phatic vessels  are  more  numerous  than  the  corresponding  blood-vessels, 


580 


THE    LYMPHATIC   SYSTEM. 


FIG.  290. 


but  are  much  smaller,  and  are  of  greater  delicacy  and  transparency,  from 
which  circumstances,  together  with  the  fact  that  they  convey  a  color- 
less liquid,  they  are  inconspicuous,  and  in  ordinary  dissections  usually 
escape  notice.  The  liquid  conveyed  by  the  lymphatics  is  lymph, 
which  is  derived  through  absorption  from  the  various  tissues  and 
organs  of  the  body,  besides  which  it  receives  constant  accessions  from 
the  dissolved  nutritive  matter  of  the  food  absorbed  from  the  stomach 
and  intestines. 

In  the  different  parts  of  the  body  the  lymphatics  generally  consist 
of  a  deep  and  a  superficial  set,  the  former  commencing  everywhere  in 
the  interstices  of  the  tissues  and  organs,  and  thence  pursuing  the  course 

of  the  blood-vessels,  while  the  latter  com- 
mence in  intricate  plexuses  on  the  surface 
of  organs,  freely  communicate  with  the  deep 
set,  and  unite  in  trunks  which  pursue  the 
course  of  the  superficial  venous  trunks. 

The  larger  lymphatic  vessels  mostly  run 
in  nearly  direct  lines  with  a  straight  or 
slightly  flexuose  course,  but  sometimes  more 
irregularly  ;  and  usually  they  are  pretty  uni- 
form in  their  diameter  when  undivided. 
They  are  especially  remarkable  in  the  pos- 
session of  numerous  valves,  which  are  uni- 
formly disposed  in  pairs  at  short  distances 
apart, — about  the  fourth  to  the  third  of  an 
inch  in  the  largest  vessels  and  a  line  or  less 
in  smaller  ones.  The  valves  have  the  same 
form  and  arrangement,  together  with  corre- 
sponding saccular  expansions  of  the  vessels, 
as  in  the  veins,  and  their  frequent  succession 
in  the  distended'  condition  of  the  lymphatics  gives  these  vessels  a 
jointed  or  beaded  appearance. 

In  proportion  to  their  size  the  lymphatic  vessels  have  thin  walls, 
and  these,  as  in  the  case  of  the  blood-vessels,  consist  of  three  tunics. 
The  external  tunic,  or  adventitia,  is  a  delicate  fibro-connective-tissue 

FIG.  291. 


NET-WORK  OF  LYMPHATIC  VES- 
SELS IN  THE  SKIN  OF  THE  EAR. 


A  LYMPHATIC  VESSEL,  laid  open  and  exhibiting  the  arrangement  of  its  valves :  magnified. 

layer  associated  with  longitudinal  elastic  fibres  and  unstriped  muscle- 
fibres.  The  media  is  composed  of  transverse  muscle-fibres  with  some 
elastic  fibres;  and  the  intima  is  composed  of  longitudinal,  reticular 


THE   LYMPHATIC   SYSTEM.  581 

elastic  fibres  lined  by  an  endothelium  of  elongate  lozenge-shaped  cells 
with  sinuous  outlines.  The  valves  are  semilunar  folds  of  the  intima. 

The  lymphatic  vessels  com- 
mence in  intricate  plexuses,  which  FIG.  292. 
occupy  the  interstices  of  most  tis- 
sues and  organs  of  the  body,  where 
they  are  commonly  associated  with 
the  capillary  blood-vessels.  The 
lymphatics  immediately  proceed- 
ing from  the  plexuses,  generally 
more  regularly  tubular  than  those  ENDOTHELIUM  OF  A  COMMENCING  LYMPHATIC 

VESSEL.    250  diameters, 
which  precede  them  and  provided 

with  valves,  are  regarded  as  the  commencement  of  the  lymphatic 
trunkst  while  the  others  are  distinguished  as  the  lymphatic  capil- 
laries. These  are  as  numerous  as  the  capillary  blood-vessels  with 
which  they  are  commonly  interwoven,  but  are  of  less  uniform  calibre, 
very  variable,  and  often  greatly  exceed  the  blood-capillaries,  and 
frequently,  also,  the  lymphatic  trunks  they  join.  They  are  often 
irregularly  expanded,  and  are  devoid  of  valves.  In  the  intestinal 
villi  they  mostly  appear  as  single  club-like  vessels,  which  join  the 
reticular  plexus  at  their  base.  The  walls  of  the  lymphatic  capillaries 
and  of  the  commencing  trunks,  like  those  of  the  capillary  blood-vessels, 
are  composed  of  a  single  layer  of  elongate  lozenge-shaped  endothelial 
cells,  of  which  those  of  the  capillaries  are  generally  proportionately 
shorter  and  more  sinuous  at  the  borders  than  in  the  trunks. 

The  lymphatic  capillaries  commonly  communicate  with  or  com- 
mence in  clefts,  or  lymph-spaces,  which  occupy  the  intervals  of  the 
connective-tissue  bundles  of  most  other  tissues  of  the  body.  The 
lymph-spaces  conform  to  the  intervals  of  the  surrounding  elements 
of  structure  of  the  tissues,  and  are  lined  with  endothelial  cells  contin- 
uous with  those  of  the  more  distinct  lymphatic  capillaries.  The  latter, 
also,  commence  in  spaces  which  include  the  connective-tissue  corpus- 
cles and  the  similar  corpuscles  of  the  bones  and  of  the  cornea  of  the 
eye,  all  of  which  freely  communicate  with  one  another  by  minute 
canaliculi.  In  like  manner,  lymphatics  commence  in  spaces  enclosing 
the  nerve-cells  of  the  brain  and  spinal  marrow.  In  some  positions, 
as  in  the  latter  organs  and  the  vascular  canals  of  bones,  lymphatic 
capillaries  ensheathe  the  capillary  blood-vessels,  constituting  the  peri- 
vascular  lymphatics,  which  are  lined  by  endothelial  cells. 

The  lymphatics  of  the  peritoneum  of  the  diaphragm  and  of  the 
intercostal  pleura  communicate  with  the  cavities  of  these  membranes 
by  minute  apertures  or  stomata,  which  are  enclosed  by  a  circle  of 
small  polyhedral,  granular  cells  pertaining  to  the  endothelium. 

Lymphatic  glands.  These  are  solid,  mostty  flattened,  oval  or 
spheroidal  bodies  situated  in  the  course  of  the  chief  lymphatic  vessels, 
usually  of  a  reddish-gray  color,  and  ranging  in  size  from  a  hemp-seed 


582 


THE   LYMPHATIC   SYSTEM. 


FIG.  293. 


to  an  almond  or  larger.     They  are  most  numerous  along  the  course  of 

the  great  blood-vessels  of  the  neck,  thorax, 
abdomen,  and  pelvis,  and  especially  in  the 
mesentery  and  mesocolon.  There  are  also 
many  in  the  armpit  and  groin,  and  a  few  at 
the  back  part  of  the  head,  in  the  popliteal 
space,  and  in  the  bend  of  the  elbow.  Com- 
monly several  of  the  chief  lymphatic  ves- 
sels, proceeding  from  the  periphery  of  the 
body,  on  reaching  the  vicinity  of  a  lym- 
phatic gland  break  up  into  many  branches, 
the  afferent  vessels,1  which  enter  and 
are  distributed  through  the  gland,  whence 
another  series,  the  efferent  vessels,2 
emerge  and  unite  in  a  similar  manner  to 
form  a  smaller  number  of  trunks  than 
those  approaching  the  gland.  In  the 
position  at  which  the  efferent  glands  make 
their  exit,  the  gland  usually  exhibits  a 
depression,  the  hilus,  at  which,  also,  the 
principal  blood-vessels  and  nerves  enter 
to  supply  the  body. 

The  lymphatic  glands  consist  of  an 
outer,  lighter-colored,  cortical  portion  and 
an  inner,  darker,  medullary  portion,  which  latter  approaches  the  sur- 
face at  the  hilus.  They  are  invested  with  a  capsule  of  fibro-connective 
tissue,  which  extends  into  the 
hilus  upon  the  blood-vessels. 
From  the  capsule  lamina?  and 
bands  of  the  same  tissue  ex- 
tend through  the  interior  of 
the  gland,  forming  a  trabec- 
ular  framework,3  which  sup- 
ports the  proper  gland-sub- 
stance. In  the  largest  glands 
the  cortical  substance  is  from 
half  a  line  to  a  line  in  thick- 
ness. In  the  more  superficial 
subcutaneous  glands  it  is  pro- 
portionately less  than  in  those 
occupying  the  great  cavities 
of  the  body,  being  apparently 
substituted  by  more  connec- 
tive tissue. 


LYMPHATIC  GLAND  AND  VESSELS,  l 
lymphatic  gland ;  2,  afferent  vessels 
3,  efferent  vessel. 


FIG.  294. 


A  SMALL  LYMPHATIC  GLAND,  in  section,  a,  the  fibro- 
connective-tissue  capsule ;  b,  partitions  of  the  same ; 
d,  nodules  or  follicles  of  lymphoid  tissue  of  the  cor- 
tex ;  e,  bars  of  the  same  tissue  of  the  medulla ;  /,  affe- 
rent vessels  opening  into  lymph-spaces ;  c,  g,  efferent 
vessels  converging  to  a  single  vessel,  h,  passing  out  at 
the  hilus  of  the  gland :  magnified. 


1  Vasa  afferentia. 


2  V.  efferentia. 


3  Trabeculae. 


THE    LYMPHATIC   SYSTEM. 


583 


FIG.  295. 


In  the  cortical  portion  of  the  lymphatic  glands  the  trabecular  frame- 
work forms  spheroidal  receptacles,  or  follicles,1  and  in  the  medullary 
portion  cylindrical  passages,  which  communicate  with  the  former  and 
in  all  directions  with  one  another.  The  follicles  and  interior  passages 
are  continuously  filled  throughout  by  the  proper  gland-substance,2 
which  is  lymphoid  or  adenoid  tissue.  This  consists  of  a  delicate 
reticular  connective  tissue  with  its  interspaces  occupied  by  lymphoid 
corpuscles.  The  interior  of  the  lymphoid  tissue  is  more  dense,  and 
the  lymphoid  corpuscles  differ  from  the  ordinary  lymph-corpuscles 
in  having  a  larger  nucleus  and  a  smaller  proportion  of  enveloping 
protoplasm.  The  peripheral  portion  of  the  lymphoid  tissue,  in  a  nar- 
row space  of  pretty  uniform  width,  is  of  looser  texture  than  the 
interior,  and  the  included  corpuscles  are  more  like  ordinary  lymph- 
corpuscles.  This  peripheral  space  of  the  glandular  substance  is  in 
free  communication  with  the  afferent  and  efferent  lymphatic  vessels, 
is  traversed  by  the  lymph  passing  from  one  to  the  other,  and  is 
named  the  lymph-path.3  The  afferent  vessels  after  entering  the 
gland  continue  to  branch, 
and  finally  end  in  the  cor- 
tical lymph-paths,  with  the 
endothelium  of  the  vessels 
continued  as  a  lining  of  the 
latter.  The  efferent  vessels 
in  like  manner  commence 
in  the  lymph-paths  of  the 
medullary  portion  of  the 
gland,  and  thence  emerge 
at  the  hilus. 

From  the  latter  and 
other  positions  the  blood- 
vessels traverse  the  trabec- 
ular framework  and  com- 
municate with  capillary  nets 
of  the  lymphoid  tissue.  The 
nerves  which  accompany 
the  blood-vessels  are  mainly 
derived  from  the  sympa- 
thetic system. 

As  part  of  the  lymphatic 
system,  accumulations  of 
lymphoid  or  adenoid  tissue, 
in  variable  nodular  masses 

or  in  a  more  diffused  condition,  exist  in  many  organs.     The  essential 
structure  of  the  tonsils  consists  of  nodular  masses  of  lymphoid  tissue 


A  FOLLICLE  FROM  THE  CORTEX  OF  A  LYMPHATIC  GLAND, 

in  longitudinal  section,  a,  nodular  mass  of  lymphoid 
tissue;  b,  sustaining  reticular  connective  tissue,  with 
most  of  the  lymph-corpuscles  washed  out ;  c,  d,  e,  bars 
of  lymphoid  tissue  of  the  medulla ;  /,  portion  of  the  in- 
vesting flbro-connective-tissue  capsule;  g.  partitions  of 
the  same;  h,  afferent  vessel  opening  into  the  lymph- 
spaces,  i :  magnified. 


1  Alveoli. 


2  Glandular  pulp. 


Lymph-sinus. 


584  THE    LYMPHATIC   SYSTEM. 

embedded  in  the  submucosa  of  follicles  of  the  mucous  membrane. 
Nodular  masses  also  constitute  many  of  the  glands  of  the  root  of  the 
tongue,  the  upper  part  of  the  pharynx,  the  soft  palate,  and  the  uvula. 
Similar  nodules  form  the  solitary  glands  of  the  small  and  large  intes- 
tine, in  addition  to  which  diffused  lymphoid  tissue  enters  into  the  con- 
stitution of  the  mucous  membrane,  including  that  of  the  villi.  Nodules 
or  more  diffused  masses  also  occur  in  the  mucous  membrane  of  the 
oasophagus  and  pyloric  extremity  of  the  stomach,  in  that  of  the  larynx 
and  air-passages,  and  in  the  conjunctiva.  Nodules  and  tracts  in  the 
course  of  the  blood-vessels  are  also  found  in  serous  membranes,  as  in 
the  mediastinal  pleura  and  the  omentum.  Further,  cord-like  masses 
often  with  nodular  enlargements1  sheathe  many  of  the  arteries  dis- 
tributed in  the  spleen. 

LYMPH. 

The  lymph,2  contained  in  the  lymphatic  vessels  generally  through- 
out the  body,  is  a  transparent,  pale  amber-colored  liquid.  Examined 
with  the  microscope,  it  is  observed  to  consist  of  a  clear  liquid,  the 
lymph-plasma^3  which  is  like  that  of  the  blood,  and  lymph-corpus- 
cles,4 which  are  identical  with  the  white  corpuscles  of  the  latter.  The 
lymph-corpuscles  are  more  numerous  in  the  lymphatic  vessels  after 

FIG.  297. 


LYMPH-CORPUSCLES,  highly  magnified,  l.cor-  LYMPH-CORPUSCLES,  more  highly  magnified, 

puscle  at  rest ;  2-10,  in  movement,  exhibiting  and  observed  at  the  temperature  of  the  body, 

projections  of  the  protoplasm  called  pseudo-  exhibiting  the  changes  of  shape  in  movement, 
pods ;  6,  one  which  has  assumed  a  stellate  shape. 

they  have  emerged  from  the  lymphatic  glands  than  in  those  which 
enter  them,  indicating  these  bodies  to  be  an  important  source  of  the 
corpuscles.  These  probably  have  their  source  in  many  other  positions, 
especially  in  the  solitary  and  agminated  glands,  the  lymphoid  follicular 
glands,  and  the  more  generally  diffused  lymphoid  tissue  of  the  mucous 
membrane  of  the  alimentary  canal,  also  in  the  spleen  and  in  the  mar- 
row of  the  bones,  and  through  proliferation  of  connective-tissue  cor- 
puscles in  the  fibro-connective  tissue  generally. 

1  Corpuscles  of  Malpighi.  2  Lympha ;  white  blood. 

3  Coagulable  lymph.  *  Lymph-globules  ;  white  corpuscles. 


THE   LYMPHATIC   SYSTEM. 


585 


Chyle1  is  lymph,  mingled  with 
some  of  the  absorbed  products  of 
digestion,  contained  in  the  lym- 
phatic vessels  of  the  stomach  and 
intestines.  The  visible  products 
mainly  consist  of  fine  molecules 
and  minute  globules  of  fat,  which 
give  to  the  chyle  a  milky  aspect, 
whence  the  name  of  lacteals2 
applied  to  the  lymphatics  contain- 
ing it. 

THE   CHIEF   TKUNKS  OF  THE 
LYMPHATICS. 

The  lymphatics  terminate  in 
two  principal  trunks,  which  are 
distinguished  as  the  thoracic  duct 
and  the  right  lymphatic  duct,  the 
former  being  very  much  the  longer 
and  larger,  and  receiving  all  the 
lymphatics  of  the  left  side  of  the 
body,  together  with  those  of  the 
lower  half  of  the  right  side,  while 
the  remainder  join  the  smaller  duct. 

THE   THOKACIC   DUCT. 

The  thoracic  duct3  ascends 
from  the  abdomen  through  the 
thorax,  lying  in  front  of  the  spine, 
between  the  aorta  and  azygos 
vein.  It  is  from  fifteen  to  eigh- 
teen inches  long,  and  more  or  less 
flexuose  in  its  course.  It  usually 
commences  in  front  of  the  first 
lumbar  vertebra,  behind  the  aorta, 
and  thence  passes  between  this 
and  the  right  crus  of  the  dia- 
phragm through  the  aortic  orifice. 
The  commencement  commonly 
presents  a  variable  expansion,  an 
inch  or  more  in  length,  named  the 
receptacle  of  the  chyle,4  which 


VIEW  OF  THE  GREAT  LYMPHATIC  TRUNKS.  1, 

2,  thoracic  duct ;  3,  its  termination  at  the  angle 
of  conjunction  of  the  left  internal  jugular  and 
subclavian  veins;  4,  the  right  lymphatic  duct; 
5,  lymphatics  of  the  thigh  ;  6,  iliac  lymphatics ; 
7,  lumbar  lymphatics ;  8,  intercostal  lymphatics, 
a,  superior  cava ;  b,  left  innominate  vein ;  c, 
right  innominate  vein;  d,  aorta;  e,  inferior 
cava ;  /,  psoas  muscle ;  g,  origin  of  the  dia- 
phragm. 


is  inconstant,  and  often  obscurely 


1  Chylus  ;  succus  entericus.  2  Vasa  lactea  or  chylifera ;  chyliferous  vessels. 

z  Ductus  thoracicus  or  chyliferus  ;  truncus  lymphaticus  sinister. 
4  Keceptaculum  chyli ;  r.  Pecqueti ;  cisterna  chyli ;  saccus  lacteus. 


586  THE    LYMPHATIC   SYSTEM. 

defined.  In  the  upper  part  of  its  course  the  duct  inclines  to  the  left, 
and  reaching  the  fourth  thoracic  vertebra  passes  behind  the  aortic  arch, 
and  ascends  between  the  oesophagus  and  the  left  subclavian  artery 
into  the  neck.  On  a  level  with  the  last  cervical  vertebra  it  turns  out- 
ward and  downward,  in  an  arch  over  the  apex  of  the  pleura,  and  ends 
in  the  angle  of  union  of  the  left  internal  jugular  and  subclavian  veins. 
The  duct  is  usually  narrowest  about  the  middle  of  its  course,  where 
it  is  about  two  lines  wide,  and  enlarges  towards  the  extremities,  espe- 
cially the  commencement,  where  it  is  about  three  lines  wide.  It  is 
subject  to  considerable  variation,  and  frequently  is  more  or  less  divided 
in  its  course,  once,  twice,  or  oftener,  and  sometimes  for  a  short  distance 
may  have  a  plexiform  arrangement.  Earely  it  is  double  throughout ; 
and  it  has  been  observed  ending  in  the  azygos,  or  some  other  neighbor- 
ing vein. 

The  valves  of  the  thoracic  duct  are  fewer  than  in  its  tributaries, 
usually  being  an  inch  or  more  apart,  but  are  nearer  approaching  its 
termination,  where  a  pair  of  valves  prevents  the  reflux  of  the  blood 
from  the  veins. 

The  thoracic  duct  receives  the  lymphatics  of  the  left  half  of  the 
body,  and  those  of  the  right  lower  limb  and  right  side  of  the  abdomen. 

THE   EIGHT   LYMPHATIC   DUCT. 

The  right  lymphatic  duct l  is  commonly  from  a  quarter  to  half 
an  inch  in  length,  and  about  a  line  in  width,  and  ends  in  the  angle  of 
union  of  the  internal  jugular  and  subclavian  veins  of  the  right  side.  It 
receives  the  lymphatics  of  the  right  side  of  the  upper  half  of  the  body 
extending  to  the  upper  surface  of  the  liver.  The  duct  is  formed  by 
the  conjunction  usually  of  two  or  three  principal  vessels,  which  some- 
times end  separately  in  the  contiguous  veins. 

LYMPHATICS   OF   THE   LOWER   LIMBS. 

The  deep-seated  lymphatics  of  the  lower  limb  pursue  the 
course  of  the  corresponding  blood-vessels.  Those  accompanying  the 
blood-vessels  of  the  foot  and  leg  enter  the  popliteal  glands,  while  the 
trunks  from  the  latter  and  other  deep  lymphatics  of  the  thigh  pursue 
the  course  of  the  femoral  blood-vessels  and  enter  the  deep  inguinal 
glands.  Deep  lymphatics  from  the  gluteal  region  and  the  femoral  ad- 
ductors accompany  the  gluteal,  sciatic,  and  obturator  blood-vessels  into 
the  pelvis  to  the  internal  iliac  glands. 

The  superficial  lymphatics  form  two  series,  of  which  the  inner 
and  more  numerous  arise  from  the  inner  side  of  the  back  and  sole  of 
the  foot,  commencing  in  the  toes ;  thence  proceed  in  front  and  behind 
the  inner  ankle,  and  ascend  on  the  inner  side  of  the  leg  and  knee  to 

1  Truncus  lymphaticus  dexter  or  minor. 


THE   LYMPHATIC   SYSTEM.  587 

the  thigh,  whence  they  continue  in  the  general  direction  of  the  long 
saphenous  vein  and  enter  the  lower  superficial  inguinal  glands.  The 
outer  series  arise,  like  the  former,  on  the  outer  side  of  the  foot,  ascend 
on  the  outer  side  of  the  leg  in  the  direction  of  the  short  saphenous 
vein,  and  partly  enter  the  popliteal  glands,  while  others  ascend  obliquely 
across  the  popliteal  space  and  join  the  inner  series.  From  the  back  of 
the  thigh  the  superficial  lymphatics  pass  around  on  both  sides  to  enter 
the  superficial  inguinal  glands. 

The  popliteal  glands,1  commonly  four  or  five  little  ones,  are 
embedded  in  the  connective  tissue  and  fat  surrounding  the  popliteal 
blood-vessels.  They  receive  the  deep  lymphatics  of  the  leg  and  a  few 
superficial  ones  accompanying  the  short  saphenous  vein.  Their  efferent 
vessels  usually  give  rise  to  four  trunks,  which  follow  the  course  of  the 
popliteal  and  femoral  blood-vessels  to  the  deep  inguinal  glands. 

The  deep  inguinal  glands,2  commonly  three  or  four,  surround  the 
femoral  blood-vessels ;  one  of  them  occupying  the  femoral  ring.  They 
receive  the  deep  lymphatics  of  the  lower  limb  and  some  of  those  of 
the  superficial  inguinal  glands.  Their  efferent  vessels  ascend  with 
most  of  those  of  the  latter  through  the  femoral  ring  and  along  the 
femoral  blood-vessels  to  join  the  external  iliac  lymphatics. 

The  superficial  inguinal  glands3  vary  from  eight  to  a  dozen  or 
more,  and  from  the  size  of  a  small  pea  to  that  of  an  almond-kernel. 
The  largest  occupy  the  inner  or  lower  part  of  the  groin,  extending  a 
couple  of  inches  around  the  long  saphenous  vein,  and  the  others  ex- 
tend outward  along  the  groin.  They  receive  the  superficial  lymphatics 
of  the  abdomen,  the  buttock,  the  perineum,  and  the  genital  organs,  and 
most  of  those  of  the  lower  limb.  The  efferent  vessels  pierce  the  sub- 
jacent fascia,  and  mainly  enter  the  saphenous  opening  partly  to  join 
the  deep  inguinal  glands,  and  partly  ascend  to  join  the  external  iliac 
lymphatics. 

The  superficial  lymphatics  of  the  abdomen  mostly  converge 
in  the  general  direction  of  the  superficial  epigastric  and  circumflex 
iliac  blood-vessels,  and  end  in  the  superficial  inguinal  glands. 

The  superficial  lymphatics  of  the  penis  commence  in  copious 
plexuses  of  the  prepuce  and  skin  of  the  glans,  whence  they  proceed 
around  the  cervix  to  the  dorsum,  and  there  converge  in  a  pair  of  lateral 
trunks  or  a  single  large  median  trunk.  The  former  run  backward  on 
each  side  of  the  dorsal  blood-vessels,  and  at  the  root  of  the  penis  turn 
outwardly  to  end  in  the  lower  superficial  inguinal  glands.  In  the  case 
of  a  single  trunk  this  divides  at  the  root  of  the  penis,  and  the  branches 
proceed  as  in  the  former.  The  urethral  lymphatics,  remarkable  for 
their  size,  form  a  reticular  plexus  the  whole  length  of  the  urethra. 
They  communicate  with  the  superficial  plexus  of  the  glans,  and  at  the 
frsenum  form  two  trunks,  which  join  the  others  at  the  cervix.  The 

1  Glandulae  popliteae  profundae.  2  G.  inguinales  prof.  3  G.  ing.  sup. 


588  THE    LYMPHATIC   SYSTEM. 

deep  lymphatics  of  the  penis  pursue  the  course  of  the  pudic  blood- 
vessels, and  end  in  the  internal  iliac  glands. 

The  lymphatics  of  the  scrotum  are  abundant,  and  form  from 
ten  to  twelve  trunks,  which  pursue  the  course  of  the  external  pudic 
blood-vessels  to  the  superficial  inguinal  glands. 

The  lymphatics  of  the  external  genital  organs  of  the  female 
accord  with  those  of  the  male,  are  proportioned  in  development  with 
the  parts,  and  pursue  a  similar  course. 

LYMPHATICS  OF  THE  PELVIS  AND  ABDOMEN. 

The  external  iliac  lymphatics,  continued  from  the  femoral  lym- 
phatics, ascend  along  the  external  iliac  blood-vessels,  and  are  commonly 
associated  with  three  or  four  glands  surrounding  the  latter  just  above 
the  femoral  ring.  They  are  joined  by  the  lymphatics  of  the  abdominal 
wall,  converging  in  the  direction  of  the  epigastric  and  circumflex  iliac 
blood-vessels.  Two  or  three  trunks  ordinarily  proceed  from  the  external 
iliac  glands  to  join  the  internal  iliac  and  lumbar  lymphatics. 

The  internal  iliac  lymphatics  pursue  the  general  course  of  the 
corresponding  blood-vessels,  and  are  associated  with  many  glands,  at 
the  side  of  the  pelvis  in  the  interval  of  the  external  iliac  and  internal 
iliac  blood-vessels.  They  receive  the  obturator,  gluteal,  ischiatic, 
and  pudic  lymphatics,  pursuing  the  course  of  the  corresponding 
blood-vessels,  and  also  the  lymphatics  from  the  pelvic  viscera. 

The  sacral  lymphatics,  associated  with  glands,  occupy  the  hollow 
of  the  sacrum,  receive  lymphatics  from  the  contiguous  walls  and  pelvic 
viscera,  and  communicate  with  the  internal  iliac  and  lumbar  lymphatics. 

The  lymphatics  of  the  rectum  are  numerous  and  of  considerable 
size,  and  at  the  anus  communicate  with  the  cutaneous  lymphatics.  The 
trunks  partially  join  the  sacral  lymphatics,  and  partially  ascend  to  the 
glands  of  the  mesorectum. 

Though  lymphatics  have  been  abundantly  attributed  to  the  urinary 
bladder,  it  would  appear  from  the  researches  of  Sappey  that  this  organ 
is  remarkable  for  their  absence.  A  few  trunks  at  the  base  of  the  blad- 
der emanate  from  numerous  lymphatics  of  the  prostate  and  seminal 
vesicles,  and  proceed  to  join  the  internal  iliac  and  inguinal  lymphatics. 

The  lymphatics  of  the  vagina  partly  join  the  inguinal  lymphatics 
and  partly  the  internal  iliac  lymphatics. 

The  lymphatics  of  the  uterus  are  small  in  the  ordinary  condition 
of  the  organ,  but  in  gestation  are  observed  to  be  exceedingly  numerous 
and  enlarged  to  an  extraordinary  degree.  Issuing  from  the  sides  of 
the  uterus  in  the  broad  ligament,  they  partially  pursue  the  course  of 
the  uterine  blood-vessels,  and,  in  company  with  the  vaginal  lymphatics, 
join  the  internal  iliac  vessels,  while  others  are  joined  by  the  lymphatics 
of  the  ovary  and  oviduct,  and  proceed  with  the  ovarian  blood-vessels 
to  join  the  lumbar  lymphatics. 

The  lumbar  lymphatics  of  the  two  sides  of  the  body  freely  com- 


THE   LYMPHATIC   SYSTEM.  589 

municate,  and  lie  in  front  and  behind  the  psoas  muscles,  and  the  great 
abdominal  blood-vessels  between  these,  extending  from  the  common 
iliac  blood-vessels  to  the  first  lumbar  vertebra,  where  they  communi- 
cate with  the  cceliac  glands.  They  are  associated  with  many  glands, 
large  and  small,  twenty  to  thirty  or  more,  the  largest  lying  in  front 
of  the  aorta  and  the  smallest  behind  the  psoas  muscles,  in  the  intervals 
of  the  lumbar  transverse  processes. 

The  lumbar  glands l  receive  several  trunks  from  the  external  iliac 
lymphatics,  and  others  from  the  internal  iliac  and  sacral  lymphatics. 
They  also  receive  lymphatics  from  the  rectum  and  sigmoid  flexure 
of  the  colon,  from  the  uterus  with  those  of  the  ovary  and  oviduct, 
those  of  the  testicle,  kidney,  and  suprarenal  body,  and  those  from  the 
vertebral  portion  of  the  diaphragm  and  the  deep  ones  of  the  posterior 
abdominal  wall.  The  efferent  vessels  mostly  unite  on  each  side  in  a 
short  lumbar  lymphatic  trunk,2  which  joins  its  fellow  and  with 
several  smaller  vessels  forms  the  commencement  of  the  thoracic  duct. 

The  renal  lymphatics  consist  of  a  deep  set  pursuing  the  course 
of  the  blood-vessels,  and  a  superficial  set  of  small  vessels  which  form  a 
plexus  in  the  capsule  of  the  kidney.  The  two  sets  unite  in  the  hilus, 
where  they  are  also  joined  by  lymphatics  from  the  ureter  .and  the 
suprarenal  body,  and  thence  proceed  to  end  in  the  upper  lumbar  glands. 

The  spermatic  lymphatics  commence  in  the  testicle,  where  they 
are  remarkable  for  their  comparative  abundance.  A  half-dozen  or 
more  trunks,  also  remarkable  for  their  great  proportionate  size,  ascend 
in  the  spermatic  cord,  and,  after  passing  through  the  inguinal  canal, 
accompany  the  spermatic  blood-vessels,  and  terminate  in  the  upper 
lumbar  glands. 

The  deep  lymphatics  of  the  posterior  wall  of  the  abdomen 
follow  the  direction  of  the  lumbar  and  ilio-lumbar  blood-vessels,  are 
joined  by  the  lymphatics  from  the  dorsal  muscles  and  the  spinal  canal, 
and  end  in  the  lumbar  glands  behind  the  psoas  muscles. 

The  lymphatics  of  the  alimentary  canal,  as  usual  in  the  viscera, 
originate  in  a  deep  series  forming  an  abundant  plexus  in  the  mucous 
membrane,  and  a  superficial  series  from  the  serous  and  muscular  coats. 
They  absorb  and  convey  the  dissolved  nutritive  matter,  the  result  of 
digestion  of  the  food,  as  well  as  the  ordinary  lymph.  The  nutritive 
liquid  derived  from  the  small  intestine,  commonly  emulsified  with  fat 
and  distinguished  under  the  name  of  chyle,  gives  to  the  lymphatics 
of  this  portion  of  the  canal  a  milk-white  appearance,  whence  they  are 
called  the  lacteals. 

The  lacteals  on  leaving  the  small  intestine  pass  through  the  mes- 
entery, converging  to  its  root,  and  traverse  in  their  course  the  numerous 
mesenteric  glands.  These  range  from  a  hundred  to  double  the 
number,  and  from  the  size  of  a  hemp-seed  to  that  of  an  almond-kernel, 

1  Glandulae  lumbales.  2  Truncus  lymphaticus  lumbalis. 


590  THE    LYMPHATIC   SYSTEM. 

in  the  healthy  condition,  but  often  appear  much  larger  from  disease. 
They  have  a  general  arrangement  in  three  imperfect  rows,  of  which 
those  of  the  first  row,  nearest  the  intestine,  are  most  numerous  and 
smallest,  and  those  of  the  last  row  are  fewest,  largest,  and  crowded 
around  the  trunk  of  the  mesenteric  blood-vessels.  The  outer  rows  oc- 
cupy loops  of  the  latter,  and  they  are  usually  removed  an  inch  or  more 
from  the  intestine.  The  efferent  vessels  commonly  unite  in  a  single 
intestinal  lymphatic  trunk,  or  in  two  or  three  smaller  ones,  opening 
into  the  commencement  of  the  thoracic  duct. 

The  colic  lymphatics  on  leaving  the  colon  traverse  thirty  or  more 
colic  glands  lying  along  the  course  of  attachment  of  the  intestine  and 
within  the  layers  of  the  mesocolon.  Those  of  the  sigmoid  flexure, 
together  with  part  of  those  of  the  rectum,  terminate  in  the  lumbar 
glands,  while  those  of  the  rest  of  the  colon  converge  to  unite  with  the 
mesenteric  lymphatics  to  form  the  intestinal  lymphatic  trunk. 

The  gastric  lymphatics  pass  from  the  walls  of  the  stomach  to  its 
curvatures,  where  they  run  in  company  with  the  blood-vessels,  trav- 
ersing in  their  course  a  number  of  little  gastric  glands.  Those  of 
the  small  curvature  proceed  to  the  cardia  and  descend  behind  the 
pancreas  to  join  the  coeliac  glands.  Those  from  the  great  curvature 
on  the  right  proceed  to  the  pylorus,  and  also  join  the  latter;  while 
those  on  the  left  proceed  to  join  the  splenic  lymphatics. 

The  splenic  lymphatics  arise  in  a  deep  series,  and  pursue  the 
course  of  the  blood-vessels  of  the  spleen  and  emerge  at  the  hilus,  where 
they  are  joined  by  a  superficial  series,  and  form  a  plexus  beneath  the 
peritoneal  investment  of  the  organ.  The  trunks  continue  in  the  course 
of  the  splenic  blood-vessels,  where  they  traverse  eight  or  ten  splenic 
glands,  which  also  receive  the  pancreatic  lymphatics,  and  they 
finally  end  in  the  coeliac  glands. 

The  hepatic  lymphatics  also  consist  of  a  deep  and  superficial 
series,  both  exceedingly  abundant,  but  the  former  much  the  larger. 
The  deep  lymphatics  form  two  sets,  of  which  one  pursue  the  reverse 
course  of  the  portal  blood-vessels  and  emerge  at  the  transverse  fissure,' 
where  they  enter  a  lymphatic  gland  resting  on  the  neck  of  the  gall- 
bladder, whence  the  efferent  vessels  descend  in  the  small  omentum  to 
the  coeliac  glands.  The  other  set  of  deep  lymphatics,  more  numerous 
and  larger  than  the  former,  follow  the  hepatic  veins  and  converge  to 
half  a  dozen  trunks,  which  accompany  the  inferior  cava  through  the 
diaphragm  to  a  group  of  small  glands  surrounding  the  termination  of 
the  latter  vessel.  The  efferent  vessels  from  these  superior  phrenic 
glands  descend  behind  the  crura  of  the  diaphragm,  and  end  in  the 
commencement  of  the  thoracic  duct.  Of  the  superficial  lymphatics, 
many  of  those  beneath  the  liver  join  the  deep  lymphatics  issuing  from 
the  transverse  fissure,  while  others  run  backward  to  the  coeliac  glands, 
and  others  of  the  left  lobe  join  the  gastric  lymphatics  from  the  small 
curvature.  The  lymphatics  of  the  gall-bladder  usually  converge  to 


THE   LYMPHATIC   SYSTEM.  591 

two  or  three  trunks,  which  descend  to  the  coaliac  glands.  Most  of 
the  lymphatics  from  the  upper  surface  of  the  liver  proceed  to  the  sus- 
pensory ligament,  and  thence  pass  in  front,  through  the  diaphragm, 
behind  the  ensiform  process,  to  the  anterior  mediastinal  lymphatics. 
Others  are  directed  backward  to  the  lateral  ligaments  and  descend  to 
the  coeliac  glands,  while  an  intermediate  series  converge  and  ascend  to 
the  superior  phrenic  glands. 

The  cceliac  glands,  sixteen  to  twenty,  and  of  considerable  size, 
surround  the  cceliac  axis  and  aorta,  extending  to  the  superior  mes- 
enteric  blood-vessels.  They  communicate  with  the  lumbar  glands, 
and  receive  the  lymphatics  of  the  stomach,  the  spleen  and  pancreas, 
the  greater  part  of  those  of  the  liver,  and  those  of  the  gall-bladder. 
Their  efferent  vessels  commonly  unite  with  the  mesenteric  lymphatics 
to  form  the  intestinal  lymphatic  trunk,  ending  in  the  commence- 
ment of  the  thoracic  duct. 

LYMPHATICS   OP   THE   THORAX. 

The  cardiac  lymphatics  proceed  from  a  deep  and  superficial  set 
in  the  walls  of  the  heart,  and  thence  mainly  pursue  the  course  of  the 
coronary  blood-vessels.  Those  accompanying  the  left  coronary  vessels 
end  in  a  single  trunk,  which  ascends  behind  the  pulmonary  artery,  and 
then  forward  between  this  and  the  aorta  to  the  front  of  the  arch,  above 
which  it  joins  one  of  the  cardiac  glands.  Those  accompanying  the  right 
coronary  vessels  likewise  end  in  a  single  trunk,  which  joins  the  left 
trunk  between  the  commencement  of  the  aorta  and  pulmonary  artery, 
or  proceeds  to  join  one  of  the  cardiac  glands  behind  the  aortic  arch. 

The  cardiac  glands,1  eight  to  ten,  occupy  the  superior  mediastinum 
around  the  aortic  arch  and  innominate  veins,  extending  in  front  of  the 
trachea  below  and  communicating  with  the  bronchial  glands.  They 
receive  the  cardiac  lymphatics,  most  of  those  of  the  pericardium,  and 
those  of  the  thymus  gland.  Their  efferent  vessels  form  two  or  three 
trunks,  which  proceed  left  and  right  on  the  trachea  to  join  the  thoracic 
and  right  lymphatic  ducts. 

The  pulmonary  lymphatics  consist  of  a  deep  series  pursuing  the 
course  of  the  bronchial  tubes  and  accompanying  blood-vessels,  and  a 
superficial  series  forming  an  abundant  reticular  plexus  beneath  the 
pleura.  Both  series  converge  to  the  root  of  the  lung,  where  they  enter 
the  bronchial  glands. 

The  bronchial  glands  are  numerous,  twenty  to  thirty,  large  and 
small,  and  occupy  the  interval  of  the  bifurcation  of  the  trachea  ;  thence 
extending  on  the  bronchi  and  their  primary  divisions  into  the  hilus  of 
the  lungs.  They  receive  the  pulmonary  lymphatics,  and  their  efferent 
vessels  form  several  considerable  trunks,  which  ascend  on  the  trachea 
to  join  the  thoracic  and  right  lymphatic  ducts.  The  bronchial  glands 

1  Superior  mediastinal  glands. 


592  THE    LYMPHATIC   SYSTEM. 

are  remarkable  for  their  liability  to  alteration,  both  ordinarily  and 
pathologically.  In  infancy  they  are  pink  in  hue ;  later  they  become 
grayish  and  more  or  less  mottled ;  and  in  advanced  age  they  assume  a 
variable  dark  slate  hue  to  an  intense  black  color. 

The  oesophageal  lymphatics  form  a  plexus  between  the  mucous 
and  muscular  coats  of  the  oesophagus,  and  pierce  the  latter  to  join  the 
posterior  mediastinal  glands. 

The  posterior  mediastinal  lymphatics,  with  from  eight  to  a 
dozen  glands,  are  situated  along  the  oesophagus,  from  which  they 
receive  many  tributaries,  and  others  from  the  back  of  the  diaphragm 
and  pericardium.  Their  efferent  vessels  above  partly  join  the  bronchial 
glands  and  partly  end  in  the  thoracic  duct. 

The  intercostal  lymphatics  pursue  the  course  of  the  correspond- 
ing blood-vessels,  and  usually  form  two  trunks,  which  run  backward 
and  commonly  enter  a  couple  of  glands  situated  between  the  heads 
of  the  ribs  beneath  the  pleura.  The  efferent  vessels  either  open  into 
the  thoracic  duct  with  a  few  of  the  upper  right  ones  into  the  right 
lymphatic  duct,  or,  in  whole  or  part,  they  form  a  pair  of  lateral  trunks, 
which  descend  on  the  sides  of  the  spine  and  join  the  lower  extremity 
of  the  thoracic  duct. 

The  sternal  lymphatics  ascend  along  the  course  of  the  internal 
mammary  blood-vessels,  and  commonly  form  two  or  three  trunks  asso- 
ciated with  half  a  dozen  or  more  little  glands.  They  receive  lymphatics 
from  the  upper  part  of  the  front  wall  of  the  abdomen,  the  fore  part  of 
the  diaphragm,  and  the  front  wall  of  the  thorax,  including  the  inner 
part  of  the  mamma3.  Some  of  their  efferent  vessels  below  join  the 
anterior  mediastinal  lymphatics,  and  those  above  terminate  in  the 
thoracic  and  right  lymphatic  ducts. 

The  anterior  mediastinal  lymphatics,  with  usually  three  or  four 
small  glands,  are  situated  in  the  corresponding  space  in  front  of  the 
pericardium.  They  receive  lymphatics  from  the  mesial  portion  of  the 
upper  surface  of  the  liver,  others  from  the  fore  part  of  the  diaphragm, 
and  some  from  the  lower  sternal  lymphatics.  Their  efferent  vessels 
ascend  to  join  the  thoracic  and  right  lymphatic  ducts. 

The  lymphatics  of  the  diaphragm,  forming  a  plexus  of  small 
vessels  in  the  tendinous  centre  and  of  conspicuously  large  ones  in  the 
muscular  portion,  mainly  converge  to  four  trunks,  of  which  a  pair 
proceed  to  join  the  sternal  lymphatics,  and  the  others  descend  to  join 
one  of  the  cceliac  glands. 

LYMPHATICS  OF  THE   UPPEK   LIMBS. 

The  deep  lymphatics  of  the  upper  limb,  together  with  some  of 
those  from  the  exterior  of  the  walls  of  the  chest,  accompany  the  corre- 
sponding deep  blood-vessels  and  converge  to  the  axillary  glands.  Com- 
monly each  artery  is  accompanied  by  a  pair  of  lymphatic  trunks,  as  in 
the  case  of  the  veins.  Several  little  glands  not  unfrequently  exist  in  the 


THE    LYMPHATIC   SYSTEM.  593 

course  of  the  radial  and  ulnar  lymphatic  trunks,  and  more  constantly 
three  or  four  in  the  course  of  the  brachial  lymphatic  trunks. 

The  superficial  lymphatics  commence  in  the  hand,  in  an  ex- 
tremely rich  and  close  plexus  of  the  palmar  surface,  and  are  joined 
by  others  from  the  dorsal  surface.  The  trunks  proceeding  from  the 
hand  form  three  series,  following  the  principal  superficial  veins  of  the 
forearm,  and  thence  ascending  on  the  front  and  inner  surface  of  the 
arm  to  the  axillary  glands.  They  are  joined  by  others  from  the  back 
of  the  arm ;  and  two  or  three  trunks,  joined  by  others  from  over  the 
shoulder,  follow  the  cephalic  vein  and  enter  the  infraclavicular  fossa 
to  join  the  axillary  glands.  Several  of  the  lymphatics  from  the  inner 
side  of  the  forearm  after  passing  the  elbow  enter  one,  two,  or  three 
glands  situated  a  short  distance  above  the  internal  condyle. 

The  lymphatics  of  the  mamma  are  large  and  extremely  nu- 
merous. The  trunks  converge  from  between  and  around  the  lobes  to 
the  areola,  where  they  unite  in  a  subareolar  plexus,  which  is  also 
joined  by  the  finer  lymphatics  of  the  skin  of  the  areola  and  nipple. 
From  the  subareolar  plexus  the  large  vessels  are  directed  outwardly, 
and  converge  commonly  into  two  or  three  trunks,  which  proceed  to 
enter  the  more  anterior  of  the  axillary  glands. 

The  superficial  lymphatics  of  the  side  and  front  of  the  chest, 
including  those  of  the  upper  part  of  the  abdomen,  derived  from  the 
skin,  subjacent  fascia,  and  superficial  muscles,  converge  and  ascend  out- 
wardly to  the  axillary  glands.  In  the  loins  they  communicate  with  the 
lymphatics,  which  converge  to  the  inguinal  glands. 

The  superficial  lymphatics  of  the  back  of  the  trunk,  over  the 
position  of  the  trapezius.  deltoid,  and  latissimus  muscles,  communicate 
with  the  former,  and  likewise  converge  to  the  axillary  glands. 

The  axillary  glands,  ten  to  a  dozen,  are  very  unequal,  large  and 
small,  and  are  mostly  collected  around  the  axillary  blood-vessels.  A  few 
lie  forward  on  the  great  serratus  at  the  lower  border  of  the  pectoral 
muscles,  and  receive  the  lymphatics  from  the  front  of  the  chest  and 
the  mamma ;  others  are  situated  at  the  back  of  the  axilla  on  the  sub- 
scapular  blood-vessels,  and  especially  receive  the  lymphatics  of  the 
back;  and  one  or  two  small  ones  occupy  the  infraclavicular  fossa,  com- 
municate with  the  inferior  cervical  glands,  and  receive  the  lymphatics 
accompanying  the  cephalic  vein.  The  glands  on  the  axillary  blood- 
vessels especially  receive  the  brachial  lymphatics. 

The  efferent  vessels  of  the  axillary  glands  ascend  with  the  sub- 
clavian  vein,  and  sometimes  unite  in  a  single  subclavian  lymphatic 
trunk,  or  two  or  three  trunks  of  unequal  calibre.  On  the  left  side  the 
trunk  opens  into  the  thoracic  duct  near  its  termination,  and  on  the  right 
side  into  the  right  lymphatic  duct,  or  on  either  or  both  sides  it  may  end 
directly  in  the  corresponding  subclavian  vein.  When  there  are  several 
trunks,  one  may  end  in  the  duct  of  the  corresponding  side,  and  the  other 
in  the  contiguous  subclavian  vein. 

38 


594 


THE    LYMPHATIC   SYSTEM. 


LYMPHATICS   OF   THE   HEAD   AND   NECK. 

The  lymphatics  of  the  upper  part  of  the  head,  proceeding  from 
the  scalp  and  subjacent  structures,  form  three  series,  the  frontal,  parietal, 
and  occipital  lymphatics. 

The  frontal  lymphatics,  from  the  forehead  and  eyebrow,  con- 
verge in  ten  or  more  trunks  to  the  front  of  the  ear,  where  they  enter 

FIG.  299. 


LYMPHATICS  OF  THE  HEAD  AND  NECK.  1,  facial  lymphatics:  2,  temporal  lymphatics;  3,  poste- 
rior auricular  and  occipital  lymphatics ;  4,  cervical  lymphatics  ;  5,  the  right  lymphatic  duct ;  6, 
internal  jugular  vein ;  7,  subclavian  vein. 


the  parotid  lymphatic  glands.  The  parietal  lymphatics  communicate 
with  the  former  and  the  occipital  lymphatics,  and  converge  in  six  or 
more  trunks,  which  descend  behind  the  ear  to  the  mastoid  glands. 

The  occipital  lymphatics  partly  converge  to  a  trunk  which  de- 
scends behind  the  sterno-mastoid  muscle,  and  then  beneath  it  to  the 
deep  cervical  glands,  and  partly  join  one  or  two  occipital  glands,  resting 


THE   LYMPHATIC   SYSTEM.  595 

on  the  complexus  in  advance  of  the  occipital  attachment  of  the  tra- 
pezius  muscle.  The  efferent  vessels  of  the  occipital  glands  enter  the 
superficial  cervical  glands. 

The  parotid  lymphatic  glands,  four  or  five  small  ones,  lie  under 
the  parotid  fascia,  and  in  part  are  embedded  in  the  parotid  gland. 
The  largest  one  is  placed  immediately  in  front  of  the  tragus,  and 
receives  the  frontal  lymphatics  accompanying  the  temporal  blood- 
vessels and  the  lymphatics  of  the  fore  part  of  the  pinna.  The  others 
receive  the  lymphatics  of  the  eyebrow  and  outer  part  of  the  eyelids, 
of  the  parotid  gland  and  the  cheek.  The  efferent  vessels  enter  the 
superficial  cervical  and  submaxillary  lymphatic  glands. 

The  mastoid  glands,  four  or  five,  lie  partly  on  and  partly  under 
the  insertion  of  the  sterno-mastoid  muscle.  They  receive  the  parietal 
lymphatics  and  those  from  the  back  of  the  pinna,  and  their  efferent 
vessels  join  the  cervical  glands. 

The  lymphatics  of  the  external  ear,  or  pinna,  form  a  rich,  close 
plexus  in  the  integument,  from  which  the  trunks  joined  by  deeper  ones 
converge  towards  the  meatus,  whence  those  in  front  proceed  to  the 
parotid  glands,  and  those  behind  to  the  mastoid  glands. 

The  facial  lymphatics  are  derived  from  the  region  of  the  face  oc- 
cupied by  the  corresponding  blood-vessels,  and  mainly  descend  in  their 
course  to  enter  the  submaxillary  glands.  The  deep  facial  lymphatics, 
from  the  orbit,  nasal  fossa,  roof  of  the  mouth,  and  inside  of  the  cheek, 
join  the  internal  maxillary  lymphatics.  These  pursue  the  course  of  the 
corresponding  blood-vessels,  and  further  receive  lymphatics  from  the 
temporal  and  zygomatic  fossae  and  upper  part  of  the  pharynx.  They 
are  associated  with  several  glands  lying  on  the  blood-vessels  and  on 
the  back  part  of  the  buccinator  muscle  and  pharynx.  Their  efferent 
vessels  enter  the  deep  cervical  glands. 

The  lymphatics  of  the  cranial  cavity  mainly  originate  in  the 
peri  vascular  lymphatics  of  the  brain  and  pia  mater,  whence  the  trunks 
proceed  and  accompany  the  internal  carotid  and  vertebral  arteries  and 
the  internal  jugular  vein  to  enter  the  deep  cervical  glands. 

The  lymphatics  of  the  eyeball  are,  for  the  most  part,  perivascu- 
lar,  and  accompany  the  blood-vessels  to  join  those  of  the  orbit. 

The  lymphatics  of  the  middle  ear  accompany  the  corresponding 
blood-vessels  to  the  internal  maxillary  and  deep  cervical  lymphatics. 
The  relation  of  the  internal  ear  to  the  lymphatic  system  is  not  satis- 
factorily determined. 

The  lymphatics  of  the  nasal  cavity  form  a  rich  plexus  in  the 
mucous  membrane,  from  which  the  trunks  pass  backward  and  enter 
the  deep  cervical  glands. 

The  lymphatics  of  the  tongue  form  a  close  plexus  in  the  mucous 
membrane,  especially  in  that  of  the  dorsum,  while  a  deep  set  proceed 
from  the  muscles.  The  trunks  mainly  pursue  the  course  of  the  lingual 
blood-vessels,  in  which  they  are  associated  with  two  or  three  little 


596  THE    LYMPHATIC   SYSTEM. 

glands,  and  terminate  partly  in  the  submaxillary  and  partly  in  the  deep 
cervical  glands. 

The  submaxillary  lymphatic  glands,  eight  to  ten  or  more,  lie 
below  and  within  the  base  of  the  mandible,  and  receive  the  superficial 
lymphatics  of  the  face,  those  of  the  floor  of  the  mouth  and  of  the  sub- 
lingual  and  submaxillary  salivary  glands,  and  most  of  those  from  the 
parotid  lymphatic  glands.  Their  efferent  vessels  enter  both  the  super- 
ficial and  the  deep  cervical  glands. 

The  superficial  cervical  lymphatics,  associated  with  from  four 
to  six  glands,  follow  the  course  of  the  external  jugular  vein,  and  enter 
the  deep  cervical  glands  at  the  bottom  of  the  neck.  They  receive  the 
efferent  vessels  of  the  occipital  and  mastoid  glands  and  part  of  those 
of  the  parotid  and  submaxillary  glands,  and  the  superficial  lymphatics 
of  the  neck. 

The  deep  cervical  lymphatics,  with  twenty  to  thirty  glands, 
large  and  small,  form  a  chain  along  the  great  blood-vessels  from  the 
base  of  the  cranium  to  the  bottom  of  the  neck.  They  are  mostly  col- 
lected about  the  internal  jugular  vein,  and  communicate  above  with  the 
mastoid,  parotid,  and  submaxillary  lymphatic  glands,  and  below  with 
the  cardiac  and  axillary  glands.  They  receive  the  lymphatics  of  the 
cranial  cavity,  those  of  the  deeper  parts  of  the  neck,  and  those  of  the 
nasal  cavity,  the  tongue,  lower  part  of  the  pharynx  and  the  larynx,  and 
the  efferent  vessels  of  the  internal  maxillary  and  most  of  those  of  the 
submaxillary  glands.  Their  efferent  vessels  commonly  terminate  in  the 
jugular  lymphatic  trunk,  which  ends  in  the  thoracic  duct  of  one  side 
and  the  right  lymphatic  duct  of  the  other  side,  or  it  may  terminate 
in  either  of  the  contiguous  veins. 


CHAPTER  X. 

THE   RESPIRATORY   APPARATUS   AND    LARYNX. 

THE    RESPIRATORY   APPARATUS. 

THE  organs  of  'respiration  comprise  the  lungs,  with  the  windpipe 
and  the  larynx,  together  with  the  chest  and  the  appropriate  muscles. 
The  latter  are  chiefly  the  diaphragm,  and  the  scaleni,  serrati,  pectoral, 
and  intercostal  muscles,  assisted  by  those  of  the  abdominal  wall. 

THE   LUNGS. 

The  lungs1  are  two  large  spongy  organs  permeable  by  air,  and 
are  contained  within  the  chest,  with  the  heart  enclosed  in  the  pericar- 

FIG.  300: 


ANTERIOR  VIEW  OF  THE  LUNGS.  The  chest  and  pleural  cavities  laid  open.  1,  anterior  medi- 
astinum ;  2,  superior  mediastinum;  3,  4,  5,  superior,  middle,  and  inferior  lobes  of  the  right  lung; 
6,  7,  interlobular  fissures ;  8,  9,  superior  and  inferior  lobes  of  the  left  lung ;  10,  interlobular  fissure  ; 
11,  notch  of  the  left  lung;  12,  pericardium  enclosing  the  heart;  13,  diaphragm;  14,  seventh  rib. 

dium  lying  between  them.  Each  occupies  a  distinct  cavity,  lined  by  a 
serous  membrane,  the  pleura,  which  is  thence  reflected  on  and  invests 
the  lung.  Each  is  suspended  or  attached  near  the  middle  of  its  inner 
surface  by  the  root,  which  consists  of  a  branch  of  the  trachea,  named 


1  Pulmones ;  pneumones  ;  lights. 


597 


598 


THE   RESPIRATORY   APPARATUS. 


the  bronchus,  and  the  pulmonary  blood-vessels  connected  with  the 
heart.  Elsewhere  the  lungs  are  free  and  smooth,  and  closely  conform 
to  the  cavities  containing  them,  with  the  surface  of  which  they  are 
perpetually  maintained  in  all  the  movements  of  respiration ;  the 
opposed  surfaces  of  the  pleura  being  lubricated  with  serum,  which 
alleviates  friction. 

Each  lung  is  pyramidal,  with  the  base  concave,  and  closely  con- 
forming to  and  resting  on  the  diaphragm.  The  outer,  most  extensive, 
lateral  surface  is  evenly  convex,  and  the  inner  surface,  next  the  heart, 


POSTERIOR  VIEW  OF  THE  LUNGS;  the  pleural  cavities  laid  open.  1,  posterior  mediastinum, 
bounded  laterally  by  the  pleurae;  2,  lower  border  of  the  costal  pleura;  3,  outline  indicating  the 
lower  limit  of  the  pleural  cavity ;  4,  phrenic  pleura  covering  the  diaphragm ;  5,  upper  lobe  of  the 
right  lung ;  6,  lower  lobe ;  7,  fissure  separating  the  lobes ;  8,  middle  lobe ;  9,  pharynx ;  10,  its  lower 
limit;  11,  oesophagus;  12,  thoracic  aorta,  giving  off  intercostal  arteries;  13,  innominate  artery, 
dividing'into  the  right  common  carotid  and  subclavian  arteries;  14,  left  subclavian  artery;  15, 
left  common  carotid  artery  and  the  accompanying  internal  jugular  vein ;  16,  azygos  vein ;  17, 
hemi-azygos  vein ;  18,  thoracic  duct. 


is  concave,  and  for  the  most  part  in  contact  with  the  pericardium.  The 
apex  is  rounded,  and  extends  into  the  neck  above  the  position  of  the 
first  rib,  which  impresses  it ;  as  usually  does  also  the  subclavian  artery 
at  its  summit.  The  posterior  border,  the  longest  portion  of  the  lung, 
is  thick  and  convex,  and  occupies  the  dorsal  recess  of  the  chest  at  the 
side  of  the  spine.  The  anterior  border  is  thin  and  acute,  overlaps  the 


THE   RESPIRATORY   APPARATUS.  599 

front  of  the  heart  within  the  pericardium,  and  in  full  inspiration  ap- 
proaches that  of  the  opposite  side,  behind  the  middle  of  the  sternum, 
where  the  lungs  are  separated  only  by  the  two  pleurae  of  the  anterior 
mediastinum.  The  border  of  the  base  is  likewise  thin  and  acute,  and 
outwardly  descends  between  the  diaphragm  and  its  attachment  to  the 
ribs. 

The  root  of  the  lung l  is  situated  somewhat  above  the  middle  of 
the  inner  surface  nearer  the  posterior  border,  and  is  composed  of  the 
corresponding  bronchus,  the  pulmonary  artery,  two  pulmonary  veins, 
the  bronchial  vessels,  lymphatics  with  glands,  and  the  nerves,  all  en- 
veloped in  areolar  tissue  and  a  reflection  of  the  pleura.  Where  the 
bronchus,  vessels,  etc.,  enter  the  lung  and  emerge  from  it  there  is  an 
elongated  elliptical  recess,  the  hilus,2  which  is  about  three  inches  long 
and  half  an  inch  wide,  and  has  a  slightly  prominent  border  in  front 
and  behind.  Back  of  the  hilus  the  surface  of  the  lung  is  depressed 
longitudinally  to  conform  to  the  convex  side  of  the  spine. 

Bach  lung  is  divided  by  a  long  and  deep  oblique  fissure,3  which  is 
seen  on  the  outer  surface,  commencing  behind,  two  or  three  inches 
below  the  apex,  and  descending  to  the  base  in  front.  The  fissure  in- 
wardly approaches  the  root  and  divides  the  lung  into  two  lobes,4  of 
which  the  lower  is  the  larger,  but  it  does  not-  completely  separate 
them.  In  the  right  lung  a  second  fissure 5  proceeds  horizontally  for- 
ward from  the  former,  and  divides  off  above  a  smaller,  triangular  por- 
tion of  the  lower  lobe,  thus  giving  three  lobes  to  this  lung.  Occasion- 
ally the  left  lung  exhibits  a  trace  of  a  similar  division,  and  sometimes 
that  of  the  right  lung  is  less  well  produced  than  usual.  The  left  lung 
is  deeply  notched6  at  its  fore  part  below,  between  the  two  lobes,  in 
which  position  the  apex  of  the  heart  approaches  the  front  wall  of  the 
chest. 

The  right  lung 7  is  shorter,  broader,  more  bulky,  and  heavier  than 
the  left,  and  the  extent  of  its  base  is  considerably  greater. 

The  left  lung8  is  longer,  narrower,  and  deeper,  the  difference 
being  due  to  the  greater  encroachment  of  the  heart  on  the  left  and 
the  less  ascent  of  the  diaphragm  on  that  side. 

In  respiration  the  upper  extremity  and  posterior  border  of  the  lungs 
remain  in  close  contiguity  with  their  pleural  sac ;  but  in  expiration 
the  anterior  margin  retires  from  the  corresponding  border  of  the  sac, 
and  only  occupies  it  in  full  inspiration.  The  outer  basal  margin  like- 
wise retires  in  expiration,  and  probably  at  no  time  does  it  descend  to 
the  entire  depth  of  the  pleural  cavity. 

The  apex  of  the  lung,  with  the  parietal  pleura,  ascends  through  the 

1  Eadix  or  pedunculus  pulmonis.  2  Porta  pulmonis. 

8  Incisura  interlobularis. 

4  Lobus  superior  or  anterior  and  inferior  or  posterior. 

5  Incisura  interlobularis  inferioris.  6  Incisura  cardiaca. 
7  Lobus  dexter.  8  L.  sinister. 


600 


THE   RESPIRATORY   APPARATUS. 


FIG.  302. 


upper  aperture  of  the  chest,  an  inch  or  more  into  the  neck,  though 
sometimes  not  so  high,  or  even  above  the  level  of  the  first  rib.  From 
the  apex,  the  anterior  margin  of  the  lung  curves  inward  behind  the 
sterno-clavicular  articulation,  and  thence  nearly  to  the  median  line  of 
the  mesosternum,  whence  it  descends,  in  the  right  lung  to  the  sixth 
costal  cartilage,  or  lower,  and  in  the  left  lung  to  the  fourth,  and  recedes 
in  a  curve  downward,  outward,  and  backward  to  the  tenth  thoracic 
vertebra.  The  inferior  margin  of  the  lungs  descends  to  a  considerable  ex- 
tent in  inspiration,  and  in  a  corresponding  degree  ascends  in  expiration. 
The  surface  of  the  lungs  in  the  usual  disten'ded  condition  is  per- 
fectly smooth,  and  is  everywhere  marked  by  polygonal  areas,  com- 
monly four-  to  six-sided,  and 
variably  approaching  about  half 
an  inch  in  width.  These  areas 
are  similarly  but  less  distinctly 
marked  with  smaller  ones,  about 
a  line,  more  or  less,  in  diameter. 
The  marks  are  the  outlines  of 
subdivisions  or  lobules  of  which 
the  lung-substance  is  composed, 
the  whole  being  united  by  con- 
nective tissue  and  invested  by 
the  pleura.  In  infancy  the  lungs 
are  of  a  pale-pink  or  rose  color, 
but  as  life  advances  they  be- 
come more  or  less  violaceous 
and  gray,  and  marked  by  spots 
and  streaks  of  dull  bluish-black 
or  slate  color,  all  of  which  ap- 
pear darker  in  the  collapsed  condition  of  the  organ. 

The  slate-colored  marks  commonly  increase  with  age,  and  appear  in 
considerable  measure  to  be  promoted  by  certain  pursuits,  as  those  of 
the  smith,  the  miner,  and  the  collier.  The  coloring-matter  is  disposed 
to  accumulate  between  the  lobules,  thus  rendering  their  outlines  more 
distinct,  and  not  unfrequently  it  is  observed  in  greater  degree  along 
the  position  of  the  ribs,  giving  the  lungs  a  banded  appearance. 

The  lung-substance  is  of  a  loose  or  spongy  texture,  and  even  in  the 
collapsed  condition  readily  floats  on  water ;  its  specific  gravity  ranging 
from  0.345  to  0.746,  and  when  fully  distended  being  only  0.126.  Com- 
pletely deprived  of  air,  or  in  the  foetus  before  breathing,  it  has  a  spe- 
cific gravity  of  1.056,  and  sinks  in  water.  When  pressed  between  the 
fingers  the  lungs  crepitate,  from  the  escape  of  air  from  the  tissue  ;  and 
when  torn  they  exude  a  reddish  frothy  liquid,  consisting  of  mucus 
tinged  with  blood  and  mingled  with  air-bubbles. 

The  lungs  are  highly  elastic,  so  that  they  collapse  to  about  a  third 
of  their  bulk  when  exposed  by  opening  the  chest.  They  range  from 


PORTION  OF  THE  EXTERIOR  SURFACE  OF.  THE  IN- 
FLATED LUNG  ;  magnified  and  exhibiting  the  hex- 
agonal outlines  of  the  bases  of  the  primary  lobules 
or  infundibula,  with  the  air-cells,  1. 


THE    RESPIRATORY   APPARATUS.  601 

two  to  three  pounds  avoirdupois,  and  commonly  are  rather  above  the 
average  of  these  weights.  In  the  female  they  weigh  about  a  fourth 
less. 

The  lungs  are  provided  each  with  a  serous  membrane,  the  pleura, 
which  forms  a  closed  sac,  and  consists  of  a  parietal  portion  lining  the 
cavity  containing  the  lung,  and  a  visceral  portion  reflected  from  the 
cavity  over  the  root  and  investing  the  lung,  whence  it  is  called  the  pul- 
monary pleura.2  Where  the  visceral  portion  lines  the  ribs  and  costal 
cartilages  it  is  named  the  costal  pleura,3  that  covering  the  diaphragm 
is  the  phrenic  pleura,  and  inwardly  the  two  pleurae  together  form  the 
mediastinum  and  envelop  the  pericardium.  From  the  root  of  the 
lung  a  narrow  fold  of  the  pleura,  the  pulmonary  ligament,4  descends 
to  the  base  of  the  lung,  connecting  the  posterior  border  of  its  inner 
surface  to  the  contiguous  border  of  the  spine. 

The  apex  of  the  pleura,  with  that  of  the  lung,  rises  into  the  root  of 
the  neck  an  inch  or  two  above  the  fore  end  of  the  first  rib,  and  a  short 
distance  above  the  clavicle  under  the  attachment  of  the  scaleni  muscles. 
In  front,  the  pleura?  come  nearly  or  quite  into  contact  behind  the  meso- 
sternum,  but  at  the  lower  end  of  the  latter,  while  the*  right  pleura 
remains  at  or  near  the  median  line,  the  left  pleura  retires  to  a  vari- 
able distance  from  it.  Behind,  the  pleura?  descend  as  low  as  the  head 
of  the  last  rib ;  in  the  line  of  the  axilla  the  right  pleura  reaches  the 
lower  margin  of  the  ninth  rib,  and  the  left  pleura  the  lower  margin 
of  the  tenth  rib.  In  front,  the  former  reaches  the  junction  of  the 
seventh  rib  with  its  cartilage,  and  the  left  one  a  little  lower. 

The  pleura  resembles  other  serous  membranes  in  structure,  and  has 
the  same  object,  to  facilitate  the  movement  of  the  lungs  on  the  surface 
of  the  cavities  containing  them.  The  costal  pleura  is  the  thickest,  and 
is  strengthened  by  a  considerable  connective-tissue  layer,  by  which  it 
adheres  to  the  subjacent  parts,  and  more  firmly  to  the  ribs  than  to  the 
intercostal  muscles.  The  phrenic  pleura  is  thinner  and  more  tightly 
adherent  than  the  former.  That  of  the  mediastinum  and  that  covering 
the  pericardium  is  also  thin,  and  is  the  most  disposed  to  the  accumula- 
tion of  fat  in  its  subserous  connective  tissue.  The  pulmonary  pleura  is 
the  most  delicate,  is  colorless  and  transparent,  and  is  always  clear  of 
subjacent  fat.  Though  easily  detached  from  the  lung,  it  closely  adheres 
to  the  surface  by  a  thin,  firm  layer  of  connective  tissue,  with  consid- 
erable elastic  tissue,  continuous  with  the  intervening  areolar  tissue  of 
the  lobules.  This  subserous  layer  contains  a  uniform  net  of  capillary 
blood-vessels  supplied  by  the  bronchial  arteries.  It  further  contains  an 
abundant  plexus  of  lymphatics,  which  communicate  by  stomata  with 
the  pleural  cavity  and  with  the  lymphatics  in  the  interior  of  the  lung. 

1  Pleurum  ;  membrana  pleuritica. 

2  Pleura  pulmonalis  ;  membrana  or  velamentum  pulmonis. 

3  P.  costalis.  4  Ligamentum  pulmonis. 


602 


THE    RESPIRATORY   APPARATUS. 


The  trachea,  or  windpipe,1  is  the  common  air-passage  of  both 

lungs,  commences  at  the  larynx 
on  a  level  with  the  lower  border 
of  the  fifth  cervical  vertebra,  and 
descends  through  the  fore  part 
of  the  neck  into  the  chest,  where 
it  forks  into  two  branches,  the 
bronchi,  or  bronchial  tubes,2 
opposite  tfye  upper  border  of  the 
fifth  thoracic  vertebra.  It  is. 
a  cylindrical  tube,  about  four 
inches  long  and  from  three- 
fourths  to  one  inch  in  diameter, 
but  of  slightly  less  width  fore  and 
aft ;  and  is  proportionately  smaller 
in  the  female.  It  is  retained  per- 
manently open  by  a  series  of  car- 
tilaginous rings,  which  are,  how- 
ever, incomplete  behind,  where 
the  trachea  is  solely  membranous, 
and  is  there  somewhat  flattened. 
The  lower  end  slightly  expanded 
laterally  divides  at  an  obtuse  an- 
gle into  the  right  and  left  bronchi, 
which  have  the  same  form  and 
construction  as  the  trachea.  The 
right  bronchus3  is  the  shorter 
and  wider,  about  an  inch  long, 
and  is  directed  obliquely  outward 
and  downward  to  the  root  of  the 

corresponding  lung,  which  it  enters  opposite  the  fifth  thoracic  vertebra. 
The  left  bronchus,4  twice  the  length  of  the  former,  but  narrower,  is 
directed  more  obliquely  to  the  root  of  the  left  lung,  which  it  enters 
opposite  the  sixth  vertebra. 

In  th^e  neck  the  common  carotid  artery  lies  on  each  side  of  the 
trachea,  and  its  upper  extremity  is  embraced  by  the  thyroid  gland.  It 
is  covered  in  front  by  the  sterno-thyroid  and  -hyoid  muscles,  with  a 
narrow  interval  occupied  by  the  deep  cervical  fascia.  At  the  bottom 
of  the  neck  it  is  received  in  the  angle  of  divergence  of  the  innominate 
and  left  common  carotid  arteries,  and  above  these  the  inferior  thyroid 
veins  lie  upon  it.  In  the  thorax  the  trachea  is  situated  behind  the 
presternum  covered  by  the  origin  of  the  sterno-hyoid  and  -thyroid 

1  Aspera  arteria ;  bronchus  ;  canna ;  syrinx  ;  weasand  ;  throttle  ;  fistula  pulmo- 
nalis. 

2  Bronchia  ;  bronchiae  ;  cannulae  pulmonum. 

3  Bronchus  dexter.  *  B.  sinister. 


FRONT  VIEW  OF  THE  LARYNX,  TRACHEA,  AND 
BRONCHI.  1,  hyoid  bone;  2, thyro-hyoid  mem- 
brane ;  3,  thyroid  cartilage ;  4,  lower  part  of  the 
vocal  membrane ;  5,  cricoid  cartilage  ;  6,  trachea ; 
7,  8,  cartilaginous  rings ;  9,  intervening  fibro- 
elastic  membrane  connecting  the  rings;  10,  11, 
right  and  left  bronchi  dividing  into  the  bronchial 
tubes. 


THE   RESPIRATORY   APPARATUS.  603 

muscles.  Lower,  it  is  covered  in  front  by  the  left  innominate  vein, 
then  by  the  diverging  innominate  and  left  carotid  arteries,  and  finally 
by  the  arch  of  the  aorta.  Placed  between  the  pleurae  in  the  superior 
mediastinum,  to  its  right  is  the  corresponding  vagus  nerve,  and  to  its 
left  are  the  corresponding  common  carotid  artery,  the  vagus,  and  the 
inferior  laryngeal  nerve. 

The  root  of  the  right  lung  extends  behind  the  superior  cava  and 
ascending  portion  of  the  aortic  arch,  and  has  the  azygos  vein  arching 
from  behind  forward  above  and  over  it  to  join  the  cava.  The  root  of 
the  left  lung  extends  beneath  the  aortic  arch  in  front  of  the  descend- 
ing aorta.  The  phrenic  nerve  descends  in  front  of  the  root  of  each 
lung,  and  the  vagus  nerve  behind  it. 

The  bronchi  diverge  from  the  trachea  back  of  the  pulmonary  ves- 
sels, and  enter  the  hilus  between  the  artery  above  and  the  veins  below 
and  in  front.  They  divide  at  the  entrance  of  the  hilus  each  into  two 
principal  branches  for  the  upper  and  lower  lobes  of  the  lung,  and  the 
lower  branch  of  the  right  bronchus  gives  a  division  to  the  third  lobe. 

The  right  bronchus  proceeds  from  above  downward  and  outward 
behind  the  right  pulmonary  artery  to  the  hilus  of  the  lung,  and  the  left 
bronchus  passes  in  the  same  manner  beneath  the  left  pulmonary  artery 
to  the  corresponding  lung.  Within  the  lungs  the  bronchi,  or  bronchial 
tubes,  ramify  throughout  the  organs,  branching  at  acute  angles  and 
diverging  in  all  directions,  the  terminal  branches  being  distinguished 
as  the  bronchioles.  The  pulmonary  blood-vessels  accompany  the 
bronchi  and  ramify  in  the  same  manner,  the  arteries  running  behind 
and  the  veins  in  front  of  them.  The  bronchial  arteries  and  veins,  the 
lymphatics,  and  the  nerves  likewise  pursue  the  same  course. 

The  trachea  and  its  chief  divisions,  the  bronchi,  are  composed  of  in- 
complete cartilaginous  rings l  joined  by  intervening  ligaments,  united 
by  a  posterior  membranous  layer  and  lined  by  mucous  membrane. 
The  rings  form  about  two-thirds  of  a  circle,  with  the  inner  surface 
convex  from  above  downward,  the  outer  surface  flat,  and  the  ends 
rounded.  In  the  trachea  there  are  usually  from  sixteen  to  twenty, 
each  about  two  lines  deep  and  half  a  line  thick ;  in  the  bronchi  they 
are  proportionately  smaller,  from  six  to  eight  in  the  right  bronchus 
and  from  nine  to  twelve  in  the  left.  They  are  generally  parallel  with 
one  another  across  the  trachea,  and  are  most  uniform  along  the  middle 
of  the  latter,  but  are  variable  especially  at  the  extremities.  Often 
several  fork,  usually  on  alternate  sides,  so  as  to  preserve  the  con- 
formity of  the  series,  and  sometimes  those  adjacent  unite  at  the  ends. 
The  last  tracheal  ring  is  especially  variable,  and  usually  is  prolonged  in 
front  in  a  downward  angle  so  as  to  conform  to  the  first  pair  of  rings 
of  the  bronchi.  The  rings  of  the  latter  are  even  more  variable  than 
those  of  the  trachea,  and  are  often  more  or  less  irregularly  conjoined. 

1  Annul!  cartilaginei. 


604  THE   RESPIRATORY   APPARATUS. 

The  tracheal  and  bronchial  cartilages  are  non-vascular,  and  are  in- 
vested with  a  dense  and  closely-adherent  perichondrium,  which  is  con- 
tinuous with  the  intervening  ligaments.  The  latter  are  strong,  thin 
bands  of  fibro-connective  with  considerable  elastic  tissue.  A  mem- 
branous layer  -of  the  same  character  but  of  looser  texture  is  extended 
across  the  interval  of  the  cartilages  at  the  back  of  the  trachea  and 
bronchi.  "Within  the  position  of  this  layer  is  a  pale-reddish  layer  of 
unstriped  muscular  fibres,  which  pass  transversely  between  the  rings 
and  are  attached  to  their  ends,  and  for  a  short  distance  to  their 
inner  surface.  The  ligament  connecting  the  trachea  with  the  larynx 
is  stronger  than  the  rest. 

The  lining  mucous  membrane  of  the  trachea  is  mostly  even  and  of 
a  pale  pink  hue,  though  it  readily  assumes  a  crimson  or  purple  color 
from  inflammation  and  congestion.  Along  the  membranous  back  part 
of  the  passage  it  is  finely  wrinkled  longitudinally,  especially  approach- 
ing the  bronchi,  the  wrinkles  being  mainly  due  to  subjacent  longitudinal 
bundles  of  elastic  tissue.  The  membrane  exhibits  in  many  positions 
a  finely-punctate  appearance,  especially  in  the  intervals  of  the  tracheal 
rings  and  between  the  posterior  wrinkles,  due  to  the  orifices  of  the 
ducts  of  the  numerous  subjacent  mucous  glands  of  the  trachea.  The 
epithelium  of  the  mucous  membrane  consists  of  a  layer  of  compara- 
tively long  columnar,  ciliated  cells,  which  taper  and  are  more  or  less 
irregular  at  their  deeper  extremity,  where  they  are  intercalated  with 
a  stratum  of  short,  immature  cells  conforming  to  the  intervals  they 
occupy.  The  mucosa  of  the  tracheal  mucous  membrane  consists  of 
a  well-marked  basement  membrane  with  a  layer  of  fibro-connective 
tissue  containing  capillary  blood-vessels  and  lymphatics,  and  associated 
with  some  lymphoid  tissue. 

Following  the  fibro-connective-tissue  layer  there  is  a  considerable 
layer  of  elastic  tissue  collected  in  longitudinal  reticular  bundles.  The 
submucous  layer  of  the  trachea,  composed  of  areolar  with  elastic  tis- 
sue, contains  the  larger  blood-vessels,  lymphatics,  and  nerves  of  the 
mucous  membrane,  together  with  numerous  small  racemose  glands 
whose  ducts  open  into  the  trachea.  The  tracheal  glands  are  largest 
and  most  numerous  in  the  posterior  membranous  layer  of  the  trachea, 
where  many  of  them  extend  from  the  submucous  layer  between  the 
muscular  fibres  into  the  exterior  fibro-connective-tissue  layer.  They 
are  also  especially  numerous  between  the  tracheal  rings,  but  are  there 
smaller. 

The  bronchi  as  forks  of  the  trachea  are  identical  in  structure. 

The  arteries  of  the  trachea  and  bronchi  are  derived  from  the  inferior 
thyroid  and  bronchial  arteries,  and  for  the  most  part  terminate  in 
the  submucous  coat  in  a  plexus,  which  is  connected  with  the  ample 
capillary  nets  of  the  mucosa  of  the  mucous  membrane  and  of  the  tra- 
cheal and  bronchial  glands.  The  veins  end  in  the  thyroid  and  bronchial 
veins.  Rich  plexuses  of  lymphatics  occupy  the  mucosa  and  submu- 


THE   RESPIRATORY   APPARATUS. 


605 


cous  layer  of  the  lining  membrane  of  the  trachea  and  bronchi,  and  the 
chief  vessels  join  the  cervical  and  bronchial  lymphatic  glands.  The 
nerves  are  derived  from  the  trunk  of  the  vagus,  from  its  inferior 
laryngeal  branch,  and  from  the  sympathetic  nerve. 

Structure  of  the  lungs.  The  substance  of  the  lungs  is  composed 
of  small  polyhedral  subdivisions,  the  primary  lobules,  which  are 
closely  associated  into  larger  lobules  from  about  a  fourth  of  a  line  to 
a  line  in  diameter,  and  these  again  into  still  larger  ones  variably  ap- 
proximating half  an  inch,  and  aggregated  in  the  formation  of  the 
lobes  of  the  lungs.  The  lobules  of  the  lungs  are  connected  together 
by  the  bronchi  and  blood-vessels,  as  the  foliage  of  a  tree  is  attached  to 
its  boughs,  but  are  closely  aggregated  and  conjoined  by  interstitial 
areolar  tissue.  The  primary  lobules  are  somewhat  pyramidal,  whence 
they  are  also  called  infundibula,  and  are  composed  of  rounded  sac- 
cules,  the  air-cells.  These  do  not  directly  communicate  with  one 
another,  but  are  closely  grouped  around  a  central  air-passage,  into 
which  they  open.  The  air-passage  narrows  and  proceeds  from  the 
apex  of  the  infundibulum  as  a  bronchiole,  which  joins  others  in  the 
formation  of  the  larger  bronchial  tubes  or  bronchi.  At  the  surface 

FIG.  305. 


TWO   PRIMARY   LOBULES    OF    THE    LUNGS.      tt, 

lobules;  b,  air-cells;  c,  bronchioles.    From  an 
infant :  magnified  25  diameters. 


DIAGRAM  OF  TWO  PRIMARY  LOBULES  OF  THE 
LUNGS,  magnified.  1,  bronchiole  ;  2,  a  pair  of 
primary  lobules  connected  by  fibro-connective 
tissue ;  3,  intercellular  air-passages ;  4,  air-cells ; 
5,  branches  of  the  pulmonary  artery  and  vein. 

of  the  lungs  the  bases  of  the  con- 
tiguous primary  lobules  appear 
in  polygonal  areas,  which  include 
from  four  or  five  to  double  the 
number  of  air-cells.  Both  the  for- 
mer and  the  latter  are  larger  at  the  periphery  than  in  the  interior  of 
the  lungs.  The  air-cells  generally  range  from  about  -j-^  of  an  inch 
to  double  the  size.  In  the  infant  they  are  about  ^fa  of  an  inch,  and 
they  increase  in  size  with  the  advance  of  age.  They  are  smaller  in 
the  female  than  in  the  male. 

The  bronchi,  traced  from  the  main  trunks  after  ramifying  through- 
out the  lungs,  by  their  terminal  branches  or  bronchioles  end  in  the 
primary  lobules.  They  are  permanently  open  cylindrical  tubes,  and  in 
general  are  composed  of  an  outer  fibro-connective-tissue  coat,  with  an 


606 


THE   RESPIRATORY   APPARATUS. 


FIG.  306. 


inner  layer  of  circular,  unstriped  muscular  fibres  and  a  lining  mucous 
membrane.  The  latter  is  like  that  of  the  chief  bronchi,  but  is  more 
uniformly  longitudinally  striate  or  narrowly  wrinkled,  and  possesses 
the  same  kind  of  columnar,  ciliated  epithelium  throughout.  The  mu- 
cosa  also  contains  considerable  elastic  tissue  collected  in  longitudinal 
bundles.  In  the  larger  bronchi  the  wall  is  furnished  with  plates  of  car- 
tilage, mostly  irregular  both  in  shape  and  in  their  disposition  around 
the  tubes.  At  the  division  of  the  tubes,  plates  of  crescentic  form  are 
placed  below  the  entrance  of  branches,  with  the  concave  border  em- 
bracing the  orifice  so  as  to  retain  it  open.  The  cartilaginous  plates 
gradually  diminish  in  number  and  size  as  the  bronchi  decrease,  and 
they  finally  disappear.  The  bronchi  are  also  furnished  with  small 
racemose  mucous  glands,  which  are  more  numerous  in  the  larger  tubes 
and  cease  in  the  smaller  ones. 

The  smallest  bronchi,  or  bronchioles,  merge  into  the  central  air- 
passages  of  the  primary  lobules  of 
the  lung.  The  fibro-connective- 
tissue  coat  of  the  bronchioles  with 
elastic  tissue  extends  between  the 
lobules  and  surrounds  the  air-cells. 
The  ciliated  columnar  epithelium 
of  the  bronchioles  merges  in  the 
air-passages  of  the  lobules  into 
the  condition  of  short,  polygonal, 
non-ciliated  cells. 

The  air-cells  open  by  large  ori- 
fices into  the  central  air-passage 
of  the  lobules,  but  their  walls  and 
bottom  are  entire.  They  are  com- 
posed of  a  delicate  membrana  pro- 
pria  of  fibro-connective  with  elastic 
tissue  enclosing  a  close  net  of  cap- 
illary blood-vessels,  the  meshes  of 
which  are  scarcely  wider  than  the 
vessels.  A  single  net  is  included 
between  the  air-cells  laterally,  and 
is  continued  around  their  fundus, 
where  it  is  distinct  from  that  of 
the  air-cells  of  the  contiguous  lob- 
ules. At  the  mouths  of  the  air-cells 


SECTION  OF  THE  TISSUE  OF  THE  LUNG,  highly 
magnified.  1,  an  intercellular  air-passage;  2, 
air-cells ;  3,  fibro-connective  with  elastic  tissue, 
surrounding  them,  in  which  lie  the  capillary 
blood-vessels;  4.  5,  small  granular  nucleated 
cells ;  6.  large  pavement  epithelial  cells  lining 
the  air-cells. 


the  capillary  nets  are  defined  by 
circular  vessels  twining  along  their 

border.  The  air-cells  are  lined,  for  the  most  part,  with  a  single  layer 
of  irregular,  clear,  pavement,  non-nucleated  cells.  Scattered  among  the 
latter,  here  and  there,  are  small,  granular,  polygonal,  nucleated  cells, 
single  or  two  or  three  together,  and  forming  rows  at  the  mouths  of  the 


THE   RESPIRATORY   APPARATUS. 


607 


air-cells,  where  they  are  continuous  with  the  similar  epithelium  of  the 
air-passage. 

The  nets  of  capillary  blood-vessels  of  the  air-cells  of  the  lungs 
receive  the  terminal  branches  of  the  pulmonary  artery,  which  accom- 
panies the  bronchus  in  its  distribution ;  the  arterial  branches  generally 
running  above  and  behind  the  bronchial  tubes,  and  finally  entering 
between  the  primary  lobules.  The  veins  from  the  capillary  nets 
emerge  from  between  the  lobules  and  pursue  the  same  course  as  the 
arteries,  generally  in  front  and 

below  the  bronchial  tubes.    The  Fio.  307. 

veins  from  the  peripheral  lobules 
also  in  part  unite  in  a  super- 
ficial plexus,  from  which  the 
main  vessels  converge  and  join 
the  deep  veins  as  they  emerge 
at  the  hilus  of  the  lungs. 

The  bronchial  blood-vessels, 
very  small  in  comparison  with 
the  special  pulmonary  blood- 
vessels, are  devoted  to  the  nu- 
trition of  the  component  parts 
of  the  lungs.  Accompanying 
the  bronchi,  they  are  distributed 
to  their  walls,  to  those  of  the 
pulmonary  vessels,  the  bron- 
chial lymphatic  glands,  the  in- 
terlobular  connective  tissue,  and 

to  the  pulmonary  pleura.  Capillary  plexuses  of  blood-vessels  of  the 
bi'onchi,  of  their  mucous  membrane,  glands,  muscular  and  connective 
tissue  and  elastic  coat,  and  the  subserous  connective-tissue  layer  of 
the  pleura,  are  supplied  by  the  bronchial  arteries.  The  corresponding 
veins  accompanying  the  arteries  are  smaller,  as  part  of  the  blood  dis- 
tributed by  the  bronchial  veins  is  returned  from  the  lungs  through 
the  pulmonary  veins. 

The  lymphatics  of  the  lungs  are  numerous,  commencing  in  the  walls 
of  the  air-cells  and  bronchioles,  and  forming  intricate  plexuses  in  the 
intervals  of  the  primary  lobules.  A  rich  plexus  also  exists  in  the 
bronchial  mucous  membrane,  and  a  superficial  one  in  the  subserous 
connective  tissue  of  the  pulmonary  pleura.  From  all  the  plexuses,  the 
principal  lymphatic  vessels  follow  the  course  of  the  bronchi  and  blood- 
vessels, and  emerge  at  the  hilus  of  the  lungs,  where  they  are  joined 
by  other  branches  emerging  from  the  surface  of  the  lungs,  derived 
from  the  superficial  plexus.  The  latter  communicates  by  stomata  of 
the  pulmonary  pleura  with  the  pleural  cavity.  The  deep  lymphatic 
plexuses  are  also  said  to  communicate  with  the  air-cells ;  and  these 
frequently  contain  free  lymphoid  corpuscles,  which  under  favorable 


CAPILLARY  NETS  OF  THE  AIK-CELLS  OF  THE  LUNG: 
magnified  60  diameters. 


608  THE   LARYNX. 

circumstances  exhibit  amoeboid  movements.  The  lymphatic  vessels 
emerging  from  the  lungs  enter  the  bronchial  lymphatic  glands. 

The  nerves  of  the  lungs  are  derived  from  the  pulmonary  plexus, 
which  is  mainly  formed  by  branches  of  the  vagus  nerve,  with  others 
from  the  sympathetic  nerve.  Fine  nerves  from  the  plexus  accompany 
the  bronchi  in  their  distribution,  and  are  associated  in  their  course 
with  minute  ganglia,  consisting  of  single  nerve-cells  or  little  groups 
of  cells.  The  nerves  contain  both  medullated  and  non-medullated 
fibres,  the  former  probably  pertaining  to  the  vagus,  and  the  latter  to 
the  sympathetic  nerve. 

The  black  coloring-matter  of  the  lungs  appears  as  minute  granules, 
and  especially  occurs  as  a  deposit  in  the  interstitial  areolar  tissue  of  the 
lobules  and  air-cells,  more  abundantly  at  and  near  the  surface  than  in 
the  interior  of  the  lungs.  It  also  occurs,  often  in  considerable  quantity, 
in  the  bronchial  lymphatic  glands,  in  which  it  appears  to  accumulate 
from  the  lungs.  It  is  also  occasionally  observed  in  the  free  mucous 
corpuscles  expectorated  with  the  mucus  of  the  lungs. 

THE   LARYNX. 

The  larynx  forms  the  commencement  of  the  respiratory  passage, 
and  serves  to  prevent  the  entrance  of  foreign  bodies,  while  it  also  acts 
as  the  especial  organ  of  the  voice.  It  is  placed  in  front  of  the  neck, 
producing  in  the  male  the  prominence  known  as  "  Adam's  apple," 1  but 
this  in  the  female,  and  likewise  in  the  boy  before  puberty,  from  less  de- 
velopment, is  inconspicuous.  It  is  situated  in  advance  of  the  pharynx, 
with  which  it  communicates  by  its  upper  orifice,  and  opens  below  into 
the  trachea,  or  windpipe.  Attached  above  to  the  hyoid  bone,  it  is 
subcutaneous  in  the  median  line,  and  at  the  sides  is  covered  by  the 
infra-hyoid  muscles,  the  inferior  constrictor  of  the  pharynx,  and  the 
thyroid  body.  It  is  a  three-sided  receptacle,  narrowing  below  in  a 
short  cylinder,  and  is  composed  of  a  framework  of  cartilages  which 
are  connected  with  one  another,  the  hyoid  bone  and  the  trachea  by 
ligaments,  is  provided  with  muscles,  and  is  lined  by  mucous  membrane 
continuous  with  that  of  the  pharynx  and  trachea. 

For  the  relative  position  of  the  larynx,  see  Fig.  194,  page  376. 

THE  CARTILAGES  OF  THE  LARYNX. 

The  larynx  is  composed  of  five  principal  cartilages,  the  thyroid,  cri- 
coid,  epiglottic,  and  two  arytenoid  cartilages.  Small  ones  in  pairs  are 
the  corniculate  and  cuneiform  cartilages,  the  latter  often  being  absent. 

The  thyroid  cartilage,2  the  largest,  occupies  the  front  and  sides 
of  the  larynx,  and  embraces  nearly  all  the  rest  of  the  organ,  besides 

1  Pomum  Adami ;  protuberantia  or  prominentia  laryngea  ;  nodus  gutturis. 

2  Cartilage  thyreoidea  or  scutiformis. 


THE    LARYNX. 


609 


contributing  to  form  the  lateral  walls  of  the  pharynx.  It  consists  of 
a  pair  of  broad  quadrate  plates,  or  alae,  united  in  an  angle  in  front, 
and  diverging  behind,  and  in  a  less  degree  above,  into  the  cavity  of  the 
pharynx.  The  alse  are  widest  fore  and  aft,  have  nearly  plane,  slanting 
surfaces  and  sinuous  free  borders,  which  are  prolonged  behind  in  the 
horns.  The  angle  formed  by  the  union  of  the  ate  is  rounded  below, 
and  is  produced  prominently  forward  above  in  a  beak,  which  is  deeply 


FIG.  308. 


FIG.  309. 


12 


FKONT  VIEW  OF  THE  LARYNX.  1,  hyoid  bone; 
2,  greater  cornu;  3,  small  cornu;  4,  lateral 
thyro-hyoid  ligament;  5,  nodular  cartilage; 
6,  middle  thyro-hyoid  ligament;  7,  thyroid  car- 
tilage ;  8,  superior  horn ;  9,  inferior  horn ;  10, 
cricoid  cartilage;  11,  crico-thyroid  ligament; 
12,  crico-ary-thyroid  ligament;  13, 14,  first  and 
second  rings  of  the  trachea. 


BACK  VIEW  OF  THE  LARYNX.  1,  thyroid  car- 
tilage; 2,  superior  horn;  3,  inferior  horn;  4, 
cricoid  cartilage ;  5,  crico-thyroid  ligament ; 
6,  arytenoid  cartilage ;  7,  prominent  external 
angle  of  the  base  into  which  the  crico-aryt- 
enoid  muscles  are  inserted ;  8,  epiglottic  carti- 
lage ;  9,  thyro-epiglottic  ligament ;  10,  posterior 
membrane  of  the  trachea. 


notched  from  the  upper  border  of  the  cartilage.  The  beak  is  more  or 
less  conspicuously  prominent  in  the  male  after  puberty,  but  does  not 
become  so  in  the  female. 

The  outer  surface  of  each  ala  at  the  posterior  third  is  divided  by  a 
slight  ridge,  the  oblique  line,1  which  descends  from  the  upper  to  near 
the  lower  border  and  then  proceeds  more  abruptly  forward.  The  ridge 
is  variably  more  prominent  at  the  upper  extremity,  and  below  where  it 
turns  forward.  In  front  it  gives  origin  to  the  thyro-hyoid  muscle,  and 
behind  to  the  inferior  constrictor  of  the  pharynx  and  the  sterno-thyroid 
muscle.  Sometimes  the  ridge  is  scarcely  produced,  or  is  absent,  when 


1  Linea  obliqua ;  limbus  angulosus. 
39 


610  THE    LARYNX. 

it  is  substituted  by  a  tendinous  line.  Not  unfrequently  the  ala  is 
perforated,  on  one  or  both  sides,  near  the  upper  eminence  of  the  ridge, 
by  a  foramen  of  variable  size,  which  gives  passage  to  a  branch  of  the 
superior  thyroid  artery. 

The  inner  surface  of  the  ala,  more  uniformly  even  than  the  outer 
one,  is  slightly  concave,  and  is  somewhat  everted  near  the  lower  border 
to  accommodate  the  insertion  of  the  crico-thyroid  muscle.  Above  this 
position  the  surface  is  in  contact  with  the  muscles  intervening  between 
it  and  the  crico-ary-thyroid  ligament,  the  ventricle  of  the  larynx,  and 
behind  these  with  the  mucous  membrane  of  the  pharynx. 

The  angle  between  the  alee  within  is  more  acute,  and  exhibits  a 
variable  recess  in  the  position  of  the  beak  for  the  attachment  of  the 
thyro-epiglottic  ligament,  and  below  this  a  slight  prominence  for  the 
attachment  of  the  vocal  cords. 

The  superior  horn L  of  the  ala  curves  backward  and  inward  from 
the  back  border,  and  is  cylindrical  and  rounded  at  the  end ;  the  infe- 
rior horn,2  shorter  than  the  former,  curves  forward,  inclines  inward, 
and  ends  in  a  circular  facet,  which  is  directed  downward  and  inward 
and  articulates  with  the  cricoid  cartilage. 

The  upper  border  of  the  ala  from  the  end  of  the  superior  horn  pur- 
sues a  sigmoid  course  to  the  notch  of  the  beak,  which  extends  half  the 
depth  of  the  cartilage.  The  lower  border,  shorter  and  less  deeply  sinu- 
ous, joins  that  of  the  opposite  side  in  a  downward  convexity,  which 
gives  attachment  to  the  crico-ary-thyroid  ligament.  The  posterior 
border  of  the  ala  is  long,  sigmoid,  slightly  thickened,  and  rounded, 
and  in  greater  part  gives  attachment  to  the  stylo-  and  palato-pharyngeal 
muscles. 

The  cricoid  cartilage,3  second  in  size  and  thickest  of  the  carti- 
lages, occupies  the  lower  part  of  the  larynx,  and  joins  the  trachea.  It 
is  below  the  thyroid  cartilage,  is  included  between  the  inferior  horns 
of  the  latter,  and  rises  behind  into  the  space  embraced  by  the  ala3.  It 
resembles  a  seal  ring  in  shape,  is  narrowest  in  front,  and  widens  to  the 
back  part,  where  it  is  three  or  four  times  the  depth  of  the  fore  part. 
Its  passage  is  circular  below,  conforming  to  that  of  the  trachea,  but 
is  somewhat  laterally  narrowed  above,  so  that  the  upper  aperture  is 
oval,  and  it  is  lined  by  the  laryngeal  mucous  membrane.  The  lower 
border  is  horizontal  and  sinuous,  convex  downward  in  front,  and  emar- 
ginate  behind,  and  joins  the  trachea  by  a  ligament.  The  upper  border 
ascends  obliquely  from  the  front  to  the  back  part,  where  it  is  trans- 
versely horizontal,  and  forms  a  pair  of  articular  facets,  separated  by  a 
slight  median  notch.  The  facets  for  articulation  with  the  arytenoid 
cartilages  are  convex  and  elliptical,  with  the  longer  diameter  nearly 


1  Cornu  superius,  longus,  or  majus. 
a  C.  inferius,  brevis,  or  minus. 
3  Cartilage  cricoidea  or  annularis. 


THE   LARYNX.  611 

twice  that  fore  and  aft,  and  directed  outward  and  slightly  downward 
and  forward.  Below  and  in  advance  of  each  facet  the  border  exhibits 
a  triangular  surface,  which  gives  origin  to  the  lateral  crico-arytenoid 
muscle.  The  outer  surface  of  the  cartilage  on  each  side  in  front  is 
convex,  and  gives  origin  to  the  crico-thyroid  muscle.  Behind  this  it 
presents  a  variable  low  tubercle  l  with  wide  base  and  truncated  sum- 
mit, which  forms  a  circular  facet  for  articulation  with  the  inferior  horn 
of  the  thyroid  cartilage.  The  facet,2  nearly  flat  or  feebly  depressed, 
looks  outward,  with  a  slight  inclination  upward  and  backward.  Its  base 
behind  affords  partial  origin  to  the  inferior  constrictor  of  the  pharynx. 
The  posterior,  broad  surface  of  the  cartilage  is  divided  by  a  low  median 
ridge 3  expanding  at  the  ends,  and  gives  attachment  above  to  the  com- 
mencement of  the  longitudinal  muscular  layer  of  the  oesophagus.  The 
surface  on  each  side  of  the  ridge  is  variably  depressed,  and  is  occupied 
by  the  posterior  crico-arytenoid  muscle. 

The  arytenoid  cartilages 4  are  placed  at  the  back  of  the  larynx, 
on  the  upper  border  of  the  cricoid  cartilage,  separated  from  each  other 
by  a  rectangular  interval,  which  may  be  widened  or  narrowed  by 
movement  of  the  two  cartilages.  Each  is  a  trilateral  pyramid  curved 
backward,  with  the  inner  surface  vertical,  and  the  outer  border,  sepa- 
rating the  front  and  back  surfaces,  oblique  and  sigmoid.  The  inner 
surface  is  narrowest  and  flat,  abruptly  tapers  above,  and  is  covered 
by  the  laryngeal  mucous  membrane.  The  back  surface  looks  into  the 
pharynx,  is  concave  from  above  downward,  and  straight  transversely, 
and  with  that  of  the  other  cartilage  forms  a  recess,  which  is  occupied 
by  the  arytenoid  muscle.  The  front  surface  looks  into  the  cavity  of 
the  larynx,  is  in  general  convex  from  above  downward,  and  is  directed 
slightly  outward.  Below  the  apex  of  the  cartilage  it  presents  a  low 
tubercle,5  and  beneath  this  is  divided  into  two  fossae,  of  which  the  lower 
one 6  gives  attachment  to  the  thyro-arytenoid  and  lateral  crico-arytenoid 
muscles,  and  the  upper,  smaller  one 7  forms  the  posterior  extremity  of 
the  laryngeal  ventricle.  The  base  of  the  cartilage  has  its  inner  anterior 
angle  prolonged  and  tapering  forward,  as  the  vocal  process,8  which 
gives  attachment  to  the  back  end  of  the  vocal  cord.  The  inner  pos- 
terior angle  is  truncated  and  rounded,  and  gives  attachment  to  the 
crico-arytenoid  ligament.  The  external  angle9  is  prominent,  thick 
and  rounded,  and  receives  the  insertion  of  the  crico-arytenoid  muscles. 
Beneath  this  angle  is  a  circular  facet,  for  articulation  with  the  cricoid 
cartilage,  concave  from  within  outward  and  backward,  and  straight  in 
the  opposite  direction.  The  apex  of  the  arytenoid  cartilage  curves 


1  Eminentia  lateralis.         2  Superficies  articularis.         3  Linea  eminens  or  media. 
*  C.  arytaenoideae,  pyramidales,  triquetrse,  or  gtitturales. 

5  Spina  superior ;  colliculus.  6  Fossa  inferior  or  obliqua. 

7  F.  superior  or  triangularis.  8  Processus  vocalis  or  glottidis  ;  mucro  baseos. 

9  P.  muscularis  ;  tubereulum  baseos. 


612  THE  LARYNX. 

backward,  and  has  appended  inwardly  the  corniculate  cartilage.1 
This  is  a  little,  conical  nodule  of  fibro-cartilage,  which  is  movably  con- 
nected with  the  former  by  an  elastic  ligament,  and  is  directed  back- 
ward and  inward,  and  may  come  in  contact  with  its  fellow.  It  is  en- 
veloped in  the  mucous  membrane  and  produces  the  rounded  eminence 
of  the  ary-epiglottic  fold  on  each  side  of  the  lower  extremity  of  the 
laryngeal  aperture.  It  is  sometimes  a  continuous  structure  with  the 
apex  of  the  arytenoid  cartilage. 

The  epiglottic  cartilage2  forms  the  basis  of  the  epiglottis,  a  trap- 
door-like arrangement  in  front  of  the  entrance  of  the  larynx,  and  pro- 
jecting upward  and  backward  behind  the  root  of  the  tongue.  It  is  a 
cordate  or  oval  leaf-like  plate  of  elastic  fibro-cartilage  prolonged  below 
in  a  stem  or  pedicle,  by  which  it  is  attached  within  the  beak  of  the  thy- 
roid cartilage.  The  upper  or  anterior  surface  is  in  general  convex,  and 
the  lower  or  posterior  surface  concave,  but  becomes  convex  along  the 
middle  part  below  extending  on  the  pedicle.3  The  edges  are  thin,  and 
the  surfaces  are  more  or  less  irregularly  pitted  with  recesses  for  the 
lodgement  of  glands.  It  is  enveloped  beneath  and  for  the  upper  half 
above  by  the  mucous  membrane. 

The  cuneiform  cartilages4  are  variable  in  development,  and  fre- 
quently are  absent.  They  occur,  one  on  each  side,  in  association  with 
a  little  group  of  glands,  which  produce  an  eminence  of  the  ary-epiglottie 
fold  just  in  advance  of  that  formed  by  the  corniculate  cartilage.  They 
are  fusiform  or  conical,  straight  or  bent,  and  from  one  to  three  lines  long. 
When  absent,  the  eminence  of  the  ary-epiglottic  fold  is  produced  alone  by 
the  accumulation  of  glands,  which  ordinarily  occupy  the  same  position. 

The  chief  cartilages  of  the  larynx,  except  that  of  the  epiglottis,  are 
composed  of  pure  or  hyaline  cartilage.  They  ai'e  prone  to  ossification 
towards  the  middle  of  life,  and  the  process  continues  with  the  advance 
of  age.  It  occurs  later  in  the  female  and  is  usually  less  complete.  It 
commences  in  the  thyroid  cartilage  with  the  horns  and  posterior  border, 
thence  extends  along  the  inferior  border,  and  subsequently  spreads  up- 
ward and  forward.  Following  in  the  cricoid  cartilage,  it  proceeds  from 
the  sides  forward  and  backward,  and  occurring  last  in  the  arytenoids, 
they  ossify  from  below  upward. 

LIGAMENTS  AND   AKTICULATIONS   OF   THE   LARYNX. 

The  larynx  is  connected  with  the  hyoid  bone  by  the  middle  and  lat- 
eral thyro-hyoid  ligaments.  The  cricoid  cartilage  is  connected  with  the 
thyroid  and  both  arytenoid  cartilages  by  the  crico-ary-thyroid  ligament. 

1  Cartilage  corniculata,  teres,  or  Santorini ;  corniculum,  corpusculum,  or  capitu- 
lum  arytsenoideum. 

2  C.  epiglottica ;  lingula.  3  Petiolus  ;  radix. 

4  C.  cuneiformes  or  cruciformes  ;  cartilages  of  Wrisberg  ;  corpuscula  Wrisbergii ; 
fibro-cartilage  of  the  arytenoid  gland. 


THE   LARYNX.  613 

It  also  forms  two  pairs  of  movable  synovial  joints,  the  crico-thyroid  and 
the  crico-arytenoid  articulations.  The  epiglottic  cartilage  is  connected 
with  the  thyroid  cartilage  by  the  thyro-epiglottic  ligament,  and  with  the 
hyoid  bone  by  the  by o- epiglottic  ligament.  It  is  further  connected  with 
the  thyroid  and  arytenoid  cartilages  by  the  thyro-ary-epiglottic  fascia. 

The  middle  thyro-hyoid  ligament l  is  a  broad,  fibro-elastic  mem- 
brane extended  between  the  upper  border  internally  of  the  hyoid  bone 
and  the  upper  border  of  the  thyroid  cartilage ;  an  arrangement  which 
permits  the  larynx  to  be  raised  within  the  position  of  the  hyoid  bone. 
The  median  portion  of  the  ligament  is  strongest,  and  commonly  is 
bounded  in  front  by  a  subcutaneous  synovial  bursa,2  which  commences 
behind  the  body  of  the  hyoid  bone  and  reaches  variably  downward 
towards  the  beak  of  the  thyroid  cartilage.  The  sides  of  the  ligament 
are  thin  and  of  looser  texture,  are  perforated  by  the  superior  laryngeal 
blood-vessels  and  nerve,  are  covered  by  the  thyro-hyoid  and  inferior 
constrictor  muscles,  and  internally  are  invested  with  the  mucous  mem- 
brane of  the  pharynx. 

The  lateral  thyro-hyoid  ligaments3  are  fibro-elastic  rounded 
cords,  of  variable  length  and  thickness,  connecting  the  superior  horns 
of  the  thyroid  cartilage  with  the  ends  of  the  hyoid  bone.  Each  com- 
monly contains  a  spheroidal  nodule*  of  cartilage,  thicker  than  the 
ligament  and  prone  to  ossification. 

The  crico-ary-thyroid  ligament,5  or  vocal  membrane,  is  a 
strong,  yellowish  membrane,  which  is  attached  to  the  upper  border 
of  the  cricoid  cartilage  from  in  front  along  the  inner  lateral  margin  to 
the  crico-arytenoid  articulation,  and  is  attached  above  in  front  to  the 
lower  border  and  lower  half  of  the  entering  angle  of  the  thyroid  car- 
tilage, and  behind  to  the  vocal  process  of  the  arytenoid  cartilage.  It 
is  composed  of  elastic  and  fibro-connective  tissue,  is  lined  by  the  laryn- 
geal mucous  membrane,  and  is  closely  connected  externally  with  the 
lateral  crico-arytenoid  and  thyro-arytenoid  muscles,  which  separate  it 
from  the  inner  side  of  the  thyroid  cartilage.  It  is  thickest  and  densest 
in  front,  where  it  occupies  an  interval  between  the  thyroid  and  cricoid 
cartilages  bounded  laterally  by  the  crico-thyroid  muscles.  In  this  posi- 
tion it  presents  several  small  but  conspicuous  foramina  for  blood-vessels, 
is  partly  subcutaneous  and  partly  covered  by  the  sterno-hyoid  muscles. 
At  the  sides  the  ligament  is  thinner  and  extends  from  the  cricoid  car- 
tilage within  the  position  of  the  thyroid  ala,  and  terminates  above  in  a 
defined  border  enclosed  by  the  mucous  membrane,  forming  the  inferior 

1  Ligamentum  hyo-thyroideum  medium ;    membrana  hyo-thyroidea  or  obtura- 
toria  laryngis. 

2  Bursa  mucosa  hyoidea.  3  L.  hyo-thyroideum  laterale. 
*  Cartilago  triticea ;  corpusculum  triticeum. 

5  Crico-thyroid  membrane,  including  the  inferior  thyro-arytenoid  ligament  or 
vocal  cord  ;  ligamentum  crico-thyroideum  medium  ;  1.  conicum,  conoideum,  or  pyra- 
midale;  1.  crico-thyreo-arytsenoidea. 


614  THE   LARYNX. 

thyro-arytenoid  fold,  or  vocal  cord.1  This  appears  as  a  band  ex- 
tending from  within  the  thyroid  angle  backward  and  slightly  divergent 
from  its  fellow  to  the  vocal  process  of  the  arytenoid  cartilage. 

The  crico-thyroid  articulation,  on  each  side  of  the  larynx,  is 
formed  by  the  lateral  articular  eminence  of  the  cricoid  cartilage  and 
the  end  of  the  inferior  thyroid  horn.  It  is  a  synovial  joint  enclosed 
by  a  strong  capsular  ligament.2  The  opposed  articular  facets,  nearly 
flat  and  circular,  permit  a  slight  rotary  and  gliding  motion  of  the  thy- 
roid on  the  cricoid  cartilage.  The  capsular  ligament  is  reinforced  by 
bands,  of  which  the  stronger3  proceeds  from  within  the  thyroid  horn 
upward  and  inward  to  the  posterior  contiguous  portion  of  the  cricoid 
cartilage,  and  another*  proceeds  from  the  end  of  the  horn  forward  to 
the  side  of  the  latter. 

The  crico-arytenoid  articulation,  formed  between  the  base  of 
the  arytenoid  cartilage  and  the  upper  border  of  the  cricoid  cartilage, 
is  a  freely  movable  synovial  joint  enclosed  by  a  capsular  ligament.6 
The  cricoid  articular  facet  is  twice  the  width  of  the  opposed  facet  of 
the  arytenoid  cartilage,  from  side  to  side,  but  is  of  the  same  width  in 
the  opposite  or  fore  and  aft  direction.  The  capsular  ligament  is  thin  at 
its  outer  part,  where  it  is  supported  by  the  tendinous  insertion  of  the 
crico-arytenoid  muscles,  and  it  is  reinforced  on  its  inner  side  by  a 
strong,  fan-shaped  band,  the  crico-arytenoid  ligament.6  This  starts 
from  the  highest  point  behind,  of  the  cricoid  cartilage,  and  passes  up- 
ward and  outward  to  be  attached  to  the  truncated  inner  posterior  angle 
of  the  base  of  the  arytenoid  cartilage. 

In  the  articulation  just  described  the  cricoid  cartilage  is  immovable, 
while  the  arytenoids  move  freely  on  it,  and  from  their  connection  with 
the  vocal  cords  are  the  chief  agents  of  change  in  their  lax  or  tense  state. 
At  rest,  the  arytenoids  are  supported  on  the  outer  part  of  the  articular 
facets  of  the  cricoid  cartilage,  and  thence  may  be  moved  to  the  inner 
part  and  may  be  inclined  in  any  direction,  and  also  permit  a  limited 
degree  of  rotation. 

The  thyro-epiglottic  ligament7  is  a  fibro-elastic  band,  which 
springs  from  the  pedicle  of  the  epiglottic  cartilage,  and  is  attached  to 
a  recess  within  the  thyroid  angle  below  the  notch  of  the  beak.  It  is 
continuous  with  the  adjacent  ligamentous  structures  and  is  invested 
with  the  laryngeal  mucous  membrane,  in  which  it  produces  a  vertical 
prominence  at  the  fore  part  of  the  cavity  of  the  larynx. 

The  hyo-epiglottic  ligament8  is  an  elastic  membrane,  which  is 

1  Inferior  or  true  vocal  cord  ;  chorda  vocalis  ;  inferior  thyro-arytenoid  ligament ; 
1.  thyreo-arytaenoideum  inferius. 

2  Ligamentum  crico-thyroideum  laterale  ;  1.  capsulare  inferius. 

3  L.  cerato-cricoideum  posticum  or  superius. 
*  L.  c.  c.  anticum  or  inferius. 

5  L.  crico-arytaenoideum  ;  1.  capsulare  superius.  6  L.  triquetrum. 

7  L.  thyreo-epiglotticum.  8  L.  hyo-glotticum. 


THE   LAEYNX. 


615 


attached  to  the  upper  internal  border  of  the  hyoid  bone  and  is  thence 
reflected  to  the  anterior  surface  of  the  epiglottic  cartilage.  It  is 
thickest  at  the  middle,  and  thins  away  laterally  where  it  blends  with 
the  middle  thyro-hyoid  ligament,  with  which  it  is  also  connected  above, 
and  with  the  thyro-epiglottic  ligament  below.  In  an  intermediate  po- 
sition the  conjunction  of  the  three  ligaments  is  occupied  by  a  consider- 
able accumulation  of  areolar  tissue  and  fat,  bounded  in  front  by  the 
middle  thyro-hyoid  ligament,  behind  and  above  by  the  hyo-epiglottic 
ligament,  and  below  by  the  thyro-epiglottic  ligament. 

The  laryngeal  fascia l  is  a  layer  of  fibre-connective  with  elastic 
tissue,  which  extends  from  the  vocal  membrane  between  the  thyroid 
and  arytenoid  cartilages  upward  to  the  lateral  border  of  the  epiglottic 
cartilage,  where  it  is  continuous  with  the  thyro-  and  hyo-epiglottic  liga- 
ments. It  is  slightly  thickened  along  the  upper  edge  of  the  entrance 
of  the  ventricle  of  the 
larynx,  where  it  forms 
the  basis  of  the  superior 
thyro-arytenoid  fold,  or 
so-called  false  vocal  cord,2 
and  its  upper  margin  is  the 
basis  of  the  ary-epiglottic 
fold  at  the  entrance  of 
the  larynx.  It  invests  the 
thyro-arytenoid  muscle,  is 
in  contact  internally  with 
the  lining  mucous  mem- 
brane of  the  larynx  and 
externally  with  the  inner 
surface  of  the  thyroid  ala. 


FIG.  310. 


MUSCLES  OF   THE 
LAKYNX. 

Besides  the  muscles 
connected  with  the  lar- 
ynx already  described, 
there  are  a  number  of 
others,  more  especially 
concerned  in  producing 
changes  in  the  vocal  cords, 
by  which  they  modify  the 

sound  of  the  voice.  These  consist  of  the  crico-thyroid,  the  lateral  and 
posterior  crico-arytenoid,  and  the  thyro-arytenoid  muscles,  in  pairs, 
and  the  arytenoid  muscle,  which  is  single. 


MUSCLES  OF  THE  LARYNX.  1,  right  ala  of  the  thyroid  car- 
tilage, turned  forward ;  2,  superior  horns ;  3,  inferior  horn 
marked  by  the  crico-thyroid  articulation ;  4,  the  other  por- 
tion of  the  latter  on  the  side  of  the  cricoid  cartilage ;  5, 
arytenoid  cartilage,  surmounted  by  the  corniculate  carti- 
lage; 6,  epiglottis;  7,  the  two  laminae  of  the  ary-epiglottic 
fold  separated  so  as  to  expose  the  muscles ;  8,  lower  part 
of  the  vocal  membrane ;  9,  crico-thyroid  muscle ;  10,  pos- 
terior crico-arytenoid  muscle;  11,  lateral  crico-arytenoid; 
12,  thyro-arytenoid ;  13,  thyro-epiglottic  muscular  fibres ; 
14,  ary-epiglottic  muscular  fibres ;  15,  arytenoid  muscle. 


1  F.  thyreo-arytaeno-epiglottica. 

2  Ligamentum  thyreo-arytaenoideum  superior. 


616 


THE   LARYNX. 


FIG.  311. 


The  crico-thyroid  muscle *  is  situated  externally  at  the  side  of 
the  larynx,  and  is  short,  thick,  and  fan-shaped.  It  arises  tendinous  and 
fleshy  near  the  middle  in  front  and  from  the  side  of  the  cricoid  cartilage, 
and  ascends  outward  and  backward  to  be  inserted  into  the  inferior 
border  and  horn  and  adjacent  inner  surface  of  the  ala  of  the  thyroid 
cartilage.  An  offset  from  the  muscle  commonly  joins  the  inferior  con- 
strictor of  the  pharynx. 

The  posterior  crico-arytenoid  muscle 2  is  situated  at  the  back 
of  the  larynx,  covered  by  the  fore  part  of  the  commencement  of  the 

oesophagus.  It  lies  behind  the 
cricoid  cartilage  and  occupies  its 
lateral  depressed  surface,  from 
which  it  arises  at  the  inner  and 
lower  portion,  and  thence  con- 
verges and  ascends  outwardly  to 
be  inserted  into  the  external  angle 
of  the  base  of  the  arytenoid  car- 
tilage. 

The  lateral  crico-arytenoid 
muscle,3  smaller  than  the  former, 
is  situated  at  the  side  of  the  larynx, 
internal  to  the  thyroid  ala.  It  lies 
along  the  outer  part  of  the  upper 
lateral  border  of  the  cricoid  car- 
tilage, from  which  and  the  adja- 
cent portion  of  the  vocal  mem- 
brane it  arises,  thence  passes 
backward  and  upward  and  is  in- 
serted into  the  lower  fossa  and 

external  angle  of  the  arytenoid  cartilage.     It  is  in  contact  above  with 
the  thyro-arytenoid  muscle  and  is  often  more  or  less  united  with  it. 

The  thyro-arytenoid  muscle 4  is  situated  above  the  former,  internal 
to  the  thyroid  ala,  with  which  it  lies  in  contact.  It  exhibits  much  vai'ia- 
bility  in  the  development  and  arrangement  of  its  fascicles.  It  arises 
from  the  side  of  the  entering  angle  of  the  thyroid  cartilage  extending 
along  the  thyro-epiglottic  ligament,  and  thence  passes  backward  to  be 
inserted  into  the  vocal  process  and  outer  portion  of  the  front  surface 
of  the  arytenoid  cartilage.  Its  upper  thinner  part,5  usually  not  well  de- 
fined, passes  backward  and  upward  in  the  thyro-ary-epiglottic  fascia. 


VIEW  OF  THE  VOCAL  MEMBRANE.     1,  left  ala 

of  the  thyroid  cartilage ;  2,  right  ala  turned 
forward  and  partly  cut  away ;  3,  cricoid  carti- 
lage ;  4,  arytenoid  cartilages ;  5,  right  half  of 
the  vocal  membrane;  6,  upper  border  of  the 
left  half;  7,  arytenoid  muscle.  The  upper 
borders  of  the  vocal  membrane,  extended  be- 
tween the  thyroid  and  arytenoid  cartilages, 
form  the  basis  of  the  vocal  cords. 


1  M.  crico-thyreoideus  ;  m.  c.-t.  rectus  et  obliquus. 

2  M.  crico-arytaenoideus  posticus. 

8  M.  crico-arytamoideus  lateralis  or  anterior. 

4  M.  thyreo-arytaenoideus ;  m.  t.-a.  externus  et  internus. 

5  M.  thyreo-epiglotticus  ;  m.  thyreo-epiglottidaeus  major;  m.  thyreo-ary-epiglot- 
ticus ;  stratum  thyreo-membranosum. 


THE    LARYNX.  617 

and  thins  away  approaching  the  ary-epiglottic  fold  at  the  entrance  of 
the  larynx.  Commonly  a  variable  band1  crosses  the  general  plane 
of  the  muscle  externally  from  the  upper  border  of  the  thyroid  ala  to 
the  external  angle  of  the  arytenoid  cartilage.  Internally  the  muscle 
is  in  contact  with  the  vocal  membrane,  the  laryngeal  ventricle,  and  the 
thyro-ary-epiglottic  fascia. 

The  arytenoid  muscle 2  is  a  quadrate,  fleshy  layer  occupying  the 
recess  behind  the  arytenoid  cartilages  and  extending  between  them. 
It  mainly  consists  of  transverse  fascicles  attached  to  the  outer  portion 
of  the  posterior  surfaces  and  external  borders  of  the  cartilages,  some 
of  the  fascicle's  turning  outward  and  forward  to  reinforce  the  thyro- 
arytenoid  muscles.  Oblique  fascicles,3  behind  and  intimately  con- 
nected with  the  former,  arise  from  the  external  angles  of  the  aryt- 
enoid cartilages  and  cross  one  another  to  the  summits  of  the  latter, 
to  which  they  are  partially  attached,  partially  reinforce  the  thyro- 
arytenoid  muscles,  and  partially  *  ascend  in  the  ary-epiglottic  fold.  In 
front,  the  muscle  is  in  contact  with  the  arytenoid  cartilages  and  laryn- 
geal mucous  membrane,  and  behind  with  the  pharyngeal  mucous 
membrane. 

The  lateral  crico-arytenoid  muscles  draw  the  external  angles  of  the 
arytenoid  cartilages  forward  and  downward,  which  action  rotates  the 
vocal  processes  inward  and  approximates  and  relaxes  the  vocal  cords. 
The  posterior  crico-arytenoid  muscles  draw  the  external  angles  of  the 
same  cartilages  backward  and  inward,  which  rotates  the  vocal  pro- 
cesses outward  and  separates  and  renders  more  tense  the  vocal  cords. 
When  both  sets  of  the  muscles  act  together  the  arytenoid  cartilages 
are  drawn  outward  and  the  vocal  cords  widely  separated.  The  thyro- 
arytenoid  muscles  mainly  draw  the  arytenoid  cartilages  forward  and 
relax  the  vocal  cords.  The  arytenoid  muscle  draws  the  arytenoid 
cartilages  together  and  approximates  the  vocal  cords. 

INTEKIOK   OF   THE   LAKYNX. 

The  aperture  of  the  larynx 6  occupies  an  inclined  plane  beneath 
the  root  of  the  tongue,  and  looks  upward  and  backward  into  the  cavity 
of  the  pharynx.  It  is  angular  ovate,  and  more  than  twice  the  length 
of  the  breadth.  Its  upper,  rounded  extremity  is  formed  by  the  pro- 
jecting part  of  the  epiglottis,  its  lower,  narrow  end  by  a  notch  be- 
tween the  summits  of  the  arytenoid  cartilages,  and  its  sides  by  the 
ary-epiglottic  folds,6  extended  between  the  summits  of  the  arytenoid 

1  M.  thyreo-arytaenoideus  superior  or  minor. 

2  M.  arytsenoideus ;  m.  a.  transversus;  m.  ary-arytsenoideus. 

3  M.  arytaenoideus  obliquus  ;  m.  thyreo-ary-epiglotticus. 

4  M.  arytseno-epiglotticus,  ary-epiglottidseus,  or  thyreo-ary-epiglotticus  ;  stratum 
ary-membranosum  obliquum. 

5  Aditus  laryngis  or  a.  ad  glottidem. 

6  Aryteno-epiglottic  folds ;  plicae  arytaeno-epiglottideae. 


618 


THE   LARYNX. 


FIG.  312. 


cartilages  and  the  lateral  borders  of  the  epiglottis.  A  pair  of  rounded 
eminences  on  each  side  of  the  lower  extremity  of  the  aperture  indicate 
the  position  of  the  summits  of  the  arytenoid  and  corniculate  cartilages, 
and  of  the  cuneiform  cartilages  with  the  arytenoid  glands. 

From  the  aperture  of  the  larynx,  the  cavity 1  descends  and  contracts 
laterally  to  the  glottis,  which  is  the  narrowest  portion  of  the  passage, 
whence  it  again  expands  to  a  cylindrical  form  within  the  cricoid 
cartilage,  thence  continued  into  the  trachea. 

The  glottis 2  is  the  space  between  the  vocal  cords  and  thence  ex- 
tended backward  between  the  aryt- 
enoid cartilages.3  "When  closed  it 
appears  as  a  fore  and  aft  fissure, 
nearly  an  inch  long  in  the  male, 
and  about  a  third  less  in  the  female. 
When  moderately  open,  as  in  or- 
dinary breathing,  it  resembles  the 
opening  of  the  half-closed  eyelids, 
being  acute  in  the  thyroid  angle, 
whence  it  gradually  widens  to  the 
arytenoid  vocal  processes  and  is 
again  slightly  narrowed  to  its  pos- 
terior obtuse  extremity.  When 
widely  open,  it  assumes  a  more  loz- 
enge shape,  and  is  widest  opposite 
the  ends  of  the  arytenoid  vocal 
processes,  where  it  may  be  nearly 
half  an  inch. 

The  cavity  of  the  larynx  above 
the  glottis  is  oval  in  horizontal  sec- 
tion, with  the  longer  diameter  fore 
and  aft.  Its  fore  part  presents  a 
convex  projection,  the  epiglottic 
cushion,  corresponding  with  the 
lower  median  portion  of  the  epi- 
glottis. The  sides  are  nearly  verti- 
cal planes,  slightly  divergent  from 
the  cushion  to  the  arytenoid  car- 
tilages and  slightly  approaching 
in  their  descent  to  the  ventricles 
of  the  larynx.*  These  are  half- 
elliptical,  horizontal  recesses,  im- 
mediately above  the  glottis,  opening  into  the  larynx  opposite  each  other 
by  a  slightly  constricted  orifice,  which  is  close  to  its  fellow  in  the  thyroid 


224 


INNER  VIEW  OF  THE  EIGHT  SIDE  OF  THE 
LARYNX.  1,  section  of  the  hyoid  body;  2, 
greater  cornu ;  3,  section  of  the  thyroid  carti- 
lage ;  4,  superior  horn ;  5,  lateral  thyro-hyoid 
ligament,  and  in  advance  part  of  the  middle 
thyro-hyoid  ligament;  6,  epiglottis;  7,  7,  ary- 
epiglottic  fold ;  8,  its  free  edge ;  9,  position  of 
the  cuneiform  cartilage ;  10,  position  of  the 
arytenoid  gland;  11,  position  of  the  arytenoid 
cartilage ;  12,  section  of  the  arytenoid  muscle ; 
13,  13,  anterior  and  posterior  median  sections 
of  the  cricoid  cartilage;  14,  15,  its  upper  and 
lower  borders;  16,  vocal  membrane  seen 
through  the  lining  mucous  membrane ;  17,  its 
free  border,  the  vocal  cord ;  18,  superior  thyro- 
arytenoid  fold;  19,  ventricle ;  20, 21,  connective 
and  adipose  tissue ;  22,  first  ring  of  the  trachea. 


Cavitas  laryngis.  2  Rima  glottidis  or  vocalis.  3  Lumen  glottidis. 

Ventriculi  laryngis  or  Morgagni ;  alveoli ;  sinuses. 


THE    LARYNX.  619 

angle  and  diverges  to  the  front  surface  of  the  arytenoid  cartilages.  The 
inferior  border  of  the  orifice  is  straight  and  is  formed  by  the  inferior 
thyro-arytenoid  fold,1  or  vocal  cord  ;  and  its  upper,  arched  border 
is  the  superior  thyro-arytenoid  fold.2  At  their  fore  part  the  ven- 
tricles are  prolonged  as  the  laryngeal  pouch,3  which  extends  upward 
in  the  laryngeal  fascia  within  the  position  of  the  thyroid  ala  and  is 
covered  externally  by  the  thyro-arytenoid  muscle.4  It  is  half  oval, 
laterally  compressed,  about  half  an  inch  in  height,  and  about  half  the 
width  of  the  ventricle  into  which  it  opens. 

From  the  aperture  of  the  larynx  the  pharyngeal  mucous  membrane 
extends  to  the  hyoid  bone  and  the  inside  of  the  thyro-hyoid  ligaments 
and  thyroid  cartilage,  and  thence  to  the  sides  of  the  pharynx  behind, 
and  it  extends  downward  back  of  the  arytenoid  cartilages  and  the  cri- 
coid  cartilage  to  the  oesophagus.  Covering  the  upper  part  of  the  epi- 
glottis, the  mucous  membrane  extends  thence  to  the  root  of  the  tongue 
and  forms  the  three  glosso-epiglottic  frsena,  previously  indicated. 

The  pharyngeal  mucous  membrane  is  bright  red  and  furnished  with 
squamous  epithelium.  The  laryngeal  mucous  membrane  lines  the  cavity 
throughout,  including  the  ventricles  and  laryngeal  pouches.  It  is  pale 
pink  and  thin,  and  adheres  intimately  to  the  subjacent  parts,  especially 
to  the  lower  surface  of  the  epiglottis,  and  yet  more  closely  to  the  vocal 
cords.  For  the  most  part,  like  the  tracheal  mucous  membrane,  it  is 
provided  with  a  ciliated  columnar  epithelium,  which  extends  upward 
in  front  to  about  the  middle  of  the  epiglottis,  and  at  the  sides  a  short 
distance  above  the  orifice  of  the  ventricles.  Above  these  points,  and 
on  the  vocal  cords,  the  epithelium  is  squamous,  like  that  of  the  pharynx. 

The  laryngeal  mucous  membrane  is  provided  with  numerous  small, 
racemose  mucous  glands,  like  those  of  the  trachea,  the  ducts  of  which 
open  upon  the  surface  everywhere  except  on  the  vocal  cords  and  their 
immediate  vicinity.  They  are  especially  numerous  in  the  mucous  mem- 
brane of  the  epiglottis,  where  they  are  distinguished  as  the  epiglottic 
glands,5  and  deeply  impress  the  epiglottic  cartilage.  An  accumulation, 
as  the  arytenoid  glands,6  forms  a  variably  distinct  prominence  of  the 
ary-epiglottic  fold  adjacent  to  the  arytenoid  cartilage.  Many  glands 7 
are  also  embedded  in  the  laryngeal  fascia  and  open  into  the  laryngeal 
pouches. 

The  arteries  of  the  larynx  are  derived  from  the  superior  and  in- 
ferior thyroids,  and  the  veins  join  the  superior,  middle,  and  inferior 
thyroids.  The  lymphatics  in  their  origin  are  like  those  of  the  trachea, 
and  they  join  the  neighboring  cervical  glands.  The  nerves  are  sup- 
plied from  the  superior  and  inferior  laryngeal  branches  of  the  vagus, 


1  Plica  thyreo-arytaenoidea  inferior. 

2  P.  th.-aryt.  sup.  ;  superior  vocal  cord.  3  Sacculus  laryngis. 
*  Compressor  sacculi  laryngis  ;  m.  arytaeno-epiglottideus  inferior. 

5  Glandulae  epiglotticse.  •  G.  arytaenoideae.  7  G.  ventriculorum. 


620  THE   LARYNX. 

joined  by  branches  from  the  sympathetic  system.  The  superior  laryn- 
geal  nerve  supplies  the  laryngeal  mucous  membrane,  the  crico- thyroid 
muscle,  and  partially  the  arytenoid  muscle.  The  inferior  laryngeal 
nerve  supplies  all  the  other  muscles,  and  partially  the  latter,  but  not 
the  former.  The  mucous  membrane  is  very  sensitive  at  the  upper 
portion  of  the  larynx,  and  where  covered  with  squamous  epithelium 
contains  bodies  like  the  taste-buds  of  the  tongue.  End-bulbs  are  also 
attributed  to  the  mucous  membrane  on  the  under  surface  of  the  epi- 
glottis. The  superior  and  inferior  laryngeal  nerves  communicate  behind 
the  larynx  under  the  pharyngeal  mucous  membrane,  and  at  the  side 
of  the  larynx  under  the  thyroid  ala.  Numerous  ganglion  cells  are 
attached  to  the  branches,  both  those  which  enter  the  muscles  and 
those  which  pass  beneath  the  mucous  membrane. 


OHAPTEE    XL 

THE   URINARY   ORGANS. 

THE  urinary  organs  consist  of  the  two  kidneys,  with  their  excretory 
ducts,  named  the  ureters,  the  urinary  bladder,  and  the  urethra. 

THE   KIDNEYS. 

The  kidneys l  are  the  glandular  organs  which  excrete  the  urine, 
and  are  situated  in  the  loins,  one  on  each  side  of  the  spine,  resting 
behind  on  contiguous  portions  of  the  diaphragm,  psoas,  and  lumbar 
quadrate  muscles.  They  extend  from  in  front  of  the  last  thoracic 
vertebra  to  near  the  iliac  crest,  opposite  the  former  and  the  two  or 
three  upper  lumbar  vertebrae.  The  right  kidney  is  a  little  lower  than 
the  left,  apparently  to  accommodate  the  liver,  which  is  impressed  by 
its  upper  part.  The  kidneys  are  placed  behind  the  peritoneum,  which 
covers  their  upper  fore  part ;  and  they  are  maintained  in  position  by 
their  blood-vessels  and  a  quantity  of  connective  tissue,  which  attaches 
them  to  the  adjacent  parts. 

The  kidneys  are  indian-red  in  color,  and  are  elliptical,  fore  and  aft 
flattened,  and  notched  on  the  inner  side,  the  shape  being  so  marked 
that  similar-formed  bodies  are  said  to  be  kidney-shaped  or  reniform. 
The  front  surface  is  the  more  convex,  and  the  upper  extremity  is  the 
larger,  and  is  placed  rather  more  outward  than  the  lower  end,  which  is 
nearer  that  of  the  opposite  kidney.  The  left  kidney  is  commonly 
somewhat  narrower  and  larger  than  the  right.  Their  length  is  about 
four  inches,  their  greatest  width  two  and  a  half  inches,  and  their  thick^ 
ness  one  and  a  quarter  inches.  The  weight  of  each  is  between  four 
and  five  ounces,  and  is  less  in  the  female. 

The  notch,  or  hilus,2  of  the  kidney  communicates  with  an  interior 
recess,  the  sinus,  both  of  which  accommodate  the  chief  vessels  and 
excretory  duct  of  the  organ. 

The  surface  of  the  kidney  is  smooth,  but  not  always  perfectly  even, 
and  not  unfrequently  is  more  or  less  marked  with  linear  furrows,  which 
remain  from  the  foetal  condition  of  the  organ  when  it  is  divided  into 
lobes.  The  substance  of  the  kidney  is  firm,  but  is  not  tenacious,  and 
is  readily  broken. 


1  Kenes.     Singular :  ren  ;  nephros.  a  Porta  renis. 

621 


622 


THE   URINARY    ORGANS. 


The  kidney  is  provided  with  a  thin,  firm  membranous  capsule,1 
which  is  closely  adherent  but  readily  detached.  It  extends  from  the 
hilus  into  the  sinus,  where  it  is  continuous  with  the  sheath  and  external 
coat  of  the  blood-vessels  and  duct.  It  is  composed  of  fibre-connective 
tissue  in  interlacing  bundles,  mingled  with  elastic  fibres  and  with  an 
inner  incomplete  stratum  of  unstriped  muscular  fibres.  Its  outer  sur- 
face is  continuous  with  the  looser  investing  areolar  tissue,2  and  there- 
fore does  not  present  the  usual  smooth  shining  appearance  of  the 
peritoneal  covering  of  most  other  of  the  abdominal  viscera. 

The  upper  extremity  of  the  kidney,  thick  and  convex,  supports  the 
suprarenal  body.  The  right  kidney  in  front  is  in  contact  above  with  the 
under  surface  of  the  liver,  and  below  with  the  duodenum  and  transverse 
colon,  which  in  this  position  are  destitute  of  peritoneum  behind.  The 
left  is  in  contact  with  the  stomach  and  below  this  with  the  pancreas. 

The  kidneys  are  liable  to  variation.     They  are  sometimes  longer 
and  narrower  than  usual,  at  other  times  shorter  and  more  oval,  and 
occasionally  one  is  small  and  the  other  proportionately  larger.  •  Occa- 
sionally they  are  situated  in  a  lower  position,  and  even  in  the  pelvic 
cavity.     Earely  the  two  are  united  by  their  lower  extremities  across 
the  spine  and  great  vessels,  so  as  to  present  together  a  horseshoe  shape. 
A  median  longitudinal  section  through  the  kidney  from  within  out- 
ward exposes  the  sinus,  which  ex- 

pIG-  313.  tends  into  the  interior  about  half 

its  depth,  and  is  enclosed  by  the 
solid  substance  of  the  organ,  ex- 
cept at  the  hilus.  This  is  deepest 
in  front,  and  is  bordered  by  a  thick, 
rounded  anterior  and  posterior 
lip.  Within  the  sinus  the  blood- 
vessels penetrate  its  sides  and 
bottom,  and  from  among  the  ves- 
sels the  excretory  duct  has  its 
origin  in  branches  which  unite  to 
form  the  renal  pelvis.3  This  is 
a  flattened  funnel-shaped  recep- 
tacle situated  behind  the  blood- 
vessels, whence  it  descends  from 
the  hilus  to  become  the  ureter. 
The  branches  of  the  renal  artery 
enter  the  hilus  in  advance  of  the 
pelvis,  and  the  branches  of  the 
renal  vein  emerge  in  front  of  the 
The  intervals  of  the  vessels  and  pelvis  are  occupied  by  areo- 


LONGITUDINAL  SECTION  OF  A  KIDNEY.     1,  COlti- 

cal  substance ;  2,  renal  pyramid ;  3,  renal  pa- 
pillae; 4,  pelvis;  5,  ureter;  6,  renal  artery;  7, 
renal  vein  ;  8,  branches  of  the  latter  vessels  in 
the  sinus  of  the  kidney. 


former. 


1  Tunica  propria ;  capsula  fibrosa. 

3  P.  renalis  ;  sinus,  venter,  or  alvus  renum. 


2  Tunica  or  capsula  adiposa. 


THE    URINARY.  ORGANS.  623 

lar  tissue  and  fat,  together  with  the  lymphatics  and  nerves  of  the 
kidney. 

The  substance  of  the  kidney  as  seen  in  the  section  consists  of  two 
portions,  of  which  the  inner  is  distinguished  as  the  medulla  and  the 
outer  as  the  cortex. 

The  medulla1  is  collected  in  conical  masses,  the  renal  pyramids,2 
which  are  embedded  the  greater  part  of  their  depth  in  the  cortex,  and 
have  only  their  summits  free  and  projecting  into  the  sinus  as  the  renal 
papillae.3  The  cortex*  forms  the  superficial  part  of  the  kidney,  gen- 
erally reaching  several  lines  in  depth,  but  also  extends  between  the 
pyramids  to  the  sinus,  where  it  is  defined  by  low  convex  prominences5 
in  the  intervals  of  the  papillae.  It  is  of  uniform  light  brownish  red,  of 
granular  aspect,  and  is  especially  friable  in  the  direction  vertical  to  the 
surface  of  the  kidney.  The  medulla  mostly  is  lighter  colored,  but  is 
darker  and  usually  purplish  at  the  base  of  the  pyramids,  and  is  dis- 
tinctly striated  longitudinally,  radiating  from  the  summits.  The  renal 
pyramids  vary  in  size  and  in  number,  there  commonly  being  from  seven 
to  nine,  sometimes  more,  sometimes  less,  and  they  are  single  or  isolated, 
or  partly  more  or  less  connate  in  groups  of  two  or  three.  They  are 
disposed  irregularly  in  three  rows,  outward,  in  front,  and  behind,  with 
their  free  summits,  the  renal  papillae,  convergent  in  the  sinus  of  the 
kidney. 

The  renal  pelvis  commences  by  two  or  three  divisions,  each  formed 
by  several  short,  cup-like  branches,  the  calyces.6  Each  calyx  receives 
in  its  expanded  mouth  a  renal  papilla,  around  the  base  of  which  the 
calyx  is  attached.  On  pressing  the  kidney,  urine  may  be  observed  to 
appear  at  the  summits  of  the  renal  papillae  and  thence  trickle  into 
the  calyces.  The  summits  of  the  papillae  exhibit  a  number  of  minute 
orifices,  usually  one  to  two  dozen,  which  are  the  terminations  of  the 
excretory  ducts,  named  the  uriniferous  tubules.7  Traced  back- 
ward in  the  pyramids,  the  tubules  are  observed  repeatedly  to  fork 
at  very  acute  angles,  and  lie  side  by  side  slightly  diverging.8  In 
the  base  of  the  pyramids  they  are  collected  into  narrow  bundles,  the 
medullary  rays,9  which  pass  into  the  cortex,  the  central  tubules  con- 
tinuing farthest  and  approaching  nearest  the  exterior  surface  of  the 
kidney.  In  the  pyramids  the  medullary  rays  are  separated  by  pencil- 
like  bundles  of  blood-vessels,  while  in  the  cortex  the  corresponding 

1  Substantia  medullaris,  cineritia,  tubulosa,  fibrosa,  or  interna. 

2  Pyramides  Malpighianse ;  coni  tubulosi ;  lobi  medullares ;  pyramids  of  Mal- 
pighi. 

3  P.  renales. 

*  Substantia  corticalis,  glandulosa,  rubicunda,  or  externa. 

5  Columnae  Bertini ;  septula  renum. 

6  Infundibula.  7  Tubuli  uriniferi. 

8  Ductus  recti,  medullares,  or  renales  ;  tubuli  Bellini. 

9  Pyramides  Ferreinii ;  lobuli  renales  ;  fasciculi  tubulosi. 


624 


THE   URINARY   ORGANS. 


intervals  are  occupied  by  tortuous  uriniferous  tubules  and  blood-ves- 
sels, named   together   from   the   intricacy  of  their  arrangement   the 

cortical  labyrinth.  In  this  the 
uriniferous  tubules  have  their  ori- 
gin, each  commencing  in  a  spher- 
ical capsule,1  which  encloses  a 
similar-shaped  mass  of  capillary 
blood-vessels,  named  the  renal 
glomerulus,2  separated,  however, 
from  the  cavity  of  the  capsule  by 
the  epithelial  lining,  which  is  re- 
flected from  the  latter.  Starting 
from  the  capsule  with  a  narrowed 
neck,  the  uriniferous  tubule  widens 
and  pursues  a  tortuous  course3  in 
the  cortical  labyrinth,  then  enters 
a  medullary  ray,  and  proceeds  in 
a  flexuose  manner*  into  the  cor- 
responding pyramid.  Here  becom- 
ing much  narrowed,  the  tubule 
continues  a  greater  or  less  distance, 
and  turns  back  producing  a  long 
loop,5  of  which  the  return  portion 
is  flexuose  and  widens,  and  again 
enters  the  cortical  labyrinth,  where 
it  forms  a  second  and  tortuous 
loop.6  This  widens  irregularly,7 
finally  narrows.8  and  once  more 
enters  the  medullary  ray,  where 
with  others  it  successively  joins 
the  collecting  tubules.9  These 
pursue  a  straight  course  through 
the  pyramid,  and  unite  with 
others  in  the  formation  of  the  prin- 
cipal uriniferous  tubules,  which 
end  at  the  summit  of  the  renal 
papilla. 

The    uriniferous    tubules    are 
composed  of  a  basement  membrane 

supported  by  connective  tissue  and  lined  by  a  single  layer  of  epithelial 
cells,  which,  except  in  the  capsule,  are  mostly  proportioned  in  length 

1  Capsule  of  Bowman.  *  Glomeruli  renum. 

3  Laquei  tubulorutn  corticalium  ;  first  convoluted  tubule. 

4  Spiral  tubule  of  Schachowa.  5  Looped  tubule  of  Henle. 
6  Second  convoluted  tubule.  7  Irregular  tubule. 

8  Junctional  tubule.  9  Excretory  tubes. 


DIAGRAM  OF  URINIFEROUS  TUBULES.  1,  com- 
mencing capsule;  2,  tortuous  tubule  of  the  cor- 
tex ;  3,  straight  tubule  of  a  medullary  ray ;  4, 
first  loop  in  the  pyramid ;  5,  enlarging  return 
portion  of  the  tubule ;  6,  second  and  tortuous 
loop  of  the  cortex ;  7,  narrowed  portion  join- 
ing a  collecting  tubule,  8,  descending  to  end  at 
the  summit  of  a  renal  papilla :  magnified. 


THE   URINARY    ORGANS. 


625 


with  the  diameter  of  the  tubules.  The  capsule  is  lined  by  a  layer  of 
flat,  nucleated  cells,  and  the  layer  is  reflected  upon  and  invests  the 
enclosed  glomerule.  In  the  first 

convoluted   portion  of  the   tubule  FIG.  315. 

the  cells  form  short,  stout,  granu- 
lar columns  with  a  large  nucleus, 
and  for  the  greater  part  of  their 
length  towards  the  base  have  the 
appearance  of  bundles  of  vertical 
rods.  In  the  narrow  portion  of 
the  looped  tubule  the  cells  are  flat- 
tened, being  shorter  than  wide, 
are  clear,  and  have  a  large  nucleus. 
In  the  wider,  tortuous,  ascending 
portion  of  the  loop  the  cells  as- 
sume the  appearance  of  those  of 
the  first  convoluted  portion,  but 
are  smaller.  In  the  irregular  por- 
tion of  the  second  convolution  they 
are  proportionately  longer  and 
shorter  with  the  variation  of  the 
tubule,  and  are  remarkable  for  their 
well-marked  rod-like  structure.  In 
the  even  portion  of  the  convolu- 
tion following,  the  cells  are  identi- 
cal with  those  of  the  first  convo- 
luted portion  of  the  tubule.  As 
the  tubule  narrows  and  returns  to 
the  ray  the  cells  become  short, 
flattened,  and  clear.  The  descend- 
ing terminal  branches  and  trunks 
of  the  tubules  have  a  distinct 

lumen,  and  are  lined  with  clear  cells,  at  first  of  about  equal  length 
and  breadth,  but  gradually  becoming  longer  and  decidedly  columnar 
as  they  approach  their  termination. 

The  kidneys  are  exceedingly  vascular,  and  receive  blood  from  the 
renal  arteries,  which  are  very  large  in  proportion  to  the  size  of  the 
organs  they  supply.  Each  artery  divides  into  four  or  five  branches, 
which  pass  from  the  hilus  into  the  sinus,  where  they  subdivide  and 
penetrate  the  walls  in  the  intervals  of  the  calyces.  Proceeding  through 
the  cortical  substance  between  the  pyramids,  they  continue  to  branch, 
and  finally  reach  the  base  of  the  latter,  where  they  form  numerous 
arches.1  From  the  convexity  of  these,  they  give  off  branches J  which 
pass  directly  outward  in  the  cortical  labyrinth,  between  the  medullary 


DIAGRAM  OF  THE  STRUCTURE  OF  THE  KIDNEYS. 
1,  two  uriniferous  tubules  lined  with  epithe- 
lium ;  2,  capsule  enclosing  a  renal  glomerule ; 
3,  branch  of  the  renal  artery  ending  in  afferent 
vessels  which  enter  the  glomerules  as  seen  at 
4, 5 ;  6,  glomerule  freed  from  its  investment ;  7, 
efferent  veins ;  8,  plexus  formed  by  the  latter 
veins  among  the  uriniferous  tubules,  from 
which  plexus  originate  the  branches  of  the 
renal  vein :  highly  magnified. 


1  Arcus  or  fornices  arteriosi. 


2  Arteriola3  radiatae  ;  interlobular  arteries. 
40 


626  THE   URINARY   ORGANS. 

rays,  to  end  near  the  surface  of  the  kidney.  In  their  course  they  give 
off  short,  lateral,  mostly  curved  branches,  the  afferent  arteries,1  which 
proceed  to  the  capsules  of  the  uriniferous  tubules.  Each  capsule  receives 
an  afferent  artery,  which  ends  in  a  spherical  body,  named  the  renal 
glomerule.2  This  consists  of  branching  tufts  of  looped  convoluted 
capillaries,  united  in  a  mass  by  connective  tissue.  Close  to  the  entrance 
of  the  afferent  artery  there  issues  from  the  glomerule  a  smaller  effer- 
ent vein,3  which,  instead  of  joining  others  to  form  trunks  as  usual, 
ends  in  a  capillary  plexus-*  surrounding  the  neighboring  uriniferous 
tubules.  Among  the  convoluted  tubules  of  the  cortical  labyrinth  the 
meshes  of  the  capillary  plexus  are  of  uniform  diameters,  but  are  elon- 
gated in  the  direction  of  the  straight  tubules  of  the  medullary  rays. 
The  efferent  veins  from  the  lowest  series  of  glomerules  break  up  into 
pencils 5  of  straight  vessels,  which  descend  between  the  medullary  rays 
to  the  capillary  plexus  surrounding  the  tubules  of  the  pyramids.  The 
latter  are  chiefly  supplied  by  branches  from  the  arterial  arches  at  their 
base,  whence  they  descend  in  pencil-like  bundles,6  alternating  with  the 
medullary  rays,  and  end  in  the  capillary  plexus  which  surrounds  the 
uriniferous  tubules  extending  to  those  of  the  renal  papillae.  Yeins 
commence  at  the  summit  of  the  papillae  in  a  net-work  surrounding  the 
orifices  of  the  uriniferous  tubules,  and  thence  proceed  to  the  base  of 
the  pyramids  in  pencil-like  bundles,*  which  are  mingled  with  the  ar- 
terial bundles,  receive  in  their  course  lateral  tributaries  from  the  capil- 
lary plexus  of  the  uriniferous  tubules,  and  finally  unite  in  arching 
trunks,8  accompanying  the  corresponding  arteries.  The  venous  trunks 
then  pursue  the  course  of  the  arteries  through  the  cortical  substance 
between  the  pyramids,  and  emerge  into  the  sinus  of  the  kidney.  The 
principal  veins9  of  the  cortex  accompany  the  arteries  of  the  laby- 
rinth, receive  in  their  course  branches  from  the  capillary  plexus  of  the 
neighboring  tubules,  together  with  branches  ascending  from  the  pyra- 
mids, and  join  the  convexity  of  the  venous  arches  at  their  base.  Other 
veins  commence  at  the  surface  of  the  kidney,  beneath  the  capsule,  and 
converge  in  a  stellate  manner 10  to  branches  which  descend  through  the 
cortex  to  join  the  venous  arches.  The  stellate  veins  at  their  commence- 
ment communicate  freely  with  the  veins  of  the  cortical  labyrinth.  The 
veins  within  the  sinus  of  the  kidney  converge  and  pass  from  the  hilus 
and  unite  in  a  trunk,  the  renal  vein,  which  proceeds  in  front  of  the 
renal  artery  and  ends  in  the  inferior  cava. 

Though  the  uriniferous  tubules  and  renal  vessels  are  closely  and 

1  Vasa  afferentia. 

2  Glomeruli  renum ;  corpuscula,  glomeruli,  or  acini  Malpighiani ;  corpuscles  of 
Malpighi. 

3  Vas  efferens.  *  Vasa  urinifera. 

6  Vasa  recta  spuria.  8  Arteriae  rectae. 

7  Venae  rectae.  8  Arcus  venosi. 

9  Interlobular  veins.  10  Venae  stellulae  Verheyenh. 


THE   URINARY   ORGANS.  627 

compactly  arranged  together,  they  are  separated  from  one  another  by 
a  small  proportion  of  connective  tissue,  which  is  most  abundant  around 
the  larger  vessels  and  the  tubules  of  the  pyramids. 

The  lymphatics  of  the  kidney  are  numerous,  and  consist  of  a  super- 
ficial plexus  in  the  capsule  communicating  with  the  deep  series.  This  is 
composed  of  a  net-work  of  lymphatic  spaces  occupying  the  connective 
tissue  surrounding  the  uriniferous  tubules,  especially  abundant  in  the 
cortex,  and  communicating  with  lymphatic  vessels  which  accompany 
the  blood-vessels  to  emerge  in  the  sinus. 

The  nerves  of  the  kidney  are  derived  from  the  renal  plexus  of  the 
sympathetic  nerve,  and  accompany  the  arteries. 

The  pyramids  of  the  mature  kidney,  together  with  the  contiguous 
portion  of  the  cortex  of  each,  correspond  with  the  separation  of  the 
organ  into  lobes  in  the  foetus.  Later  the  lobes  coalesce  and  the  kid- 
ney becomes  a  continuous  mass ;  but  not  unfrequently  some  of  the 
original  lines  of  separation  may  be  observed  on  the  surface  in  the  adult. 
In  many  animals  of  our  class  the  lobar  construction  is  permanently 
retained,  as  exemplified  in  the  kidney  of  the  ox. 

THE   UKETEKS. 

The  excretory  duct  of  the  kidney,  as  previously  mentioned,  com- 
mences in  cup-like  tubes,  the  calyces,1  which  enclose  the  renal  pa- 
pillae and  receive  from  them  the  excreted  urine.  The  calyces  unite  in 
two  or  three  common  tubes,2  which  conjoin  to  form  the  renal  pel- 
vis.3 This  is  fore  and  aft  flattened  funnel-shaped,  and  turns  inward 
and  downward  from  the  sinus  of  the  kidney,  and  narrows  at  the  lower 
part  of  the  hilus  into  the  ureter,4  a  compressed  cylindrical  tube  about 
the  diameter  of  a  goose-quill.  The  ureter  is  from  a  foot  to  fifteen 
inches  long,  and  descends  to  the  bladder,  to  which  it  conveys  the  urine. 
In  its  course  it  rests  on  the  psoas  fascia  covered  by  the  peritoneum, 
then  passes  over  the  iliac  blood-vessels  into  the  pelvis,  and  proceeds  to 
the  side  of  the  bladder  near  the  base  on  which  it  runs  forward.  The 
right  ureter  is  close  to  the  inferior  cava,  and  descends  behind  the  ileum ; 
and  the  left  ureter  descends  behind  the  sigmoid  flexure  of  the  colon. 
The  ureters  are  crossed  by  the  spermatic  blood-vessels  in  front  of  the 
psoas  muscle,  and  in  the  pelvis  they  cross  to  the  inner  side  of  the  defer- 
ent canal,  which  descends  between  the  ureter  and  the  bladder.  In  the 
female  the  ureter  descends  in  the  broad  ligament  at  the  side  of  the 
neck  of  the  uterus  and  upper  part  of  the  vagina  before  reaching  the 
bladder.  The  lower  extremity  of  the  ureter  narrows  and  descends 
obliquely  through  the  wall  of  the  bladder  for  half  an  inch  or  more,  and 
opens  into  the  cavity  about  an  inch  and  a  quarter  from  its  fellow  and 


1  Calyces  minores.  2  Calyces  majores. 

3  Pelvis  renum.  *  Ductus  urinse  ;  vas  urinarium. 


628 


THE   URINARY   ORGANS. 


FIG.  316. 


about  the  same  distance  from  the  orifice  of  the  urethra.  The  openings 
of  the  ureters  into  the  bladder  are  narrow,  elliptical,  and  oblique,  well 
adapted  to  permit  the  ready  entrance  of  the  urine  into  the  bladder  while 
they  prevent  its  reflux. 

The  walls  of  the  ureter,  including  the  pelvis  and  calyces,  are  mem- 
branous, thin,  and  moderately  strong  and  somewhat  extensible.  They 
consist  of  three  tunics,  of  which  the  outer  one  is  thin,  and  is  composed 
of  an  intertexture  of  fibro-connective  tissue  with  elastic  fibres.  The 
middle  coat  is  thickest,  and  is  composed  of  unstriped  muscular  tissue  in 
three  strata,  of  which  the  inner  and  outer  consist  of  longitudinal  fibres, 
and  the  middle  one  of  transverse  fibres. 

The  lining  mucous  membrane  is  grayish  and  smooth,  or  may  be 
slightly  wrinkled  longitudinally.  It  is  composed  of  a  mucosa  of  con- 
nective tissue  pervaded  with  a 
dense  net-work  of  capillary  blood- 
vessels and  a  peculiar  stratified  epi- 
thelium. The  superficial  stratum 
of  the  latter  consists  of  variable- 
sized,  thick,  polyhedral  cells,  from 
one  to  several  times  the  breadth 
of  those  of  the  succeeding  layer, 
by  which  their  under  surface  is 
impressed.  They  are  provided 
with  granular  contents,  and  have 
one  or  several  spherical  or  oval 
nuclei.  In  the  second  stratum  the 
cells  are  vertically  clavate,  with 
their  lower  part  tapering  away  among  the  cells  of  the  succeeding 
strata.  These  consist  of  fusiform  and  obovate  cells  occupying  the  in- 
tervals of  the  second  stratum  and  also  forming  several  strata  beneath. 
The  contents  of  the  deeper  cells  are  of  the  same  character  as  those 
of  the  superficial  stratum. 

The  ureters  appear  to  be  destitute  of  mucous  glands.  The  blood- 
vessels are  branches  of  the  renal,  spermatic,  internal  iliac,  and  inferior 
vesical  arteries  and  veins.  The  nerves  are  derived  from  the  inferior 
mesenteric,  spermatic,  and  hypogastric  plexuses  of  the  sympathetic. 
They  form  plexuses  with  a  few  ganglion  cells  in  the  outer  coats  of  the 
ureter. 

The  ureters  are  liable  to  considerable  variation.  Not  unfrequently 
from  the  passage  of  calculi  they  become  more  or  less  dilated,  some- 
times to  an  enormous  extent.  Occasionally  the  calyces  unite  in  several 
narrow  tubes  which  do  not  conjoin  in  a  renal  pelvis,  and  coalesce  lower 
down  in  the  ureter.  Rarely  the  division  continues  so  as  to  produce  a 
double  ureter. 


EPITHELIUM  OF  THE  URETER,  highly  magni- 
fied. 1,  superficial  layer  of  flattened  polyhe- 
dral cells ;  2,  columnar  cells ;  3,  deep  layers  of 
irregular  polyhedral  cells. 


THE   URINARY   ORGANS.  629 


THE   UEINAKY    BLADDER 

The  urinary  bladder1  is  a  musculo-membranous  reservoir  for  the 
urine,  situated  within  the  pelvis  behind  the  pubes,  in  advance  and 
above  the  rectum  in  the  male,  and  in  advance  of  the  uterus  and  above 
the  vagina  in  the  female.  Its  capacity  varies  under  many  circum- 
stances, such  as  age,  sex,  habit,  disease,  etc.  Its  ordinary  capacity  in 
the  adult  male  is  about  a  pint,  more  or  less,  but  is  capable  of  consider- 
able increase.  It  is  larger  in  individuals  who  by  necessity  are  obliged 
to  retain  the  urine  during  long  periods,  and  is  smaller  when  the  organ 

FIG.  317. 


SIDE  VIEW  OF  THE  MALE  PELVIS  AND  ITS  CONTENTS.  1,  the  right  pubis  sawed  through ;  2, 
sacrum;  3,  bladder;  4,  its  summit;  5,  its  base;  6,  right  ureter;  7,  fore  part  of  the  bladder;  8, 
attachment  of  the  pelvic  fascia;  9,  prostate;  10,  membranous  portion  of  the  urethra;  11,  trian- 
gular ligament ;  12,  suburethral  gland  between  the  two  layers  of  the  latter ;  13, 14,  spongy  body  ; 
15,  right  cavernous  body ;  16,  sigmoid  flexure  of  colon ;  17,  recto-vesical  fold  of  peritoneum ;  18, 
rectum,  with  its  muscular  coat  seen ;  19,  right  seminal  vesicle ;  20,  spermatic  duct ;  21,  pelvic 
fascia  descending  to  the  rectum ;  22,  anal  elevator  muscle ;  23,  anal  sphincter ;  24,  union  of  the 
superficial  perineal  fascia  with  the  triangular  ligament  or  deep  fascia ;  25,  peritoneum  passing 
from  the  summit  of  the  bladder  to  the  anterior  abdominal  wall. 

is  irritated  by  the  presence  of  a  calculus  or  by  other  conditions  which 
lead  to  a  frequent  discharge  of  the  contents. 

When  empty  the  bladder  is  smallest  and  its  walls  are  thickest,  and 
in  this  condition  it  lies  deeply  in  the  pelvic  cavity,  where  it  appears  as  a 
fore  and  aft  flattened  conical  body,  with  the  base  downward  and  the  apex 
directed  forward  and  resting  against  the  pubic  symphysis.  As  the  blad- 
der begins  to  fill  it  becomes  more  regularly  conical,  and  when  moder- 
ately distended  assumes  a  spheroidal  shape  and  still  occupies  the  pelvic 
cavity.  When  completely  distended  it  nearly  fills  the  latter,  and  rises 
partially  above  the  pubic  symphysis  into  the  hypogastrium,  assuming  an 
ovoid  or  oval  form,  of  which  the  upper  part  is  called  the  summit2  and 

1  Vesica  urinaria.  a  Superior  fundus. 


630  THE    URINARY   ORGANS. 

the  lower  part  the  base.1  In  this  condition  the  bladder  often  appears 
slightly  compressed  fore  and  aft  or  broader  from  side  to  side,  usually 
with  the  base  somewhat  larger.  The  summit  is  placed  below  and  in 
advance  of  the  highest  level  of  the  bladder,  and  is  retained  in  contact 
with  the  linea  alba  by  means  of  a  narrow  fibrous  cord.  In  the  dis- 
tended bladder  the  long  axis  is  oblique,  and  nearly  corresponds  with 
that  of  the  superior  strait  of  the  pelvis.  The  base  of  the  bladder  con- 
verges downward  and  forward  in  front  in  a  funnel-like  portion,  called 
the  neck,2  which  terminates  in  the  urethra.  In  the  male  it  is  con- 
nected with  the  prostate,  and  in  the  female  with  the  anterior  wall  of 
the  vagina. 

The  bladder  is  commonly  smaller  in  the  female,  and  is  also  more 
variable  in  shape  and  size  than  in  the  male.  Occasionally  it  is  larger, 
and  usually  it  is  proportionately  shorter,  more  spheroidal,  and  sometimes 
broader.  At  birth  the  distended  bladder  chiefly  occupies  the  abdomen 
above  the  pubes,  but  as  growth  proceeds  and  the  pelvis  enlarges,  it  in 
greater  part  retires  within  the  latter. 

The  fibrous  cord  which  attaches  the  summit  of  the  bladder  to  the 
linea  alba  extends  to  the  umbilicus,  and  is  the  remains  of  the  urachus, 
which  in  the  embryo  is  a  tube  communicating  between  the  bladder  and 
the  allantoid  vesicle  situated  outside  the  abdomen.  A  pair  of  fibrous 
cords  also  proceed  from  the  sides  of  the  bladder  and  converge  to  ascend 
with  the  former  to  the  umbilicus.  These  are  the  remains  of  the  ob- 
literated hypogastric  arteries  of  the  foetus,  and  are  continuous  with  the 
superior  vesical  arteries,  the  trunks  of  which  originally  formed  those 
of  the  hypogastric  arteries.  The  three  fibrous  cords  maintain  the 
median  position  of  the  bladder,  and  thus  serve  as  suspensory  ligaments. 
They  are  enclosed  by  slight  folds  of  the  adjacent  peritoneum,  commonly 
called  false  ligaments  of  the  bladder. 

From  the  summit  of  the  bladder  backward  to  the  base  the  surface 
is  free,  but  invested  by  the  peritoneum.  In  the  male  it  comes  into 
contact  with  the  rectum,  in  the  female  with  the  uterus,  and  in  both 
sexes  with  the  small  intestine.  From  the  summit  of  the  bladder  the 
peritoneum  is  reflected  upward  to  the  front  wall  of  the  abdomen  and 
on  each  side  to  the  pelvis.  In  the  male  the  peritoneum  is  reflected 
from  the  bladder  to  the  rectum,  producing  the  recto-vesical  pouch, 
which  descends  to  the  base  and  is  bounded  laterally  by  the  recto-vesi- 
cal folds  of  the  peritoneum  passing  between  the  sides  of  the  rectum 
and  bladder.  In  the  female,  in  the  same  manner,  the  peritoneum  is 
reflected  from  the  bladder  to  the  uterus,  producing  the  vesico-uterine 
pouch,  of  less  depth  than  the  former,  and  laterally  bounded  by  the 
vesico-uterine  folds  of  the  peritoneum.  In  front  and  below,  the  bladder 
is  destitute  of  peritoneum,  and  is  attached  to  the  adjacent  part  of  the 
pelvis,  behind  the  pubes,  by  loose  areolar  tissue. 

1  Inferior  fundus ;  bas-fond.  2  Cervix. 


THE   URINARY  ORGANS.  631 

The  base  of  the  bladder,  which  is  commonly  its  widest  portion,  in 
the  male  rests  on  the  rectum,  where  this  curves  forward,  and  is  firmly 
attached  thereto  by  connective  tissue  over  a  triangular  space  bounded 
laterally  by  the  deferent  canals  and  seminal  vesicles  extending  in  front 
to  the  prostate.  In  the  female  it  rests  in  front  of  the  neck  of  the 
uterus  firmly  attached  to  the  upper  part  of  the  vagina. 

The  recto-vesical  fascia,  a  connective-tissue  layer,  which  invests 
the  rectum  and  bladder  at  the  base  on  each  side,  is  continuous  with 
the  pelvic  fascia,  the  lines  of  conjunction  being  distinguished  as  the 
lateral  ligaments  of  the  bladder.  Stronger  bands  of  the  same 
fascia,  extending  from  the  neck  of  the  bladder,  one  on  each  side  of  the 
prostate,  to  the  pubic  symphysis,  form  the  anterior  ligaments  of  the 
bladder. 

The  walls  of  the  bladder  are  ordinarily  proportioned  in  thickness 
to  the  degree  of  contraction  or  expansion  of  the  organ,  ranging  from 
about  half  an  inch  in  the  collapsed  state  to  about  a  line  in  the  fully  dis- 
tended condition.  Exclusive  of  the  peritoneal  covering  above  and  be- 
hind, the  bladder  is  composed  of  two  principal  layers,  the  muscular 
coat  and  the  lining  mucous  membrane. 

The  muscular  coat  of  the  bladder  is  thickest,  and  is  externally  in- 
vested with  a  thin,  extensible,  fibro-connective-tissue  layer  forming 
part  of  the  recto-vesical  fascia.  It  is  composed  of  unstriped  fibres, 
which  are  collected  in  flattened,  cylindrical  fascicles  of  variable  size, 
anastomosing  with  one  another  and  disposed  in  two  principal  strata. 
The  external  stratum *  is  best  produced  in  front  and  behind  the  bladder, 
and  has  its  fascicles  in  general  pursuing  a  longitudinal  course.  From 
the  neck  and  base  of  the  bladder  they  ascend  in  front  and  behind,  and 
pass  around  the  top,  many  of  them  converging  to  the  summit.  Others 
from  the  sides  of  the  base  and  around  the  termination  of  the  ureters 
ascend  and  curve  both  fore  and  aft,  and  intersect  one  another.  In  the 
male,  at  the  neck  of  the  bladder,  the  fascicles  spring  from  the  anterior 
ligaments  and  the  fore  part  and  base  of  the  prostate ;  and  in  the  female, 
instead  of  the  latter,  from  the  vagina.  The  internal  muscular  stratum2 
has  its  fascicles  in  general  pursuing  a  transverse  course  united  in  a 
reticular  manner,  while  many,  especially  at  the  sides,  curve  into  and 
join  those  of  the  external  stratum.  Other  fascicles,  in  variable  pro- 
portion in  diiferent  cases,  turn  in  at  the  base  of  the  bladder  and  ascend 
on  the  inner  surface  of  the  internal  stratum,  and  thus  form  an  imper- 
fect third  stratum.  At  the  neck  of  the  bladder  the  internal  stratum 
is  thicker,  and  thence  extends  upon  the  urethra,  where  it  forms  the 
circular  vesical  sphincter.3  The  muscular  strata  and  their  individual 
fascicles  vary  in  thickness  and  compactness  with  the  degree  of  con- 
traction of  the  bladder,  and  the  intervals  of  their  fascicles  enlarge  or 
diminish  accoi'dingly. 

1  Musculus  detrusor  urinae.  2  Circular  fibres.  3  Sphincter  vesicae. 


632 


THE   URINARY   ORGANS. 


The  lining  mucous  membrane  of  the  bladder  is  soft,  smooth, 
shining,  and  commonly  of  a  grayish  color,  but  later  in  life  becomes  of 
a  pinkish  color.  It  is  united  with  a  fibro-connective-tissue  layer,  the 
submucous  coat,  with  which  it  forms  a  continuous  elastic  membrane, 
much  thinner  than,  and  loosely  attached  to,  the  muscular  coat.  In  the 
contraction  of  the  bladder  it  becomes  thicker,  but  also  becomes  wrinkled 
in  the  collapsed  condition  of  the  organ.  Prom  its  close  adherence  to 
the  muscular  coat  it  appears  more  or  less  reticular,  and  this  condition 
becomes  especially  conspicuous  in  hypertrophy  of  the  latter. 

The  mucous  membrane  is  destitute  of  mucous  glands.  The  mucosa 
is  provided  with  a  dense  net  of  capillary  blood-vessels,  but  is  devoid  of 
a  muscularis.  The  epithelium  is  like  that  of  the  ureters. 

The  surface  of  the  bladder  between  the  orifices  of  the  ureters  and 
the  urethra  is  slightly  prominent  and  convex,  and  is  named  the  vesical 

triangle.1    This  is  concave  at  the  sides 

FIG.  318.  and  base,  and  its  rounded  apex  pro- 

jecting upward  into  the  mouth  of  the 
urethra  is  called  the  vesical  uvula.2 
The  triangle  is  produced  by  a  corre- 
sponding muscle,3  subjacent  to  and 
united  with  the  mucous  membrane, 
and  attached  beneath  to  the  internal 
stratum ,  of  the  muscular  coat  of  the 
bladder.  It  is  a  compact  layer  of  un- 
striped  muscular  fibres,  not  fasciculate 
like  the  latter,  and  in  its  relation  with 
the  mucous  membrane  substitutes  the 
submucous  coat.  It  is  continuous  with 
the  muscular  walls  of  the  ureters,  and 
thence  extends  to  the  mouth  of  the 
urethra. 

The  triangular  muscle  probably 
regulates  the  orifices  of  the  ureters, 
and  closes  them  during  the  discharge 
of  the  urine  from  the  bladder. 

The  bladder  is  supplied  on  each  side 
by  the  superior  and  inferior  vesical 
arteries,  branches  of  the  internal  iliacs, 
the  former  proceeding  from  the  re- 
maining pervious  portion  of  the  hypo- 
gastric  artery.  In  the  female  the 
uterine  arteries  also  give  branches 
to  the  bladder.  The  veins  of  the  bladder  collect  in  large  plexuses 


PART  OF  THE  BLADDER  AND  PENIS,  WITH 
THE  URETHRA  LAID  OPEN  FROM  ABOVE.  1, 
internal  surface  of  the  bladder ;  2,  vesical 
triangle ;  3,  position  of  the  orifice  of  the 
ureter  on  each  side ;  4,  vesical  uvula ;  5, 
urethral  crest ;  6,  position  of  the  utricle ; 
7,  8,  prostatic  sinus ;  9,  prostate,  a,  mem- 
branous portion  of  the  urethra;  b,  sub- 
urethral  gland;  c,  position  at  which  the 
ducts  of  the  latter  open ;  d,  spongy  por- 
tion of  the  urethra  within  the  bulb,  e;  f, 
crura  of  the  cavernous  bodies ;  g,  erectile 
tissue ;  h,  continuation  of  the  urethra. 


1  Trigonum  vesicse  ;  t.  Lieutaudi ;  corpus  trigonum. 
8  Muscle  of  the  vesical  triangle ;  muscles  of  the  ureters. 


2  Uvula  vesicae. 


THE   URINARY   ORGANS.  633 

upon  the  base  and  around  the  neck,  and  finally  join  the  internal  iliac 
veins. 

Lymphatics,  according  to  Sappey.  are  absent  in  the  mucous  mem- 
brane of  the  bladder.  The  nerves  are  partly  derived  from  the  hypo- 
gastric  plexus  of  the  sympathetic,  and  partly  from  the  sacral  plexuses 
of  the  spinal  nerves.  They  form  gangliated  plexuses,  accompanying 
the  blood-vessels,  and  are  thence  distributed  in  the  muscular  coat  and 
mucous  membrane. 


GHAPTEE  XII. 

THE  MALE  REPRODUCTIVE  APPARATUS. 

THE  reproductive  apparatus  of  the  male l  consists  of  the  testi- 
cles with  their  appendages  and  the  penis  with  certain  accessories.  The 
urethra  of  the  male  is  the  outlet  from  the  bladder  for  the  discharge  of 
the  urine,  and  also  serves  as  the  passage  for  the  emission  of  the  sper- 
matic liquid.  Extending  from  the  bladder,  its  first  portion,  included 
within  the  pelvis,  is  surrounded  by  the  prostate  and  here  receives  the 
ejaculatory  ducts;  its  second  shortest  portion  passes  through  the  trian- 
gular ligament  of  the  pubic  arch,  and  its  third  or  longest  portion  trav- 
erses the  spongy  body  of  the  penis  and  terminates  at  the  summit  of 
the  head  or  glans. 

THE   PENIS. 

The  penis,2  of  variable  size,  is  appended  to  the  front  of  the  pelvis, 
and  is  formed  by  a  group  of  three  columns,  named  the  cavernous  and 
spongy  bodies,  sheathed  by  the  skin.  Its  attached  portion  is  the  root, 
its  free  extremity  the  glans,  and  the  intermediate  portion  the  body. 
In  the  ordinary  condition  the  root  ascends  from  the  pubic  arch  to  the 
front  of  the  symphysis,  and  thence  the  body  hangs  downward ;  its 
fore  part  is  called  the  dorsum,  or  back,  because  this  is  directed  back- 
ward in  the  erect  condition  of  the  organ.  The  cavernous  bodies  lie 
parallel  with  each  other  along  the  dorsum,  and  the  spongy  body  is 
placed  between  them  along  the  opposite  surface,  which  is  directed  for- 
ward during  erection.  The  three  bodies  are  fibrous  cylinders  occupied 
by  erectile  tissue,  which  freely  communicates  with  the  blood-vessels, 
and  under  excitement  becomes  distended  with  blood  and  thus  pro- 
duces erection  of  the  penis.  The  cavernous  bodies  have  alone  the 
construction  indicated,  but  the  spongy  body  in  addition  is  traversed 
by  the  urethra. 

Viewed  in  the  erect  condition,  the  body  of  the  penis  appears  as 
a  rounded,  three-sided  prismatic  column,  somewhat  narrowed  towards 
the  extremities.  The  wider,  more  flattened  side  directed  backward 
and  upward  is  the  dorsum,  and  the  lateral,  lower  sides  are  convex. 
The  glans,3  or  head  of  the  penis,  is  conical,  with  rounded  summit  and 
expanded  base,  broader  than  the  adjacent  body,  and  slanting  from  be- 

1  Organa  sexualia  masculina  or  virilia. 

2  Membrum  virile ;  virga  ;  priapus  ;  yard.  3  Caput ;  cuspis  ;  balanus. 

634 


THE   MALE   REPRODUCTIVE   APPARATUS.  635 

fore  backward  and  downward.  It  is  hollowed  beneath,  and  caps  the 
conical  end  of  the  united  cavernous  bodies.  The  border  of  the  base, 
named  the  corona,1  is  rounded  and  projecting  and  extends  forward  in 
a  notch  to  the  summit  of  the  glans,  where  the  urethra  terminates  in  a 
narrow,  fore  and  aft,  elliptical  orifice.  Below  the  glans  the  narrowed 
part  of  the  penis  is  the  neck.2 

The  skin  of  the  penis  continued  from  that  of  the  pubes  and 
scrotum  envelops  the  organ,  and  at  the  extremity  forms  a  collar-like 
doubling,  the  prepuce  or  foreskin,3  which  encloses  the  glans.  It  is 
thin  and  extensile,  and  is  movably  attached  by  a  loose  membranous 
layer,  the  fascia  of  the  penis.  Approaching  the  prepuce,  the  skin  be- 
comes thinner  and  more  translucent,  and  permits  its  blood-vessels  to 
be  seen.  It  is  furnished  with  hairs,  which  are  absent  on  the  prepuce, 
become  numerous  at  the  root  of  the  penis,  and  project  from  conspicu- 
ously whitish  prominent  groups  of  sebaceous  glands.  Underneath,  it 
is  divided  by  a  median,  slightly  elevated  line,  the  raphe,  which  con- 
tinues on  the  scrotum  and  thence  on  the  perineum.  The  prepuce  is 
a  loose  and  movable  doubling  of  the  skin,  the  internal  layer  of  which 
is  thinner,  redder,  and  more  translucent,  assuming  the  condition  of  a 
mucous  membrane.  Reflected  upon  the  neck,  it  becomes  more  closely 
attached,  and  is  here  provided  with  numerous  small  sebaceous  glands, 
the  preputial  glands/  the  secretion  of  which  moistens  the  part. 
The  inspissated  secretion  mingled  with  the  shed  epithelium  forms  the 
smegma,5  which  quickly  decomposes  and  emits  a  peculiar  odor.  On 
the  glana  the  skin  becomes  firmly  attached  to  the  subjacent  structure, 
and  at  the  urethral  orifice  is  continuous  with  the  mucous  membrane. 
In  this  position  it  is  bright  red,  devoid  of  glands,  and  is  furnished 
with  numerous  vascular  and  highly  sensitive  papilla?.  From  the  fore 
part  of  the  urethral  orifice  and  the  notch  of  the  glans  a  median  fold, 
the  fraenum,6  is  continuous  with  the  prepuce. 

The  fascia  of  the  penis T  is  a  fibro-connective-tissue  layer,  with 
elastic  and  unstriped  muscle-fibres,  enveloping  the  penis  and  continuous 
with  the  superficial  fascia  of  the  abdomen  and  the  dartos  of  the  scro- 
tum. It  resembles  the  latter  membrane,  like  it  being  completely  des- 
titute of  fat,  but  is  paler  and  less  muscular.  Loosely  connecting  the 
skin  with  the  penis,  it  permits  free  movement  between  them,  except 
on  the  glans,  where  it  merges  into  the  union  of  the  skin  with  the  albu- 
ginea.  At  the  root  of  the  penis  dense  bundles  of  connective  and  elastic 
tissue  descend  from  the  pubic  symphysis  to  the  dorsum,  and  spread  on 
the  sides  of  the  penis,  constituting  its  suspensory  ligament.8  Many 
of  the  bundles  spring  from  the  aponeurosis  of  the  abdominal  muscles, 


1  Corona  glandis.  2  Cervix  ;  collum.  3  Prseputium. 

4  Glandulse  odoriferae  Tysoni,  or  Litrii  ;  cryptae  praeputiales. 

5  S.  praeputii.  6  Frsenulum  glandis.  T  Fascia  penis. 
8  Ligamentum  suspensorium  penis. 


636          THE  MALE  REPRODUCTIVE  APPARATUS. 

especially  the  linea  alba,  and  converge  to  the  pubic  symphysis,  thence 
descending  to  the  penis. 

The  cavernous  bodies.1  These  form  the  principal  part  of  the 
body  of  the  penis,  and  mainly  determine  its  shape  and  rigidity  in  the 
erect  state  of  the  organ.  They  are  cylindrical  columns,  which  are  flat- 
tened and  closely  united  in  the  median  line  for  three-fourths  their  length, 
but  separate  at  the  root  in  a  pair  of  tapering  crura.2  These  proceed 
from  the  everted  borders  of  the  pubic  arch,  to  which  they  are  firmly 
attached  by  tendinous  fibres.  Intermediately  the  crura  are  more  or  less 

FIG.  319. 


'20 


VERTICAL  SECTION  OF  THE  PENIS  AND  BLADDER.  1,  pubic  symphysis ;  2,  triangular  ligament; 
3,  linea  alba ;  4,  crus  of  the  right  cavernous  body ;  5,  pectiniform  septum ;  6,  glans ;  7,  spongy 
body;  8,  its  bulb;  9,  bladder;  10,  its  summit;  11,  its  base;  12,  its  neck;  13,  prostatic  portion  of 
the  urethra ;  14,  membranous  portion  ;  15,  spongy  portion ;  16,  navicular  fossa ;  17,  prostate ;  18, 
suburethral  gland;  19,  right  seminal  vesicle;  20,  deferent  canal;  21,  ejaculatory  duct;  22, 
suspensory  ligament ;  23,  peritoneum ;  24,  its  recto-vesical  fold. 

bulging,  and  they  are  embraced  by  the  ischio-cavernous  muscles.  The 
upper  extremity  of  the  cavernous  bodies  together  end  in  a  blunt  coni- 
cal point,  which  is  received  in  a  pit  in  the  base  of  the  glans  and  is 
firmly  united  with  it  by  fibro-connective  tissue.  The  dorsal  surface  of 
the  cavernous  bodies  is  impressed  with  a  median  groove,  which  is  oc- 
cupied by  the  dorsal  vein  of  the  penis,  and  the  opposite  surface  forms 
a  more  capacious  groove  for  the  accommodation  of  the  spongy  body. 

The  cavernous  bodies  possess  a  strong  exterior  envelope,  the  al- 
buginea,3  from  half  a  line  to  a  line  thick,  enclosing  erectile  tissue. 
The  albuginea  consists  mainly  of  two  closely-connected  strata  of  fibro- 
connective  tissue  collected  into  glistening  tendinous  bands,  which  are 
longitudinal  in  the  outer  and  transverse  in  the  inner  stratum.  The 
bands  conjoin  in  a  reticular  manner,  and  the  narrow  intervals  permit 
the  passage  of  blood-vessels.  With  the  albuginea  there  is  associated 
some  elastic  and  unstriped  muscular  tissue.  Where  the  cavernous 
bodies  unite  they  are  separated  by  a  partition,  named  from  its  comb- 

1  Corpora  cavernosa,  spongiosa,  lateralia,  flbro-spongiosa,  or  tendinea. 

2  Radices,  thalami,  or  capita  corporum  cavernosum.  3  Tunica  albuginea. 


THE   MALE   REPRODUCTIVE   APPARATUS.  637 

like  appearance  the  pectiniform  septum.1  It  is  composed  of  fibrous 
bands  proceeding  from  the  inner  stratum  of  the  albuginea  directed 
fore  and  aft.  It  is  thicker  and  complete  towards  the  root  of  the 
penis,  but  is  rendered  incomplete 
in  advance  from  numerous  fissures 
widening  towards  the  dorsal  bor- 
der. Through  the  fissures  the  erec- 
tile tissue  of  both  cavernous  bodies 
is  continuous.  From  the  pectini- 
form septum  numerous  bands  ra- 
diate to  the  interior  surface  of  the 
albuginea.  • 

The  erectile  tissue  of  the  cav- 

,      ,.                .           „  TRANSVERSE  SECTION  OF  THE  PENIS,  a,  cavern- 

ernOUS  bodies  Consists  Ot  a  sponge-  ous  bodies:  the  vertical  line  in  the  middle  is 

like  matrix   Of  narrow  COrds,  thin  the  pectiniform  septum ;  those  diverging  from 

,,            j  i                        11    j  .t      i_  it  are  trabeculfie;  the  intervening  spaces  are 

bands,  and  laminae,  called  trabec-     occupied  by  erectile  tissue.  bi  spongy  body. 
ulae.     These  are  strongest  at  the     c,  urethra. 
circumference  of  the  erectile  tissue 

and  within  the  crura,  and  are  weakest  centrally  and  at  the  dorsal  part 
of  the  cavernous  bodies.  They  spring  from  the  inner  surface  of  the 
albuginea  and  the  pectiniform  septum,  and  in  all  directions  intersect 
one  another.  The  interspaces  of  the  trabecul®,  or  caverns,  form  to- 
gether a  plexus  of  venous  channels,  which  are  largest  centrally,  and 
finally  merge  in  the  efferent  veins  of  the  cavernous  bodies.  They  are 
lined  by  endothelial  cells  continuous  with  the  endothelium  of  the  veins. 
The  arteries  of  the  cavernous  bodies  end  in  capillary  nets,  the  vessels 
of  which  are  enclosed  by  the  trabeculse  of  the  erectile  tissue  and  finally 
for  the  most  part  open  into  the  caverns  of  the  latter,  while  others 
directly  terminate  in  the  efferent  veins.  Some  of  the  terminal  arterial 
branches  form  dilated  curls  or  loops,  the  helicine  arteries,  which 
end  abruptly  in  capillaries  terminating  in  the  caverns  of  the  erectile 
tissue.  The  helicine  arteries  are  most  abundant  in  the  root  of  the 
penis,  both  in  the  cavernous  and  spongy  bodies. 

The  chief  arteries  which  supply  the  cavernous  bodies  are  the 
cavernous  branches  of  the  pudic  arteries,  while  others  proceed  from 
the  dorsal  arteries.  The  cavernous  artery  penetrates  the  inner  side  of 
the  corresponding  crus  of  the  cavernous  body  and  proceeds  through 
the  erectile  tissue  to  its  extremity,  giving  off  in  its  course  numerous 
branches,  which  are  sheathed  in  the  trabecula?.  Branches  of  the  dorsal 
artery  penetrate  the  albuginea,  especially  near  the  glans,  and  are  in 
like  manner  distributed  to  the  erectile  tissue.  The  chief  veins  pass 
from  the  cavernous  bodies  in  the  course  of  the  cavernous  arteries,  while 
others  pass  through  the  albuginea  in  the  course  of  the  dorsal  vein  and 
open  directly  into  it,  and  still  others  pass  out  between  the  cavernous 

1  Septum  pectiniforme. 


638  THE  MALE  REPRODUCTIVE  APPARATUS. 

and  spongy  bodies  and  turn  round  the  former  also  to  end  in  the  dorsal 
vein. 

The  spongy  body.1  This  commences  in  an  enlarged  portion,  the 
bulb,  placed  in  front  of  the  triangular  ligament  of  the  pubis  between 
the  crura  of  the  cavernous  bodies.  Thence  it  extends  in  a  cylindrical 
slightly  tapering  column,  lodged  in  the  groove  in  advance  of  the  con- 
joined cavernous  bodies,  to  their  extremity,  where  it  expands  to  form 
the  glans  which  caps  them.  The  bulb2  is  pyriform,  of  variable  size, 
and  has  its  base  slightly  divided  below  by  a  median  groove.  It  is 
adherent  behind  to  the  triangular  ligament,  from  which  it  receives  an 
investing  fibro-connective-tissue  layer,  and  it  is  embraced  by  the  ure- 
thro-bulbar  muscles.  The  urethra,  after  passing  through  the  triangular 
ligament,  enters  the  upper  part  of  the  bulb  and  thence  traverses  the 
axis  of  the  spongy  body  to  the  summit  of  the  glans. 

The  spongy  body  has  essentially  the  structure  of  the  cavernous 
bodies,  but  is  of  much  less  strength  and  does  not  acquire  the  same 
degree  of  firmness  or  rigidity  during  erection.  The  albuginea  is  thin, 
does  not  present  the  fasciculate,  tendinous  appearance  of  that  of  the 
cavernous  bodies,  and  is  mostly  composed  of  transverse  fibro-con- 
nective-tissue bundles  with  considerable  elastic  tissue.  In  the  bulb  it 
forms  a  partial  septum  extending  from  the  median  groove  of  its  base, 
and  on  the  glans  it  merges  into  the  derm  of  the  skin.  The  erectile 
tissue  occupying  the  interval  of  the  albuginea  and  urethra  is  of  more 
delicate  texture  than  that  of  the  cavernous  bodies,  having  its  trabec- 
ula3  finer  and  its  venous  channels  smaller,  more  uniform,  and  in  general 
longitudinally  disposed.  The  urethra  is  immediately  surrounded  with 
a  plexus  of  smaller  veins  associated  with  longitudinal  bundles  of  un- 
striped  muscular  fibres.  In  the  superficial  part  of  the  glans  the  veins 
pursue  a  more  tortuous  course. 

The  arteries  which  supply  the  spongy  body  are  the  urethro-bulbar 
and  dorsal  arteries.  Of  the  former,  on  each  side,  the  principal  branch 
enters  the  base  of  the  bulb,  while  a  smaller  one  enters  its  upper  fore 
part,  and  both  proceed  in  the  erectile  tissue  to  the  glans,  which  is 
chiefly  supplied  by  the  terminal  branches  of  the  dorsal  arteries.  The 
veins  return  the  blood  from  the  spongy  body  partly  in  the  course  of 
the  urethro-bulbar  arteries,  while  others  issue  at  the  base  of  the  glans 
and  adjoining  portion  of  the  column  and  converge  to  form  the  com- 
mencement of  the  dorsal  vein  of  the  penis. 

The  skin  of  the  penis  is  supplied  by  branches  of  the  dorsal  and 
external  pudic  arteries,  and  the  veins  join  the  dorsal  vein  and  the 
external  pudic  veins. 

The  lymphatics  of  the  penis  form  a  close  plexus  in  the  skin  of  the 
glans  and  prepuce  and  in  the  mucous  membrane  of  the  urethra,  and 
the  principal  trunks  accompany  the  dorsal  vein  and  enter  the  inguinal 

1  Corpus  spongiosum  or  cavernosum  urethra.  2  Bulbus  urethrse. 


THE   MALE   REPRODUCTIVE   APPARATUS.  639 

glands.  Others  from  the  cavernous  and  spongy  bodies  pursue  the 
course  of  the  corresponding  blood-vessels  and  join  the  internal  iliac 
lymphatics. 

The  nerves  of  the  penis  are  chiefly  derived  from  the  dorsal  and 
superficial  perineal  branches  of  the  pudic  nerve,  and  are  distributed 
to  the  skin,  including  that  of  the  glans.  Many  of  them  terminate 
in  pacinian  corpuscles  and  end-bulbs.  Other  nerves  from  the  hypo- 
gastric  plexus  of  the  sympathetic  accompany  the  blood-vessels  to  the 
cavernous  and  spongy  bodies. 

THE   PROSTATE. 

The  prostate 1  of  the  male,  an  enigmatic  organ  which  is  probably 
homologous  with  the  uterus  and  vagina  of  the  female,  is  situated  within 
the  pelvis,  below  and  in  advance  of  the  bladder,  surrounding  the  com- 
mencement of  the  urethra.  It  has  nearly  the  shape  and  size  of  a  large 
chestnut,  but  is  variable,  and  commonly  enlarges  later  in  life.  It  is  usu- 
ally about  an  inch  and  a  quarter  from  apex  to  base,  a  little  wider  trans- 
versely, and  rather  less  in  thickness.  It  is  placed  obliquely  with  the 
apex  directed  downward  and  forward  to  the  triangular  ligament  of  the 
pubes  and  the  base  directed  upward  to  the  bladder.  Its  front  surface  is 
smallest,  laterally  rounded,  and  looks  forward  and  upward  to  the  pubic 
symphysis ;  its  back  surface  is  largest,  flat  or  variably  concave  trans- 
versely, is  directed  downward  and  backward,  and  is  attached  to  the 
rectum.  The  base  of  the  prostate  is  closely  united  with  the  neck  of  the 
bladder,  behind  which  it  strongly  projects,  while  the  urethra  descends 
obliquely  through  the  prostate  in  advance  of  the  middle.  The  sides  of 
the  base  are  variably  convex  and  prominent,  and  form  its  lateral  lobes,2 
between  which  the  prostate  is  excavated  in  a  fore  and  aft  compressed 
conical  pit,  receiving  the  conjoined  ends  of  the  deferent  canals  and. 
seminal  vesicles.  In  front  of  these  the  lateral  lobes  are  commonly 
united  by  a  variably  prominent  rounded  isthmus,  named  the  middle 
lobe3  of  the  prostate,  attached  to  the  neck  of  the  bladder,  but  some- 
times absent.  In  the  enlargement  to  which  the  prostate  is  liable  in  the 
advance  of  life,  the  lobes  become  more  conspicuous,  and  not  uncom- 
monly undue  increase  in  the  middle  lobe  produces  a  corresponding 
projection  within  the  bladder,  obstructing  the  orifice  of  the  urethra. 

The  prostate  is  invested  with  a  compact  fibro-connective-tissue  layer, 
which  is  continuous  with  the  recto-vesical  fascia  and  the  posterior 
layer  of  the  triangular  ligament  of  the  pubes.  Its  back  part  is  pro- 
vided with  a  compact  layer  of  unstriped  muscular  tissue  in  transverse 
fascicles,  which  also  extend  across  the  base  of  the  prostate  behind 
the  seminal  vesicles  and  deferent  canals,  closely  connecting  the  whole 
together. 

1  Prostate  gland  ;  prostata  ;  parastata  adenoides. 

2  Lobi  laterales.  3  Lobus  medius  ;  isthmus  prostatae. 


640  THE  MALE  REPRODUCTIVE  APPARATUS. 

The  substance  of  the  prostate  is  reddish  gray,  firm  and  tenacious, 
and  is  chiefly  composed  of  a  matrix  of  unstriped  muscle-fibres  including 
numerous  small  racemose  glands. 

According  to  Sappey,  the  basal  third  of  the  prostate  is  mainly 
formed  by  a  compact  muscular  bundle  encircling  the  commencement 
of  the  urethra  as  the  vesical  sphincter.  It  is  continuous  above  with 
the  internal  stratum  of  the  muscular  coat  of  the  bladder  and  below 
with  the  circular  fibres  x>f  the  urethra.  From  its  outer  part  spring 
many  of  the  fibres  of  the  external  stratum  of  the  muscular  coat  of  the 
bladder.  The  posterior  surface  of  the  prostate  is  formed  by  a  layer  of 
transverse  muscular  fibres.  Elsewhere  the  muscular  fibres  proceed  in 
different  directions  and  intersect  one  another  in  the  intervals  of  the 
glands. 

The  prostatic  glands  are  numerous  and  of  variable  size.  Their 
ducts  converge  to  the  urethra,  and  for  the  most  part  open  into  the 
prostatic  sinuses,  into  which  they  emit  an  opalescent  viscid  secretion.1 
They  have  the  usual  construction  of  racemose  glands,  the  branching 
ducts  commencing  in  alveoli  of  variable  length.  The  alveoli  are  of 
two  kinds, — those  in  which  the  epithelium  consists  of  a  single  stratum 
of  long,  narrow  columnar  cells,  and  those  in  which  there  is  a  stratum 
of  short  columnar  cells  succeeded  by  a  second  of  small  polyhedral  cells. 
The  ducts  also  are  lined  by  a  stratum  of  columnar  cells  succeeded  by 
another  of  small  polyhedral  cells. 

The  prostate  is  supplied  by  branches  of  the  vesical,  hemorrhoidal, 
and  pudic  arteries.  The  veins,  enclosed  in  the  investing  capsule,  form 
a  plexus  especially  produced  at  the  sides,  communicating  below  with 
the  pudendal  plexus,  and  above  and  behind  with  the  vesical  plexus, 
and  discharging  into  the  internal  iliac  veins.  The  nerves  are  derived 
from  the  hypogastric  plexus  of  the  sympathetic  and  in  their  distribu- 
tion are  associated  with  ganglionic  cells.  Pacinian  corpuscles  also  occur 
on  some  of  the  nerves. 

THE   UKETHKA. 

The  urethra  extends  from  the  bladder  to  the  end  of  the  penis, 
and  varies  in  length  mainly  in  accordance  with  it.  When  distended  it 
is  cylindrical,  but  variable  in  diameter  in  different  positions.  In  the 
collapsed  state  in  section  it  is  narrowly  transverse  elliptical  and  the 
lining  membrane  is  finely  folded  longitudinally. 

The  lining  mucous  membrane  is  sustained  by  a  fibre-connective 
submucosa,  succeeded  by  a  stratum  of  erectile  tissue  with  longitudinal 
bundles  of  unstriped  muscular  fibres,  and  with  the  venous  channels 
disposed  longitudinally  and  tortuously,  the  whole  being  enclosed  by  a 
stratum  of  circular  muscular  bundles. 

The  urethra  consists  of  the  prostatic,  membranous,  and  spongy 
portions. 

1  Liquor  prostaticus. 


THE  MALE  REPRODUCTIVE  APPARATUS. 


641 


FIG.  321. 


The  prostatic  portion  of  the  urethra  descends  obliquely  forward 
and  passes  through  the  fore  part  of  the  prostate,  with  which  it  corre- 
sponds in  length.  It  is  the  widest  and  most  dilatable  portion  of  the 
canal,  but  is  most  resistant  at  its  commencement,.  When  distended 
it  is  elliptical,  widest  at  the  middle 
and  narrowest  at  the  termination. 
Along  the  bottom  there  extends  a 
median  fold,  the  urethral  crest,1 
which  is  most  elevated,  thickest  and 
rounded  at  the  middle,  and  tapers 
away  towards  the  extremities.  On 
each  side  of  the  crest  the  bottom  of 
the  urethra  is  more  depressed,  and 
forms  the  prostatic  sinus,  into 
which  open  the  ducts  of  the  prostatic 
glands.  At  the  fore  part  of  the  more 
prominent  portion  of  the  crest  is  a 
fore  and  aft  elliptical  aperture,  the 
mouth  of  the  utriculus.2  This  is  a 
little  clavate  pouch,  from  one-fourth 
to  half  an  inch  in  length,  directed 
from  its  mouth  upward  and  backward 
behind  the  middle  lobe  of  the  pros- 
tate. It  is  lined  by  the  mucous  mem- 
brane, containing  minute  glands,  and 
is  enclosed  in  a  stratum  of  erectile 
tissue.  On  each  side  of  the  mouth 
of  the  utriculus,  the  aperture  of 
the  ejaculatory  duct  opens  into  the 
urethra. 

The  lining  mucous  membrane  of 
the  prostatic  portion  of  the  urethra  at 

its  commencement  has  the  same  kind  of  epithelium  as  that  of  the 
bladder,  but  lower  it  is  provided  with  a  stratified  pavement  epithelium. 
This  is  succeeded  by  a  layer  of  erectile  tissue  forming  a  longitudinal 
venous  plexus,  and  then  by  a  muscular  layer  continuous  with  the 
muscular  coat  of  the  bladder.  The  urethral  crest  is  a  fold  of  the 
mucous  membrane. 

The  membranous  portion  of  the  urethra 3  is  the  shortest,  nar- 
rowest, and  least  dilatable,  and  passes  from  the  apex  of  the  prostate 
to  the  upper  part  of  the  bulb  of  the  spongy  body.  It  is  a  cylindrical 

1  Crista  urethralis  ;  caput  gallinaginis  ;  veru  montanum  ;  colliculus  or  caruncula 
seminalis. 

2  U.  prostaticus  ;  vesica  prostatica ;  vesicula  spermatica  spuria ;  sinus  pocularis  ; 
prostatic  sinus. 

3  Pars  membranacea  or  muscularis,  or  isthmus  urethrse. 

41 


PART  OF  THE  BLADDER  AND  PENIS,  WITH 
THE  URETHRA  LAID  OPEN  FROM  ABOVE.  1, 
internal  surface  of  the  bladder ;  2,  vesical 
triangle;  3.  position  of  the  orifice  of  the 
ureter  on  each  side;  4,  vesical  uvula;  5, 
urethral  crest ;  6,  position  of  the  utricle ; 
7,  8,  prostatic  sinus ;  9,  prostate,  a,  mem- 
branous portion  of  the  urethra ;  b,  sub- 
urethral  gland ;  c,  position  at  which  the 
ducts  of  the  latter  open ;  d,  spongy  por- 
tion of  the  urethra  within  the  bulb;  e, 
f,  crura  of  the  cavernous  bodies ;  g,  erectile 
tissue ;  h,  continuation  of  the  urethra. 


642  THE  MALE  REPRODUCTIVE  APPARATUS. 

tube,  little  more  than  half  an  inch  long  and  scarcely  that  width,  issuing 
from  the  pelvis  through  the  triangular  ligament,  about  an  inch  below 
the  pubic  symphysis.  Between  the  layers  of  the  triangular  ligament 
it  is  enclosed  above  by  the  pudendal  plexus  of  veins,  and  below  is  in 
relation  with  the  interval  between  the  bulb  of  the  spongy  body  and 
rectum,  occupied  by  connective  tissue  and  fat,  in  which  are  embedded 
the  suburethral  glands.  Its  walls  are  formed  of  the  lining  mucous 
membrane,  sustained  by  a  submucous  layer  of  fibro-connective  tissue, 
enclosed  by  erectile  tissue  and  a  muscular  layer.  The  erectile  tissue 
consists  of  a  longitudinal  venous  plexus  with  longitudinal  muscular 
bundles,  while  the  succeeding  muscular  layer  consists  of  circular  bun- 
dles. The  epithelium  of  the  mucous  membrane  consists  of  stratified 
pavement  cells. 

The  spongy  portion  of  the  urethra l  traverses  the  spongy  body, 
and  accords  with  it  in  length  and  direction.  It  is  cylindrical,  but  is 
slightly  more  expanded  within  the  bulb,  and  is  again  considerably  ex- 
panded within  the  glans,  where  it  forms  the  navicular  fossa.2  This 
contracts  at  the  summit  of  the  glans  in  the  mouth  of  the  urethra,3 
the  narrowest  part  of  the  canal,  forming  a  fore  and  aft  narrow  elliptical 
aperture  bounded  by  slightly  prominent  lateral  lips. 

In  the  closed  urethra  the  lining  membrane  is  thrown  into  numerous 
fine  longitudinal  folds,  which  disappear  on  distention  of  the  canal.  It 
consists  of  the  mucous  membrane  sustained  by  a  submucous  layer  of 
fibro-connective  tissue  mingled  with  considerable  elastic  tissue.  This 
is  succeeded  by  a  layer  of  erectile  tissue  and  a  circular  muscular  layer, 
as  in  the  membranous  portion.  The  epithelium  for  the  most  part 
superficially  is  columnar,  but  in  the  bulb  passing  into  the  former  and 
in  the  navicular  fossa  it  is  of  the  stratified  kind. 

The  mucous  membrane  of  the  spongy  portion  of  the  urethra  is  pro- 
vided with  many  minute  racemose  mucous  glands,4  whose  ducts  are 
directed  forward  to  open  in  the  canal.  Besides  these,  numerous  little 
pockets  or  lacunae  open  in  the  same  direction  on  the  surface  of  the 
mucous  membrane,  their  mouths  being  sufficiently  large  to  admit  a 
bristle.  A  larger,  conspicuous  recess  of  the  same  character  on  the 
upper  surface  of  the  navicular  fossa  is  named  the  great  lacuna.6 

The  suburethral  glands.6  These  are  two  whitish,  rounded  bodies, 
situated  below  the  membranous  portion  of  the  urethra,  close  to  the  bulb 
of  the  spongy  body.  They  are  enclosed  by  the  urethral  compressor 
muscle,  between  the  layers  of  the  triangular  ligament,  and  are  closely 
adherent  to  the  adjacent  structures.  They  are  of  variable  size,  com- 
monly about  that  of  a  pea,  are  of  firm  consistence,  and  lobulated. 
Sometimes  they  are  feebly  produced,  and  occasionally  there  is  but  a 

1  Pars  spongiosa,  or  cavernosa  urethras. 

2  F.  navicularis,  or  of  Morgagni.  3  Meatus  urinarius. 
4  Glands  of  Littre,  or  of  Morgagni.  5  Lacuna  magna. 

6  Glands  of  Mery  ;  Cowper's  glands  ;  bulbo-urethral  glands. 


THE   MALE    REPRODUCTIVE   APPARATUS.  643 

single  gland.  They  are  racemose  mucous  glands,  and  their  ducts,  after 
entering  the  spongy  body,  proceed  near  together  through  the  erectile 
tissue,  and  then  beneath  the  mucous  membrane  of  the  urethra  to  open 
into  it,  an  inch  to  an  inch  and  a  half  from  their  commencement. 

THE   TESTICLES. 

The  testicles1  are  two  glandular  organs  which  secrete  the  charac- 
teristic male  element,  the  sperm,  or  semen.  They  are  each  suspended 
from  the  pubic  region  by  the  spermatic  cord  within  a  pouch  of  the 
skin,  the  scrotum. 

The  scrotum  hangs  from  the  pubes  at  the  root  of  the  penis,  and 
is  variable  in  extent  and  in  other  respects,  under  different  conditions. 
Thus,  it  is  shorter,  rounder,  more  contracted  and  wrinkled  in  the  young 
and  vigorous,  especially  under  the  impression  of  cold,  and  it  becomes 
more  pendulous  and  lower  in  the  aged  and  feeble  and  under  the  influ- 
ence of  warmth. 

The  skin  of  the  scrotum  is  thin  and  extensible,  darker  than  else- 
where, and  is  free  from  subcutaneous  fat.  It  has  a  rather  thick  epi- 
dermis, and  is  provided  with  long,  scattered,  crisp,  and  flattened  hairs, 
which  project  from  conspicuous,  oblong,  whitish  groups  of  sebaceous 
glands.  It  is  divided  by  a  median  line  or  slight  ridge,  the  raphe, 
continuous  with  that  of  the  penis  and  perineum.  In  the  contracted 
condition  the  skin  becomes  proportionately  thicker,  and  is  thrown  into 
numerous  more  or  less  corrugated  folds  generally  proceeding  outwardly 
from  the  raphe. 

Within  the  scrotum  the  testicle  and  spermatic  cord  have  several 
additional  envelopes,  named  the  dartos  and  the  spermatic  fascia. 

The  dartos  is  a  loose  extensible  membrane  continuous  with  the 
superficial  fascia  of  the  abdomen,  from  which  it  differs  in  structure  and 
in  the  fact  that  it  is  completely  destitute  of  fat.  It  is  of  a  pale-reddish 
color,  and  is  composed  of  fibre-connective  with  elastic  tissue  and  a  large 
proportion  of  unstriped  muscular  tissue,  the  fibres  of  which  generally 
pursue  a  longitudinal  course.  It  outwardly  blends  with  the  skin  of 
the  scrotum  and  inwardly  is  connected  with  the  spermatic  fascia.  It  is 
thickest  at  the  fore  part  of  the  scrotum,  and  it  forms  a  median  parti- 
tion extending  from  the  root  of  the  penis  to  the  perineum,  separating 
the  testicles.  The  muscular  fibres  of  the  septum  mainly  proceed  fore 
and  aft.  To  the  dartos  is  due  the  remarkable  contractility  of  the 
scrotum. 

The  spermatic  fascia2  is  a  thin,  fibro-connective-tissue  layer  suc- 
ceeding the  dartos  and  enveloping  the  spermatic  cord  and  testicle,  and 
enclosing  between  its  laminae  the  cremaster  muscle.  Along  the  cord 
it  is  of  looser  texture,  forms  partitions  between  its  constituents,  and 
usually  contains  considerable  fat  in  the  fore  part  of  the  cord  associ- 

1  Testes  ;  didymi ;  orchides.  2  Tunica  vaginalis  communis. 


644          THE  MALE  REPRODUCTIVE  APPARATUS. 

ated  with  the  spermatic  veins.  Its  outer  lamina1  above  is  connected 
with  the  margin  of  the  external  abdominal  ring,  and  its  inner  lamina2 
extends  upon  the  cord  within  the  inguinal  canal,  and  at  the  internal 
abdominal  ring  becomes  continuous  with  the  transversalis  fascia.  Ap- 
proaching the  testicle,  the  spermatic  fascia  becomes  more  compact  and 
distinctly  membranous,  and  thus  spreads  over  the  vaginal  tunic,  with 
which  and  the  back  of  the  testicle  it  is  closely  united. 

The  cremaster  muscle3  forms  a  thin  stratum  of  fascicles  of  striped 
muscular  fibres  enclosed  in  the  spermatic  fascia  and  descends  from  the 
inguinal  canal  to  the  testicle.  It  arises  by  an  inner  portion  from  the 
spine  and  crest  of  the  pubis,  and  by  an  outer  usually  better  developed 
portion  from  Poupart's  ligament  below  the  inferior  attachment  of  the 
internal  oblique  and  transversalis  muscles.  Descending  on  opposite  sides 
of  the  cord,  the  fascicles  mostly  curve  forward  and  form  a  series  of  loops 
successively  longer  and  more  separated,  with  the  lower  ones  spreading 
in  the  spermatic  fascia  and  embracing  the  sides  and  front  of  the  upper 
half  or  three-fourths  of  the  vaginal  tunic.  Some  of  the  fascicles  di- 
verge and  end  in  the  spermatic  fascia  without  joining  in  loops.  The 
inner  portion  of  the  cremaster  muscle  is  often  feebly  produced  or  even 
absent,  but  rarely  it  is  even  stronger  than  the  outer  portion.  ' 

The  testicles  are  suspended  obliquely,  each  from  the  spermatic  cord, 
which  is  attached  along  their  back  part,  where  the  vessels  and  nerves 
are  transmitted ;  and  the  left  one  commonly  hangs  a  little  lower  than 
the  right.  They  are  oval  bodies  slightly  compressed  laterally,  and  have 
their  upper  extremity  divergent  and  directed  forward  and  outward, 
with  their  lower  extremity  and  posterior  border  directed  in  the  oppo- 
site direction  and  nearer  each  other.  The  fore  part  and  sides  are 
smooth  and  free,  but  to  the  back  part  the  epididymis  and  spermatic 
cord  are  attached. 

The  epididymis  *  is  an  elongated,  curved,  leech-shaped  appendage 
lying  along  the  back  of  the  testicle,  largest  above  and  narrowing  below. 
Its  upper  posterior  surface  is  convex  and  free,  and  directed  outwardly, 
while  its  under  surface,  resting  on  the  testicle,  is  concave  and  separated 
from  it  outwardly  by  a  fissure  which  is  lined  by  an  inflection  of  the 
vaginal  tunic.  Its  inner  border  is  attached  both  to  the  testicle  and  the 
spermatic  cord.  Its  upper  end,  or  head,5  is  thick  and  rounded,  and 
projects  forward  on  the  testicle  to  which  it  is  attached.  The  lower, 
narrower  end,  or  tail,8  is  attached  by  fibrous  tissue  to  the  testicle,  and 
thence  turns  upward  internally  as  the  commencement  of  the  deferent 
canal. 

The  testicles,  though  variable,  are  commonly  one  and  a  half  inches 

1  Intel-columnar  fascia ;  spermatic  fascia. 

2  Infundibuliform  fascia ;  tunica  vaginalis  propria. 

3  Tunica  carnea ;  t.  erythroides. 

*  Parastata  or  p.  cirsoides  ;  glandula  supergeminalis. 

5  Caput  epididymis  ;  globus  major.          6  Cauda  epididymis ;  globus  minor. 


THE  MALE  REPRODUCTIVE  APPARATUS. 


645 


or  more  long,  one  to  one  and  a  quarter  inches  fore  and  aft,  and  from 
three-quarters  to  one  inch  transversely.  The  weight  of  each  is  from 
three-quarters  to  one  ounce ;  and  one  is  not  unfrequently  a  little  larger 
than  the  other. 

The  testicle  and  epididymis  are  provided  with  an  outer  tunic,  named 
the  albuginea,  which  is  closely  invested  with  a  serous  membrane,  the 
vaginal  tunic.  The  testicle  is  smooth  and  white,  while  the  epididymis 
is  less  white  from  the  greater  thinness  of  its  albuginea. 

The  albuginea *  of  the  testicle  is  a  thick,  dense,  inextensible  mem- 
brane enclosing  the  glandular  substance  of  the  organ.  It  is  com- 
posed of  bundles  of  fibrous  tissue  interlacing  in  all  directions,  and  is 
but  slightly  vascular.  Its  outer  surface  is  closely  invested  by  the 

FIG.  323. 


TRANSVERSE  SECTION  OF  THE  TESTICLE,  a, 
spermatic  fascia ;  b,  reflected  portion  of  the 
vaginal  tunic ;  c,  cavity  of  the  latter ;  d,  in- 
vesting portion  of  the  same  membrane ;  e,  al- 
buginea ;  /,  vaginal  tunic  and  albuginea  of  the 
epididymis;  g,  its  interior  tubular  structure; 
h,  mediastinum ;  i,  branches  of  the  spermatic 
artery;  k,  spermatic  vein;  I,  deferent  canal; 
m,  deferent  artery ;  n,  lobules  of  the  testicle ;  o, 
septula  between  them. 


TESTICLE,  WITH  THE  VAGINAL  TUNIC  LAID 
OPEN.  1,  lower  part  of  the  spermatic  cord ;  2, 
body  of  the  testicle ;  3,  head,  and  4,  tail,  of  the 
epididymis ;  5,  reflected  portion  of  the  vaginal 
tunic. 


vaginal  tunic  except  along  the  back  part  of  the  testicle,  where  it  is 
connected  with  the  epididymis  and  spermatic  fascia,  and  is  perforated 
for  the  ducts,  vessels,  and  nerves  of  the  organ.  At  the  back  part  of 
the  interior  of  the  testicle,  the  albuginea  forms  a  prismatic,  longitu- 
dinal projection,  the  mediastinum,2  from  which  diverge  numerous 
fibrous  bands,  or  septula,  which  extend  between  the  lobes  of  glandu- 
lar substance  to  the  inner  surface  of  the  albuginea. 

The  albuginea  of  the  epididymis  is  much  thinner  than  that  of  the 
testicle,  and  on  the  inner  side  is  connected  with  the  spermatic  fascia 
of  the  cord. 

The  vaginal  tunic 3  is  a  serous  membrane,  forming  a  closed  sac,  of 
which  the  visceral  portion  closely  invests  the  testicle  and  epididymis, 


1  Tunica  albuginea,  fibrosa,  anonyma,  or  propria ;  dura  mater  testis. 

2  Corpus  Highmori.  s  Tunica  vaginalis  propria. 


646 


THE  MALE  REPRODUCTIVE  APPARATUS. 


while  the  parietal  portion  is  reflected  from  their  inner  posterior  bor- 
der and  forms  for  them  a  second  envelope.  It  covers  the  albuginea 
evenly  except  along  the  back  of  the  testicle  and  inner  border  of  the 
epididymis,  where  these  are  connected  together  and  with  the  sper- 
ma'tic  cord.  Outwardly  it  dips  into  and  lines  the  intervening  fissure 
of  the  testicle  and  epididymis.  It  is  intimately  united  to  the  albuginea 
of  the  testicle,  but  is  less  closely  joined  to  that  of  the  epididymis.  The 
parietal  portion  of  the  vaginal  tunic  is  stronger,  and  is  closely  con- 
nected with  the  spermatic  fascia,  which  encloses  it.  When  inflated  the 
cavity  of  the  vaginal  tunic  is  double  the  volume  of  the  testicle ;  but 
in  the  usual  condition  the  opposed  surfaces  lie  in  contact,  bathed  with 

the    serous    secretion   of  the 

Fia.  324.  membrane.      The    epithelium 

is   like   that  of  other  serous 
membranes. 

The  arteries  of  the  scrotum 
and  of  other  envelopes  of  the 
testicle  and  spermatic  cord  are 
derived  from  several  sources. 
The  external  pudic  branches 
of  the  femoral  artery  proceed 
to  the  scrotum  and  supply  the 
skin  and  dartos;  the  superfi- 
cial perineal  artery  supplies 
the  back  part  of  the  scrotum ; 
and  a  branch  of  the  epigastric 
artery  supplies  the  cremaster 
muscle  and  spermatic  fascia. 
The  veins  accompany  the  ar- 
teries. Of  the  nerves,  the  ilio- 
inguinal,  a  branch  of  the  lum- 
bar plexus,  emerges  at  the 
external  abdominal  ring  and 
is  distributed  to  the  scrotum; 
while  the  superficial  perineal 
branches  of  the  pudic  nerve 
supply  its  back  part.  The 
spermatic  branch  of  the  gen- 
ito-crural  nerve  joins  the  sper- 
matic cord  at  the  internal  abdominal  ring,  and  thence  is  distributed  to 
the  cremaster  muscle. 

The  glandular  substance  of  the  testicle1  forms  a  yellow-brown 
inelastic  mass  of  dough-like  consistence.  It  is  composed  of  numerous 
elongated  pyramidal  lobes 2  of  different  sizes  and  rounded  on  the  OX- 


TESTICLE,  DEPRIVED  OF  ITS  TUNICS,  o,  body  of  the 
testicle ;  6,  lobules ;  e,  position  at  which  they  end  in 
the  straight  tubules;  d,  spermatic  rete;  e,  efferent 
vessels;  /,  spermatic  cones;  g,  epididymis;  h,  com- 
mencement of  deferent  canal ;  i,  vas  aberrans ;  m,  n, 
branches  of  the  spermatic  artery ;  o,  deferent  artery ; 
p,  anastomosis  between  the  two  vessels. 


1  Pulpa  or  parenchyma  testiculi. 


2  Lobi  testis. 


THE  MALE  REPRODUCTIVE  APPARATUS.  647 

terior,  the  longest  ones  in  the  middle  and  the  shortest  laterally.  The 
number  varies  with  the  size  of  the  testicle,  and  is  estimated  from  several 
hundred  to  more  than  double  that  number.  They  are  closely  aggre- 
gated, enclosed  by  the  albuginea  with  their  bases  next  the  surface  of 
the  membrane  and  their  apices  converging  to  the  mediastinum.  They 
are  separated  by  the  septula  diverging  from  the  latter  and  by  their 
delicate  connective-tissue  sheaths  with  the  blood-vessels. 

According  to  the  size  of  the  glandular  lobes,  each  is  composed  of 
from  one  to  half  a  dozen  seminiferous  tubules,1  which  when  un- 
ravelled appear  as  very  long,  flexuose,  cylindrical  threads  of  uniform 
diameter  and  commonly  from  the  y^  to  the  -j-^  of  an  inch.  The  tubules 
average  about  two  feet  in  length,  but  are  closely  convoluted  and  occa- 
sionally anastomose  through  communicating  branches,  or  they  conjoin 
in  loops.  In  each  lobe  the  tubules  finally  join  one  another  at  acute 
angles,  and  the  common  tubule  becomes  less  convoluted  and  tapers 
into  a  short,  narrower,  straight  tubule.  The  tubules  of  contiguous 
lobes  also  occasionally  anastomose  through  communicating  branches. 

The  straight  tubules2  enter  the  mediastinum,  and  there  communi- 
cate with  a  longitudinal  series  of  larger  and  closely-anastomosing  chan- 
nels, which  form  the  spermatic  rete.3  From  the  upper  part  of  this, 
there  commonly  proceed  from  nine  to  a  dozen  or  more  efferent  tu- 
bules,4 which  pierce  the  albuginea  and  enter  the  head  of  the  epididy- 
mis.  At  first  straight,  each  tubule  becomes  closely  coiled  into  a  sper- 
matic cone,5  about  the  third  of  an  inch  in  length,  the  series  of  cones 
occupying  the  head  of  the  epididymis.  Unravelled,  the  tubule  of  each 
cone  is  from  six  to  ten  inches  long,  about  one-fortieth  of  an  inch  at 
the  commencement  and  narrowed  to  one-sixtieth  at  the  termination. 
The  tubules  at  the  base  of  the  cones,  generally  at  intervals  of  several 
inches  in  the  uncoiled  state,  successively  unite  in  the  single  canal  of 
the  epididymis.  This  is  also  exceedingly  tortuous,  forming  a  multitude 
of  coils  in  lobar  masses  extending  to  the  tail.  Here  it  turns  upward, 
enlarges,  and  still  much  convoluted  ascends  in  the  spermatic  cord  as  the 
deferent  canal,  which  approaching  the  top  of  the  testicle  becomes 
straight,  and  in  this  position  is  a  line  or  more  in  diameter.  Uncoiled, 
the  canal  of  the  epididymis  is  observed  to  be  about  twenty  feet  in 
length,  about  one-sixtieth  of  an  inch  at  its  commencement  and  gradually 
increasing  to  the  tail. 

The  seminiferous  tubules  are  provided  with  a  thick  epithelium,  and 
have  their  wall  outwardly  defined  by  a  hyaline,  elastic  basement  mem- 
brane. The  epithelium  consists  of  a  number  of  strata  of  seminal 
cells,  which  exhibit  variable  phases  in  the  production  of 'the  sperm. 
The  stratum  next  the  basement  membrane  consists  mostly  of  uniform, 

1  Tubuli  or  canaliculi  seminiferi  or  seminales ;  vascula  serpentina. 

2  Tubuli  or  ductuli  seminiferi  recti.  3  Kete  vasculosum  testis  Halleri. 

4  Vasa  efferentia ;  v.  Graafiana.  5  Conus  vasculosus  ;  corpus  pyramidali. 


e 


648  THE  MALE  REPRODUCTIVE  APPARATUS. 

polygonal,  transparent  nucleated  cells  with  little  difference  in  their 
diameters.  Within  is  a  stratum,  or  several  strata,  of  larger,  rounded 
and  less  regular  transparent  cells,  which  together  with  their  nuclei  show 
evidences  of  proliferation.  Inwardly  succeed  a  variable  number  of  strata 
of  more  or  less  ill-defined  cells,  forming  a  granular  layer  with  small, 

scattered,  indistinct  nuclei.  Embedded  in 
the  epithelium,  spermatozoa  are  observed 
in  different  stages  of  development ;  in  an 
early  condition  appearing  as  groups  of  nar- 
row clavate  cells  standing  vertically  with 
the  thick  end  upward ;  later  as  bunches  of 
long  filaments  partially  embedded  at  variable 
depths  in  the  epithelium  and  partially  pro- 
jecting into  the  lumen  of  the  seminiferoua 
tubule ;  and  finally  as  the  complete  sperma- 
tozoa with  the  heads  embedded  in  the  sur- 
face of  the  epithelium  and  the  tails  extending 

along  the  passage  of  the  tubule.     In  those 
PORTION  OF  A  SEMINIFEROUS  TU-  & 

BULE,  highly  magnified,  a,  fibrous  tubules  in  which  the  semen  has  been  re- 
coat;  6,  basement  membrane;  c,  Cently  discharged  the  superficial  granular 
seminal  cells.  J 

layer  is  in  a  great  measure  absent,  and  its 

position  occupied  by  several  layers  of  more  distinct  proliferating  cells. 

The  straight  tubules  differ  from  the  seminal  tubules  in  structure,  in 
that  the  epithelium  consists  of  a  single  layer  of  short  columnar  cells. 
The  channels  of  the  spermatic  rete,  wider  than  the  former,  are  provided 
with  a  similar  epithelium. 

The  interior  surface  of  the  albuginea,  the  mediastinum,  and  the  sep- 
tula  of  the  testicle  are  closely  invested  with  a  delicate  vascular  tunic * 
composed  of  fibro-connective  tissue,  in  which  the  spermatic  blood- 
vessels ramify.  Laminae  and  bands  of  the  same  enclose  the  glandular 
lobes  and  seminiferous  tubules,  and  the  vessels  communicate  with  close 
capillary  nets  of  the  latter.  The  cleft-like  interstices  of  the  vascular 
tunic  are  lymph-spaces  lined  by  endothelial  cells. 

The  efferent  tubules  forming  the  cones  and  the  canal  of  the  epidid- 
ymis  have  a  thin  wall  with  a  proportionately  large  lumen.  Next  the 
basement  membrane  outwardly,  they  are  composed  chiefly  of  circular, 
unstriped  muscular  fibres,  and  are  provided  with  a  close  net  of  capil- 
lary blood-vessels.  The  epithelium  consists  of  narrow,  prismatic, 
columnar  cells,  shortest  in  the  cones,  and  provided  with  long  cilia, 
except  in  the  lower  part  of  the  epididymis.  The  cilia  produce  an 
outward  current. 

Succeeding  the  albuginea,  the  epididymis  is  invested  with  connec- 
tive tissue,  which  surrounds  the  tubes,  sustains  their  convolutions,  and 
supports  the  branches  of  the  spermatic  artery  and  veins. 

1  Tunica  vasculosa  testis ;  pia  mater  testis. 

fr 


THE  MALE  REPRODUCTIVE  APPARATUS.  649 

The  deferent  canal,1  or  excretory  duct  of  the  testicle,  is  the  con- 
tinuation of  the  convoluted  canal  of  the  epididymis,  from  the  inner  side 
of  the  tail  of  which  it  ascends  at  the  back  of  the  testicle  as  part  of  the 
spermatic  cord.  It  is  separated  from  the  epididymis  and  testicle  by  the 
spermatic  blood-vessels  passing  in  and  out  of  the  organ,  and  thence  as- 
cends to  the  external  abdominal  ring  behind  the  vessels,  where  it  may 
be  readily  distinguished  by  its  wiry  feel.  Passing  through  the  inguinal 
canal  at  the  internal  abdominal  ring,  it  leaves  the  spermatic  blood- 
vessels and  curves  downward  and  backward  into  the  pelvis.  It  pro- 
ceeds beneath  the  peritoneum  to  the  side  and  then  behind  the  bladder, 
converging  to  the  base  of  the  prostate  close  to  that  of  the  opposite  side. 
From  the  internal  abdominal  ring  it  turns  outwardly  around  the  epi- 
gastric blood-vessels  and  crosses  the  external  iliac  vessels  to  the  inner 
side,  then  passes  over  the  cord  of  the  obliterated  hypogastric  artery 
and  crosses  the  ureter  to  its  inner  side.  After  leaving  the  peritoneum 
it  adheres  to  the  bladder  and  less  closely  to  the  contiguous  portion  of 
the  rectum,  and  then  passes  along  the  inner  border  of  the  seminal 
vesicle,  the  duct  of  which  it  joins  to  form  the  ejaculatory  duct. 

The  deferent  canal  is  usually  about  eighteen  inches  long,  but  with 
its  commencement  uncoiled  is  about  two  feet.  In  the  greater  portion 
of  its  course  it  is  nearly  uniformly  cylindrical,  and  from  a  line  to  a 
line  and  a  half  in  diameter,  proportioned  to  the  size  of  the  testicle. 
Approaching  its  termination  for  about  three  inches  it  becomes  enlarged 
and  flexuose,  as  the  ampulla,  which  tapers  below  and  joins  the  duct 
of  the  seminal  vesicle  to  end  in  the  ejaculatory  duct. '  The  ampulla 
varies  considerably  in  different  individuals,  in  some  being  small  and  in 
others  two  or  three  times  larger,  more  or  less  tortuous,  and  occasionally 
provided  with  a  few  short  caecal  pouches.  It  is  fore  and  aft  compressed, 
attached  to  the  bladder,  and  lies  close  to  that  of  the  opposite  side  and 
to  the  seminal  vesicle. 

The  deferent  canal  is  remarkable  for  its  thick,  dense  wall  and  the 
narrowness  of  its  passage,  which  is  about  a  fifth  of  the  whole  diameter 
and  barely  admits  an  ordinary  bristle.  In  the  ampulla  the  wall  is 
thinner  and  the  passage  considerably  more  capacious. 

The  wall  of  the  deferent  canal  is  chiefly  composed  of  yellowish, 
unstriped  muscular  tissue  lined  by  mucous  membrane  and  invested  with 
a  fibro-connective-tissue  layer,  which  externally  merges  into  the  sper- 
matic fascia.  The  muscular  tunic  consists  of  a  thicker  inner  stratum 
of  circular  fascicles  and  an  outer  stratum  of  longitudinal  fascicles.  The 
mucous  membrane,  slightly  wrinkled  longitudinally,  or  smooth  when 
distended,  consists  of  a  propria  of  connective  tissue  with  elastic  fibres, 
mostly  circular  inwardly  and  longitudinal  outwardly,  and  an  epithe- 
lium of  columnar  cells  devoid  of  cilia.  In  the  ampulla  the  mucous 
membrane  is  reticularly  folded  and  encloses  numerous  angular  pits, 

1  Ductus  or  vas  deferens ;  ductus  spermaticus. 


650          THE  MALE  REPRODUCTIVE  APPARATUS. 

and  in  miniature  resembles  the  condition  of  the  mucous  membrane  of 
the  gall-bladder,  or  of  the  honey-comb  stomach  of  ruminating  animals. 
Embedded  in  the  mucous  membrane  are  numerous  flask-like  tubular 
glands,  like  those  of  the  intestines,  but  in  many  cases  compounded  by 
the  union  of  several  in  a  common  outlet  or  duct. 

The  spermatic  cord  consists  of  the  deferent  canal,  the  spermatic 
artery,  veins,  lymphatics,  and  nerves,  and  the  cremaster  muscle  en- 
closed in  the  spermatic  fascia.  As  the  complete  cord,  it  extends 
through  the  inguinal  canal  to  the  back  of  the  testicle. 

The  deferent  canal  ascends  from  the  inner  part  of  the  tail  of  the 
epididymis,  along  the  back  of  the  spermatic  cord,  to  the  external  ab- 
dominal ring  and  thence  passes  along  the  inguinal  canal  to  the  internal 
abdominal  ring,  where  it  leaves  all  other  constituents  of  the  cord  and 
enters  the  pelvis  as  above  described. 

The  spermatic  artery,  a  long,  narrow  vessel,  springs  from  the 
aorta  below  the  renal  artery,  descends  along  the  psoas  muscle,  crosses 
the  ureter  and  external  iliac  blood-vessels,  and  enters  the  internal  ab- 
dominal ring,  where  it  joins  the  spermatic  cord  and  descends  in  advance 
of  the  deferent  canal  to  the  testicle.  Approaching  the  latter  it  gives  off 
a  smaller  branch  to  the  epididymis,  while  the  larger  one  divides  into 
others  which  penetrate  the  albuginea  along  the  back  of  the  testicle 
and  enter  the  mediastinum,  whence  they  are  distributed  in  the  vascular 
tunic,  partly  on  the  inner  surface  of  the  albuginea  and  partly  along 
the  septula  between  the  lobes  of  the  testicle. 

A  long  thread-like  vessel,  the  deferent  artery,  comes  from  one  of 
the  vesical  arteries  and  runs  upon  the  deferent  canal  its  entire  length, 
supplying  it  in  its  course  and  terminating  by  anastomosing  with  the 
branch  of  the  spermatic  artery  distributed  to  the  epididymis. 

The  spermatic  veins,  passing  from  the  vascular  tunic  of  the  tes- 
ticle, emerge  from  the  albuginea  in  a  number  of  branches  along  the 
back  of  the  testicle,  where  they  are  joined  by  others  from  the  epididy- 
mis. The  veins  ascend  in  company  with  the  spermatic  artery  in  the 
fore  part  of  the  cord  and  anastomose  with  one  anot'n'er,  forming  a 
plexus.  From  this  two  or  three  veins  enter  the  abdomen  and  unite  in 
a  single  trunk,  which  follows  the  course  of  the  spermatic  artery ;  that 
of  the  right  side  terminating  in  the  inferior  cava  and  that  of  the  left 
side  in  the  corresponding  renal  vein. 

The  lymphatics  of  the  testicle  are  numerous  and  chiefly  commence 
in  the  lymph-spaces  in  the  intervals  of  the  seminiferous  tubules.  From 
finer  plexuses  in  the  vascular  tunic  and  epididymis  a  half-dozen  large 
trunks  pursue  the  course  of  the  spermatic  veins  and  terminate  in  the 
lumbar  lymphatic  glands. 

The  nerves  of  the  testicle  are  mainly  those  of  the  spermatic  plexus 
of  the  sympathetic  accompanying  the  spermatic  artery.  Other  nerves 
from  the  hypogastric  plexus  accompany  the  deferent  artery. 

The  spermatic  fascia  and  the  included  cremastermuscle  have  already 


THE   MALE   REPRODUCTIVE   APPARATUS. 


651 


been  described.  Accompanying  the  vessels  of  the  spermatic  cord  are 
isolated  longitudinal  fascicles  of  unstriped  muscle-fibres,  distinguished 
by  the  name  of  the  internal  cremaster  muscle. 

Enigmatic  appendages  of  the  testicle.  Among  the  blood-vessels 
of  the  spermatic  cord,  between  the  head  of  the  epididymis  and  the 
deferent  canal,  there  commonly  lie  two  or  three  small,  irregular,  rounded 
bodies,  which  consist  each  of  a  convoluted  tube  with  expanded  caecal 
ends.  They  have  been  named  the  par-epididymis,1  and  are  regarded 
as  vestiges  of  the  Wolffian  body  of  the  embryo. 

On  the  head  of  the  epididymis  there  is  commonly  a  little  spheroidal 
pediculate  appendage,2  which  is  regarded  as  the  remains  of  the  duct 
of  Miiller  of  the  embryo.  One  or  more  similar  clavate  appendages 
occur  on  the  top  of  the  testicle  near  or  under  the  head  of  the  epidid- 
ymis. These  sometimes  communicate  with  the  interior  of  the  testicle 
and  contain  seminal  elements. 

In  the  epididymis  there  commonly  occurs  a  long  narrow  tube,  the 
vas  aberrans,3  which  is  coiled  into  an  elongated  lobe  lying  usually 
along  the  lower  part  of  the  epididymis.  The  tube  is  mostly  closed  at 
the  upper  extremity,  and  opens  below  into  the  canal  of  the  epididymis 
or  the  commencement  of  the  deferent  canal.  Rarely  similar  vessels 
are  found  in  other  parts  of  the 
epididymis.  FlG-  326- 

The  seminal  vesicles  *  are  two 
bodies,  which  serve  as  reservoirs 
for  the  semen,  situated  nearly  ver- 
tically on  the  base  of  the  bladder, 
converging  downward  and  forward 
and  firmly  attached  to  the  base  of 
the  prostate.  They  are  very  vari- 
ble  in  size  and  shape  in  different 
individuals  and  often  on  the  two 
sides.  They  are  commonly  fore 
and  aft  compressed  elliptical,  from 
an  inch  to  two  inches  long,  a  half 
to  two-thirds  of  an  inch  where 
widest,  and  a  third  of  an  inch  or 
•more  where  thickest.  They  have 
an  uneven,  tuberculate  surface, 
flattened  in  front,  where  they  are 
closely  attached  to  the  bladder  by 

connective  tissue,  and  are  more  convex  behind,  where  they  are  less 
closely  attached  by  the  same  means  to  the  rectum.  The  upper  ex- 


POSTERIOR  VIEW  OF  THE  FUNDUS  OF  THE  BLAD- 

DEK.  1,  peritoneum  extending  as  far  down  as 
the  transverse  line ;  2,  ureters ;  3,  deferent  ca- 
nals; 4,  seminal  vesicle  of  the  left  side;  5,  right 
seminal  vesicle  dissected  so  as  to  show[its  tubu- 
lar character ;  6,  duct  of  the  seminal  vesicle, 
joining  the  deferent  canal  to  form,  7,  the  ejacu- 
latory  duct ;  8,  prostate ;  9,  membranous  portion 
of  the  urethra. 


1  Corpus  innominatum  ;  organ  of  Giraldes. 

2  Hydatid  of  Morgagni ;  hydatis  tunicse  vaginalis. 

8  V.  a.  Halleri.  4  Vesiculse  seminales. 


652          THE  MALE  REPRODUCTIVE  APPARATUS. 

tremity  is  rounded  and  most  remote  from  that  of  the  other  side,  and 
the  lower  narrowed  extremity  joins  the  deferent  canal  internally  and 
enters  the  median  pit  in  the  base  of  the  prostate.  The  outer  border  is 
convex,  free  above  and  contiguous  to  the  termination  of  the  ureter,  and 
firmly  connected  below  with  the  lateral  lobe  of  the  prostate.  The 
inner  border  below  is  closely  adherent  to  the  deferent  ampulla,  is 
sometimes  grooved  and  overlaps  the  latter  behind,  or  in  this  position 
joins  the  opposite  vesicle  and  thus  encloses  the  deferent  canals,  with 
the  bladder  in  front. 

The  narrowed  terminations  of  the  seminal  vesicles  and  intervening 
deferent  canals  are  closely  united  side  by  side  and  enter  a  compressed 
conical  pit  at  the  base  of  the  prostate  between  the  lateral  lobes  and 
behind  the  middle  lobe.  They  are  here  firmly  connected  by  connective 
tissue  and  transverse  fascicles  of  unstriped  muscular  tissue. 

Each  seminal  vesicle  consists  of  an  irregular,  tortuous  tube  about 
the  width  of  a  small  goose-quill,  wound  upon  itself  and  provided  with 
a  few  short  or  longer  csecal  branches.  The  tube  tapers  below  in  a 
short,  straight  duct,  which  joins  the  deferent  canal  to  form  the  ejacu- 
latory  duct.  It  is  enveloped  in  connective  tissue  continuous  with 
the  recto-vesical  fascia  and  containing  the  principal  blood-vessels, 
lymphatics,  and  nerves  of  the  organ.  In  structure  the  tube  resem- 
bles the  ampulla  of  the  deferent  canal.  The  muscular  coat  is  thinner 
and  consists  of  an  inner  longitudinal  and  an  outer  circular  stratum  of 
unstriped  fibres.  The  mucous  membrane  presents  a  minutely  honey- 
combed appearance  and  is  furnished  with  tubular  glands,  as  in  the 
deferent  ampulla.  The  epithelium  is  columnar,  with  a  substratum  of 
small  polyhedral  cells. 

The  seminal  vesicles  receive  branches  from  Uae  inferior  vesical  and 
middle  hemorrhoidal  arteries  and  are  accompanied  by  corresponding 
veins.  The  numerous  lymphatics  end  in  glands  at  the  side  of  the 
pelvis.  The  nerves  are  derived  from  the  hypogastric  plexus  of  the 
sympathetic. 

The  ejaculatory  duct,1  formed  on  each  side  by  the  union  of  the 
corresponding  duct  of  the  seminal  vesicle  and  deferent  canal,  is  a  taper- 
ing tube  about  three-fourths  of  an  inch  long.  From  the  pit  in  the  base 
of  the  prostate  it  proceeds  in  a  deep  groove  between  the  lateral  and 
the  middle  lobe,  converging  downward  and  lorward  to  end  in  a  minute 
elliptical  orifice,  in  the  prostatic  portion  of  the  urethra,  at  the  side  of 
the  mouth  of  the  utriculus.  The  passage  of  the  duct  at  its  commence- 
ment is  about  one-twenty-fifth  of  an  inch,  and  gradually  decreases  to 
the  termination,  where  it  is  about  one-half  that  size. 

The  wall  of  the  ejaculatory  duct  is  thin  and  consists  of  a  muscular 
coat  with  a  mucous  membrane  like  that  of  the  deferent  canal  and  semi- 
nal vesicle,  but  becoming  smooth  approaching  its  termination.  The 

1  D.  ejaculatorius. 


THE   MALE   REPRODUCTIVE   APPARATUS. 


653 


FIG.  3'27. 


muscular  coat  consists  of  an  inner  longitudinal  stratum  and  an  outer 
circular  stratum  of  fibres,  with  elastic  tissue,  and  a  venous  plexus  con- 
tinuous with  that  of  the  urethra. 

The  semen,  or  sperm.1  This  is  a  glairy,  whitish  liquid  secreted 
by  the  testicles,  mingled  with  the  mucoid  secretion  of  the  deferent 
ampullae  and  seminal  vesicles.  It  contains 
a  multitude  of  exceedingly  minute  filamen- 
tary bodies,  about  -^  of  an  inch  long,  the 
spermatozoa,2  which  constitute  the  es- 
sential element  of  the  male  in  reproduction. 
Each  spermatozoon  consists  of  a  com- 
pressed ovoid  extremity,  the  head,  about 
gQ^Q  of  an  inch  long,  succeeded  by  a  slightly 
thickened  neck  about  as  long  as  the  former 
and  then  a  long,  tapering  tail.  The  narrow 
end  of  the  head  is  free,  the  flattened  sides 
are  slightly  depressed  centrally,  giving  the 
appearance  of  a  nucleus,  and  the  tail  be- 
comes more  abruptly  narrowed  towards  the 
extremity. 

The  spermatozoa  are  endowed  to  a  won- 
derful degree  with  the  power  of  motion, 
which  persists  after  discharge  of  the  semen, 

under  favorable  circumstances,  for  several  days.  The  movement,  which 
is  of  the  nature  of  ciliary  motion,  consists  in  rapid  undulation  of  the 
tail,  by  which  the  spermatozoa  progress,  head  forward,  in  any  direction. 

Another  less  important  element  of  the  semen,  in  small  comparative 
number,  consists  of  minute  highly  refracting  globules,  the  seminal 
granules. 

The  fully-formed  semen  is  first  found  in  the  straight  seminiferous 
tubules,  thence  in  the  spermatic  rete,  the  epididymis,  and  the  deferent 
canal.  In  the  ampullae  of  the  latter  and  the  seminal  vesicles  it  accu- 
mulates prior  to  discharge. 


\ 


SPERMATOZOA.  1,  magnified  350 
diameters ;  2,  magnified  800  diam- 
eters ;  a,  viewed  on  the  narrower 
side ;  b,  on  the  broader  side. 


1  Semen  virile. 


2  Animalcula  or  filamenta  spermatica ;  spermatozoids. 


CHAPTER  XIII. 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 

IN  the  female  the  reproductive  apparatus  consists  of  the  ovaries, 
the  oviducts,  and  the  uterus  with  its  appendages,  included  together  as 
the  internal  organs  of  generation ;  and  the  vagina,  clitoris,  and  vulva, 
with  certain  accessories,  as  the  external  organs.  The  urethra  of  the 

FIG.  328 


SECTION  OF  FEMALE  PELVIS,  FROM  BEFORE  BACKWARD.  1,  sacrum ;  2,  coccyx ;  3,  pubic  sym- 
physis;  4,  rectum;  5,  one  of  its  valvular  folds;  6,  anus;  7,  uterus;  8,  vagina;  9,  right  labium; 
10,  right  nympha;  11,  clitoris,  attached  by  the  suspensory  ligament  to  the  front  of  the  pubic 
symphysis;  12,  glans;  13,  prepuce;  14,  urethra;  15,  entrance  of  the  vagina;  16,  bladder. 

female,  comparatively  very  short,  serves  alone  as  the  outlet  of  the 
urinary  bladder  and  terminates  in  the  vulva.  The  mammary  glands 
are  accessories  to  the  reproductive  apparatus. 

THE   VULVA. 

The  vulva *  occupies  the  exterior  of  the  pelvis  at  the  entrance  of 
the  genital  organs.     It  appears  as  a  triangular  prominence  with  the 


1  Pudendum ;  cunnus. 


654 


THE  FEMALE  REPRODUCTIVE  APPARATUS.         655 

base  upward  and  extends  from  the  front  of  the  pubic  symphysis  down- 
ward and  backward  between  the  thighs  to  the  perineum.  From  the 
thighs  it  is  sharply  defined  by  a  pair  of  narrow  grooves  descending 
from  the  groins  and  converging  to  the  perineum.  Its  upper  part,  rest- 
ing on  the  pubic  symphysis,  is  named  the  mons  veneris,  and  from 
this  descend  a  pair  of  rounded  columns,  the  labia,  separated  by  a 
median  cleft,  the  fissure1  or  orifice  of  the  vulva.  The  mons  is  a 
cushion-like  eminence  of  the  skin  abundantly  furnished  with  crisp 
hairs.  The  labia a  are  rounded  folds  of  the  skin,  thickest  at  their  con- 
junction with  the  mons  and  gradually  narrowing  to  their  conjunction 
in  the  perineum.  They  are  convex  outwardly  and  furnished  with 
hairs  like  those  of  the  mons,  but  fewer  and  more  scattered  and  dimin- 
ishing behind.  In  the  fissure  of  the  vulva  the  sides  are  flat  and  come 
into  contact  with  each  other,  and  the  extremities  of  the  fissure  are 
called  the  commissures.  When  the  fissure  is  expanded,  it  appears  as 
an  elliptical  orifice,  with  the  anterior  commissure  more  rounded  and 
situated  immediately  below  the  mons.  The  posterior  commissure,  at 
the  perineum,  -is  about  an  inch  in  advance  of  the  anus.  Just  within 
it,  the  labia  are  united  by  a  narrow  crescentic  fold  of  the  skin,  com- 
monly known  by  the  French  name  of  the  "  fourchette."  3  Between 
this  and  the  entrance  of  the  vagina  above  is  a  depression  called  the 
navicular  fossa.* 

The  prominence  of  the  mons  is  due  to  an  accumulation  of  areolar 
and  adipose  tissue.  The  labia  are  likewise  rendered  prominent  and 
firm  by  an  accumulation  of  the  same  materials;  but  after  repeated 
childbirth  and  in  the  aged  and  emaciated  they  become  more  or  less 
relaxed  and  flaccid.  The  mons  and  labia  further  contain  beneath  the 
skin  a  variable  yellowish  layer  of  elastic  tissue  -with  unstriped  mus- 
cular fibres,  which  corresponds  with  the  dartos  of  the  male  scrotum. 
The  skin  of  the  mons  and  labia  is  abundantly  furnished  with  large 
sebaceous  and  sweat  glands.  On  the  inner  surface  of  the  labia  it 
partakes  of  the  character  of  mucous  membrane ;  is  thin,  smooth,  red, 
and  moist. 

THE   CLITOKIS. 

The  clitoris5  is  a  reduced  representative  of  the  penis,  with  which 
it  essentially  accords  in  construction,  but  differs  in  having  its  spongy 
body  divided  and  not  enclosing  the  urethra. 

The  body  of  the  clitoris  appears  in  the  recess  at  the  upper  part  of 
the  fissure  of  the  vulva  as  a  median  rounded  ridge,  which  is  directed 
downward  from  the  anterior  commissure  and  ends  in  a  rounded  papilla, 

1  Kima  or  fissura  pudendi.  2  L.  pudendi ;  1.  majora ;  1.  externa. 

3  Navicula,  frenulum. 

4  F.  navicularis,  scaphula.    The  English  anatomists  have  it  below  the  fourchette ; 
the  French  and  German  above. 

8  Membrum  muliebre. 


656 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


the  glans.1  It  is  covered  by  the  mucous  membrane,  which  is  ex- 
tended between  the  labia  and  forms  the  prepuce  of  the  clitoris  and  the 
nymphse  below.  The  body  is  an  inch  and  a  half  in  length,  is  cylin- 
drical, and  is  composed  of  a  pair  of  cavernous  bodies2  like  those  of  the 


FIG.  329. 


FEMALE  ORGANS  OF  GENERATION  ;  the  vulva  laid  open  and  viewed  in  front ;  the  internal  organs 
turned  down  and  viewed  on  their  posterior  surface,  with  the  vagina  laid  open.  1,  labium  ;  2, 
nymphae;  3,  glans  of  the  clitoris  surrounded  by  the  prepuce;  4,  vestibule;  5,  urinary  meatus;  6, 
hymen ;  7,  posterior  wall  of  the  vagina;  8,  anterior  wall;  9,  extremity  of  the  uterus  ;  10,  fundus  of 
the  uterus;  11,  mouth  of  the  uterus;  12,  broad  ligament;  13,  portion  extending  to  the  oviduct,  14; 
15,  flmbriated  extremity;  16,  ovary ;  17,  ovarian  ligament. 

penis.  From  its  upper  part,  at  the  superior  commissure  of  the  vulva, 
the  crura,  about  as  long  as  the  body,  diverge  and  descend  to  be  con- 
nected with  the  pubic  arch  in  the  same  manner  as  those  of  the  penis. 
The  clitoris  thus  appears  like  a  tripod,  to  the  summit  of  which  the 
suspensory  ligament3  proceeds  from  the  pubic  symphysis.  The 


Glans  clitoridis. 

Lig.  suspensorium  clitoridis. 


a  Corpora  cavernosa  clitoridis. 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


657 


FIG.  330. 


composition  of  the  cavernous  bodies,  and  their  muscles,  vessels,  and 
nerves,  are  the  same  as  in  the  penis. 

The  glans  of  the  clitoris  consists  of  a  little  mass  of  erectile  tissue 
at  the  lower  extremity  of  the  or- 
gan, invested  by  a  reflection  of  the 
mucous  membi*ane,  which  is  con- 
tinuous with  that  of  the  prepuce. 

The  spongy  body1  of  the  clit- 
oris chiefly  consists  of  a  pair  of 
flattened  elliptical  masses,  the 
semi-bulbs,2  which  are  over  an 
inch  long  and  less  than  half  as  wide 
and  are  composed  of  erectile  tissue 
enclosed  in  a  fibrous  membrane. 
They  appear  to  be  suspended 
from  behind  the  body  of  the  clit- 
oris, from  which  they  extend  be- 
neath the  vestibule  downward  at 
the  sides  of  the  entrance  of  the 
vagina  behind  the  nymphae.  They 
are  widest  and  are  rounded  below 
and  are  narrowest  at  the  upper 
extremity,  where  they  are  con- 
tinuous with  a  plexus  of  vessels3 
which  join  those  of  the  glans.  The 

vessels  and  nerves  of  the  spongy  body  likewise  correspond  with  those 
of  the  same  part  of  the  penis. 

Nymphae.4  These  are  a  pair  of  conspicuous  falcate  folds  of  the 
mucous  membrane  within  the  fissure  of  the  vulva.  Starting  from  the 
lower  end  of  the  clitoris,  they  diverge,  extend  backward,  and  narrow 
away  at  the  sides  of  the  entrance  of  the  vagina.  Externally  they  lie 
in  contact  with  the  inner  surface  of  the  labia  and  are  continuous  with 
them ;  internally  they  are  continuous  with  the  vestibule  and  vagina. 
At  their  upper  extremity  they  fork  and  together  encircle  the  glans  to 
form  the  prepuce,5  which  is  free  from  the  glans  in  front  but  joins  it 
behind.  Commonly  the  nymphae  are  concealed  within  the  vulva,  but 
sometimes  they  are  larger  than  usual  and  project  more  or  less  from  the 
fissure.  In  such  cases  the  exposed  part  assumes  the  appearance  of  the 
skin.  In  some  of  the  African  tribes,  as  the  Hottentots,  the  nymphae 
are  reputed  to  be  greatly  enlarged  and  to  project  from  the  vulva  to  the 
extent  of  from  three  to  six  inches.  It  is  also  stated  that  the  operation 
of  circumcision  in  the  women  of  Abyssinia  refers  to  the  removal  of 
enlarged  nymphae. 


EXTERNAL  ORGANS  OF  GENERATION.  1,  right 
pubis;  2,  tuberosity  of  the  ischium;  3,  sym- 
physis  of  the  pubes ;  4,  left  half  of  the  mons 
veneris ;  5,  left  labium  ;  6,  clitoris ;  7,  cms  of 
the  right  cavernous  body  ;  8,  suspensory  liga- 
ment; 9,  dorsal  vein;  10,  glans;  11,  pedicle  of 
the  right  half  of  the  spongy  body;  12,  right 
semi-bulb ;  13,  left  nympha,  terminating  above 
in  the  prepuce ;  14,  urethral  orifice  at  the  base 
of  the  vestibule ;  15,  vagina ;  16,  right '  sub- 
urethral  gland. 


1  Corpus  cavernosum  uretrae. 
4  Labia  minora  ;  1.  interim. 


1  Bulbi  vestibuli.  s  Pars  intermedia. 

5  Prseputium  clitoridis. 

42 


658  THE   FEMALE   REPRODUCTIVE   APPARATUS. 

Vestibule.1  Below  the  clitoris  and  in  advance  of  the  orifice  of  the 
vagina  the  interval  of  the  nymphaa  forms  a  triangular  recess  of  the 
mucous  membrane,  named  the  vestibule.  At  the  middle  of  its  base 
immediately  in  front  of  the  orifice  of  the  vagina  is  the  orifice  of  the 
urethra,2  a  round  aperture  usually  marked  by  a  rounded  and  variably 
prominent,  wrinkled,  papillary  eminence. 

At  the  back  part  of  the  fissure  of  the  vulva,  extending  to  within 
about  half  an  inch  of  the  posterior  commissure,  is  the  orifice  of  the 
vagina.  This  is  an  oval  aperture,  which  in  the  virgin  is  commonly 
more  or  less  narrowed  by  a  thin  fold  of  the  mucous  membrane,  called 
the  hymen,3  variable  in  its  form  and  development.  It  is  usually  cres- 
centic,  with  the  concave  edge  directed  forward,  but  sometimes  annular, 
of  variable  breadth,  and  with  an  irregular,  rounded  opening  commonly 
in  advance  of  the  centre.  Occasionally  it  is  pierced  with  several  aper- 
tures, rarely  is  completely  imperforate,  and  sometimes  is  almost  obso- 
lete. In  intercourse  it  is  ordinarily  ruptured,  and  after  parturition  its 
remains  appear  as  papillary  eminences,  which  are  called  the  myrtiform 
caruncles.4 

The  lining  mucous  membrane  of  the  vulva  is  red,  smooth,  and  pro- 
vided with  a  squamous  epithelium,  beneath  which"*R,  is,  furnished  with 
minute  papillae,  which  are  most  numerous  and  largest  on  the  inner 
surface  of  the  nymphae.  It  is  also  supplied  with  sebaceous  glands, 
which  are  most  numerous  on  the  inner  surface  of  the  nymphge. 

Suburethral  glands.5  These  are  two  variable,  flattened  oval  or 
rounded  bodies,  commonly  about  half  an  inch  in  their  largest  diameter ; 
of  a  reddish-yellow  color,  and  situated  near  the  entrance  of  the  vagina, 
behind  the  lower  extremity  of  the  semi-bulbs  of  the  spongy  body. 
They  are  lobulated,  racemose  glands,  and  their  duct,  about  half  an  inch 
long,, is  directed  forward  and  opens  near  the  orifice  of  the  vagina,  on 
the  inner  surface  of  the  nymphse. 

Vessels  and  nerves.  The  vulva  is  supplied  by  the  external 
pudic  and  perineal  arteries,  and  the  deeper  parts,  as  in  the  male,  by 
corresponding  branches  of  the  internal  pudic  arteries.  The  veins  also 
have  the  same  general  arrangement.  The  dorsal  vein  of  the  clitoris 
receives  branches  from  the  glans,  the  cavernous  bodies,  and  the  semi- 
bulbs  of  the  spongy  body.  Veins  of  the  latter  also  pass  back  to  the 
vaginal  plexus.  The  lymphatics  follow  the  course  of  the  blood-vessels. 
The  nerves  are  derived  from  the  genito-crural,  inferior  pudendal,  and 
pudics,  while  branches  of  the  sympathetic  accompany  the  arteries. 

The  urethra.  A  comparatively  short  canal  in  the  female,  about 
an  inch  and  a  half  long  and  a  fourth  of  an  inch  wide,  descends  from  the 
bladder  in  the  anterior  wall  of  the  vagina.  Curving  slightly  forward, 

1  Vestibulum  pudendi.  2  Orificium  uretrse  ;  meatus  urinarius. 

3  Valvula  vaginae ;  maidenhead.  4  Carunculae  myrtiformes. 

5  Vulvo-vaginal  glands ;  glands  of  Cowper,  of  Bartholin,  of  Duverney,  etc. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          659 

it  ends  near  the  base  of  the  vestibule  in  the  fissure  of  the  vulva,  its 
terminal  orifice *  being  usually  marked  by  a  papillary  elevation  of  the 
mucous  membrane. 

The  lining  mucous  membrane  is  longitudinally  folded,  is  furnished 
with  many  mucous  glands,  and  is  provided  with  a  stratified  squamous 
epithelium.  It  is  sustained  by  a  fibro-connective- tissue  layer  with 
elastic  fibres,  outside  of  which  is  a  vascular  plexus  consisting  mostly 
of  veins.  As  the  urethra  passes  through  the  triangular  ligament  be- 
tween the  layers  it  is  ensheathed  by  the  urethral  compressor  muscle. 

The  vessels  and  nerves  of  the  urethra  are  derived  from  the  same 
sources  as  those  of  the  vagina. 

THE   VAGINA. 

The  vagina  is  a  musculo-membranous  passage  within  the  pelvis, 
communicating  from  the  vulva  below  to  the  uterus  above.  It  is  di- 
rected obliquely  backward  and  upward  between  the  bladder  in  front 
and  the  rectum  behind,  and  together  with  these  is  enclosed  at  the  sides 
by  the  anal  elevator  muscles.  Slightly  curved  in  its  course,  its  axis  cor- 
responds with  that  of  the  pelvic  cavity  and  its  outlet.  Ordinarily  the 
cavity  of  the  vagina  does  not  exist  as  such,  and  the  inner  surfaces  for 
the  most  part  lie  fore  and  aft  in  contact  with  each  other.  When  ex- 
panded it  is  club-shaped,  being  narrowest  at  the  lower  end,  and  gradu- 
ally expanded  above  to  the  summit,  where  it  is  rounded  and  receives 
the  extremity  of  the  uterus.  In  the  virgin,  from  the  orifice  of  the 
hymen  it  expands  in  a  hemi-oval,  widest  fore  and  aft,  but  at  the  middle 
is  widest  transversely.  Its  upper  extremity  embraces  the  neck  of  the 
uterus,  with  which  it  is  continuous,  and  it  is  attached  at  a  higher  point 
behind  than  in  front.  From  the  direction  and  curve  of  the  vagina  and 
its  higher  attachment  to  the  uterus  at  the  back  part,  it  is  an  inch  or 
more  longer  behind  than  in  front.  Commonly  it  is  about  four  inches 
in  length  at  the  fore  part  and  from  five  to  five  and  a  half  inches  at 
the  back. 

The  wall  of  the  vagina  is  not  of  uniform  thickness,  and  is  thinnest 
above,  where  it  is  about  a  line,  and  is  thickest  at  the  lower  extremity 
and  especially  in  front,  where  it  is  intimately  connected  with  the  neck 
of  the  bladder  and  encloses  the  urethra.  Behind,  it  is  loosely  attached 
by  connective  tissue  with  the  rectum,  but  for  an  inch  or  more  at  the 
upper  part  is  separated  from  the  latter  by  a  peritoneal  fold,  the  recto- 
vaginal  pouch.2 

The  vagina  is  lined  with  mucous  membrane  continuous  below  with 
that  of  the  vulva,  and  above  with  that  of  the  uterus.  It  is  red  or  red- 
dish gray,  and  in  the  virgin  state  is  more  or  less  rugose  below,  but 
nearly  or  quite  smooth  above.  At  the  lower  extremity,  both  in  front 
and  behind,  it  presents  a  variably  prominent  median  ridge,  named  the 

1  Meatus  urinarius.  2  Pouch  of  Douglas. 


660          THE  FEMALE  REPRODUCTIVE  APPARATUS. 

column  of  the  vagina.1  This  is  thick  and  rounded  near  the  hymen, 
or  the  remains  of  it  at  the  orifice  of  the  vagina,  and  tapers  away 
towards  the  middle  of  the  latter. 

Of  the  two  columns  the  anterior  is  usually  the  more  marked  and 
constant.  From  both  numerous  folds2  more  or  less  broken,  or  rows  of 
oblong  papillae,  proceed  transversely  and  upward  towards  the  sides  of 
the  vagina,  gradually  diminishing  and  at  the  upper  part  completely 
subsiding.  These  folds  or  papillae  possess  a  certain  amount  of  firmness 
unusual  in  similar  processes  of  the  mucous  membranes.  From  the 
distention  of  the  vagina  attending  parturition  the  folds  are  perma- 
nently obliterated ;  and  this  also  is  the  case,  for  the  most  part,  with 
the  columns  of  the  vagina,  the  lower  thickened  ends  of  which  alone 
persist. 

The  mucous  membrane  of  the  vagina  has  a  stratified  squamous 
epithelium,  beneath  which  it  is  furnished  with  minute  papillae.  Ac- 
cording to  both  Henle  and  Sappey,  it  is  not  provided  with  mucous 
glands,  though  others  assert  the  contrary.3 

Externally  the  vagina  is  furnished  wijii  a  thin  but  moderately  firm 
fibrous  tunic  composed  of  an  intertexture  of  connective-tissue  bundles 
with  mingled  elastic  fibres. 

The  intermediate  tunic  of  the  vagina,  forming  two-thirds  the  thick- 
ness of  its  wall,  is  muscular,  and  consists  of  an  outer  layer  of  longitu- 
dinal bundles  of  unstriped  fibres  and  an  inner  layer  of  circular  bundles, 
with  oblique  bundles  connecting  the  layers.4  The  longitudinal  bundles 
are  especially  abundant  in  the  anterior  wall  of  the  vagina,  where  it 
is  connected  with  the  bladder. 

The  mucosa  of  the  mucous  membrane  also  contains  intermingled 
unstriped  muscular  fibres. 

The  lower  extremity  of  the  vagina  is  likewise  enclosed  by  the 
sphincter  muscle.  (See  page  678.) 

A  close  venous  plexus  occupies  the  external  fibrous  tunic  next  the 
muscular  tunic,  whence  fibres  proceed  through  the  meshes  of  the 
plexus. 

Vessels  and  nerves.  The  vagina  is  highly  vascular,  and  its 
arteries  are  chiefly  supplied  by  the  vaginal  branch  of  the  internal  iliac 
artery.  The  veins  derived  from  the  vaginal  plexus  take  a  corresponding 
course.  The  lymphatics  likewise  join  those  accompanying  the  internal 
iliac  blood-vessels.  The  numerous  nerves  mostly  proceed  from  the 
hypogastric  plexus,  but  others  are  derived  from  the  fourth  sacral  and 
the  pudic  nerves. 


1  Columna  vaginalis  ;  c.  carneopapillosa. 

2  Kugse;  columna  rugarum  ;  c.  plicarum. 

3  Quain's  Anatomy  states  that  it  is  provided  with  numerous  mucous  glands, 
especially  in  its  upper,  smoother  portion  and  round  the  neck  of  the  uterus. 

*  Henle  says  the  two  layers  hold  the  reverse  position. 


THE  FEMALE   EEPKODUCTIVE  APPAEATUS. 


661 


THE  UTEEUS. 

The  uterus,1  or  womb,  is  the  receptacle  in  which  the  embryo,  or 
offspring,  undergoes  development  from  the  egg.  In  its  ordinary  condi- 
tion at  maturity  it  appears  as  a  flattened  pear-shaped  body,  and  it  has 
an  interior  narrow  cleft-like  cavity  enclosed  by  thick,  compact  walls.  It 
is  situated  within  the  pelvis  between  the  bladder  and  the  rectum,  and 
below  joins  the  vagina,  into  which  its  cavity  opens.  From  the  vagina, 
the  uterus  with  its  long  axis  is  directed  obliquely  forward  and  upward 
in  the  axis  of  the  inlet  of  the  pelvis,  from  which  it  variably  inclines 
according  as  it  may  be  affected  by  the  more  or  less  distended  condition 
of  the  bladder.  The  larger  portion,  or  body/  of  the  uterus  is  upward 


10 


5  5 

VIRGIN  UTERUS  AT  MATURITY  ;  two-thirds  size.  A,  anterior  view ;  B,  fore  and  aft  median  sec- 
tion, looking  at  the  left  half;  C,  vertical  section  from  side  to  side.  1,  body  of  the  uterus ;  2,  cavity 
of  the  body;  3,  neck ;  4,  cavity  of  the  neck ;  5,  mouth  of  the  uterus  ;  6,  anterior  lip;  7,  posterior 
lip;  8,  oviduct;  9,  peritoneum;  10,  vagina  laid  open. 

and  projects  free  into  the  pelvic  cavity,  lying  in  contact  with  the  blad- 
der in  front,  the  rectum  behind,  and  the  small  intestine  above ;  while 
the  narrow  portion,  or  neck,3  is  downward  and  is  embraced  by  the 
vagina,  into  which  its  end  projects.  The  -uterus  is  enclosed  and  in  a 
measure  retained  in  its  median  position  by  a  broad  fold  of  the  peri- 
toneum, which  extends  from  its  sides  to  those  of  the  pelvis  as  the 
broad  ligaments.  The  peritoneum  closely  and  smoothly  invests  the 
body  above,  in  front  and  behind,  and  from  its  lower  part  is  reflected 
to  the  bladder ;  but  at  the  back  part  descends  to  the  vagina  and  is 
thence  reflected  to  the  rectum. 

The  size  of  the  uterus  in  the  usual  condition  at  maturity  is  about 
three  inches  long,  two  inches  where  widest  from  side  to  side,  and 


1  Matrix,  hystera,  metra. 


Corpus. 


3  Cervix ;  collum. 


662 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


nearly  an  inch  thick  fore  and  aft.  In  the  uterus  which  has  been  par- 
turient the  body  is  larger  and  the  neck  about  a  third  of  the  length  of 
the  whole ;  in  the  virgin  the  body  is  proportionately  narrower  and  the 
neck  longer,  or  two-fifths  of  the  whole.  In  infancy  the  uterus  is  less 
pyriform  and  more  cylindroid,  and  the  neck  is  larger  and  longer  than 
the  body. 

From  the  upper  part  of  the  sides  of  the  uterus  the  oviducts,  or  fal- 
lopian tubes,  proceed  outwardly  enclosed  within  the  upper  border  of 
the  broad  ligaments,  and  near  the  same  points  the  round  and  ovarian 
ligaments  are  attached.  The  convex  portion  of  the  body  projecting 
above  the  oviducts  is  the  fundus,1  and  from  this  the  convex  sides  grad- 
ually narrow  to  the  neck.  The  anterior  surface  of  the  body  is  slightly 
convex  and  the  posterior  is  considerably  more  so.  The  neck  is  flattened 

FIG.  332. 


UTERUS  WHICH  HAS  GIVEN  CHILDBIRTH:  two-thirds  size.  A,  anterior  view  of  the  uterus;  B, 
vertical  section  from,  side  to  side.  1,  body  of  the  uterus ;  2,  cavity  of  the  body ;  3,  neck ;  4,  cavity 
of  the  neck ;  5,  mouth  of  the  uterus ;  6,  vagina  laid  open  ;  7,  oviducts ;  8,  peritoneum. 

cylindroid,  or  in  the  virgin  somewhat  widened  at  the  middle  so  as  to 
appear  more  oval.  The  lower  rounded  extremity  projects  into  the 
vagina,  where  it  presents  a  central  funnel-like  depression  with  a  round 
or  transverse  oval  aperture,  which  is  the  mouth  of  the  uterus.2  This 
is  enclosed  by  a  thick  convex  border  forming  the  lips,  of  which  the 
anterior  descends  lower  in  the  vagina,  though  the  posterior  appears 
the  longer  from  the  higher  attachment  of  the  latter  behind.  From  the 
obliquity  of  the  uterus  and  the  different  depths  to  which  the  lips 
descend,  both  come  into  contact  with  the  posterior  wall  of  the  vagina, 
and  the  mouth  is  directed  backward  and  downward.  The  mucous 
membrane  of  the  vagina  is  smoothly  extended  over  the  lips  to  the 
mouth  of  the  uterus.  After  childbirth  the  mouth  of  the  uterus  is 
larger,  transversely  elliptical,  and  often  appears  roughened. 


1  Basis  uteri. 


2  Os  uteri  externum  ;  os  tineas ;  orificium  vaginale. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          663 

In  the  body  of  the  uterus  the  cavity  extends  from  side  to  side  as  a 
broad  triangular  cleft,  and  in  a  vertical  fore  and  aft  section  of  the 
organ  appears  as  a  linear,  nearly  straight  slit.  The  base  of  the  trian- 
gular cavity  at  the  fundus.and  the  sides  are  convex  inward,  while  the 
flat  surfaces  in  front  and  behind  come  into  contact.  The  upper  angles 
are  prolonged  into  narrow  canals  continued  into  the  oviducts,  and  the 
lower  angle  descends  into  the  cavity  of  the  neck,  the  communication 
being  slightly  narrowed,  and  distinguished  as  the  internal  orifice1 
of  the  uterus. 

The  cavity  of  the  neck2  in  the  virgin  uterus  is  elliptical,  and 
widest  from  side  to  side.  In  the  uterus  which  has  been  parturient  it 
widens  downward  to  the  transversely  elliptical  mouth. 

The  inner  surface  of  the  cavity  of  the  body  is  dull  reddish,  ordina- 
rily smooth  and  finely  punctate.  In  the  cavity  of  the  neck,  both  in 
front  and*  behind,  it  presents  a  median  longitudinal  fold,  from  which 
a  number  of  oblique  folds  ascend  at  the  sides,  giving  rise  to  a  tree-like 
appearance,  named  the  arbor  vitse. 

After  death  the  uterus  commonly  appears  more  or  less  hard  and 
rigid,  which  does  not  accord  with  its  condition  in  life,  when  it  is  softer 
and  flexible,  and  the  body  readily  bends  backward  or  forward  on  the 
neck. 

Structure.  The  walls  of  the  uterus  consist  of  an  outer  thin  serous 
layer  derived  from  the  peritoneum,  an  inner  lining  mucous  membrane, 
and  an  intermediate  muscular  layer,  which  forms  four-fifths  or  more  of 
their  thickness.  The  three  layers  are  closely  united,  and  are  not  readily 
separated. 

The  muscular  layer  is  composed  of  bundles  of  unstriped  fibres,  the 
course  of  which  differs  in  different  parts,  and  is  obscurely  defined. 
According  to  Henle,  it  consists  of  three  strata.  On  the  body  a  thin 
superficial  stratum  consists  chiefly  of  longitudinal  fibres,  in  the  deeper 
part  mingled  with  oblique  fibres.  The  succeeding  strata  are  thick,  and 
mainly  consist  of  circular  bundles  of  fibres  with  numerous  small  longi- 
tudinal and  oblique  bundles.  Usually  the  deeper  strata  on  the  body 
consist  of  circular  bundles  in  the  vicinity  of  the  oviducts  and  thence 
approach  from  opposite  sides  to  the  middle  of  the  uterus.  In  the 
neck  the  three  strata  consist  of  an  outer  and  an  inner  longitudinal  and 
an  intermediate  circular  stratum.  All  the  strata  are  intimately  asso- 
ciated through  an  intertexture  of  bundles  of  fibres.  From  the  outer 
stratum  bundles  pass  into  the  contiguous  parts,  the  oviducts,  the  round 
ligaments,  and  the  wall  of  the  vagina. 

The  mucous  membrane  of  the  cavity  of  the  body  and  upper  part  of 
the  neck  of  the  uterus  is  furnished  with  an  epithelium  consisting  of  a 
single  layer  of  ciliated  columnar  cells.  In  the  vaginal  extremity  of 
the  neck  extending  to  the  middle  it  has  the  same  kind  of  epithelium  as 

1  Os  uteri  internum  ;  ostium  or  isthmus  uteri.  2  Canalis  cervicis. 


664          THE  FEMALE  REPRODUCTIVE  APPARATUS. 

that  of  the  vagina.  The  mucous  membrane  is  provided  with  numer- 
ous glands,  the  uterine  glands.  These  are  simple  cylindrical  tubes, 
which  descend  in  the  thickness  of  the  membrane  in  a  somewhat  tort- 
uous or  convoluted  course  and  terminate  in  a  single  or  forked  csecal 
dilatation.  They  are  lined  with  a  layer  of  epithelium  like  that  of  the 
uterine  cavity.  The  glands  are  embedded  in  the  connective  tissue  of 
the  mucosa,  which  also  serves  as  a  matrix  for  the  blood-vessels.  During 
menstruation  and  pregnancy  the  uterine  mucous  membrane  becomes 
much  thickened,  and  the  glands  much  elongated  and  enlarged.  The 
mucous  membrane  of  the  neck  is  likewise  provided  with  tubular  glands 
which  accord  in  structure  with  those  of  the  body  of  the  uterus.  Not 
unfrequently  in  the  aged  some  of  these  glands  are  observed  to  be 
transformed  into  little  cysts,  which  are  of  no  interest  other  than  that 
they  formerly  were  regarded  as  eggs1  which  had  dropped  from  the 
body  of  the  uterus. 

During  pregnancy  the  glands  of  the  neck  secrete  a  tenacious  yellow 
mucus,  which  serves  to  plug  up  the  mouth  of  the  uterus. 

The  broad  ligaments.2  These  extend  from  the  sides  of  the  uterus 
as  a  double  layer  of  the  peritoneum  to  the  sides  of  the  pelvis,  dividing 
the  cavity  of  the  latter  into  two  portions,  of  which  the  anterior  con- 
tains the  bladder  and  the  posterior  the  rectum.  Approaching  the  bot- 
tom of  the  pelvis,  they  are  continued  into  the  vesico-uterine  and  recto- 
uterine  folds.  The  two  peritoneal  layers  of  the  broad  ligaments  are 
united  by  connective  tissue  containing  unstriped  muscular  fibres  pro- 
longed from  the  walls  of  the  uterus  and  mostly  pursuing  a  transverse 
direction.  This  intermediate  stratum  is  pervaded  by  the  vessels  and 
nerves  of  the  uterus,  vagina,  and  ovaries. 

Along  the  upper  folded  border  of  the  broad  ligament  runs  the  ovi- 
duct, and  near  it,  starting  from  the  uterus  a  little  lower  in  front,  is  the 
round  ligament.  Projecting  from  it  behind  is  the  ovary,  which  is 
further  connected  with  the  uterus  by  the  ovarian  ligament  immediately 
behind  and  below  the  connection  of  the  oviduct. 

The  round  ligaments3  are  flat,  fibre-muscular  cords,  which  trav- 
erse the  broad  ligaments,  occupying  a  slight  superficial  fold  in  the  an- 
terior layer.  Each  starts  from  the  ftmdus  of  the  uterus  in  front  of 
the  oviduct  and  proceeds  outward  and  forward  to  the  inguinal  canal, 
through  which  it  continues  of  diminished  size  to  finally  end  in  the 
tissues  of  the  mons  veneris.  They  are  five  or  six  inches  long,  and  are 
composed  of  connective  with  elastic  tissue,  and  unstriped  muscular 
fibres  proceeding  from  the  wall  of  the  uterus  and  joined  in  their  course 
by  some  striped  fibres. 

Vessels  and  nerves.  The  uterus  is  supplied  by  the  ovarian  and 
uterine  arteries,  which  reach  the  organ  through  the  broad  ligaments 

1  Ovula  Nabothi ;  glandulae  Nabothi. 

2  Ligamenta  lata ;  alse  vespertilionis.  3  Ligamenta  rotunda. 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


665 


FIG.  333. 


and  enter  its  sides  in  numerous  branches.  Pursuing  a  remarkably  tort- 
uous course  and  frequently  anastomosing,  they  are  distributed  through- 
out the  thick  muscular  layer  and  the  mucous  membrane,  and  in  the 
latter  terminate  in  a  superficial  net-work  of  large  capillaries.  The 
veins  correspond  with  the  arteries,  but  are  much  larger.  As  they 
emerge  from  the  muscular  wall  they  form  an  intricate  superficial  plexus, 
from  which  the  chief  veins  pursue  the  course  of  the  principal  arteries. 
The  lymphatics  commence  as  clefts  and  vessels  in  both  the  mucous 
membrane  and  muscular  layer,  and  communicate  with  a  superficial 
plexus  from  which  the  chief  vessels  accompany  the  corresponding 
blood-vessels.  The  nerves  are  derived  from  the  hypogastric  and 
ovarian  plexuses,  and  consist  of  both  medullated  and  non-medullated 
fibres. 

Periodic  changes  in  the  uterus.  The  function  of  menstruation 
is  accompanied  by  changes  in  the  condition  of  the  uterus.  From  tur- 
gescence  of  the  vessels  the  organ 
becomes  somewhat  enlarged.  At 
the  same  time  the  mucous  mem- 
brane of  the  cavity  of  the  body  is 
thickened,  softens,  undergoes  dis- 
integration, and  is  shed ;  its  prod- 
ucts, together  with  blood  from  the 
ruptured  capillaries,  forming  the 
menstrual  discharge.  The  process 
commences  at  the  inner  orifice  of 
the  uterus  and  thence  proceeds  to 
the  fundus,  and  in  the  subsequent 
repair  the  same  course  is  pursued. 
The  destruction  of  the  mucous 
membrane  extends  deeply,  and  its 
reproduction  takes  place  from  the 
deeper  epithelial  cell-elements. 

In  pregnancy  still  more  re- 
markable changes  occur  in  the 
uterus.  Gradually  enlarging,  it 
becomes  egg-shaped,  and  finally 
over  a  foot  in  length,  eight  or  nine 
inches  in  breadth,  and  from  one 
and  a  half  to  two  or  three  pounds 
in  weight.  Rising  from  the  pelvis 
into  the  abdomen,  the  small  intes- 
tine is  displaced  backward  and  the 

abdominal  parietes  are  greatly  distended.  The  wall  of  the  uterus  loses 
its  compact  texture  and  becomes  loose,  spongy,  more  extensible,  and 
darker.  The  blood-vessels  greatly  increase  in  size,  especially  the  veins, 
and  the  arteries  are  exceedingly  tortuous.  The  lymphatics  and  nerves 


MUSCLE-FIBRE  CELLS  OF  THE  UTERUS,  in  the 
fifth  month  of  pregnancy,  a,  preformative 
muscle-cells;  b,  young  muscle- fibres;  c,  more 
developed  muscle-fibres.  Magnified  350  diam- 
eters. 


666 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


also  increase.  In  the  muscular  structure  the  bundles  are  rendered  more 
evident,  and  the  fibres  enlarge  to  seven  times  their  former  length 
and  from  three  to  five  times  the  breadth,  while  new  fibres  are  added. 
The  round  ligaments  likewise  are  greatly  enlarged  and  their  muscular 
structure  made  more  distinct.  The  broad  ligaments  expand  with  the 
enlarging  uterus  and  also  become  more  extended.  The  mucous  mem- 
brane of  the  cavity  of  the  body  of  the  uterus  undergoes  transformation, 
gives  rise  to  the  production  of  the  decidua  and  contributes  to  the 
formation  of  the  placenta,  both  essential  to  the  development  of  the 
new  being.  After  parturition  the  uterus  rapidly  subsides,  and  with  its 
appendages  gradually  approximates  the  original  condition,  though  the 
uterus  subsequently  remains  several  times  larger  than  it  was  before 
impregnation.  The  enlarged  muscular  bundles  degenerate  and  are 
absorbed,  to  be  replaced  by  new  ones. 

THE   OVIDUCTS. 

The  oviducts,  or  fallopian  tubes,1  are  enclosed  within  the  upper 
free  border  of  the  broad  ligaments,  and  serve  as  a  communication  be- 

FIG.  334. 


OVARY,  PAKOVARIUM,  AND  OVIDUCT  OF  THE  LEFT  SIDE.  1,  broad  ligament ;  2,  oviduct ;  3,  its 
canal ;  4,  its  pavilion ;  5,  mouth  of  the  latter ;  6,  process  attached  to  the  ovary,  7 ;  8,  ovarian  liga- 
ment; 9,  orifice  from  which  an  ovum  had  recently  escaped;  10,  a  cicatrix;  11,  parovarium;  12, 
remains  of  the  duct  of  Mtiller.  From  a  virgin  about  eighteen  years  of  age. 

tween  the  ovaries  and  uterus.  Commencing  at  the  upper  angles  of 
the  latter  they  proceed  outward,  are  flexuose  in  their  course,  and  then 
curve  downward,  backward,  and  inward  towards  the  ovary.  To  the 
outer  side  they  terminate  in  a  widely-expanded '  and  open  trumpet- 
like  mouth,  named  the  pavilion,2  or,  from  its  deeply-fringed  border,  the 
fimbriated  extremity.3  The  oviducts  range  from  three  to  five  inches 


1  Tubae  ;  t.  uterinae ;  t.  Fallopiae  ;  cornua  uteri. 

2  Of  the  French  anatomists.     Infundibulum  ;  trumpet.          8  Morsus  diaboli. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          667 

in  length,  and  are  about  a  tenth  of  an  inch  thick  at  their  commence- 
ment, from  which  they  gradually  increase  to  about  the  fourth  of  an  inch 
or  more,  when  they  become  again  slightly  narrowed,  and  then  abruptly 
expand  in  the  pavilion.  Their  capacity  is  variable,  and  usually  at  the 
commencement1  in  the  uterus  they  barely  admit  an  ordinary  bristle; 
but  gradually  enlarge  to  the  pavilion,  where  they  contract  to  a  round 
aperture,  from  one  to  three  lines  in  diameter,  communicating  with  the 
abdominal  cavity,  and  hence  named  the  abdominal  orifice.2  The 
pavilion  hangs  movably  free  from  the  broad  ligament,  directed  down- 
ward and  backward,  with  its  mouth  inward  towards  the  ovary.  Its 
breadth  is  very  variable,  but  commonly  about  three-fourths  of  an  inch 
or  more,  and  by  a  narrow  prolongation  is  extended  and  connected  with 
the  outer  extremity  of  the  ovary. 

The  lining  mucous  membrane  of  the  oviducts  is  finely  folded,  and 
that  to  such  a  degree  that  the  folds  fill  up  their  cavity.  From  the 
abdominal  orifice  the  folds  multiply,  enlarge,  and  radiate  within  the 
pavilion,  whence  they  are  extended  in  numerous  irregular  laminar 
processes3  of  different  lengths  to  form  the  fimbriated  border.  The 
mucous  membrane  is  rose-colored,  is  provided  with  a  ciliated  columnar 
epithelium  like  that  of  the  uterus,  but  contains  no  glands. 

The  exterior  of  the  pavilion  with  its  fimbriated  border  is  invested 
with  the  peritoneal  extension  of  the  broad  ligament,  is  white,  and  is 
furnished  with  the  usual  pavement  endothelium  of  serous  membranes. 

The  oviducts  are  provided  with  a  muscular  coat,  to  which  the  lining 
mucous  membrane  is  closely  adherent.  The  muscular  coat,  of  unstriped 
fibres,  is  composed  of  an  outer  longitudinal  layer  extending  from  that 
of  the  wall  of  the  uterus  and  an  inner  layer  of  circular  bundles. 

The  ovarian  artery  in  its  course  along  the  oviduct  supplies  it  with 
numerous  branches.  The  emerging  venous  branches  join  the  ovarian 
vein.  The  lymphatics  join  those  of  the  uterus  and  ovary.  The  nu- 
merous nerves  are  derived  from  the  sympathetic  plexus  accompanying 
the  ovarian  blood-vessels. 

THE   OVAEIES. 

The  ovaries*  are  the  organs  from  which  the  ova,  or  eggs,  are  de- 
rived, and  are  two  flattened  oval  bodies  suspended  one  on  each  side 
from  behind  the  broad  ligaments.  They  are  placed  behind  and  below 
the  oviducts  next  to  the  rectum,  and  have  their  long  diameter  directed 
obliquely  between  the  fundus  of  the  uterus  and  the  pavilion  of  the 
oviduct.  They  are  attached  to  the  broad  ligament  along  their  anterior 
border,  which  is  narrow  and  nearly  straight,  and  forms  their  hilus, 
or  position  along  which  the  vessels  and  nerves  enter  the  organ.  Else- 
where they  are  free,  and  their  posterior  border,  which  is  thick  and  con- 

1  Ostium  uterinum.  2  O.  abdominale. 

8  Fimbriae,  laciniae.  *  Sing.,  ovarium  ;  pi.,  ovaria  ;  testes  muliebres. 


668         THE  FEMALE  BEPEODUCTIVE  APPAEATUS. 

vex,  is  directed  upward.  Of  the  broad  convex  surfaces,  one  is  directed 
upward  and  forward  and  the  other  downward  and  backward.  The 
inner,  narrower  extremity  is  connected  with  the  uterus  by  the  ovarian 
ligament,  and  its  outer,  more  rounded  extremity  is  connected  with  a 
prolongation  of  the  pavilion  of  the  oviduct. 

The  ovaries  are  variable  in  size  in  different  individuals.  Commonly 
they  are  about  an  inch  and  a  half  long,  three-fourths  of  an  inch  between 
the  anterior  and  posterior  borders,  and  half  an  inch  thick.  The  weight 
is  proportioned  to  the  size,  and  ordinarily  each  ovary  ranges  from  sixty 
grains  to  twice  that  much. 

The  ovaries,  prior  to  the  commencement  of  menstruation,  are  even, 
white,  and  shining.  After  puberty,  from  the  periodic  escape  of  ova 
and  the  subsequent  reparation  and  formation  of  cicatrices,  they  grad- 
ually become  more  or  less  uneven.  After  middle  age  they  often  appear 
irregularly  furrowed  and  tuberculate,  and  yellowish  or  brownish  in 
color. 

The  ovarian  ligament  is  a  cord  which  attaches  the  inner,  narrower 
end  of  the  ovary  with  the  fundus  of  the  uterus  immediately  below  and 
behind  the  oviduct.  It  is  about  an  inch  and  a  half  long,  often  more  or 
less,  is  composed  of  bundles  of  connective  tissue  and  unstriped  mus- 
cular fibres,  and  is  enclosed  in  a  superficial  fold  of  the  posterior  layer 
of  the  broad  ligament. 

Structure.  The  ovary  is  composed  of  an  interior  reddish  spongy 
stroma  with  an  outer  more  compact,  paler  layer,  in  which  the  ovisacs 

containing  the  ova  are  embedded,  whence 
it  is  named  the  ovigenous  layer.  It  is 
defined  by  a  thin,  dense,  white,  connective- 
tissue  layer,  the  albuginea,1  invested  ex- 
ternally with  a  simple  columnar  epithelium, 
which  at  the  hilus  is  continuous  with  the 
pavement  epithelium  of  the  broad  ligament. 
The  interior  stroma  extends  from  the  hilus, 
where  it  transmits  the  vessels  and  nerves  of 
the  ovary.  It  is  composed  of  an  intertexture 
of  connective-tissue  bundles  with  blood-™,. 
pregnancy,  a,  b,  ovisacs ;  c,  ova-  sels,  which  in  general  have  a  radial  disposi- 

rian   ligament;    e,  stroma.     In      t[  d   outwar(Jly  become   associated   with 

the  interior,   two   old   corpora  ' 

lutea  are  visible.  bundles   of    spindle-shaped,   nucleated   cells. 

The   numerous  vessels  are  accompanied  by 

considerable  bundles  of  unstriped  muscle-fibres  continuous  with  those 
of  the  ovarian  and  broad  ligaments.  The  arteries  are  remarkable  for 
their  serpentine  and  often  spiral  course.  The  ovigenous  layer,  though 
not  distinct  from  the  interior  stroma,  appears  more  or  less  defined, 
and  is  chiefly  composed  of  an  intertexture  of  the  spindle-shaped  cells 

1  Tunica  albuginea.     Sappey  denies  its  existence  altogether. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          669 

surrounding  the  ovisacs.  The  albuginea,  continuous  with  the  former, 
is  mainly  composed  of  fibro-connective  tissue  in  several  strata,  and 
contains  no  ovisacs. 

In  the  infant  at  birth  the  ovigenous  layer  is  densely  crowded  with 
ovisacs  of  uniform  size  and  estimated  at  many  thousands ;  but  subse- 
quently they  become  more  diffused,  through  the  greater  development 
of  the  stroma.  At  puberty  the  ovisacs,  for  the  most  part,  retain  their 
original  condition,  spherical  shape,  and  uniform  size,  from  0.03  to  0.04 
millimetre  in  diameter,  and  they  form  an  almost  continuous  layer  be- 
neath the  albuginea  from  one  to  three  deep.  In  the  ovary  of  a  maiden 
of  eighteen  years,  Henle  estimated  there  were  about  thirty-six  thou- 

FIQ.  336. 


SECTION  OF  AN  OVARY  OF  THE  BABBIT,  a,  columnar  epithelium  of  the  free  surface ;  &,  external 
fibrous  layer;  c,  young  ovisacs  embedded  in  the  stroma,  and  each  containing  an  ovum  enveloped 
in  a  layer  of  epithelial  cells ;  d,  a  more  advanced  ovisac,  lined  with  an  epithelial  layer  and  con- 
taining an  ovum  invested  with  another  layer,  the  space  between  filled  with  liquid. 

sand  of  them.  Embedded  more  deeply  in  the  ovary  are  less  numerous 
ovisacs,  which  present  every  gradation  of  size  from  the  former  to  that 
of  a  large  pea.  The  largest  ovisacs,  always  few,  are  commonly  deepest, 
although  one  or  more  may  extend  through  the  ovigenous  layer  from  the 
surface  of  the  ovary  into  the  stroma  beneath  in  a  degree  proportioned 
to  its  size,  which  in  the  ripe  condition  may  be  half  an  inch  or  more  in 
diameter. 

The  larger  ovisacs  possess  a  more  distinct  and  vascular  envelope,1 
separable  into  two  layers,2  which  are  composed  of  the  elements  of  the 
stroma  concentrically  arranged. 

After  puberty,  among  the  multitude  of  ovisacs,  some  of  them  period- 

1  Theca  folliculi.  2  Tunica  propria  and  fibrosa  of  Henle. 


670         THE  FEMALE  REPRODUCTIVE  APPARATUS. 

ically  undergo  more  rapid  development  with  increase  of  size,  and  every 
month  one,  or  rarely  several,  at  the  surface  of  the  ovary  bursts  and  dis- 
charges its  contents  from  the  organ,  the  process  being  accompanied 
by  the  usual  phenomena  of  menstruation. 

The  facts  observed  in  the  condition  of  the  ovary  appear  to  demon- 
strate that  as  the  ovisacs  grow  they  retire  from  the  more  crowded 
portion  of  the  ovigenous  layer  to  the  deeper  portion  of  the  stroma, 
where  they  secure  more  room  and  nutriment  for  development.  From 
time  to  time  the  most  advanced  ovisac  reverses  its  course  to  the  surface 
of  the  ovary,  where  it  becomes  prominent,  and  finally  bursts  and  dis- 
charges its  contents,  including  the  ovum,  which  is  received  by  the 
pavilion  of  the  oviduct.  Previous  to  the  bursting  of  the  ovisac  its 
capsule  exhibits  the  highest  degree  of  vascularity,  and  the  vessels 
converge  to  the  most  projecting  part  of  the  ovisac,  which  is  named 
the  stigma,,  the  point  at  which  the  ovisac  finally  bursts. 

'  Remains  of  ovisacs  in  various  stages  of  atrophy  in  the  deeper  part 
of  the  ovarian  stroma  indicate  that  many,  after  development  to  some 
extent,  undergo  a  retrograde  course  and  disappear. 

The  ovisacs *  are  generally  spherical,  though  some  of  the  larger 
ones  may  be  oblong,  or  the  largest  even  irregular  in  shape.  They  are 
provided  with  a  transparent  homogeneous  membrane,2  which  is  thickest 
in  the  larger  ones,  and  here  and  there  presents  a  nucleus.  The  smallest 
ovisacs  are  lined  with  an  epithelial  layer3  of  flat,  nucleated  cells,  which 
closely  envelop  an  ovum.  With  the  growth  of  the  ovisac  the  cells 
become  polyhedral  and  then  columnar.  With  a  further  growth  the 
cell-layers  multiply  to  two,  three,  four,  or  more,  the  cells  of  the  outer 
layer  maintaining  the  columnar  form,  while  the  others  are  polyhedral. 
In  the  largest  ovisacs  the  ovum  is  embedded  in  an  accumulation  of 
cells  which  projects  from  one  side  of  the  epithelial  lining  of  the  ovisac 
into  a  central  cavity  filled  with  serous  liquid.  The  accumulation  is 
named  the  proligerous  disk,4  and  its  cells, 
FIG.  337.  }ike  the  rest,  consist  of  a  columnar  layer  next 

the  ovum  with  succeeding  polyhedral  cells. 
All  transitional  stages  are  to  be  observed  be- 
tween the  primitive  ovisacs  and  the  ripe  ones 
as  described. 

The  ovum,  or  egg,5  is  essentially  a  nucle- 
ated cell,  of  globular  shape,  and  varying  in  size 
HUMAN  OVUM,  highly  magni-  '        »  .          r'  /.    & 

fled,   a,  vitelline membrane;  6,     With  that  of  the  OVlsaC  which  Contains  it.      In 

yelk;  c,  germinal  vesicle  con-    the  smallest  ovisacs  it  is  in  immediate  contact 

taining  the  germinal  spot.  .,1-1        «    ,          •-!_    •>•   i        n      •      ,    •       -T. 

with  the  flat  epithelial  cells,  but  in  the  next 
stage,  when  the  latter  are  polyhedral,  it  becomes  defined  by  a  clear 

1  Vesiculae  Graafiana ;  Graafian  follicles.  2  Membrana  propria. 

3  Stratum  granulosum  or  proligerum  ;  membrana  granulosa  or  cumuli ;  epen- 
dyma  folliculi ;  couche  celluleuse. 

*  Discus  proligenis  ;  cumulus  proligerus ;  zona  granulosa.  5  Ovulum. 


THE  FEMALE  EEPEODUCTIVE  APPARATUS. 


671 


FIG   338. 


membrane,  which  increases  in  thickness  with  the  subsequent  growth 
of  the  ovum.  The  ripe  ovum,  ready  to  be  discharged  from  the  ovisac, 
is  a  minute  spherical  body,  about  the  y^-g-  of  an  inch  in  diameter,  and 
exemplifies  a  complete  cell.  It  has  a  thick,  transparent  envelope,  named 
the  chorion,1  which  under  high  magnifying  power  exhibits  passing 
through  its  thickness  fine  striae,  regarded  as  pores,  as  is  more  evidently 
the  case  in  the  eggs  of  fishes  and  some  other  animals.  The  contents 
of  the  ovum,  called  the  yelk,  or  vitellus,  is  a  transparent  viscid  pro- 
toplasm with  diffused  oil-like  granules  of  various  sizes,  named  the  vitel- 
line  corpuscles.  To  one  side  the  yelk  contains  a  clear  spherical 
nucleus,  the  germinal  vesicle,2  which  consists  of  a  reticular  mass  of 
nucleoplasm  with  a  delicate,  vesicular,  investing  membrane.  Within 
the  vesicle  there  is  commonly  a  highly-refractive  nucleolus,  the  ger- 
minal spot,3  and  sometimes  several  are  present. 

After  the  escape  of  the  contents  of  the  ovisac  its  cavity  is  filled 
with  a  blood-clot.  The  wall  subsequently  becomes  thickened,  folded, 
and  contracted  on  -the  clot,  which  finally 
in  great  measure  loses  its  color,  and  the 
two  together  assume  the  appearance  of  a 
corrugated,  yellow  mass,  called  the  corpus 
luteum.  This  subsequently  atrophies,  and 
is  resolved  into  the  tissue  of  the  ovarian 
stroma.  The  corpus  luteum  of  preg- 
nancy4 undergoes  a  greater  degree  of 
hypertrophy  up  to  about  the  middle  of  the 
term,  after  which  it  begins  to  diminish,  but 
does  not  disappear  until  near  the  end  of 
pregnancy. 

The  ovaries  are  supplied  by  the  ovarian 
artery,  which  runs  through  the  broad  liga- 
ment, below  the  attachment  of  the  ovary, 
towards  the  uterus,  where  it  anastomoses 
with  the  uterine  artery.  Numerous  branches 
enter  the  hilus  and  are  thence  distributed 
through  the  organ.  The  veins  are  also  nu- 
merous and  large,  and  form  a  terminal 
plexus,  from  which  the  chief  veins  accom- 
pany the  ovarian  artery.  The  lymphatics, 
likewise  numerous  and  large,  emerging  from  the  hilus,  proceed  to  the 
lumbar  glands.  The  nerves  are  derived  from  the  ovarian  plexus  of  the 
sympathetic  accompanying  the  ovarian  vessels. 


Two  CORPORA  I.UTEA;  in  sec- 
tion, natural  size.  1,  eight  days 
after  conception;  2,  at  the  fifth 
month  of  pregnancy,  a,  fibrous 
tunic  of  the  ovary ;  b,  stroma ;  c, 
thickened  and  plicated  membrane 
of  the  ovisac ;  d,  blood-clot ;  e,  the 
same,  later,  without  its  red  color ; 
/,  fibrous  stroma  bounding  the  cor- 
pus luteum. 


1  Membrana  vitellina ;   oolemma   pellucidum ;    zona  pellucida,  a  common  and 
much  misleading  name,  applying  only  to  an  optical  section  of  the  membrane. 

2  Vesicula  germinativa  or  prolifera ;  Purkinjean  vesicle. 

3  Macula  germinativa.  4  True  corpus  luteum. 


672         THE  FEMALE  REPRODUCTIVE  APPARATUS. 

The  parovarium.1  This  is  a  rudimentary  organ  placed  between 
the  layers  of  the  broad  ligament,  in  the  interval  outwardly  between 
the  ovary  and  oviduct.  It  appears  as  a  series  of  irregular  whitish 
tubes,  somewhat  divergent  from  the  position  of  the  ovary  to  a  main 
tube  lying  near  to  and  parallel  with  the  oviduct.  It  is  the  remains  of 
the  primordial  kidney  or  wolffian  body  of  the  embryo.  The  outermost 
tube  sometimes  appears  as  a  little  cyst  suspended  by  a  narrow  cord 
from  the  broad  ligament.  A  similar  cyst,  not  unfrequently  suspended 
from  the  pavilion  of  the  oviduct,  is  the  remains  of  the  duct  of  Miiller, 
another  organ  of  embryonic  life. 

THE   MAMMAE. 

The  mammae,  or  mammary  glands,2  are  the  milk-secreting  organs 
of  the  female,  and  exist  only  in  a  rudimentary  condition  in  the  male. 
Their  presence  is  characteristic  of  the  highest  class  of  animals,  whence 
these  are  named  mammals,3  in  most  of  which  they  are  attached  to  the 
abdomen ;  but  in  man  and  his  order,  the  primates,  they  occupy  the  front 
of  the  chest. 

In  the  human  female,  when  fully  produced,  the  mammary  glands, 
together  with  the  enveloping  skin  and  the  fascia  associated  with  more 
or  less  fat,  form  a  pair  of  hemispherical  prominences,  the  breasts, 
surmounted  by  a  conical  eminence,  the  nipple,  or  teat.4 

The  breasts  extend  from  the  third  to  the  seventh  rib  and  from  the 
side  of  the  sternum  to  the  axilla,  and  are  variably  prominent  according 
to  the  condition  of  the  mammary  gland  and  the  general  nutritive  state 
of  the  individual. 

The  nipple  is  situated  on  a  line  with  the  fourth  rib,  and  is  directed 
forward  and  somewhat  outward  and  upward.  It  is  of  a  roseate  or 
reddish-brown  color  and  is  surrounded  at  its  base  by  a  zone  or  areola 
of  the  skin  of  the  same  color.  Both  enlarge  and  become  darker  in 
pregnancy,  and  the  change  to  some  extent  is  permanent.  The  color 
increases  with  the  advance  of  the  pregnant  condition,  grows  darker, 
but  again  diminishes  after  the  mammary  gland  ceases  its  secretory 
function.  The  skin  of  the  nipple  is  wrinkled  and  furnished  with  sensi- 
tive papilla?.  It  is  highly  vascular  and  contains  much  muscular  tissue ; 
hence  under  excitement  it  becomes  larger  and  more  rigid.  On  its 
rounded  summit  are  the  mouths  of  the  milk-ducts,  of  which  there  are 
from  fifteen  to  twenty,  each  opening  into  a  little  pit. 

The  skin  of  the  areola  is  thin  and  exhibits  a  number  of  scattered, 
whitish,  pimple-like  eminences,6  which  are  due  to  groups  of  sebaceous 
glands,  which  open  by  three  or  four  ducts  on  the  surface.  The  glands 

1  Paroarium  ;  paroophoron ;  corpus  pampiniforme  or  conicum  ;  organ  of  Rosen- 
muller. 

2  Masthos  ;  mastus ;  ruma  ;  uber.  3  Mammalia. 
4  Mammilla ;  papilla  ;  mastus  ;  uber.  6  Tubercles. 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


673 


FIG.  339. 


enlarge  during  suckling,  and  they  secrete  an  oily  matter,  which  appears 
to  protect  the  part  from  excoriation. 

The  mammary  gland1  is  a  segment  of  a  sphere,  and  is  nearly  cir- 
cular, with  its  front  surface  convex  and  prolonged  at  the  nipple,  and 
its  posterior  surface  nearly  flat  or  slightly  concave,  and  attached  by 
connective  tissue  to  the  deep  fascia  investing  the  greater  pectoral 
muscle.  From  the  weight  of  the  breasts  during  the  full  development 
of  the  mammae,  when  unsupported,  the  connective  tissue  of  attachment 
becomes  elongated  and  the  breasts  proportionately  pendent. 

The  mammary  gland  is  of  firm  consistence  and  of  a  pinkish-white 
color.  It  is  a  racemose 
gland,  and  is  composed 
of  from  fifteen  to  twenty 
lobes,  which  are  closely 
conjoined  by  fibro-con- 
nective  tissue  which  also 
invests  the  gland  and  is 
continuous  with  the  su- 
perficial fascia  of  the 
chest.  The  lobes,  which 
may  be  regarded  as  so 
many  separate  glands, 
are  pyramidal,  with  the 
bases  at  the  circumfer- 
ence of  the  mamma  and 
the  apices  convergent  to 
the  nipple.  From  each 
lobe  proceeds  a  lactiferous  or  milk  duct,2  which  expands  at  the 
areola,  and  during  lactation  becomes  enlarged  into  a  fusiform  recepta- 
cle, the  lactiferous  ampulla,3  from  a  sixth  to  a  fourth  of  an  inch 
wide.  From  the  ampullae,  which  serve  as  little  temporary  reservoirs 
of  milk,  the  milk-ducts,  again  reduced  in  size,  ascend  in  a  group  through 
the  nipple  to  its  summit,  where  they  terminate  in  contracted  and  sep- 
arate orifices.  Besides  the  milk-ducts,  of  which  the  central  ones  of 
the  group  are  larger,  the  nipple  contains  numerous  blood-vessels,  with 
bundles  of  unstriped  muscle-fibres  and  areolar  tissue  free  from  fat. 
The  muscle-fibres  form  concentric  circles  at  the  base  of  the  nipple, 
whence  others  radiate  to  its  summit. 

In  the  usual. healthful  condition  between  the  mammary  gland  and 
the  skin,  the  investing  areolar  tissue  of  the  former  is  occupied  by  a 
variable  accumulation  of  fat,  often  in  considerable  quantity  and  pro- 
portionately contributing  to  the  prominence  of  the  breasts.  The  fat  is 
intersected  by  irregular  partitions  of  fibro-connective  tissue  and  par- 


MlLK-DUCT  AND  LOBULES  OF  THE  MAMMARY  GLAND,  enlarged. 

1,  nipple;  2,  terminal  milk-duct:  3,  ampulla;  4,  principal 
duct  from  a  lobe ;  5,  lobules  composed  of  alveoli. 


1  Glandula  lactifera. 

3  Galactophorous  ampulla  or  sinus;  sinus  lactei. 

43 


Galactophorous  duct. 


674          THE  FEMALE  EEPKODUCTIVE  APPARATUS. 

tially  extends  among  the  lobes  of  the  mammary  gland.  In  thin  per- 
sons the  fat  is  in  great  measure  absent  and  its  place  is  occupied  by 
an  abundant  layer  of  areolar  tissue. 

The  lobes  of  the  mammary  gland  have  the  usual  construction  of 
racemose  glands,  and  are  composed  of  polyhedral  lobules  subdivided 
into  smaller  ones,  all  united  by  branching  ducts  with  blood-vessels 
and  conjoined  by  fibro-connective  tissue.  The  smallest  lobules  consist 
of  clusters  of  rounded  polyhedral  follicles  or  alveoli,  which  communi- 
cate with  the  smallest  milk-ducts. 

The  alveoli  of  the  mammary  gland  during  the  resting  condition  are 

filled  with  polyhedral  cells.  Dur- 
ing pregnancy  the  cells  rapidly 
multiply  and  the  alveoli  become 
enlarged.  At  the  commencement 
of  lactation,  or  the  production  of 
milk,  the  central  cells  of  the  alve- 
oli are  resolved  into  masses  of  oil- 
globules,  which  are  discharged  in 
the  first  milk  and  are  known  as 
the  colostrum-corpuscles.  The 
ALVEOLUS  OF  THE  MAMMARY  GLAND,  during  peripheral  cells  of  the  alveoli  dis- 


cieus,  and  milk-globules.  Highly  magnified.  as  a  simple  epithelium  of  flattened 

cells,  but  in  the  active  secretion 

of  milk  these  assume  a  short  columnar  polyhedral  form.  They  con- 
tain a  granular  protoplasm  with  a  large  round  nucleus  and  oil-globules. 
which  are  discharged  as  milk-globules.  The  alveoli  are  defined  by  a 
membrana  propria  supported  by  fibro-connective  tissue,  with  close  nets 
of  capillary  blood-vessels. 

The  walls  of  the  lactiferous  ducts  are  composed  of  fibro-connective 
tissue  with  longitudinal  and  circular  elastic  fibres,  and  are  lined  by  a 
columnar  epithelium,  which  near  their  termination  merges  into  strati- 
fied epithelium,  continuous  at  the  mouths  of  the  ducts  with  the  epi- 
dermis of  the  skin  of  the  nipple. 

The  mammary  gland  makes  its  appearance  in  the  fourth  month  of 
embryonic  life,  but  its  later  growth  is  slow.  There  is  no  difference  in 
the  organ  in  the  male  and  female  infant  for  some  years.  The  further 
development  of  the  gland  takes  place  in  the  female  at  puberty,  but  it  is 
not  until  pregnancy  that  it  proceeds  to  completion.  Even  in  the  male, 
at  puberty,  the  gland  undergoes  some  development,  but  this  soon  ceases 
and  it  becomes  completely  atrophied.  Cases  are  reported  in  which  it 
has  so  far  advanced  in  its  development  in  the  male  as  to  secrete  milk. 

With  the  decline  of  reproductive  power  in  the  female  the  mammary 
gland  gradually  atrophies,  the  alveoli  with  their  epithelium  and  the 
smaller  ducts  disappear,  and  finally  nothing  remains  but  the  larger 
ducts  with  areolar  tissue  and  fat. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          675 

The  arteries  which  supply  the  mammary  gland  are  derived  from  the 
thoracic  branches  of  the  axillary,  the  intercostals,  and  the  mammary. 
Those  which  directly  go  to  the  gland  become  considerably  enlarged 
during  lactation.  The  veins  correspond  with  the  arteries.  Around 
the  base  of  the  nipple  they  form  an  anastomotic  circle.  The  lymphatics 
commence  in  the  fibre-connective  tissue  surrounding  the  alveoli,  and 
the  larger  vessels  pursue  the  general  course  of  the  ducts  and  blood- 
vessels. The  chief  lymphatics,  for  the  most  part,  run  along  the  outer 
border  of  the  greater  pectoral  muscle  to  the  axillary  glands ;  others  pass 
through  the  fore  part  of  the  intercostal  spaces  and  enter  the  anterior 
mediastinal  glands.  The  nerves  are  supplied  from  the  anterior  and 
lateral  cutaneous  branches  of  the  intercostals. 

MILK. 

Milk1  is  an  emulsion  consisting  of  a  clear  liquid  in  which  innumer- 
able  minute  fat-globules  are  sus- 
pended.    The  latter  are  called  the 
milk-globules,  and  measure  from 

the  TOTIF  to  the  -STrVff  of  an  inch- 
They  seem  to  be  coated  with  an 

albuminous  substance,  which  pre- 
vents them  from  running  together 

into    larger     drops.        Chemically,         CORPUSCLES  OBSERVED  IN   MILK,     a,   milk- 
.  globules ;  b,  c,  d,  colostrum-corpuscles  in  various 

human  milk,  according  to  Simon,      stages.    Highly  magnified. 

has  the  following  composition : 

Water,  880.6 ;  casein,  37 ;  milk-sugar,  45.4 ;  fatty  matters,  34 ;  ex- 
tractives and  salts,  3 :  =  1000.  Among  the  salts  phosphatic  earths 
predominate. 

THE   PEKINEUM. 

The  perineum  is  that  portion  of  the  body  which  is  included  by  the 
outlet  of  the  pelvis ;  bounded  in  front  by  the  pubic  arch,  behind  by  the 
coccyx  and  great  sacro-sciatic  ligaments,  and  at  the  sides  by  the  ischial 
tuberosities.  The  space  within  this  boundary  is  separated  from  the 
pelvic  cavity  by  the  anal  elevator  muscles  and  recto-vesical  fascia  de- 
scending from  the  sides  of  the  cavity  to  the  bladder  and  anus.  It  is 
occupied  by  the  termination  of  the  rectum,  the  urethra,  and  the  root 
of  the  penis,  together  with  their  muscles,  fasciae,  vessels,  and  nerves. 
In  a  more  restricted  sense  the  name  of  perineum'2  is  applied  to  the 
space  in  advance  of  the  anus ;  in  the  female  occupied  by  the  termina- 
tion of  the  vagina,  the  vulva,  and  the  clitoris. 

The  skin  of  the  perineal  region  is  comparatively  thin  and  dark- 
colored,  especially  approaching  the  anus,  where  it  is  corrugated  and 
continuous  with  the  mucous  membrane  of  the  rectum.  Its  fore  part  is 
continuous  with  that  of  the  penis  and  scrotum,  and  in  the  median  line 

1  Lac.  2  True  perineum. 


676 


THE  FEMALE  REPRODUCTIVE  APPARATUS. 


FIG.  342. 


presents  a  slight  ridge,  the  raphe,  which  extends  from  the  anus  to 
the  prepuce.  In  the  female  its  fore  part  is  continuous  with  that  of  the 
labia  and  mucous  membrane  of  the  vulva,  and  the  raphe  extends  from 
the  anus  to  the  posterior  commissure  of  the  latter. 

MUSCLES   AND  FASCIAE   OF   THE   PERINEUM. 

The  superficial  fascia1  of  the  perineum,  as  elsewhere,  consists  of 

two  layers.  The  subcuta- 
neous layer,  accompanied 
by  the  usual  adipose  tis- 
sue, is  continuous  with 
that  of  the  surrounding 
parts,  the  inner  side  of 
the  thighs  and  the  but- 
tocks. Thin  immediately 
around  the  anus,  between 
this  and  the  ischial  tu- 
berosity  it  forms  a  large 
accumulation  occupying 
the  ischio-rectal  fossa,  the 
deep  interval  extending 
upward  between  the  rec- 
tum and  the  ischium. 
The  disappearance  of  the 
fat  in  this  position  in  ema- 
ciation produces  more  or 
less  depression  of  the  per- 
ineum around  the  anus. 
The  deeper  membranous 
layer  of  the  superficial 
fascia  occupies  the  fore 
part  of  the  perineum,  and 
closely  invests  the  root 
of  the  penis  with  its  muscles.  It  is  tightly  attached  to  the  sides  of 
the  pubic  arch  beneath  the  crura  of  the  penis,  and  joins  the  deep  peri- 
neal  fascia  behind  the  transverse  perineal  muscles.  In  front  it  is  con- 
tinuous with  the  investing  fascia  of  the  penis  and  with  the  dartos 
membrane  of  the  scrotum.  Behind  the  transverse  perineal  muscles 
it  is  continuous  with  the  fascia3  lining  the  ischio-rectal  fossse. 

The  deep  perineal  fascia2  is  a  strong  membranous  layer  extended 
across  the  pubic  arch  behind  the  root  of  the  penis,  attached  above  to 
the  pubic  symphysis,  continuous  with  the  subpubic  ligament  and  con- 
nected below  with  the  obturator  fascia  behind  and  the  deeper  layer 


VIEW  OF  THE  PERINEUM  :  the  superficial  fascia  removed 
from  the  left  side  of  the  figure,  a,  transverse  perineal 
muscle  proceeding  from  the  tuberosity  of  the  ischium  to 
the  perineal  centre;  b,  greater  sacro-sciatic  ligament;  c, 
anal  sphincter;  d,  anal  elevator;  e,  ischio-cavernous  mus- 
cle; /,  bulbo-urethral  muscle  enclosing  the  bulb  of  the 
spongy  body.  1,  2,  pudic  artery ;  3,  inferior  hemorrhoidal 
artery ;  4,  5,  6,  7,  superficial  perineal  branches ;  8,  bulbo- 
urethral  artery ;  9,  cavernous  artery ;  10,  dorsal  artery  of  the 
penis. 


1  Fascia  of  Colles. 

2  Anterior  or  inferior  layer  of  the  deep  perineal  fascia. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          677 

of  the  superficial  fascia  in  front.  In  contact  with  it  in  front  are  the 
crura  of  the  cavernous  body  and  the  bulb  of  the  spongy  body.  With 
the  corresponding  layer1  within  of  the  obturator  fascia,  the  deep  peri- 
neal  fascia  forms  the  triangular  ligament  of  the  urethra,2  which 
ffives  passage  to  the  isthmus  of  the  urethra  in  the  median  line,  about 

O  .t  O 

an  inch  below  the  pubic  symphysis.  At  the  latter  the  ligament  is 
strengthened  by  a  transverse  fibrous  band,8  beneath  which  it  is  per- 
forated for  the  passage  of  the  dorsal  vein  of  the  penis.  Between 
the  two  layers  of  the  triangular  ligament  are  the  urethral  com- 
pressor muscles  closely  connected  with  it,  a  venous  plexus,  the  pudic 
vessels  and  nerve  on  each  side,  and  the  suburethral  glands.  In  the 
female  the  triangular  ligament  is  partially  divided  to  accommodate 
the  vagina. 

The  anal  sphincter*  is  a  subcutaneous,  elliptical  muscle  surround- 
ing the  anus,  and  consists  of  a  fleshy  layer  on  each  side  of  the  aperture, 
convergent  and  united  with  its  fellow  behind,  and  attached  tendinously 
to  the  end  of  the  coccyx,  and  in  the  same  manner  convergent  in  front 
to  the  perineal  centre,  where  it  terminates  by  joining  the  urethro-bulbar 
muscle  and  the  adjacent  skin.  Internally  it  is  in  contact  with  the 
internal  sphincter  and  is  separated  from  the  anal  elevator  by  loose 
connective  tissue. 

The  anal  elevator 5  is  a  broad,  thin  muscle,  which  descends  from 
the  side  of  the  pelvic  cavity,  curving  inward  to  the  middle  of  the 
perineum.  It  arises  in  front  from  the  posterior  surface  of  the  body 
and  descending  ramus  of  the  pubis,  behind  from  the  spine  of  the 
ischium,  and  between  these  two  points  from  the  curved  line  of  divis- 
ion of  the  pelvic  fascia  into  the  obturator  and  recto-vesical  fasci®. 
The  anterior,  longer  fascicles  descend  to  the  side  of  the  prostate  and 
unite  beneath  it  with  those  of  the  opposite  muscle,  blending  with  the 
anal  sphincter  at  the  perineal  centre.  The  middle  fascicles,  forming 
the  thicker  portion  of  the  muscle,  descend  to  the  side  of  the  rectum 
between  the  sphincter  and  internal  sphincter  and  become  more  or  less 
blended  with  them.  The  posterior  fascicles  descend  to  be  inserted 
into  the  end  of  the  coccyx  and  into  a  median  fibrous  raphe  extend- 
ing from  it  to  the  anus.  In  the  female  the  anterior  portion  of  the 
muscle  descends  to  the  side  of  the  vagina.  Sometimes  this  portion  is 
separated  from  the  rest  and  has  been  described  as  a  distinct  muscle.6 

The  inner  surface  of  the  anal  elevator  is  invested  by  the  recto- 
vesical  fascia,  which  separates  it  from  the  peritoneum.  Its  outer  sur- 
face forms  the  inner  boundary  of  the  ischio-rectal  fossa  and  is  invested 
by  the  thin  anal  fascia  continuous  at  the  origin  of  the  muscle  with 

1  Posterior  or  superior  layer  of  the  deep  perineal  fascia. 

2  T.  1.  of  the  pubis  ;  subpubic  fascia ;  deep  perineal  fascia. 
*  Transverse  ligament  of  the  pelvis. 

4  M.  sphincter  ani ;  m.  s.  a.  externus.  5  M.  levator  ani. 

6  M.  levator  prostatse  ;  m.  adductor  or  compressor  prostat*. 


678          THE  FEMALE  REPRODUCTIVE  APPARATUS. 

the  obturator  fascia.  Its  posterior  border  is  continuous  with  the 
coccygeus  muscle,  and  its  anterior  border  is  separated  from  that  of  the 
opposite  muscle  by  a  triangular  space  traversed  by  the  urethra,  in  the 
female  giving  passage  to  the  vagina. 

The  coccygeal  muscle *  is  situated  behind,  in  the  same  plane  as 
the  preceding.  It  is  a  triangular  layer,  partly  fleshy  and  tendinous, 
which  arises  by  its  apex  from  the  spine  of  the  ischium  and  passes  back- 
ward and  inward  to  be  inserted  into  the  side  of  the  coccyx  and  last 
segment  of  the  sacrum.  The  rectum  rests  against  its  inner  surface,  and 
its  outer  surface  is  in  contact  with  the  small  sacro-sciatic  ligament. 

The  ischio-cavernous  muscle 2  is  a  fleshy  band  embracing  the 
unattached  portion  of  the  crus  of  the  cavernous  body  of  the  penis.  It 
arises  tendinous  and  partially  fleshy  from  the  inner  part  of  the  tuber- 
osity  and  ramus  of  the  ischium  and  proceeds  forward  to  terminate  in 
an  aponeurosis  which  is  inserted  into  the  under  surface  and  sides  of  the 
fore  part  of  the  crus  of  the  penis. 

The  urethro-bulbar  muscle,3  together  with  its  fellow,  forms  a 
fleshy  layer  embracing  the  bulb  of  the  spongy  body  of  the  penis.  It 
arises  from  the  perineal.  centre,  connected  with  the  anal  sphincter  and 
transverse  perineal  muscles,  and  from  a  narrow,  median  fibrous  raphe 
which  unites  it  with  its  fellow  and  extends  forward  beneath  the  urethral 
bulb.  From  this  origin  the  fleshy  fibres  proceed  outward  and  forward 
around  the  bulb  and  terminate  in  an  aponeurosis,  partly  united  with 
that  of  the  opposite  side  above  the  bulb,  partly  inserted  in  advance  into 
the  outer  side  of  the  cavernous  body,  and  partly  united  with  its  fellow 
in  a  slip  which  passes  over  the  latter  and  includes  the  dorsal  vessels 
of  the  penis. 

In  the  female  the  ischio-cavernous  muscle  *  holds  the  same  relation 
to  the  clitoris  that  it  does  to  the  penis  in  the  male,  the  size  being  in 
accordance  and  the  attachments  the  same.  The  urethro-bulbar  muscles 
become  the  vaginal  sphincter,  the  two  sides  of  which  correspond  with 
the  two  muscles  in  the  male. 

The  vaginal  sphincter5  appears  as  an  elliptical  muscle,  which 
embraces  the  orifice  of  the  vagina  and  the  vestibule  and  includes  the 
semi-bulbs  of  the  spongy  body.  It  converges  behind  to  the  perineal 
centre,  where  it  unites  with  the  anal  sphincter  and  transverse  perineal 
muscles.  It  also  converges  in  front  and  is  inserted  into  the  cavernous 
body  of  the  clitoris,  around  which  it  gives  a  loop  enclosing  the  dorsal 
vessels,  as  in  the  corresponding  muscles  of  the  male. 

The  transverse  perineal  muscle,6  a  narrow  fleshy  slip,  arises 
tendinous  from  the  inner  side  of  the  ischial  tuberosity  and  proceeds 


1  M.  coccygeus.  2  M.  ischio-cavernosus  ;  m.  erector  penis. 

3  M.  bulbo-cavernosus  ;  m.  accelerator  or  ejaculator  urinse  or  seminis. 

4  M.  erector  clitoridis.  5  M.  sphincter  or  constrictor  vaginae. 
6  M.  transversus  perinei. 


THE  FEMALE  REPRODUCTIVE  APPARATUS.          679 

obliquely  inward  and  forward  to  terminate  in  the  perineal  centre, 
where  it  is  united  with  its  fellow  and  other  contiguous  muscles.  It 
is  variable,  and  is  sometimes  very  small,  or  may  be  absent.  It  is  not 
unfrequently  accompanied  by  a  smaller  slip1  in  front  or  behind.  It 
may  be  inserted  partially  or  wholly  into  the  urethro-bulbar  or  the  anal 
sphincter  muscle. 

The  urethral  compressor 2  is  a  thin  muscle  situated  between  the 
layers  of  the  triangular  ligament  and  embracing  the  isthmus  of  the 
urethra.  Composed  of  variable  fascicles,  mostly  transverse,  it  arises 
by  an  aponeurosis  from  the  descending  ramus  of  the  pubis  and  pro- 
ceeds inwardly  to  join  its  fellow  in  the  median  line  above  and  below 
the  urethra,  partially  by  an  interchange  of  fibres  and  partially  by  a 
fibrous  raphe.  Included  by  the  compressors,  the  urethral  isthmus  is 
surrounded  with  circular  muscular  fibres  which  are  continuous  with 
the  former. 

The  anal  sphincter  is  supplied  by  branches  from  the  fourth  sacral 
and  the  inferior  hemorrhoidal  branch  of  the  pudic  nerve.  The  anal 
elevator  is  supplied  by  the  fourth  sacral  and  the  perineal  branch  of  the 
pudic  nerve,  and  the  coccygeus  muscle  by  the  former.  The  ischio- 
cavernous,  urethro-bulbar,  and  transverse  perineal  muscles  are  sup- 
plied by  the  perineal  nerve,  and  the  urethral  compressor  by  the  dorsal 
nerve  of  the  penis. 

The  action  of  the  anal  sphincter  and  anal  elevator  is  indicated  by 
the  names.  The  ischio-cavernous  muscle,  by  compression  of  the  organ, 
may  aid  in  maintaining  the  erection  of  the  penis,  but  ordinarily  would 
appear  rather  to  draw  it  downward.  The  urethro-bulbar  muscle,  by 
compressing  the  bulb,  will  forcibly  eject  liquids  from  the  urethra. 

1  M.  transversus  perinei  alter. 

a  M.  compressor  or  constrictor  urethras ;  m.  constrictor  urethra  membranacea ; 
m.  constrictor  isthmi  urethras. 


OHAPTEE    XIV. 

GLAND-LIKE   ORGANS  WHOSE    FUNCTION  IS  OBSCURE 

OR   UNKNOWN. 

CERTAIN  organs  having  the  general  appearance  of  glands,  and  dis- 
tinguished as  ductless  glands,  the  functions  of  which  are  obscure  or 
unknown,  are  the  spleen,  the  thymus,  the  thyroid  body,  the  suprarenal 
body,  and  the  carotid  and  coccygeal  glands. 

THE   SPLEEN. 

The  spleen1  is  a  massive  organ  of  a  dark-purple  color,  situated 
within  the  abdomen,  in  the  back  part  of  the  left  hypochondrium,  lying 
against  the  fundus  of  the  stomach  to  the  right,  and  in  contact  behind 
with  the  diaphragm,  opposite  the  three  or  four  lower  ribs.  It  is  vari- 
able in  shape,  and  commonly  is  demi-ovoid  with  the  broader  extremity 
upward,  the  long  diameter  directed  obliquely  downward  and  outward. 
The  external  surface  is  convex,  conforms  closely  to  the  diaphragm,  and 
is  directed  to  the  left,  backward  and  upward.  The  internal  surface 
is  divided  longitudinally  near  the  middle  by  a  ridge  usually  impressed 
by  a  shallow  furrow,  the  hilus,2  along  which  the  vessels  pass  in  and 
out  of  the  spleen.  The  narrower  back  part  of  the  surface  lies  against 
the  outer  border  of  the  left  kidney,  and  the  more  concave  anterior  part 
is  applied  to  the  fundus  of  the  stomach.  The  borders  of  the  spleen 
are  for  the  most  part  obtuse,  and  the  anterior  narrower  border,  usually 
below,  presents  one  or  more  shallow  notches  or  clefts.  The  lower 
narrow  end  of  the  spleen  rests  on  the  costo-colic  ligament,3  a  fold 
of  peritoneum  attaching  the  splenic  flexure  of  the  colon  to  the  dia- 
phragm. Sometimes  the  spleen  presents  no  ridge  on  its  inner  surface, 
and  occasionally  the  furrow-like  hilus  is  absent. 

Besides  through  its  vessels,  the  spleen  is  especially  sustained  in 
position  by  folds  of  the  peritoneum.  Of  these,  the  suspensory  liga- 
ment4 extends  from  the  upper  part  of  the  hilus  to  the  contiguous 
diaphragm  and  the  gastro-splenic  omentum  extends  from  the  sides 
of  the  hilus  to  the  fundus  of  the  stomach. 

The  spleen  is  very  variable  in  size,  but  ordinarily  is  about  five 
inches  long,  an  inch  or  two  less  in  width,  and  from  an  inch  to  an  inch 

1  Lien  ;  splen  ;  hepar  sinistrum.  2  Porta  lienis. 

3  Phrenico-colic  ligament.  *  Phrenico-splenic  ligament. 

680 


GLAND-LIKE  ORGANS   WHOSE   FUNCTION   IS   OBSCURE. 


681 


and  a  half  in  thickness,  and  weighs  six  or  seven  ounces.  In  advanced 
age  it  is  considerably  diminished ;  in  some  fevers,  like  intermittent,  it 
becomes  very  much  enlarged,  even  to  several  pounds. 

Occasionally  there  is  a  small  accessory  spleen1  and  sometimes 
several  together,  attached  to  the  gastro-splenic  omentum,  near  the 
lower  part  of  the  spleen.  It  is  commonly  spheroidal,  and  ranges  from 
the  size  of  a  pea  to  that  of  a  walnut. 

Structure  of  the  spleen.  The  spleen  is  a  highly  vascular  organ, 
proportioned  to  its  size  more  so  than  any  other  organ  of  the  body.  It 
is  comparatively  soft,  and  is  easily  broken,  and  the  ruptured  surface 
presents  a  pulpy  black  or  dark  brownish-red  appearance,  resembling 
coagulated  blood.  It  consists  of  an  elastic,  sponge-like  matrix  of  fibro- 
connective  and  elastic  tissue,  which  sheathes  and  supports  the  blood- 
vessels and  encloses  in  its  areolae  a  soft  substance,  the  splenic  pulp,  the 
whole  enveloped  in  a  membranous  capsule. 

FIG.  343. 


DIAGRAM  OF  THE  TERMINATION  OF  A  CAPILLARY  VESSEL  IN  THE  SPLENIC  PULP.  1,  capillary ;  2, 
supporting  cells  of  the  pulp ;  3.  lymph-corpuscles.  Highly  magnified. 

The  capsule  of  the  spleen  is  whitish,  smooth,  shining,  and  elastic, 
and  is  composed  of  a  proper  tunic  invested  by  a  serous  layer  derived 
from  the  peritoneum. 

The  external  serous  layer  is  thin  and  transparent,  intimately 
connected  with  the  subjacent  tunic,  and  invests  the  spleen  throughout 
except  at  the  hilus. 

The  proper  tunic 2  is  much  thicker  and  stronger  than  the  former, 
and  is  composed  of  a  dense  intertexture  of  fibro-connective  and  elastic 
tissue.  At  the  hilus,  extensions  of  the  tunic,  from  their  supporting 
character  distinguished  as  trabeculae,3  accompany  and  sheathe  the 
blood-vessels  in  their  distribution  through  the  structure  of  the  spleen. 


1  Splenculus ;  lienculus. 

3  From  the  Latin  trabs,  a  bean. 


2  Tunica  propria. 


682 


GLAND-LIKE   ORGANS   WHOSE   FUNCTION   IS   OBSCURE. 


FIG.  344. 


Numerous  other  trabeculse  proceed  from  the  interior  of  the  tunic  and 
from  the  blood-vessels  to  contribute  to  form  the  sustaining  matrix  of 
the  spleen. 

The  areola3  of  the  splenic  matrix  are  occupied  by  a  delicate  inter- 
lacement of  stellate  connective-tissue  corpuscles,  distinguished  as  the 
supporting  cells l  of  the  splenic  pulp.  These  cells  conjoin  through 
their  radial  fibres,  and  their  interstices  communicate  with  the  splenic 
capillaries  and  are  filled  with  blood. 

The  blood  of  the  splenic  pulp  diifers  from  the  blood  generally  in 
containing  a  greater  proportion  of  white  corpuscles.  Among  the  con- 
stituents of  the  pulp  are  other  cor- 
puscles resembling  the  latter,  but 
larger.  These  exhibit  amoeboid 
movement  and  often  contain  some 
red  blood-corpuscles,  together  with 
yellowish  pigment-granules.  The 
supporting  cells  of  the  pulp  are 
also  stated  to  exhibit  amoeboid 
movement  and  often  also  to  con- 
tain yellow  pigment-granules,  con- 
sidered to  be  derived  by  decom- 
position from  red  blood-corpuscles. 
The  blood-vessels  of  the  spleen 
are  remarkably  large  in  propor- 
tion to  the  size  of  the  organ.  The 
splenic  artery,  after  a  tortuous 
course  and  giving  branches  to  the 
pancreas  and  stomach,  divides  into 
from  four  to  six  branches,  which 
enter  along  the  hilus  and  are  dis- 
tributed through  the  structure  of 
the  spleen  supported  by  its  tra- 

beculae.  The  main  branches  run  outwardly  and  supply  corresponding 
regions  of  the  spleen  without  anastomosing  with  those  of  contiguous 
regions.  The  arteries  after  extensive  ramification,  sheathed  by  the 
trabecula?,  leave  these  and  break  up  into  little  tufts  of  fine,  straight 
arterioles,  the  external  coat  of  which,  from  its  ordinary  composition 
of  connective  tissue,  gradually  assumes  the  condition  of  adenoid  or 
lymphoid  tissue.  The  arterioles,  supported  by  small  trabecute,  ter- 
minate in  capillaries,  which  traverse  the  splenic  pulp  and  finally  merge 
and  end  in  the  interstices  of  its  supporting  cells. 

The  lymphoid  tissue  of  the  splenic  arterioles  resembles  that  of  the 
lymphatic  glands,  and  consists  of  delicate  interlacing  fibrils  enclosing  in 
their  meshes  lymphoid  corpuscles  and  supplied  by  small  branches  from 


SMALL  BRANCH  OF  THE  SPLENIC  ARTERY,  with 
lymphoid  nodules.  From  the  dog :  magnified 
10  diameters. 


1  Sustentacular  cells. 


GLAND-LIKE   ORGANS   WHOSE   FUNCTION   IS   OBSCURE.          683 

the  arterioles  ending  in  capillary  plexuses.  In  many  positions  the  in- 
vesting lymphoid  tissue  of  the  arterioles  forms  nodules1  surrounding 
the  vessel  or  placed  on  one  side  of  it  and  supplied  by  branches  from 
the  latter  as  elsewhere  in  the  tissue.  The  lymphoid  nodules  resemble 
the  solitary  glands  of  the  intestine  and  appear  as  whitish  dots  in  the 
dark  pulp  of  the  fresh  spleen,  measuring  a  millimetre  or  less. 

The  veins  of  the  spleen  commence  in  the  splenic  pulp  in  the  same 
manner  as  the  arteries  terminate.  Pursuing  a  different  course  from 
the  latter,  they  also  sooner  pass  to  the  trabeculse,  on  and  within  which, 
unlike  the  arteries,  they  frequently  anastomose.  Emerging  from  the 
hilus  of  the  spleen  in  from  four  to  six  branches,  they  unite  in  the 
splenic  vein,  the  largest  tributary  of  the  portal  vein. 

The  lymphatics  of  the  spleen  consist  of  two  sets.  Of  these  the 
perivascular  lymphatics  commence  in  the  lymphoid  sheath  of  the 
splenic  arterioles,  whence  the  vessels  pursue  the  course  of  the  arteries 
and  veins  from  the  spleen.  The  trabecular  lymphatics  commence 
in  the  splenic  trabeculae,  where  they  communicate  with  the  former, 
and  they  join  a  superficial  plexus  of  the  splenic  capsule,  whence  vessels 
converge  to  the  hilus  to  join  the  deep  lymphatics,  which  then  enter  the 
lymphatic  glands  of  the  gastro-splenic  omentum.  The  nerves  of  the 
spleen  are  derived  from  the  splenic  plexus  of  the  solar  plexus,  accom- 
panying the  splenic  artery  and  its  branches. 

THE   THYROID   BODY. 

The  thyroid  body,  or  gland,2  is  a  brownish-red  organ  of  unknown 
function  situated  in  the  neck,  embracing  the  front  and '  sides  of  the 
commencement  of  the  trachea,  extending  on  the  sides  of  the  larynx. 
It  consists  of  two  lateral  lobes,  united  near  their  lower  ends  by  a 
transverse  portion  or  isthmus.  In  its  position  it  produces  a  rounded 
prominence,  is  covered  by  the  infra-hyoid  muscles,  and  comes  into  con- 
tact with  the  sheath  of  the  principal  blood-vessels  of  the  neck.  Each 
lobe  is  ovoid  with  the  narrower  end  upward  and  extends  from  the  fifth 
or  sixth  ring  of  the  trachea  to  the  side  of  the  thyroid  cartilage.  The 
external  surface  is  convex  ;  the  internal  surface  is  concave  and  closely 
adheres  to  the  trachea  and  larynx.  The  isthmus,  variable  in  size, 
shape,  and  position,  usually  crosses  the  third  and  fourth  rings  of  the 
trachea. 

Not  unfrequently  a  pyramidal  process*  of  variable  length  ex- 
tends upward  from  the  thyroid  isthmus  or  from  the  adjacent  part  of 
either  lobe,  more  commonly  the  left  one,  and  is  attached  by  a  band  of 
loose  connective  tissue  to  the  body  of  the  hyoid  bone.  Occasionally  a 
muscular  slip4  is  substituted  for  the  latter  band,  or  independently 

1  Malpighian  corpuscles  ;  splenic  corpuscles. 
''Corpus  thyreoideum  ;  glandula  thyreoidea. 
3  Processus  pyramidalis.  4  Levator  glandulse  thyreoideae. 


684          GLAND-LIKE    ORGANS   WHOSE   FUNCTION    IS   OBSCURE. 


FIG.  345. 


PORTION  OF  THE  THYROID  BODY  IN  SECTION,  highly 
magnified,  a,  fibrous  stroma ;  b,  vesicles ;  c,  the  epi- 
thelium and  colloid  contents. 


extends  in  the  same  manner  from  the  thyroid  isthmus  to  the  hyoid 
bone. 

The  thyroid  body  is  solid  and  moderately  firm,  and  is  provided  with 
a  thin  connective-tissue  capsule,  from  which  processes  extend  into  the 

substance  of  the  body  and  divide 
it  incompletely  into  small,  irreg- 
ular portions  or  lobules. 

The  organ  is  highly  vascular, 
and,  besides  its  numerous  ves- 
sels, consists  of  rounded  poly- 
hedral, closed  vesicles1  of  dif- 
ferent sizes  embedded  in  a 
connective-tissue  matrix  and 
collected  into  irregular  groups 
or  lobules.  The  vesicles  range 
from  about  -fa  to  a  millimetre ; 
are  defined  by  a  basement  mem- 
brane 2  of  flat  endothelial  cells 
lined  by  an  epithelial  layer  of 
short  columnar  polyhedral  cells, 
and  contain  a  yellow  glairy 
liquid  or  colloid  substance. 

The  arteries  of  the  thyroid  body  are  the  superior  and  inferior 
thyroid.  They  are  remarkable  for  their  large  relative  size  and  fre- 
quent anastomoses,  and  they  end  in  capillary  nets  around  the  thyroid 
vesicles.  The  veins  are  numerous  and  large  and  form  a  superficial 
plexus,  from  which  proceed  the  superior,  middle,  and  inferior  thyroid 
veins. 

The  lymphatics  of  the  thyroid  are  also  numerous  and  large.  They 
originate  in  the  connective-tissue  matrix  of  the  thyroid  vesicles  and 
form  large  anastomosing  trunks  following  the  course  of  the  blood- 
vessels, joined  by  others  from  a  superficial  plexus. 

The  nerves  are  derived  from  the  middle  and  inferior  cervical  ganglia 
of  the  sympathetic  and  accompany  the  blood-vessels. 

The  thyroid  body  ordinarily  weighs  from  one  to  two  ounces,  and 
is  larger  in  the  female  than  in  the  male.  In  the  former  frequently  it 
exhibits  a  periodical  increase  about  the  time  of  menstruation.  It  is 
proportionately  larger  at  birth,  and  often  in  the  advance  of  age  its 
vesicles  become  enlarged  by  an  accumulation  of  the  colloid  substance, 
accompanied  by  a  decrease  of  the  connective-tissue  matrix.  It  is  also 
liable  to  hypertrophy,  constituting  the  affection  known  as  goitre,  in 
which  there  is  an  excessive  accumulation  of  colloid  substance  in  the 
vesicles. 


1  Alveoli. 


Membrana  propria. 


GLAND-LIKE   ORGANS   WHOSE   FUNCTION   IS   OBSCUEE. 


685 


THE   THYMUS. 

The  thymus,  or  thymus  gland,1  is  a  temporary  organ  of  un- 
known function,  situated  in  the  superior  mediastinum,  extending  into 
the  neck.  It  lies  immediately  behind  the  upper  part  of  the  sternum, 
in  front  of  the  pericardium,  between  the  pleurae,  reaching  down  as  far 
as  the  fourth  costal  cartilage  and  extending  upward  in  front  of  the 
great  blood-vessels  of  the  heart  and  the  trachea  to  the  thyroid  gland. 
It  is  a  soft,  pinkish-gray,  lobulated  body,  resembling  in  appearance  a 
racemose  gland,  and  is  very  variable  in  shape  and  size.  At  birth  it  is 
ordinarily  about  two  inches  long,  an  inch  to  an  inch  and  a  quarter 


FIG.  346. 


FIG.  347. 


b- 


ONE  LOBE  OF  THE  THYMUS  BODY  LAID  OPEN, 
AND  EXHIBITING  THE  LOBULES  AND  ACINI.     The 

lower  extremity  of  the  figure  exhibits  the  out- 
lines of  the  lobules. 


SECTION  OP  A  LOBULE  OP  THE  THYMUS  BODY, 
magnified,  a,  fibrous  investment  of  the  lobule ; 
b,  acini  penetrated  by  blood-vessels :  c,  cleft 
resulting  from  the  laceration  of  the  medulla. 


wide  below,  three  or  four  lines  thick,  and  ranges  in  weight  from  one  to 
two  drachms  or  more.  It  consists  of  a  pair  of  lateral  lobes,  mostly 
of  unequal  size  and  usually  of  elongated,  pyramidal  shape,  with  the 
broader  part  downward,  and  lying  in  contact  with  each  other  in  the 
median  line.  Sometimes  the  two  lobes  are  fused  together. 

From  birth  the  thymus  continues  to  grow  for  a  couple  of  years, 
after  which  it  gradually  atrophies  and  commonly  is  much  reduced  at 
puberty,  though  sometimes  it  remains,  partially  diminished,  to  ma- 
turity, and  commonly  traces  can  be  detected  much  later,  even  to  old 


Each  lobe  of  the  thymus  consists  of  numerous  polyhedral  lobules 


1  Glandula  thymus ;  corpus  thymianum ;  c.  incomprehensibile ;  sweetbread  of 
the  butchers. 


686  GLAND-LIKE   ORGANS    WHOSE    FUNCTION    IS    OBSCURE. 

united  by  delicate  connective  tissue,  which  also  forms  a  thin  capsule  to 
the  organ.  The  lobules  when  unravelled  by  dissection  are  found  to  be 
joined  by  an  axial  cord,  which  has  commonly  been  regarded  as  tubular,1 
but  appears  to  be  solid  and  composed  of  connective  tissue.  The  lobules 
are  aggregations  of  acini,2  from  one-half  to  two  millimetres  in  diameter, 
and  while  they  are  distinct  at  the  periphery  of  the  lobule  they  are  con- 
fluent towards  the  centre,  as  represented  in  the  figure  on  the  preceding 
page.  The  acini  and  lobules  have  been  described  as  having  an  interior 
cavity  freely  communicating  and  filled  with  liquid,3  but  from  recent 
researches  they  would  appear  to  be  solid  and  to  consist  of  a  thick 
peripheral  cortex  with  an  interior  softer  medulla.  The  cortex  resem- 
bles adenoid  or  lymphoid  tissue,  and  like  it  consists  of  a  delicate  frame- 
work of  branching  connective-tissue  corpuscles,  with  the  interspaces 
filled  with  lymphoid  corpuscles.  The  medulla  consists  of  a  similar  but 
coarser  framework  with  fewer  lymphoid  corpuscles  associated  with 
Others,  distinguished  by  their  striated  appearance  as  the  concentric 
corpuscles.  These  range  from  the  size  of  a  colorless  blood-corpuscle 
to  two  or  three  times  the  size,  and  consist  of  an  envelope  of  epithelioid 
cells  enclosing  one  or  several  granular  cells. 

In  the  retrograde  metamorphosis  of  the  thymus,  the  follicles  with 
their  lymphoid  contents  atrophy  and  the  interstitial  connective  tissue 
increases.  Plasma-cells  in  the  latter  are  transformed  into  fat-cells,  and 
the  remains  of  the  thymus  appear  composed  of  areolar  connective  with 
adipose  tissue. 

The  arteries  of  the  thymus  are  derived  from  the  mammary,  the  in- 
ferior and  superior  thyroid,  the  subclavian  and  carotid  arteries.  The 
branches  reaching  the  lobules  form  capillary  plexuses  around  the  cor- 
tex of  the  follicles,  whence  others  penetrate  to  the  cortex.  The  veins 
terminate  in  the  left  innominate  vein.  The  lymphatics  arise  around 
the  follicles  and  form  interlobular  plexuses,  whence  the  trunks  follow 
the  course  of  the  blood-vessels.  The  nerves  are  small  and  chiefly 
derived  from  the  sympathetic. 

THE  SUPRARENAL  BODIES. 

The  suprarenal  body4  is  a  flat,  triangular,  brownish-yellow  organ 
placed  on  the  upper  extremity  of  the  kidney  in  each  side  of  the  abdo- 
men. The  upper  thinnest  part  has  a  transversely  convex  border  vari- 
ably elevated  towards  the  middle  and  directed  upward  and  inward. 
The  lower  thickest  part  is  transversely  concave,  commonly  deeply 
grooved,  and  is  applied  to  the  inner  fore  part  of  the  top  of  the  kidney, 
to  which  it  is  attached  by  loose  connective  tissue.  The  posterior  sur- 

1  Central  canal ;  reservoir  of  the  thymus. 

2  Follicles  ;  granules;  nodules.  s  Thymic  juice  ;  succus  thymicus. 

*  Suprarenal  capsule  or  gland  ;  glandula  or  capsula  suprarenale  ;  capsula  atra- 
biliaria  ;  ren  succenturiatus. 


GLAND-LIKE   ORGANS  WHOSE   FUNCTION   IS   OBSCURE. 


687 


face  rests  against  the  diaphragm,  and  the  anterior  surface  presents  a 
transverse  furrow,  the  hilus.  The  right  suprarenal  body  in  front  is  in 
contact  with  the  under  surface  of  the  liver,  and  the  left  one  with  the 
spleen  and  pancreas.  The  right  body  is  usually  smaller  and  more  tri- 
angular than  the  left,  which  is  more  crescentic.  Each  weighs  about 
two  drachms,  and  they  commonly  measure  about  two  inches  high  and 
nearly  the  same  width,  and  a  fourth  of  an  inch  or  less  thick. 

The  suprarenal  body  is  invested  with  loose  areolar  tissue,  by  which 
it  adheres  to  the  contiguous  parts,  and  often  contains  more  or  less  fat. 
It  is  provided  with  a  thin  fibro-connective-tissue  capsule,  which  is  con- 
tinuous with  the  matrix  or  stroma  of  the  organ  and  consists  of  two 
portions  distinguished  as  cortical  and  medullary. 


FIG.  348. 


FIG.  349. 


aba 

SECTION  OF  THE  CORTEX  OF  A  SUPRARENAL 
BODY,  highly  magnified,  a,  stroma  of  fibro-con- 
nective  tissue ;  6,  columnar  groups  of  cells. 


CELLS  FROM  THE  SUPRARENAL  BODY,  highly 
magnified,  a,  nucleated  cells  from  the  cortex  ; 
6,  c,  d,  cells  from  the  same  containing  fat ;  e, 
cells  from  the  medulla. 


The  cortical  portion  forms  the  greater  part  of  the  thickness  of  the 
body,  is  of  a  deep  yellow  color,  of  firm  consistence,  and  has  a  distinctly 
striated  appearance  directed  through  the  thickness.  It  consists  chiefly 
of  columnar  groups  of  polyhedral  cells  with  granular  contents,  often 
mingled  with  yellow  oil-globules,  and  with  a  clear,  spherical  nucleus. 
At  the  outer  boundary  of  the  cortex  is  a  zone 1  of  small  groups  of  cells, 
and  at  the  inner  boundary  another  zone2  of  still  smaller  groups,  but 
these  do  not  appear  to  be  different  in  character  from  the  intermediate 
thicker  zone s  of  columnar  groups.  The  cell-groups  occupy  correspond- 
ing areolse  of  the  connective-tissue  matrix,  but  intercommunicate  with 
one  another. 

The  medullary  portion  is  dark  chocolate-brown  and  soft,  so  as  to 
be  readily  torn,  from  which  accident  the  suprarenal  bodies  have  often 
been  described  as  having  a  central  cavity.  It  is  composed  of  a  more 
diffused  intertexture  of  connective  tissue,  with  the  areolae  occupied 
by  groups  of  cells  of  irregular  shape,  clearer  than  those  of  the  cortex, 
free  from  yellow  oil,  and  having  a  different  chemical  reaction. 


1  Zona  reticularis. 


2  Z.  glomerulosa. 


3  Z.  fasciculata. 


688          GLAND-LIKE   OKGANS   WHOSE   FUNCTION    IS   OBSCURE. 

The  suprarenal  bodies  are  supplied  by  arteries  directly  from  the 
aorta  and  from  the  phrenic  and  renal  arteries.  These  end  in  large 
venous  capillaries  of  the  cortex,  extending  thence  into  the  medulla. 
The  capillaries  traverse  the  fibrous  matrix  and  are  associated  with 
unstriped  muscle-fibres  arranged  parallel  with  the  vessels.  The  veins 
converge  from  the  centre  of  the  body  and  emerge  at  the  hilus,  usually 
uniting  in  a  single  trunk,  which  joins  the  inferior  cava  on  the  right  and 
the  corresponding  renal  vein  on  the  left. 

Lymphatics  commence  in  clefts  of  the  connective-tissue  matrix  of 
the  suprarenal  body,  and  also,  according  to  Klein,  among  the  cells  of 
the  cell-groups.  The  vessels  pursue  the  course  of  the  blood-vessels  from 
the  organs  and  are  joined  by  others  from  a  superficial  plexus. 

The  nerves  are  remarkably  numerous,  and  are  derived  partly  from 
the  solar  plexus  and  partly  from  the  renal  plexus  of  the  sympathetic. 
The  bundles  of  nerve-fibres  pass  through  the  matrix  of  the  cortical 
substance  and  form  an  interlacement  in  the  medulla.  Some  authori- 
ties regard  the  cells  of  the  medulla  as  nerve-cells. 

THE   CAKOTID   GLAND. 

At  the  bifurcation  of  the  common  carotid  artery  is  a  minute  body 
having  a  glandular  appearance  and  hence  called  the  carotid  gland.1 
It  is  composed  mainly  of  a  plexus  of  minute  arteries  invested  by  one  or 
more  layers  of  polyhedral  cells  enveloped  in  connective  tissue.  It  is 
probably  the  remains  of  some  part  of  the  branchial  vascular  apparatus 
of  the  embryo. 

THE  COCCYGEAL  GLAND. 

The  coccygeal  gland 2  is  a  body  about  the  size  of  a  small  pea, 
situated  near  the  end  of  the  coccyx,  at  the  tendinous  insertion  of  the 
anal  elevator  muscles.  It  is  composed  of  a  tuft  of  small  vessels  derived 
from  the  middle  sacral  artery,  freely  anastomosing  and  invested  with 
polyhedral  cells  and  embedded  in  a  matrix  of  fibro-connective  tissue, 
which  also  forms  a  capsule  for  it.  It  is  furnished  with  nerves  from  the 
sympathetic  system. 

1  Glandula  carotica ;  ganglion  intercaroticum.  2  Gland  of  Luschka. 


OHAPTEE    XY. 

THE   NERVOUS    SYSTEM. 

THE  nervous  system  consists  of  the  brain  and  spinal  cord  with 
their  nerves  and  ganglia,  and  of  the  sympathetic  nerves,  likewise  with 
their  nerves  and  ganglia. 

The  brain  is  the  remarkably  large  mass  of  nervous-  substance  which, 
together  with  its  enveloping  membranes,  fills  the  cavity  of  the  cranium, 
and  the  spinal  cord  is  a  prolongation  of  that  mass  enclosed  in  a  sheath 
of  the  same  membranes  within  the  spinal  canal.  The  two  together  con- 
stitute the  cerebro-spinal  axis,  the  great  centre  of  the  nervous  system, 
but  regarded  as  consisting  of  numerous  physiological  centres,  which 
are  more  or  less  fused  with  one  another  and  therefore  not  anatomically 
distinct.  They  are  bilaterally  symmetrical,  or  consist  of  similar  halves 
united  in  the  median  line. 

The  sympathetic  nerves  consist  of  two  systems  or  sets,  one  on  each 
side  of  the  body  and  communicating  with  the  nerves  of  the  cerebro- 
spinal  system. 

The  ganglia  in  the  more  restricted  meaning  are  small  nodular 
bodies  or  nerve-centres,  situated  in  various  positions  in  the  course  of 
the  nerves.  In  a  general  sense  the  name  of  ganglion  is  synonymous 
with  a  nerve-centre,  and  this  is  regarded  to  be  the  point  or  focus  to 
which  impressions  are  communicated  and  from  which  impulses  are 
derived. 

The  nerves  in  general  are  cords  distributed  throughout  the  body 
and  connecting  the  nerve-centres  with  all  other  organs,  which  in  their 
relative  position  to  these  centres  are  distinguished  as  peripheral  organs. 
They  also  often  connect  the  nerve-centres  with  one  another,  when 
they  are  distinguished  as  commissures.  They  are  the  avenues  through 
which  impressions  and  impulses  are  conveyed  to  and  from  the  nerve- 
centres. 

The  nervous  system  is  comparable  to  a  telegraphic  system ;  the 
cerebro-spinal  axis  accords  with  the  chief  station,  the  nerves  accord 
with  the  wires,  and  the  ganglia  with  lesser  stations. 

The  larger  and  more  conspicuous  nerves  are  those  which  proceed 
from  the  cerebro-spinal  axis,  thence  called  the  cerebro-spinal  nerves. 
They  are  generally  more  or  less  distinctly  marked  in  contrast  with 
surrounding  structures  by  their  whiter  color.  They  usually  run  in  the 
most  direct  manner  for  variably  long  and  often  the  longest  distances, 

44  689 


690  THE   NERVOUS   SYSTEM. 

and  are  with  few  exceptions  distributed  to  the  skin,  the  special  sense 
organs,  and  all  the  more  distinct  muscles,  especially  those  which 
may  or  do  act  intentionally.  One  pair  only,  the  vagus  nerves,  are 
distributed  to  the  internal  viscera. 

Each  lateral  set  or  system  of  the  cerebro-spinal  nerves  in  its  distri- 
bution is  confined  to  the  corresponding  side  of  the  body,  with  perhaps 
the  exception  of  the  vagus  nerve,  though  in  many  instances  the  nerve- 
fibres  forming  the  nerves  in  part  are  derived  from  opposite  sides  of  the 
centres  in  which  they  originate. 

The  nerves  of  the  sympathetic  system  are  in  general  very  much 
smaller  than  those  of  the  cerebro-spinal  system,  much  less  conspicuous, 
mostly  of  a  gray  color,  and  not  so  readily  distinguished  among  the  sur- 
rounding structures.  They  are  provided  with  many  ganglia,  and  are 
distributed  to  the  internal  viscera  and  especially  to  the  vascular  system. 
The  two  sympathetic  nerves  freely  communicate  with  each  other,  and 
each  also  freely  communicates  with  the  corresponding  lateral  cerebro- 
spinal  system.  Where  the  sympathetic  nerves  communicate  with  those 
of  the  cerebro-spinal  system  there  is  a  mutual  interchange  of  fibres,  and 
the  former  usually  exhibit  variable  proportions  of  the  fibres  of  both 
systems  mingled. 

The  material  of  the  nervous  system,  commonly  called  nerve-matter, 
is  composed  of  a  number  of  distinct  anatomical  elements,  of  which  the 
nerve-cells  and  nerve-fibres  are  the  special  or  essential  elements,  while 
the  others  consist  of  the  connecting  or  supporting  elements  and  the 
nutrient  vessels. 

In  the  cerebro-spinal  axis  the  mass  of  nerve-matter  is  of  two  kinds, 
distinguished  by  their  color  as  the  white  and  the  gray. 

The  white  matter,1  milk-white  and  of  soft  consistence,  is  mainly 
composed  of  nerve-fibres  supported  in  a  soft  matrix,  the  neuroglia.  In 
the  fresh  state  it  appears  pulpy  and  homogeneous,  but  when  hardened 
in  alcohol  or  by  other  means  it  readily  tears  into  fibres. 

The  gray  matter2  is  mostly  pale  reddish-brown,  but  darker  or 
lighter  in  some  positions,  and  is  also  of  soft,  pulpy  consistence  when 
fresh.  It  consists  of  an  abundant  matrix  of  neuroglia  with  nerve- 
fibres  and  embedded  nerve-cells.  When  hardened  in  alcohol  it  breaks 
up  into  granular  matter. 

The  nerves  in  general  are  composed  of  bundles  of  nerve-fibres, 
enveloped  in  sheaths  of  fibro-connective  tissue.  Those  of  the  cerebro- 
spinal  system  are  opaque  white  or  pinkish  white,  flexible  and  tenacious  ; 
those  of  the  sympathetic  system  are  usually  gray  and  less  tenacious. 

The  ganglia  are  composed  of  a  matrix  of  fibro-connective  tissue 
with  embedded  groups  of  nerve-cells  and  traversed  by  bundles  of 
nerve-fibres. 

1  Medullary  matter ;  fibrous  substance. 

2  Cineritious  substance ;  vesicular  substance ;  cortical  matter. 


THE   NEBVOTJS  SYSTEM. 


691 


FIG.  350. 


THE  NERVE-FIBRES. 

The  nerve-fibres,1  one  of  the  essential  elements  of  structure  of  the 
nervous  system,  are  distinguished  as  of  two  kinds,  the  white  or  medul- 
lated  and  the  gray  or  non-medullated  fibres,  the  difference  being  due  to 
the  presence  or  absence  of  a  medullary  sheath. 

The  medullated  nerve-fibres 2  form  the  chief  component  of  the 
white  matter  of  the  brain  and  spinal  cord,  and  it  is  to  them  that  the 
white  color  is  due.  They  also 
form  the  chief  nervous  element 
of  structure  of  the  cerebro-spinal 
nerves,  to  which  they  also  give 
the  white  color.  They  further 
contribute  to  the  structure  of  the 
gray  substance  of  the  brain  and 
spinal  cord,  also  to  the  ganglia  and 
the  sympathetic  nerves. 

They  are  cylindrical'  threads, 
straight  or  slightly  flexuose,  elas- 
tic, even  and  except  near  their  ex- 
tremities uninterruptedly  continu- 
ous and  of  pretty  uniform  diameter. 
In  the  nerves  they  are  collected  in 
distinct  bundles,  which  often  di- 
vide and  conjoin  in  other  bundles. 
The  branching  of  nerves  is  due 
to  the  separation  and  distribution 
of  smaller  bundles  of  nerve-fibres. 
In  the  same  bundle  the  fibres  gen- 
erally approximate  uniformity,  but 
others  present  considerable  differ- 
ence in  size,  which  varies  greatly 
in  different  parts  of  the  nervous 
system.  The  fibres  are  mostly 

smallest  in  the  cerebro-spinal  axis,  especially  in  the  gray  matter.  In 
the  white  matter  they  are  closely  aggregated  and  vary  considerably 
in  size.  They  range  from  about  -^fay  to  y^-j-  of  a  line  in  thickness. 
Though  normally  even,  they  are  very  prone  to  change,  and  thus  after 
death  become  more  or  less  varicose,  especially  in  those  of  the  white 
matter  of  the  cerebro-spinal  axis,  where  they  assume  a  beaded  ap- 
pearance. 

In  the  fresh,  unaltered  state,  under  a  microscope  of  moderate 
power,  the  medullated  nerve-fibres  are  colorless  and  translucent,  and 
bordered  at  the  sides  by  a  distinct  double  outline,  so  that  they  appear 


STRUCTURE  OF  NERVE-FIBRES,  partly  ideal.  1, 
a  nerve-fibre  represented  in  the  fresh  condition, 
exhibiting  in  succession  its  membranous 
sheath,  medullary  sheath,  and  axis-fibre  ;  2,  3, 
4,  5,  exhibit  the  same  constituents ;  the  medul- 
lary sheath  indicated,  as  it  appears  shortly  after 
death,  by  heavy  outlines ;  the  axis-fibre  repre- 
sented as  dotted.  In  4,  5,  the  axis-fibre  is  seen 
projecting  from  the  cut  ends  of  the  nerve-fibres. 
In  4,  the  medullary  sheath  is  seen  exuding  in 
drops  through  a  rupture  of  the  membranous 
sheath.  Highly  magnified. 


Ganglionic  nerves. 


2  Dark  or  double-bordered  nerve-fibres. 


692 


THE   NERVOUS  SYSTEM. 


to  be  tubular.     In  those 
FIG.  351. 


—2 


_  1 


A  MKDULLATED    NERVE-FIBRE, 

treated  with  osmic  acid,  and 
highly  magnified.  1,  nodes  ;  2, 
membranous  sheath  of  the  inter- 
node;  3,  its  nucleus;  4,  medul- 
lary sheath  (the  thick  black 
line) ;  5,  the  axis-fibre. 

fibres  depends  more  on  it 


of  the  nerves  the  application  of  water  pro- 
duces a  division  of  the  double  border,  so  that 
the  fibres  exhibit  three  portions,  which  are 
distinguished  as  the  axis-fibre  enclosed  by 
the  medullary  sheath  and  the  outer  mem- 
branous sheath.  The  further  action  of  water 
renders  the  distinction  of  the  cylinder  axis 
from  the  medullary  sheath  less  evident.  In 
the  medullated  fibres  of  the  brain  and  spinal 
cord  the  membranous  sheath  is  absent,  and 
hence  their  greater  softness  and  delicacy. 

The  axis-fibre1  is  the  essential  portion 
of  every  nerve-fibre,  both  medullated  and 
non-medullated,  and  is  always  the  means 
of  connection  with  the  nerve-cells.  In  the 
medullated  fibres,  as  expressed  by  the  name, 
it  forms  the  axis  or  central  portion  and  is 
closely  embraced  by  the  medullary  sheath, 
which  seems  to  serve  as  an  insulator  to  it. 
Under  a  high  power  of  the  microscope  it  ex- 
hibits a  longitudinally  striated  and  granular 
appearance.  It  is  composed  of  exceedingly 
fine  filaments,  the  nerve-fibrils,2  which  are 
collected  together  in  a  bundle  united  by  a 
minutely  granular  cement  and  enclosed  in  a 
delicate  homogeneous  membranous  sheath. 
Each  fibril  appears  to  be  composed  of  a  single 
row  of  granules,  which  in  uniformity  of  size 
and  regularity  of  arrangement  resemble  the 
sarcous  elements  of  primitive  muscular  fibrils, 
though  not  so  distinctly  evident. 

The  medullary  sheath*  which  encloses 
the  axis-fibre  is  less  consistent  and  is  clearer. 
In  fresh  nerve-fibres  it  is  semi-liquid  and 
resembles  in  appearance  thick  oil.4  When 
in  manipulation  the  fibres  are  torn,  the  sub- 
stance oozes  out  and  collects  in  irregular 
drops,  like  oil-globules.  To  it  the  white  color 
and  lustre  of  the  nerves  and  of  the  medullary 
substance  of  the  centres  are  mainly  due. 

The  thickness  of  the  medullary  sheath  is 
variable,  and  the  difference  in  size  of  nerve- 
than  on  the  axis-fibre.  In  medullated  fibres 


1  Cylinder  axis. 

3  White  substance  of  Schwann. 


2  Primitive  fibrillae  ;  granular  fibrils. 
4  Mvelin. 


THE   NERVOUS   SYSTEM.  693 

of  the  sympathetic  nerves  it  is  often  so  thin  that  they  can  only  be 
distinguished  from  the  associated  non-medullated  fibres  by  their  dis- 
tinctly darker  outline.  The  substance  of  the  medullary  sheath  has 
commonly  been  regarded  as  a  homogeneous,  semi-liquid,  fat-like  mate- 
rial, but  the  able  investigator  Schmidt  describes  it  as  consisting  of  a 
more  consistent  fibrillar  material,  with  a  granular  semi-liquid  which 
predominates  next  the  axis-fibre. 

The  membranous  sheath,  or  neurilemma,1  is  a  delicate,  elastic, 
structureless  layer,  which  closely  invests  the  medullary  sheath  in  the 
peripheral  nerve-fibres,  but  is  absent  in  the  central  fibres  or  those  of 
the  brain  and  spinal  cord.  A  closer  examination  of  the  nerves  has 
shown  that  the  medullated  nerve-fibres  in  their  course  are  constricted 
at  nearly  regular  intervals,  the  constrictions  being  distinguished  as 
nodes,2  while  the  intermediate  portions  of  the  fibres  are  called  inter- 
nodes.3  The  axis-fibre  is  continued  uninterruptedly  and  evenly  through 
the  nodes,  but  the  medullary  sheath  is  interrupted  by  the  constrictions, 
which  are  filled  in,  outside  the  membranous  sheath,  with  a  clear  cement- 
ing substance.  The  arrangement  thus  described  is  rendered  more  evi- 
dent through  the  action  of  osmic  acid,  which  stains  the  medullary 
sheath  black  while  the  membranous  sheath  and  nodes  remain  nearly 
colorless  and  clear.  Silver  nitrate  stains  the  nodes  and  adjacent  por- 
tion of  the  axis-fibre,  so  as  to  give  rise  to  the  appearance  of  a  black 
cross  in  these  positions.  Perosmic  acid  causes  the  medullary  sheath  to 
break  up  into  imbricating  cylindrical  segments  of  variable  length,  but 
it  is  doubtful  whether  this  condition  is  related  with  a  pre-existing 
structure  of  the  sheath.  About  the  middle  of  the  internodes  an  oval 
nucleus  lies  within  the  membranous  sheath,  in  a  recess  of  the  contents, 
and  causes  a  slight  bulging  of  the  sheath  to  which  it  belongs.  The 
distinction  of  nodes  and  internodes  is  not  evident  in  the  central  medul- 
lated nerve-fibres. 

At  the  origin  of  the  medullated  nerve-fibres  in  the  centres  generally 
the  axis-fibre  extends  beyond  the  medullary  sheath  and  is  continuous 
with  the  prolongation  of  a  nerve-cell.  To  their  destination  they  remain 
undivided,  but  reaching  the  peripheral  tissues  in  which  they  are  dis- 
tributed they  commonly  undergo  division  at  the  nodes,  and  after 
branching  several  times  the  medullary  sheath  ceases,  but  the  axis- 
fibre  is  continued.  This,  too,  usually  branches  and  finally  breaks  up 
into  its  constituent  nerve-fibrils,  which  are  distributed  directly  to  or 
among  the  structural  elements  of  the  tissues. 

The  non-medullated  nerve-fibres*  predominate  in  the  nerves 
generally  of  the  sympathetic  system,  in  which  they  are  mingled  with 


1  Membranous  sheath  ;  tubular  membrane  ;  primitive  sheath  ;  sheath  of  Schwann. 

2  Nodes  of  Kanvier. 

3  Internodes  of  Ranvier  ;  interannular  segments. 

4  Pale,  gray,  or  gelatinous  fibres  ;  fibres  of  Remak. 


694 


THE   NERVOUS   SYSTEM. 


variable  proportions  of  medullated  fibres.    The  usually  gray  aspect  and 
less  distinct  appearance  of  the  sympathetic  nerves  are  mainly  due  to 


FIG.  352. 


FIG.  353. 


MODE  OF  BRANCHING  OP  A  MEDULLATED  NERVE-FIBRE,  at  the  nodes.    Highly  magnified. 

the  comparative  fewness,  or  it  may  be  the  absence,  of  the  medullated 
fibres,  and  the  whiteness  of  some  of  them  is  owing  to  the  preponder- 
ance of  the  latter.  Generally  the  non-medullated  fibres  are  smaller, 
but  otherwise  accord  with  them  in  structure, 
except  that  they  possess  no  medullary  sheath. 
In  nerves  they  are  furnished  with  a  delicate 
membranous  sheath,  which  is  intimately  con- 
nected with  the  axis-fibre  and  is  nucleated. 
Unlike  the  medullated  nerve-fibres,  the  non- 
medullated  fibres  in  their  course  divide  and 
anastomose  and  ultimately  are  distributed  in 
the  same  manner.  The  medullated  nerve-fibres 
commence  and  terminate  as  non-medullated 
nerve-fibres. 

The  nerve-fibres  generally  are  regarded  as 
being  functionally  of  two  kinds, — those  which 
convey  impressions  of  stimuli  from  peripheral 
and  sensory  organs  to  the  nerve-centres  and 
those  which  communicate  motor  impulses  in 
the  opposite  direction  to  muscular  and  secretory 
structures  and  the  like.  The  former  are  called 
afferent,  centripetal,  or  sensory  fibres ; 
the  latter,  efferent,  centrifugal,  or  motor  fibres.  These  are  not 
clearly  distinct  anatomically,  though  there  often  seems  to  be  some  differ- 
ence in  the  size  of  the  two  kinds  of  fibres.  Most  of  the  nerves  of  the 
brain  are  observed  to  be  distinct,  as  sensory  or  motor,  and  as  such  the 
spinal  nerves  are  completely  separated  at  their  roots.  The  destination 
of  the  nerve  ordinarily  rather  than  its  structure  serves  to  determine  its 


PORTION  OF  A  SYMPATHETIC 
NERVE,  a,  two  medullated 
nerve -fibres  with  a  number 
of  non-medullated  fibres,  b. 
Highly  magnified. 


THE  NERVOUS   SYSTEM. 


695 


physiological  character.  Thus,  a  nerve  to  a  muscle  is  almost  completely 
a  motor  nerve,  while  one  to  the  skin  is  mainly  sensory.  The  optic 
nerve  to  the  retina  of  the  eye  is  purely  sensory.  In  the  nerves  of  the 
sympathetic  system  the  same  physiological  difference  exists,  but  is 
much  more  obscure  anatomically. 

NERVE-CELLS. 

The  nerve-  or  ganglion-cells,  another  and  tne  more  essential  ele- 
ment of  the  nervous  system  as  the  immediate  centres  of  nerve-power, 
are,  for  the  most  part,  embedded  in  the  gray  matter  of  the  cerebro- 
spjnal  axis  and  in  the  ganglia.  They  also  occur  in  the  course  of  some 

FIG.  354. 


NERVE-CELLS  FROM  THE  BRAIN  :  highly  magnified.  1,  cell  with  one  of  its  processes  continuous 
as  the  axis-fibre  a  of  the  medullated  fibre  6;  2,  two  cells,  a,  6,  united  by  a  commissural  fibre  c;  3, 
three  cells  a  united  by  commissural  fibres  b,  and  joined  by  axis-fibres  with  medullated  fibres  c; 
4,  nerve-cell  with  an  accumulation  of  dark  pigment. 


of  the  sympathetic  nerves,  while  in  a  modified  form  they  enter  into 
the  composition  of  several  of  the  special  sense  organs.  They  exhibit 
considerable  variety  in  shape  and  size,  and  in  these  respects  are  to 
some  degree  characteristic  of  different  parts  in  which  they  occur. 
They  are  spheroidal,  ovoidal,  pyriform,  fusiform,  pyramidal,  and  irreg- 
ularly multangular,  and  are  provided  with  one,  two,  or  more  tapering 
processes  or  appendages,  which  are  simple  or  branched.  In  the  cere- 
bral convolutions  they  are  pyramidal,  and  of  moderate  and  variable 
sizes  at  different  depths ;  in  the  cerebellar  folds  there  is  a  deep  stratum 


696  THE   NERVOUS   SYSTEM. 

of  large  ovoid  cells  with  conspicuous  branching  processes.  In  the  an- 
terior cornua  of  the  spinal  cord  they  are  large,  multangular,  and  pro- 
vided with  many  radiating  processes,  and  in  the  posterior  cornua  there 
are  similar  but  smaller  and  narrower  cells.  In  the  spinal  ganglia  they 
are  spheroidal  or  pyriform,  with  one  or  two  processes  directed  from 
the  same  or  opposite  poles  ;  in  the  sympathetic  ganglia  they  are  smaller,, 
irregularly  angular,  and  with  more  processes.  In  the  course  of  nerves 
they  are  fusiform  and  prolonged  into  the  nerve-fibres.  In  some  parts 
of  the  brain,  as  in  the  gray  matter  of  the  cerebellar  folds  beneath 
the  stratum  of  large  nerve-cells,  there  are  numerous  small  spheroidal 
and  angular  cells  about  the  size  of  colorless  blood-corpuscles  or  much 
less.  They  appear  to  be  miniature  forms  of  the  larger  cells,  which 
they  resemble  in  composition,  and  their  processes  generally  seem  to- 
join  one  another  and  the  finer  ones  of  the  contiguous  larger  nerve- 
cells. 

In  the  ganglia  of  the  cerebro-spinal  nerves,  except  the  four  smaller 
ones  of  the  trigeminal  nerve,  the  nerve-cells  are  prolonged  into  one 
or  two  processes  and  are  thus  distinguished  as  unipolar  and  bipolar 
cells.  In  the  latter  the  processes  may  proceed  from  the  same  or  op- 
posite poles,  and  in  both  kinds  of  cells  the  processes  become  con- 
tinuous as  the  axis-fibre  of  nerve-fibres.  After  a  short  distance  the 
processes  become  invested  with  a  medullary  sheath  and  thus  become 
medullated  nerve-fibres. 

In  some  unipolar  cells  it  has  been  observed  that  after  the  fibre 
acquires  a  medullary  sheath  it  becomes  several  times  coiled  around 
the  cell  and  then  forks,  the  two  branches  proceeding  in  opposite- 
directions,  as  in  those  of  bipolar  cells. 

In  the  ganglia  of  the  sympathetic  and  the  small  ones  of  the  tri- 
facial  nerves,  many  nerve-cells  possess  a  greater  number  of  processes, 
three  or  more,  and  are  hence  called  multipolar  cells.  Most  of  the 
processes  continue  as  non-medullated  fibres,  though  usually  one  or  two, 
shortly  after  their  origin,  become  invested  with  a  medullary  sheath 
and  then  proceed  as  medullated  nerve-fibres.  In  the  bipolar  cells  of 
the  sympathetic  nerves  one  process  may  continue  as  a  non-medullated 
fibre,  while  the  other  becomes  a  medullated  fibre.  Some  nerve-cells, 
apparently  devoid  of  processes  and  hence  called  apolar,  have  been, 
regarded  as  partially-developed  forms. 

The  nerve-cells  of  the  cerebro-spinal  axis  are  multipolar  and  gener- 
ally characterized  by  many  tapering,  radiating,  and  mostly  branching 
processes.  In  the  large  nerve-cells  of  the  anterior  cornua  of  the, 
spinal  cord,  from  among  the  processes  commonly  a  single  one  is  pro- 
longed in  a  cylindrical  filament,  which  soon  becomes  furnished  with  a 
medullary  sheath  and  thus  constitutes  the  beginning  of  a  medullated 
nerve-fibre.  All  the  other  processes  taper  and  branch  into  the  finest 
filaments,  which  are  diffused  in  the  surrounding  neuroglia.  The  nerve- 
cells  generally  of  the  cerebro-spinal  axis  are  considered  to  have  a. 


THE   NERVOUS   SYSTEM. 


697 


similar  arrangement  and  relation  with  medullated  nerve-fibres  as  that 
described,  except  in  the  case  of  the  numerous  small  cells. 

The  processes  of  all  nerve-cells  are  fibrillar,  and  the  fibrils  are 
minutely  granular,  or  they  are  identical  in  structure  with  the  axis- 
fibre  of  nerve-fibres,  with  which  commonly  one  or  more  become  di- 
rectly continuous.  The  body  of  the  nerve-cell  consists  of  a  granular 
fibrillated  protoplasm,  containing  a  comparatively  clear,  distinct,  and 
highly-refracting  nucleus. 

The  cells  exhibit  a  faintly  yellowish  or  brownish  tint,  due  to  dif- 
fused colored  pigment,  which  is  often  accumulated  in  a  mass  among 
the  contents. 

In  the  cerebro-spinal  axis  the  nerve-cells,  like  the  nerve-fibres,  have 
no  membranous  sheath.  In  prepared  sections  they  are  observed  to 
occupy  clearer  areas  than  the  surrounding  matrix,  which  areas  are 
regarded  as  lymphatic  spaces.  In  the  ganglia  the  nerve-cells  are 
enclosed  in  a  membranous  sheath  which  is  continuous  with  that  of  the 
connecting  nerve-fibres. 

THE   NEKVES. 

The  nerves  are  cords  which  connect  the  nerve-centres  with  all 
other  parts  of  the  body,  to  and  from  which  they  convey  impressions. 

The  cerebro-spinal  nerves,  conspicuous  for  their  comparatively  large 
size  and  white  color,  appear  mostly  as  straight  cylindrical  or  flattened 
cylindrical  cords,  usually  pursuing  the  general  course  of  the  blood- 
vessels, but  running  more  directly  to  their  destination.  They  possess 
considerable  strength,  moderate  elasticity  and  tenacity,  which  qualities 


FIG.  355. 


FIG.  356. 


TRANSVERSE  SECTION  OF  THE  SMALL  SCIATIC 
NERVE  OF  A  CALF,  magnified  fifteen  diameters, 
a,  common  sheath,  or  epineurium  ;  b,  perineu- 
rium ;  c,  funicles,  or  bundles  of  nerve-fibres. 

are  mainly  due  to  their  abundant 
connective-tissue  envelopes.  Their 
essential  structural  element  con- 
sists chiefly  of  medullated  nerve- 
fibres,  which  pursue  an  uninter- 
rupted course  from  their  origin  to 
their  termination,  where  they  alone 

divide.  Their  connection  with  the  cerebro-spinal  axis  is  regarded  as 
their  origin,  and  their  commencement  at  the  surface  or  in  the  interior 
of  the  centre  is  distinguished  as  the  root  of  the  nerve. 


MODE   OF   ANASTOMOSIS    AND    BRANCHING    OF 

NERVES.  1,  2,  two  fasciculi  of  nerve-fibres ;  3, 
a  branch  of  three  fibres;  4,  a  branch  of  two 
fibres ;  5,  6,  branches  of  single  fibres ;  7,  anasto- 
mosis between  two  nerves. 


698  THE    NERVOUS   SYSTEM. 

In  their  distribution  the  nerves  divide  and  subdivide  mostly  at  very 
acute  angles,  and  the  branching  consists  in  the  separation  of  bundles  of 
the  nerve-fibres,  the  branches  being  proportioned  in  size  to  the  num- 
ber of  the  fibres  which  form  them.  Often  in  their  course  branches  of 
contiguous  nerves  unite  and  again  divide,  forming  an  intertexture  or 
plexus,  even  with  the  largest  nerves,  as  exemplified  by  the  brachial 
plexus.  In  all  such  cases  the  branching  and  anastomosis  of  nerves  are 
essentially  a  division  and  interchange  of  bundles  of  nerve-fibres,  not 
a  division  and  anastomosis  of  the  fibres  individually. 

The  smaller  nerves,  except  such  as  consist  of  a  single  nerve-fibre, 
are  cylindrical  bundles  of  fibres,  or  funicles,  enclosed  in  a  membra- 
nous sheath,  the  perineurium,1  and  larger  nerves  consist  of  several 
prismatic  funicles  collected  in  a  cylindrical  cord  and  enclosed  by  a 
common  perineurium.  A  number  of  such  cords  united  by  and  enclosed 
in  a  common  connective-tissue  sheath,  or  epineurium,2  form  the 
largest  nerves. 

The  funicles  of  the  same  nerve  may  frequently  divide  and  anasto- 
mose, but  in  all  cases  it  is  the  interchange  of  larger  or  smaller  bundles 
of  fibres. 

The  perineurium  in  the  smallest  nerves  consists  of  a  single  mem- 
branous lamina,3  composed  mainly  of  transverse  fibres  of  connective 
tissue  with  elastic  tissue,  invested  on  both  surfaces  with  a  delicate 
endothelium. 

In  the  larger  nerves  the  perineurium  consists  of  several  concentric 
laminae,  attached  by  fibres  of  connective  tissue,  having  the  opposed 
surfaces  invested  with  an  endothelium,  the  cell-plates  of  which  become 
evident  by  silver-nitrate  staining.  The  intervals  of  the  laminae  are 
lymph-spaces,  which  communicate  with  lymphatic  vessels  accompany- 
ing the  blood-vessels  of  the  nerves.  Partitions  from  the  innermost 
lamina  of  the  perineurium  divide  the  funicle  of  nerve-fibres  into  dif- 
ferent-sized prismatic  bundles.  The  intervals  of  the  nerve-fibres  are 
also  occupied  by  a  delicate  connective  tissue,  distinguished  as  the  endo- 
neurium  and  supporting  the  capillary  blood-vessels. 

The  sensory  nerves  of  the  cerebro-spinal  system  are  larger  than  its 
motor  nerves,  though  generally  they  possess  a  greater  proportion  of 
smaller  nerve-fibres.  Thus  the  larger  sensory  roots  of  the  spinal  nerves 
have  a  greater  proportion  of  small  nerve-fibres  than  the  corresponding 
smaller  motor  roots  of  the  same  nerves.  The  nerves  also  to  the  volun- 
tary muscles  are  mainly  composed  of  comparatively  large  nerve-fibres, 
while  those  to  the  skin  contain  many  more  small  ones. 

The  nerves  of  the  sympathetic  system  are  generally  very  much 
smaller  and  shorter  than  those  of  the  cerebro-spinal  system,  are  mostly 
gray  or  dull  reddish,  comparatively  inconspicuous,  and  more  closely 

1  Neurilemma.  2  Common  or  cellular  sheath  ;  vagina  cellulosa. 

3  Sheath  of  Henle. 


THE   NERVOUS   SYSTEM.  699 

attached  to  contiguous  parts,  from  which  they  are  often  obscurely 
denned.  They  usually  proceed  to  the  nearest  blood-vessels,  by  fre- 
quent division  and  anastomosis  form  intricate  plexuses  around  them, 
and  accompany  them  in  their  distribution.  They  are  chiefly  com- 
posed of  non-medullated  fibres,  while  those  which  appear  whiter  than 
usual  contain  a  greater  proportion  of  medullated  fibres. 

Few  nerves  of  either  system  are  composed  exclusively  of  one  kind 
of  fibres.  Those  which  go  to  the  skin  contain  a  larger  proportion 
of  non-medullated  fibres  than  those  which  go  to  the  voluntary  muscles. 
The  vagus  nerve  among  those  of  the  cerebro-spinal  system  contains  a 
more  than  usual  proportion  of  non-medullated  nerve-fibres. 

The  connection  of  the  cerebro-spinal  nerves  with  the  brain  and 
spinal  cord  is  commonly  regarded  as  their  origin  or  commencement, 
and  their  communication  with  peripheral  organs  as  their  termina- 
tion. 

The  parts  by  which  nerves  commence  in  the  cerebro-spinal  axis  are 
called  their  roots,  and  most  nerves,  as  all  those  of  the  spinal  cord  and 
the  trifacial  nerve  of  the  brain,  commence  by  two  roots  differing  in 
quality  or  function,  while  others  arise  in  a  single  root.  The  position  at 
which  the  nerve-roots  start  from  the  surface  of  the  brain  and  spinal 
cord  is  distinguished  as  their  superficial  or  apparent  origin.  The 
source  from  which  they  spring  in  the  interior  is  their  deep  or  true 
origin.  This  consists  of  gray  matter  with  embedded  nerve-cells,  some- 
times in  more  or  less  distinct  accumulations,  called  the  nuclei  of  ori- 
gin of  the  nerve-roots.  Many  of  the  individual  fibres  of  the  roots  are 
traceable  to  their  connection  with  nerve-cells  of  the  nuclei,  whence  it 
is  inferred  that  all  nerves  have  the  same  mode  of  origin. 

In  a  general  way  the  term  "  root"  is  also  applied  to  the  constituent 
fibres,  or  bundles  of  fibres,  more  or  less  distinct  or  collected  in  larger 
bundles,  composing  the  special  nerve-roots.  Thus  each  root  of  the 
spinal  nerves  comes  from  the  cord  in  a  longitudinal  series  of  smaller, 
isolated  roots  or  rootlets.  The  accessory  nerve  starts  from  both  the 
cord  and  oblongata  by  a  similar  series  of  widely-separated  rootlets. 
The  trifacial  nerve,  as  it  springs  from  the  brain,  has  its  large  root 
composed  of  a  bundle  of  numerous  loosely-attached  rootlets,  while  the 
small  root  corresponds  with  but  one  or  two  of  the  latter. 

On  reaching  the  peripheral  organs  and  tissues  in  which  the  cerebro- 
spinal  nerves  terminate,  after  repeated  branching,  which  consists  in  the 
separation  of  smaller  and  smaller  bundles  of  nerve-fibres,  these  then 
continue  singly.  Now  for  the  first  time  branching,  they  then  lose 
their  medullary  sheath,  when  the  axis-fibre  alone  proceeds,  and  still 
branching  finally  ends  among  the  structural  elements  of  the  organs 
and  tissues  in  various  ways  according  to  their  character.  Thus  in 
some  of  the  epithelial  tissues,  as  the  epidermis  and  conjunctiva,  they 
are  resolved  into  their  ultimate  nerve-fibrils,  which  are  distributed  in 
the  cell-structure.  Other  modes  of  termination  of  the  nerves  are 


700  .    THE    NERVOUS    SYSTEM. 

described  with  the  different  structures  of  the  body,  while  many  remain 
obscure  or  undetermined. 

The  non-medullated  nerve-fibres  of  the  sympathetic  system  have 
a  similar  origin  in  the  ganglia  and  a  similar  mode  of  termination  in 
peripheral  organs  like  that  which  has  been  more  definitely  recognized 
in  the  cerebro-spinal  nerves. 

The  arteries  of  nerves  are  derived  from  the  neighboring  trunks 
in  their  course.  Entering  the  common  connective-tissue  sheath  or 
epineurium  and  running  parallel  with  the  bundles  of  nerve-fibres,  the 
branches  enter  the  perineurium  of  these  and  end  in  fine  capillaries, 
which  have  an  arrangement  related  to  the  nerve-fibres  like  that  ob- 
served in  the  muscles.  The  lymphatics  commence  in  clefts  of  the 
connective  tissue  in  the  intervals  of  the  nerve-fibres  communicating 
with  the  perineurial  interspaces,  which  open  into  lymphatic  vessels 
accompanying  the  blood-vessels. 

THE   GANGLIA. 

While  the  cerebro-spinal  axis  may  be  regarded  as  an  aggregate  of 
many  nerve-centres  more  or  less  fused  together,  the  ganglia  are  small 
isolated  centres  situated  in  the  course  of  the  nerves.  They  generally 
appear  on  the  nerves  as  knots  or  swellings  of  varied  size  and  shape, 
of  a  reddish-gray  color.  The  larger  and  more  conspicuous  are  found 
on  the  sensory  roots  of  the  spinal  nerves  and  that  of  the  trifacial 
nerve.  In  the  sympathetic  system  they  form  a  connected  series  or 
chain,  the  gangliated  cord  on  each  side  of  the  spine,  and  they  also  occur 
especially  in  the  solar  plexus.  Numerous  microscopic  ones  likewise 
occur  in  the  terminal  plexuses  of  .the  sympathetic  and  vagus  nerves. 

When  a  ganglion  is  situated  in  the  course  of  a  nerve  it  is  commonly 
connected  by  its  opposite  poles,  which  may  be  its  only  connection,  as 
in  the  ganglia  on  the  roots  of  the  spinal  nerves,  but  in  other  cases  they 
may  have  additional  connections  and  also  give  off  branches  of  distribu- 
tion, as  in  the  sympathetic  ganglia. 

The  ganglia  are  generally  provided  with  a  thin  but  strong  and 
closely-adherent  capsule  or  sheath,  which  is  continuous  with  the  epi- 
neurium of  its  connecting  nerves.  They  are  composed  of  masses  of 
nerve-cells  embedded  in  a  fibro-connective-tissue  matrix,  traversed  by 
bundles  of  nerve-fibres  which  are  continuous  with  those  of  the  nerves 
joining  the  ganglia.  The  bundles  of  nerve-fibres  within  the  gan- 
glion separate  and  run  among  the  nerve-cells,  most  of  them  becoming 
connected  with  the  latter,  a  few  only  continuing  without  interruption 
through  the  ganglion.  In  the  ganglia  of  the  spinal  nerves  the  nerve- 
cells  generally  are  bipolar  and  connected  with  a  pair  of  nerve-fibres 
running  in  opposite  directions  in  the  nerve  on  which  the  ganglion  is 
situated.  In  the  sympathetic  ganglia  the  nerve-cells,  unipolar,  bipolar, 
and  multipolar,  join  nerve-fibres  of  the  nerve-trunks  and  branches  of 
the  ganglia. 


THE   NERVOUS   SYSTEM. 


701 


The  nerve-fibres  connected  with  the  nerve-cells  of  the  sympathetic 
ganglia  for  the  most  part  continue  as  non-medullated  fibres,  but  among 
them  one  or  several  may  assume  the  condition  of  medullated  fibres. 

Bach  ganglionic  nerve-cell  is  enclosed  in  a  delicate,  structureless 
membranous  sheath,  with  scattered  nuclei,  and  continuous  with  the 


FIG.  358. 


DIAGRAM  OF  A  GANGLION  OF  THE  SYMPA- 
THETIC NERVE.  The  narrow  white  are  medul- 
lated nerve-fibres ;  the  dark  shaded  with  nuclei, 
non-medullated  fibres,  a,  b,  c,  nerve-trunks; 
d,  multipolar  nerve-cells ;  e,  unipolar  cells ;  /, 
apolar  cells.  Highly  magnified. 

neurilemma  or  membranous  sheath 
of  the  nerve-fibre  connected  with 
the  cell.  After  death  the  nerve-cell 
shrinks  from  its  sheath,  leaving  a 
considerable  clear  space,  filled  with 
liquid  and  corresponding  with  a 
lymph-space. 

Supporting  material  of  the 
special  nerve-elements  of  the 

cerebro-spinal  axis.  The  special  nerve -elements  of  the  brain  and 
spinal  cord,  the  nerve-cells  and  nerve-fibres,  together  with  their 
nutrient  vessels,  are  supported  by  a  soft  matrix  or  cementing  sub- 
stance named  neuroglia.1  This  is  commonly  regarded  as  a  kind  of 
connective  tissue,  and  in  some  positions  appears  gradually  to  merge 
into  the  more  ordinary  fibrous  form.  In  the  spinal  cord  it  occurs  in  a 
considerable  but  variably  thick  layer  next  the  investing  pia,  where 
it  is  comparatively  free  from  the  characteristic  nerve-elements.  In 
thinner  strata  it  extends  along  the  septal  processes  of  the  pia  and 


DIAGRAM  OF  A  SPINAL  GANGLION  AND  ITS  CON- 
NECTIONS, a,  anterior,  motor  root  of  a  spinal 
nerve ;  b,  posterior,  sensory  root ;  c,  ganglion ; 

d,  posterior  division  of  the  trunk  of  the  nerve ; 

e,  anterior  division;  /,  unipolar  ganglion  or 
nerve-cell;  g,  bipolar  cell  with  both  nerve- 
fibres  directed  outward;  h,  bipolar  cell  with 
nerve-fibres  proceeding  in  opposite  directions ; 
i,  apolar  nerve-cell;  k,  I,  nerve-fibres  passing 
through  the  ganglion  without  connection  with 
the  nerve-cells.    Highly  magnified. 


1  Reticulum  of  Kolliker. 


702 


THE   NERVOUS   SYSTEM. 


FIG.  359. 


thence  among  the  nerve-fibres  of  the  white  matter.  From  the  latter 
it  continues  into  the  gray  matter,  where  it  forms  the  matrix  of  the 
embedded  nerve-cells  and  associated  nerve-fibres.  In  the  brain  it 
forms  a  large  proportion  of  the  cortical  gray  substance  of  the  cere- 
brum and  cerebellum,  superficially 
next  the  pia  comparatively  free  of 
the  special  nerve-elements,  which 
are  most  abundant  in  the  deepest 
part  of  the  cortex.  In  the  interior 
of  the  ventricles  it  occurs  as  a  thin 
layer 1  next  the  lining  endothelium, 
also  free  of  nerve-cells.  In  the 
white  substance  of  the  brain  it  is 
of  the  same  character  as  in  that 
of  the  spinal  cord.  In  the  various 
accumulations  or  nuclei  of  gray 
matter  in  the  interior  of  the  brain 
the  neuroglia  forms  the  matrix, 

in  variable  proportions,  in  which 

NERVE-CELLS  FROM  THE  SEMILUNAR  GANGLION 

OF   THE    TRIGEMINAL   NERVE  OF  A  CAT,  highly 

magnified.  1,  nerve-cell  exhibiting  the  origin 
of  a  nerve-fibre :  a,  sheath  of  the  cell  and  nerve- 
fibre  with  nuclei;  b,  the  nerve-cell  within ;  c, 
the  nerve-fibre  within  its  sheath :  2,  cell  with 
the  origin  of  a  nerve-fibre  deprived  of  its 
sheath ;  3,  nerve-cell  without  sheath  or  nerve- 
fibre. 


nerve-cells  are  embedded  with  as- 
sociated nerve-fibres. 

The  neuroglia  ordinarily  ap- 
pears as  a  finely-granular  fibril- 
lated  material.  In  the  white  sub- 
stance of  the  cerebro-spinal  axis, 
hardened  by  alcohol  or  chromic 
acid,  it  exhibits  a  finely-reticular  fibrillated  appearance  and  has  min- 
gled with  it  as  an  integral  element  minute  flattened  cells  which  re- 
semble ordinary  connective-tissue  corpuscles.  In  the  gray  substance  it 
generally  appears  more  densely  fibrillar,  in  a  great  measure  due  to 
the  intermingled  fibrils  from  the  branching  processes  of  the  nerve-cells. 
In  the  ganglia  and  nerves  the  neuroglia  of  the  cerebro-spinal  axis 
is  represented  by  delicate  fibro-connective  tissue  connecting  the  nerve- 
fibres  and  the  nerve-cells. 

The  nutrient  blood-vessels  of  the  nervous  system  in  their  relation 
with  the  special  nerve-elements  traverse  the  neuroglia  and  are  confined 
to  it. 

The  white  matter  of  the  cerebro-spinal  axis.  This  is  of  com- 
paratively simple  constitution,  on  the  natural  surfaces  has  more  or 
less  a  striated  appearance,  and  on  the  freshly-cut  surface,  to  the  naked 
eye,  appears  homogeneous.  It  is  mainly  composed  of  medullated  nerve- 
fibres  devoid  of  a  membranous  sheath,  embedded  in  neuroglia  traversed 
by  the  nutrient  vessels.  Examined  under  ordinary  circumstances  with 


1  Ependyma,  Quain's  Anatomy.     Henle  applies  the  name  to  the  lining  endothe- 
lium of  the  ventricles. 


THE   NERVOUS   SYSTEM. 


703 


FIG.  360. 


MEDULLATED  NERVE-FIBBES  OF  THE  WHITE 
MATTER  OF  THE  CEREBRUM.  1,  beaded  appear- 
ance  presented  by  the  fibres,  which  are  of 
various  sizes;  2,  various  irregular  forms  as- 
sumed by  the  fibres  as  they  ordinarily  appear 
when  examined  mingled  with  a  little  water ; 
3,  ideal  representation  of  the  unchanged  fibres. 
Magnified. 


the  microscope,  the  nerve-fibres  appear  as  beaded  filaments,  with  double 
outlines  and  of  various  sizes.  They  are  soft  and  with  little  manipula- 
tion assume  a  multitude  of  irreg- 
ular forms,  as  represented  in  the 
adjoining  figure.  Careful  investi- 
gation proves  them  to  have  the 
same  form  and  constitution  as  the 
more  tenacious  medullated  nerve- 
fibres  of  the  nerves,  but  to  possess 
no  membranous  sheath,  whence 
their  comparative  softness.  They 
run  in  different  but  definite  direc- 
tions in  different  portions  of  the 
spinal  cord  and  brain,  often  in  flat- 
tened bundles.  From  the  white 
they  enter  the  gray  matter  and 
become  connected  with  the  nerve- 
cells  of  the  latter,  and  on  the 
other  hand  also  become  continuous 
with  the  roots  of  the  nerves  origi- 
nating in  the  cerebro-spinal  axis. 

The  gray  matter  of  the  cerebro-spinal  axis.  Of  more  com- 
plex constitution  than  the  former,  this  consists  of  an  abundant  matrix 
of  neuroglia,  with  variable  proportions  of  embedded  nerve-cells  large 
and  small,  other  small  cells  of  uncertain  character,  nerve-fibres  both 
medullated  and  non-medullated,  and  nutrient  vessels.  It  is  commonly 
of  a  rust  color  and  is  variably  translucent  and  pulpy.  Varieties  of 
the  gray  matter  are  distinguished  as  the  spongiosa1  and  gelatinosa,2 
accordingly  as  they  appear  spongy  or  gelatinous,  due  to  differences  in 
the  proportions  and  arrangement  of  the  mingled  nerve-elements.  The 
matter  appears  to  be  more  spongy  with  an  increase  of  the  nerve-fibres 
and  more  gelatinous  with  their  decrease.  As  the  nerve-cells  vary  in 
their  depth  of  color  in  different  positions  they  accordingly  affect  the 
color  of  the  gray  matter  of  which  they  form  part. 

THE   CEREBRO-SPINAL   AXIS. 

The  cerebro-spinal  axis  consists  of  the  brain  and  spinal  cord. 
In  describing  these  it  is  usual  to  commence  with  an  account  of  the 
latter,  as  taking  precedence  of  the  former  in  development. 

THE   SPINAL  CORD. 

The  spinal  cord,  or  spinal  marrow,3  together  with  its  mem- 
branous envelopes,  is  contained  within  the  vertebral  canal.  It  is  con- 


1  Substantia  spongiosa.  2  S.  gelatinosa. 

8  Chorda  spinalis  or  dorsalis  ;  medulla  spinalis  ;  funiculus  spinalis. 


704 


THE   NERVOUS   SYSTEM. 


tinuous  with  the  oblongata  of  the  brain  on  a  level  with  the  articula- 
tion of  the  skull  and  vertebral  column,  and  extends  to  the  lower  part 
of  the  first  lumbar  vertebra.  Stripped  of  its  membranes,  it  appears 
as  a  cylindrical,  milk-white  cord,  about  eighteen  inches  long,  tapering 
at  the  lower  extremity  to  a  conical  point.  It  is  slightly  compressed 
fore  and  aft,  and  is  most  nearly  circular  in  transverse  section  in  the 
thoracic  region.  It  is  not  of  uniform  diameter,  but  is  swollen  towards 


FIG.  301. 


THE  SPINAL  COED  WITH  THE  OBLONGATA.  Posterior  view  of  the  cord  with  the  dural  sheath 
laid  open ;  in  three  sections.  1,  glosso-pharyngeal  nerve ;  2,  vagus  nerve ;  3,  accessory  nerve ;  4  to 
5,  the  eight  cervical  nerves:  6  to  7,  twelve  thoracic  nerves;  8  to  9,  five  lumbar  nerves;  10  to  11, 
five  sacral  nerves;  12,  coccygeal  nerve;  13,  quadrigeminal  body;  14,  superior  peduncle  of  the 
cerebellum ;  15,  middle  peduncle  of  the  cerebellum ;  16,  inferior  peduncle  of  the  cerebellum ;  17, 
floor  of  the  fourth  ventricle ;  18,  posterior  pyramid ;  19,  posterior  roots  of  the  spinal  nerves  of  the 
right  side;  20,  line  of  attachment  of  the  roots  of  the  spinal  nerves  on  the  left  side;  21,  anterior 
roots  of  the  spinal  nerves;  22,  ganglion  of  the  posterior  root;  23,  denticulate  ligament ;  24,  an- 
terior roots  of  the  cauda  equina ;  25,  posterior  roots  of  the  cauda  equina ;  26,  conical  end  of  the 
cord ;  27,  terminal  filum  ;  28,  anterior  division  of  a  spinal  nerve ;  29,  posterior  division. 

the  extremities,  where  it  forms  the  cervical  and  lumbar  enlargements, 
of  which  the  former  is  both  the  longer  and  larger. 

The  cord  is  of  soft  consistence,  and  ordinarily  weighs  from  an  ounce 
and  a  half  to  an  ounce  and  three-quarters. 

The  cervical  enlargement l  is  widest  opposite  the  fifth  cervical 
vertebra,  where  it  is  a  little  over  half  an  inch  from  side  to  side,  slightly 

1  Intumescentia  cervicalis. 


THE   NEKVOUS   SYSTEM.  705 

narrowing  above  and  also  below  to  about  the  second  thoracic  vertebra. 
The  lumbar  enlargement1  begins  at  the  tenth  thoracic  vertebra,  is 
largest  opposite  the  twelfth,  and  then  tapers  away  in  a  cone2  to  the 
end  of  the  cord.  It  is  less  compressed  than  the  cervical  enlargement 
and  is  about  half  an  inch  or  slightly  less  transversely. 

The  intermediate  thoracic  portion  of  the  cord,  more  uniformly 
cylindrical,  is  about  five  lines  from  side  to  side  and  slightly  less  fore 
and  aft. 

In  front  and  behind,  the  cord  is  divided  by  fissures  which  nearly 
reach  its  centre. 

The  anterior  median  fissure,3  the  wider  but  shallower,  in  the 
greater  part  of  its  extent  penetrates  about  a  third  of  the  thickness 
of  the  cord  and  receives  a  fold  of  the  investing  pia.  The  posterior 
median  fissure,4  a  narrow  slit,  penetrates  about  half  the  thickness 
of  the  cord  and  receives  a  thin  partition  of  the  pia. 

Connected  with  the  cord  on  each  side  in  front  and  behind  are  the 
numerous  rootlets  of  the  spinal  nerves  arranged  in  a  close  longitudinal 
series  and  extending  the  entire  length  of  the  cord.  The  line  of  the 
posterior  series  of  rootlets  is  marked  by  a  slight  furrow,  which  is  dis- 
tinguished as  the  posterior  lateral  fissure5  of  the  cord.  The  line 
of  the  anterior  series,  though  not  indicated  by  a  furrow  nor  so  exactly 
straight  in  its  course,  is  conveniently  called  the  anterior  lateral  fis- 
sure. These  so-called  fissures,  though  not  actually  such,  indicate  the 
lines  of  emergence  of  the  roots  of  the  nerves  from  the  substance  of 
the  cord  and  serve  to  divide  the  exterior  white  portion  of  the  latter 
into  the  anterior,6  lateral,7  and  posterior8  columns. 

The  posterior  column  in  the  cervical  enlargement  is  further  divided 
by  a  fissure9  into  two  portions,  distinguished  as  the  posterior  median 
and  posterior  lateral  columns,  of  which  the  former,  in  the  thoracic 
region,  gradually  diminishes,  while  the  fissure  separating  it  from  the 
other  column  inclines  inwardly  and  ends  in  the  posterior  median  fissure. 
At  the  bottom  of  the  anterior  median  fissure  the  anterior  columns 
are  conjoined  by  a  thin  layer  of  white  matter,  the  anterior  or  •white 
commissure.10 

The  cord  is  solid,  except  that  it  is  traversed  by  a  fine  central 
canal  and  is  composed  of  white  matter  enclosing  gray  matter  in  the 
interior.  The  gray  matter  is  in  greater  quantity  within  the  cervical 
and  lumbar  enlargements,  especially  in  the  latter,  in  which  the  white 

1  Intumescentia  lumbaris.  2  Conus  terminalis  or  medullaris. 

3  Ant.  longitudinal  fissure ;  fissura  longitudinalis  ant. 

4  Post.  long.  fis. ;  fis.  long.  post. 

5  Sulcus  lateralis  posticus  ;  posterior  lateral  groove. 

6  Funiculus  anterior.  7  F.  lateralis  ;  fasciculus  cerebralis. 

8  F.  posterior  ;  fasciculus  cerebelli. 

9  Sulcus  intermedius  posticus  ;  s.  lateralis  postremus. 
10  Commissura  ant.  or  alba. 

45 


706 


THE   NERVOUS   SYSTEM. 


FIG.  362. 


matter  is  proportionately  smaller  than  elsewhere  in  the  cord.  In  hori- 
zontal sections  of  the  cord  it  appears  of  an  irregular  H-like  form  sur- 
rounded by  the  white  matter,  and  more  or  less  modified  from  that  form 

it  extends  the  entire  length  of  the 
cord.  It  consists  of  a  pair  of 
bands,  one  on  each  side,  bent  out- 
wardly and  united  by  a  narrower 
and  thinner  straight  band.  The 
latter  reaches  the  bottom  of  the 
posterior  median  fissure,  is  named 
the  posterior  or  gray  commis- 
sure,1 and  is  in  contact  in  front 
with  the  anterior  or  white  com- 
missure. In  its  axis  is  the  central 
canal2  of  the  cord,  continuous 
above  through  the  oblongata  with 
the  fourth  ventricle  of  the  brain 
and  at  the  lower  end  opening  into 
the  posterior  median  fissure. 

Through  the  greater  part  of  the 
length  of  the  cord  the  gray  commis- 
sure joins  the  lateral  gray  bands 
about  their  anterior  third,  but  near 
the  lower  end  it  joins  them  about 
the  middle.  The  lateral  gray 
bands  in  horizontal  section  ap- 
pear curved,  club-shaped,  or  ir- 
regularly crescentic,  whence  they 
are  commonly  called  the  cres- 
cents. They  extend  fore  and  aft 
more  than  half  the  thickness  of 
the  cord,  have  their  concave  bor- 
der directed  outward  and  their 
more  convex  borders  towards  each 
other.  The  cornua  or  horns  of 
the  crescents,  called  from  their  rel- 
ative position  anterior  and  poste- 
rior, are  extended  through  the  cord 
in  continuous  bands  forming  so 
many  gray  columns. 
The  anterior  cornu,3  or  gray  column,  is  in  general  shorter  but 
larger  and  thicker  than  the  posterior  cornu,  and  is  variably  more  or 
less  angular  or  rounded  in  different  positions.  It  is  largest  in  the 


TRANSVERSE  SECTIONS  OF  THE  SPINAL  CORD  ; 
in  succession  opposite  the  cervical  enlarge- 
ment, the  thoracic  portion,  and  the  lumbar 
enlargement.  1,  anterior  median  fissure ;  2, 
posterior  median  fissure.  Magnified  about  two 
and  a  half  diameters.  For  details,  see  Fig.  363. 


1  Commissura  post.,  grisea,  or  cinerea ;  nucleus  cinereus  ;  centrum  cinereum. 

2  Canalis  centralis.  3  Crus  anterius. 


THE   NERVOUS   SYSTEM. 


707 


FIG.  363. 


cervical  and  lumbar  enlargements  and  smallest  in  the  intervening 
thoracic  region.  The  posterior  cornu,1  or  gray  column,  in  general 
is  longer  and  narrow  compared  with  the  former  and  becomes  consider- 
ably thicker  in  the  lumbar  enlargement.  From  its  conjunction  with 
the  anterior  cornu  and  gray  commissure,  passing  backward  it  slightly 
narrows  as  the  neck,2  then  slightly  enlarges  as  the  head,3  and  finally 
tapers  to  a  point,  whence  bundles  of  nerve-fibres  pass  to  the  posterior 
lateral  fissure  and  emerge  from  the  cord  as  the  posterior  roots  of  the 
spinal  nerves. 

In  the  upper  part  of  the  thoracic  region,  at  the  union  of  the  cor- 
nua  with  their  commissure,  outwardly  there  is  an  angular  projection  of 
the  gray  matter,  named  the  mid- 
dle cornu,  which  continued  in  the 
length  of  the  cord  is  the  inter- 
medio-lateral  tract.  It  merges 
above  in  the  gradually-expanding 
anterior  cornu  of  the  cervical  en- 
largement and  gradually  dimin- 
ishes and  ceases  below.  In  the 
recess  behind  it,  thin  offsets  of 
gray  matter  extend  into  the  con- 
tiguous white  matter  and  intersect 
one  another,  giving  to  horizontal 
sections  of  the  cord  in  this  position 
a  reticular  appearance.4  Similar 
offsets  extend  from  the  principal 
body  of  gray  matter  elsewhere, 
especially  from  the  anterior  cor- 
nua. 

The  gray  matter  of  the  spinal 
cord  consists  of  variable  propor- 
tions of  neuroglia  matrix  with 
embedded  nerve-cells  and  trav- 
ersed by  nerve-fibres  and  blood- 
vessels. For  the  most  part  it  is 
pervaded  by  nerve-fibres,  chiefly 
medullated  and  in  bundles,  run- 
ning in  different  directions  and 
producing  an  appearance  in  the  gray  matter  distinguished  as  the 
spongiosa.5  The  posterior  cornua  are  capped  with  neuroglia  with 
comparatively  few  nerve-fibres,  distinguished  as  the  gelatinosa.6  The 
nerve-cells  generally  are  collected  in  more  or  less  circumscribed  posi- 


13 


1   - 

TKANSVERSE  SECTION  OF  THE  LUMBAR  EN- 
LARGEMENT OF  THE  SPINAL  CORD.  1,  anterior 
median  fissure ;  2,  posterior  median  fissure ;  3, 
central  canal ;  4,  posterior  commissure ;  5,  an- 
terior commissure ;  6,  posterior  column ;  7.  lat- 
eral column ;  8,  anterior  column ;  9,  posterior 
root  of  a  spinal  nerve ;  10,  head  of  the  posterior 
cornu ;  11,  neck  of  the  posterior  cornu ;  12,  an- 
terior roots  of  a  spinal  nerve :  13,  anterior  cornu 
with  groups  of  nerve-cells  of  the  anterior 
ganglionic  tract;  14,  nerve-cells  of  the  middle 
ganglionic  tract ;  15',  nerve-cells  of  the  posterior 
ganglionic  tract.  The  fine  lines  indicate  the 
course  of  the  nerve-fibres. 


1  Cms  posticus. 

*  Processus  reticularis. 

6  Substantia  gelatinosa. 


2  Cervix.  3  Caput. 

5  Substantia  spongiosa. 


708  THE   NERVOUS   SYSTEM. 

tions;   in  horizontal   sections  of  the   cord  appearing  in  groups  and 
corresponding  with  columnar  tracts  in  the  length  of  the  cord. 

The  anterior  ganglionic  tract l  occupies  the  anterior  cornua  and 
extends  the  entire  length  of  the  cord.  It  consists  of  large  nerve-cells 
lying  among  numerous  medullated  nerve-fibres,  of  which  many  are 
connected  with  the  nerve-cells  by  their  axis-fibre  and  on  the  other 

FIG.  364. 


TRANSVERSE  SECTION  OF  A  PORTION  OF  THE  SPINAL  CORD  AT  THE  ENTRANCE  OF  THE  ANTERIOR 
ROOT  OF  A  NERVE.  1,  bundle  of  medullated  fibres  of  the  nerve-root  passing  through  the  white 
into  the  gray  matter ;  2,  sections  of  longitudinal  medullated  fibres  of  the  white  matter;  3,  large 
multipolar  cells  in  the  anterior  ganglionic  tract.  Highly  magnified. 

hand  are  collected  into  bundles,  which  pass  from  the  cord  as  the  an- 
terior roots  of  the  spinal  nerves.  In  some  positions  the  cells  of  this 
tract  are  separated  into  several  smaller  tracts  or  groups :  thus  one  is 
situated  nearer  the  lateral  column  of  the  cord,  a  second  nearer  the  an- 
terior column,  and  a  third  more  deeply  seated  in  the  lumbar  enlarge- 
ment. Some  of  the  nerve-cells  nearest  the  anterior  commissure  are 
connected  with  its  nerve-fibres  passing  to  the  opposite  side,  where  they 
appear  to  be  continuous  with  those  of  the  anterior  roots  of  the  spinal 
nerves. 

The  posterior  ganglionic  tract2  of  nerve-cells  occupies  the  inner 
portion  of  the  posterior  cornua  near  the  gray  commissure.  It  is  largest 
in  the  lower  part  of  the  thoracic  region,  in  which  position  the  anterior 
ganglionic  tract  is  smallest.  Its  cells  are  of  moderate  size,  and  are 
connected  with  medullated  nerve-fibres,  which  mostly  proceed  to  the 
lateral  columns  of  the  cord. 

The  middle  ganglionic  tract3  occupies  the  middle  lateral  gray 
cornu  of  the  thoracic  region  of  the  cord,  and  at  its  upper  part  merges 

1  Motor  ganglionic  column  ;  anterior  vesicular  column. 

2  Column  of  Clarke  ;  posterior  vesicular  column. 
8  Column  of  the  intermedio-lateral  tract. 


THE   NERVOUS   SYSTEM.  709 

into  the  anterior  ganglionic  tract,  than  which  it  consists  of  smaller 
nerve-cells.  In  the  upper  part  of  the  cervical  region  a  distinct  tract 
of  nerve-cells,  in  a  similar  position,  is  traversed  by  the  nerve-fibres  of 
origin  of  the  accessory  nerve. 

Besides  the  above  tracts  of  nerve-cells  other  nerve-cells  of  smaller 
size  and  mostly  spindle-shaped  are  scattered  in  the  posterior  cornua, 
extending  into  the  gelatinosa. 

The  gray  commissure  consists  mainly  of  a  matrix  of  neuroglia 
traversed  by  nerve-fibres,  mostly  medullated,  crossing  transversely  and 
somewhat  obliquely  between  the  gray  columns  of  the  two  sides  of  the 
cord.  The  central  canal,  situated  in  the  gray  commissure,  is  enclosed 
by  a  layer1  of  the  gelatinosa,  or  neuroglia  comparatively  free  from 
nerve-fibres.  In  infancy  the  canal  is  clothed  with  a  ciliated  columnar 
epithelium,  but  after  adult  age  becomes  more  or  less  obliterated  or  filled 
with  small  polyhedral  cells. 

Near  the  point  of  the  terminal  cone  of  the  cord  the  gray  commis- 
sure ceases  and  the  central  canal  communicates  with  the  posterior 
median  fissure  by  a  cleft. 

From  the  partitions  of  the  pia,  occupying  the  principal  fissures  of 
the  cord,  offsets  extend  into  the  white  columns  and  divide  them  into 
smaller  portions.  The  white  matter  is  chiefly  composed  of  longitudinal 
bundles  of  medullated  nerve-fibres,  the  whole  enveloped  by  a  layer 
of  neuroglia,  which  also  extends  between  and  fills  the  intervals  of  the 
fibres.  These  are  of  variable  size,  and  in  many  positions  the  larger 
and  smaller  are  intermingled,  but  in  others  there  is  a  greater  propor- 
tion of  one  or  the  other.  The  largest  fibres  occupy  the  back  part  of 
the  lateral  columns ;  the  smallest,  that  part  of  the  same  columns  which 
lies  in  the  recess  of  the  anterior  and  posterior  cornua.  The  fibres  of 
the  posterior  median  column  are  also  among  the  smallest. 

The  anterior  or  white  commissure  connects  the  anterior  columns  of 
the  cord  at  the  bottom  of  the  anterior  median  fissure  in  front  of  the  gray 
commissure,  than  which  it  is  thicker  in  the  cervical  and  lumbar  enlarge- 
ments but  considerably  thinner  elsewhere.  It  is  composed  of  medul- 
lated fibres,  which  obliquely  cross  one  another  from  side  to  side  and 
partly  become  continuous  with  the  longitudinal  fibres  of  the  anterior 
columns  and  partly  pass  into  the  anterior  gray  columns,  where  some 
of  them  join  the  anterior  roots  of  the  spinal  nerves. 

The  nerve-fibres  of  the  roots  of  the  spinal  nerves  pass  through  or 
between  the  white  columns  of  the  cord  nearly  at  right  angles  to  the 
fibres  of  the  latter.  They  proceed  outwardly  in  the  trend  of  the  cornua 
with  a  slight  downward  inclination.  Those  of  the  anterior  roots 
mainly  spring  from  the  fore  part  of  the  anterior  cornua  and  thence 
proceed  in  several  bundles  on  the  same  horizontal  plane  through  the 
antero-lateral  column  to  their  point  of  emergence  from  the  cord. 

1  Substantia  gelatinosa  centralis. 


710 


THE    NEKVOUS   SYSTEM. 


FlG.  365. 


Those  of  the  posterior  roots  are  derived  partly  from  the  posterior 
cornua  and  partly  from  the  posterior  white  columns  and  thence  pro- 
ceed in  a  single,  stouter  bundle  on  the  same  horizontal  plane  between 
the  posterior  and  lateral  white  columns. 

Many  laborious  investigations  have  been  made  to  determine  the 
course  and  connections  of  the  nerve-fibres  in  the  brain  and  spinal  cord. 

Though  much  has  been  ascertained 
through  dissection  and  the  use  of 
the  microscope,  much  yet  remains 
to  be  discovered.  Experiment  and 
observation  in  development  and 
disease  have  aided  in  tracing  the 
course  and  connections  of  different 
bundles  or  tracts  of  nerve-fibres. 

A  division  of  the  lateral  col- 
umn of  the  cord  is  named  from  its 
position  and  course  the  lateral 
or  crossed  pyramidal  tract.1 
Largest  above,  it  gradually  nar- 
rows downward.  In  the  cervical 
enlargement  it  is  enclosed  in  the 
back  part  of  the  column,  below 
comes  more  into  contact  with  the 
posterior  cornu  and  near  the  lower 
end  of  the  cord  reaches  the  outer 
surface.  Its  upper  extremity  en- 
ters the  oblongata  and  splits  into 
several  bundles,  which  obliquely 
cross  and  intersect  those  of  the 
opposite  side,  and  thus  form  the 
decussation  of  the  pyramids. 

A  smaller  division  of  the  lateral 
column  situated  at  its  outer  side 
is  the  cerebellar  tract.2  Its  upper 
extremity  enters  the  oblongata  be- 
hind the  olive  and  contributes  to 
form  the  restiform  body,  while 
below  it  tapers  and  ceases  near 
the  middle  of  the  lumbar  enlargement.  The  portion  of  the  lateral 
column  in  the  recess  of  the  gray  matter  is  the  mixed  lateral  tract, 
and  the  remainder  the  anterior  radicular  tract,  which  in  the  ob- 
longata ascends  behind  the  olive  in  the  outer  portion  of  the  reticular 
formation. 

A  narrow  division  of  the  anterior  column  of  the  cord,  the  anterior 


DIAGRAMS  OF  SECTIONS  OF  THE  SPINAL  CORD, 
exhibiting  the  relative  position  of  the  tracts  in 
the  white  matter,  in  succession  in  the  cervical 
enlargement,  the  thoracic  portion,  and  the 
lumbar  enlargement.  1,  anterior  cornu ;  2, 
posterior  cornu ;  3,  principal  tract  of  the  an- 
terior column ;  4,  mixed  lateral  and  anterior 
radicular  tracts ;  5,  cuneate  tract  of  the  pos- 
terior column ;  6,  anterior  or  direct  pyramidal 
tract ;  7,  lateral  or  crossed  pyramidal  tract ;  8, 
cerebellar  tract ;  9,  posterior  median  column. 


1  Fasciculus  of  Tiirck. 


2  Direct  cerebellar  tract ;  direct  lateral  tract. 


THE   NERVOUS  SYSTEM.  711 

or  direct  pyramidal  tract,1  occupies  the  side  of  the  anterior  median 
fissure  descending  to  about  the  middle  of  the  thoracic  portion  of  the 
cord.  Its  upper  part  enters  the  pyramid  of  the  oblongata  on  the  same 
side  and  then  ascends  in  company  with  the  lateral  pyramidal  tract. 
The  remainder  of  the  column,  for  the  most  part  as  its  principal  tract,2 
enters  the  oblongata  and  ascends  behind  the  pyramid  in  the  inner  por- 
tion of  the  reticular  formation.  This  tract  is  proportioned  in  size  with 
the  anterior  cornu  and  corresponding  roots  of  the  spinal  nerves.  By 
part  of  its  fibres  it  is  connected  with  the  anterior  cornu  of  the  same 
side  and  by  others  through  the  anterior  commissure  with  that  of  the 
opposite  side. 

The  posterior  median  column 3  of  the  cord  is  continuous  above 
with  the  gracile  funicle  of  the  oblongata.  Its  upper  part  extends  to 
the  gray  commissure,  but  recedes  below  and  ceases  about  the  middle 
of  the  thoracic  region. 

The  posterior  lateral  column 4  of  the  cord  below  occupies  all  the 
space  between  the  posterior  cornu  and  posterior  median  fissure,  but 
above  has  the  former  column  interposed  between  it  and  the  latter.  It 
increases  as  it  ascends,  and  is  thickest  in  the  lumbar  and  cervical 
enlargements.  It  appears  to  be  mainly  in  continuation  with  the  pos- 
terior spinal  nerve-roots,  which  ascend  in  it  some  distance  before  enter- 
ing the  posterior  cornu.  Its  upper  extremity  is  continuous  with  the 
cuneate  funicles  of  the  oblongata. 

OKIGIN  OF  THE   SPINAL  NEKVES. 

Thirty-one  pairs  of  nerved  are  connected  with  the  spinal  cord,  in 
which  they  are  ordinarily  said  to  have  their  origin.  Each  nerve  arises 
by  two  roots  from  the  side  of  the  cord,  one  in  front  and  the  other 
behind.  Each  root  consists  of  a  longitudinal  series  of  filaments  or 
rootlets,  which  spring  from  the  cord  in  such  near  succession  as  to 
form  a  continued  and  close  series  extending  the  whole  length  of  the 
cord.  The  anterior  roots  spring  from  a  linear  area  along  the  side 
of  the  cord  in  front,  while  the  posterior  roots  emerge  from  the 
postero-lateral  fissure. 

In  transverse  sections  of  the  cord,  the  anterior  roots  of  the  nerves 
are  observed  to  pass  through  the  white  substance  and  enter  the  gray 
cornu  in  several  bundles  of  fibres,  which  have  an  upward  inclination, 
as  indicated  by  the  oblique  cut  they  present  in  exact  horizontal  sec- 
tions of  the  cord.  On  reaching  the  gray  matter  the  fibres  diverge, 
some  proceeding  towards  the  anterior  commissure,  others  to  the  pos- 
terior commissure,  and  others  outward  to  the  anterior  part  of  the 
lateral  column  of  the  cord.  Of  those  directed  inward  some  are  con- 

1  Uncrossed  portion  of  the  pyramidal  tract. 

2  Fundamental  fasciculus  ;  tract  of  Flechsig. 

3  Tract  of  Goll.  *  Cuneate  fasciculus ;  column  of  Burdach. 


712  THE    NERVOUS   SYSTEM. 

nected  with  the  inner  group  of  nerve-cells  of  the  anterior  cornu  and 
others  appear  to  go  through  the  anterior  commissure  to  the  other  side 
of  the  cord,  probably  to  be  connected  with  the  corresponding  cells  of 
the  anterior  cornu.  The  middle  fibres  are  partly  connected  with  the 
lateral  group  of  cells  of  the  anterior  cornu  and  partly  run  to  the  pos- 
terior cornu,  without  joining  those  cells.  The  fibres  directed  outward 
are  partly  connected  with  the  lateral  group  of  cells  and  partly  enter 
and  turn  upward  in  the  lateral  white  column. 

The  posterior  roots  of  the  nerves  as  they  enter  the  cord  separate 
into  two  bundles,  which,  as  in  those  of  the  anterior  roots,  are  directed 
obliquely  upward.  The  outer  and  smaller  bundle  enters  the  posterior 
cornu,  partly  curving  round  and  partly  passing  through  the  gelatinosa. 
In  this  the  fibres  become  longitudinal,  turning  both  upward  and  down- 
ward, while  others  pass  horizontally  and  more  deeply  into  the  gray 
matter.  The  inner  and  principal  bundle  enters  the  posterior  white 
column,  in  which  it  turns  up  and  runs  longitudinally,  gradually  in- 
clines inward,  and  enters  the  base  of  the  posterior  cornu.  Here  the 
fibres  traverse  the  gray  matter,  passing  obliquely  towards  the  anterior 
cornu  and  cutting  off  a  distinct  area  of  gray  matter,  which  in  the 
thoracic  portion  of  the  cord  contains  the  cells  of  the  posterior  gangli- 
onic  tract.1  Some  of  the  fibres  enter  that  area,  others  pass  towards 
the  lateral  group  of  cells  of  the  anterior  cornu,  and  others  curve 
towards  the  anterior  commissure. 

The  trunks  of  the  spinal  nerves  emerge  from  the  spinal  canal 
through  the  intervertebral  foramina,  commencing  with  those  between 
the  occiput  and  atlas  and  terminating  with  those  between  the  first 
and  second  coccygeal  vertebrae.  In  consequence  of  the  comparative 
shortness  of  the  spinal  cord  and  the  length  of  its  canal,  the  roots  of 
the  nerves  to  reach  their  trunks  successively  increase  in  length,  so 
that  while  the  uppermost  are  short  and  directed  outward  to  the  inter- 
vertebral  foramina  .the  others  gradually  incline  more  and  more  down- 
ward and  the  lower  ones  are  collected  in  a  perpendicular  bunch,  below 
the  spinal  cord,  called,  from  its  resemblance  to  a  horse's  tail,  the  cauda 
equina. 

The  filaments  or  rootlets  of  each  nerve-root  converge  into  two 
bundles,  and  those  in  each  pair  of  roots  also  converge  together.  Those 
of  the  posterior  root  end  in  a  ganglion,  from  which  the  root  proceeds 
in  a  single  bundle  and  is  immediately  joined  by  the  bundle  of  the  ante- 
rior root  to  form  the  trunk  of  the  spinal  nerve. 

The  posterior  roots  of  the  spinal  nerves,  except  in  the  first  pair,  are 
conspicuously  larger  than  the  anterior  roots,  and  this  is  likewise  the 
case  with  their  constituent  filaments  or  rootlets.  Both  roots  are  pro- 
portioned in  size  to  the  nerve-trunks  they  form,  and  the  latter  are 
proportioned  to  the  size  of  the  parts  they  supply ;  hence  those  destined 

1  Clarke's  column. 


THE   NERVOUS   SYSTEM. 


713 


FIG.  366. 


DIAGRAM  OF  ORIGIN  OF  A  SPINAL  NERVE.  1, 
anterior  median  fissure;  2,  posterior  median 
fissure;  3,  postero-lateral  fissure;  4,  antero- 
lateral  fissure;  5,  anterior  column;  6,  lateral 
column ;  7,  posterior  column  ;  8,  anterior  com- 
missure; 9,  anterior  horn  of  the  gray  sub- 
stance ;  10,  posterior  horn ;  11,  gray  commissure ; 
12,  anterior  root  of  a  spinal  nerve  springing 
by  a  number  of  rootlets  from  the  antero-lateral 
fissure  ;  13,  posterior  root  from  postero-lateral 
fissure ;  14,  ganglion  on  the  posterior  root ;  15, 
spinal  nerve  formed  by  the  union  of  the  two 
roots. 


to  the  limbs  are  the  largest  of  the  spinal  nerves.  The  ganglia  are  also 
proportioned  in  size  to  the  nerve-trunks.  They  are  generally  situated 
in  the  intervertebral  foramina,  im- 
mediately outside  the  dural  sheath, 
as  this  is  perforated  by  the  nerve- 
roots.  Those  of  the  upper  two 
pairs  of  nerves  are  situated  op- 
posite their  respective  foramina, 
those  of  the  sacral  nerves  are  con- 
tained within  the  sacral  canal, 
while  the  last  one  is  within  the 
dural  sheath. 

The  roots  of  the  spinal  nerves 
and  the  spinal  cord  are  enclosed 
together  in  the  dural  sheath,  from 
which  the  roots  of  the  nerves  es- 
cape by  separate  apertures  oppo- 
site the  intervertebral  foramina, 
but  are  afterwards  enclosed  to- 
gether in  a  tube  of  the  dura,  con- 
tinuous with  the  periosteum  of 
the  latter.  On  the  rootlets  of  the 

nerve-roots  the  pia  of  the  cord  becomes  continuous  with  their  con- 
nective-tissue sheath,  and  the  roots  occupy  the  subarachnoid  space, 
lying  in  contact  with  the  cord  above  and  with  one  another  in  the  cauda 
equina  below  and  enclosed  in  funnel-like  sheaths  of  the  arachnoid 
extending  to  the  apertures  of  the  dura,  through  which  they  emerge. 

THE   BRAIN. 

The  brain l  is  the  large  mass  of  nerve-substance  which,  together 
with  its  investing  membranes  and  blood-vessels,  completely  fills  the 
cavity  of  the  cranium.  The  spinal  cord  is  a  prolongation  of  the  same 
structures  occupying  the  vertebral  canal. 

The  general  shape  of  the  brain  accords  with  that  of  the  cranium, 
and  it  closely  conforms  to  the  cavity,  apparently  as  if  moulded  in  it. 
Commonly  it  is  ovoid,  with  the  narrower  end  occupying  the  forehead 
and  the  broader  end  the  occiput,  but  it  varies  to  an  oval  and  a  more 
or  less  spheroid  form.  Usually  longest  fore  and  aft,  it  is  also  commonly 
of  greater  transverse  breadth  than  depth,  but  it  varies  in  its  relative 
proportions. 

The  size  of  the  brain  in  the  normal  state  independent  of  age  varies 
greatly  in  different  individuals,  as  well  as  in  different  races  and  sexes. 
To  some  extent  it  is  related  to  the  size  of  the  body,  being  usually 
larger  in  tall  than  in  short  persons.  All  other  conditions  being  equal, 


Encephalon ;  cerebrum. 


714  THE   NERVOUS   SYSTEM. 

it  is  observed  also  to  hold  a  relation  in  size  to  the  degree  of  mental 
development:  hence  the  more  civilized  races  and  the  more  cultivated 
and  intelligent  people  are  distinguished  by  a  larger  and  heavier  brain, 
while  the  opposite  condition  exists  in  the  barbarous  races  and  the  least 
cultivated  persons. 

In  the  adult  white  male  the  brain  ordinarily  averages  upwards  of 
three  pounds  avoirdupois,  and  is  about  a  third  of  a  pound  less  in  the 
female.  Commonly  among  our  own  people,  in  the  male  it  ranges  from 
forty-five  to  fifty-five  ounces,  in  the  female  from  forty  to  forty-seven 
ounces.  In  all  races  it  has  been  found  to  range  from  two  to  four 
pounds. 

The  proportionate  weight  of  the  brain  to  that  of  the  body  is  very 
variable,  especially  on  account  of  the  great  variability  of  the  latter. 
Considering  this  to  be  one  hundred  and  fifty  pounds,  that  of  the  brain 
would  be  about  one  to  fifty.  In  early  life  it  is  much  greater,  at  birth 
being  in  the  proportion  of  one  to  six,  after  which  it  gradually  decreases 
from  the  greater  rapidity  of  growth  of  the  rest  of  the  body. 

The  brain  of  the  new-born  child  averages  for  the  male  about  eleven 
and  a  half  ounces,  for  the  female  ten  ounces.  It  grows  most  rapidly  up 
to  about  the  seventh  year,  then  more  slowly  to  fifteen  or  twenty,  and 
subsequently  still  slower  to  thirty-five  or  forty,  when  ordinarily  it  has 
attained  its  full  growth.  It  then  remains  stationary  until  fifty  or  later, 
and  from  sixty  begins  to  decrease,  estimated  at  the  rate  of  an  ounce  in 
ten  years  to  the  end  of  life. 

The  human  brain  compared  with  that  of  other  animals  is  actually 
larger  than  in  any  except  the  elephants  and  great  whales ;  but  propor- 
tionately to  the  size  of  the  body  is  much  larger  than  in  these.  It  is 
twice  the  weight  of  the  brain  of  the  horse  or  ox.  In  several  elephants 
it  ranged  from  eight  to  ten  pounds,  and  in  a  whalebone  whale  of 
seventy-five  feet,  which  weighed  more  than  a  regiment  of  men,  it  was 
only  four  pounds.1 

The  brain  of  the  great  French  naturalist  Cuvier  weighed  upwards 
of  four  pounds ;  that  of  idiots  averages  about  one  and  a  half  pounds. 
The  brain  of  a  gorilla,  one  of  man's  nearest  allies,  weighed  fifteen 
ounces. 

In  the  infant  at  birth  the  brain  is  of  a  soft,  pulpy  consistence,  but 
gradually  assumes  more  firmness ;  in  the  adult  it  is  about  that  of 
freshly-made  cheese.  Its  specific  gravity,  but  little  more  than  that  of 
water,  is  about  1036. 

The  brain  is  a  symmetrical  organ  composed  of  similar  halves,  in 
the  median  line  partly  separated  by  the  great  longitudinal  fissure  and 

1  It  is  reported  that  in  some  email  animals  the  brain  is  even  proportionately 
larger  than  in  man,  as  the  common  mouse,  but  this  I  have  found  not  to  be  the  case. 
In  a  mature  male  which  weighed  three  hundred  and  fifty-six  grains  the  brain  was 
six  and  a  half  grains,  in  the  proportion  of  about  one  to  fifty-five. 


THE   NERVOUS   SYSTEM. 


715 


partly  conjoined.  The  upper  part  is  hemiovoid  and  conforms  to  the 
vault  of  the  cranium,  while  the  lower  part,  or  base,  conforms  to  the 
three  pairs  of  cranial  fossae. 

The  brain  consists  of  four  conspicuous  divisions,  the  cerebrum,  cere- 
bellum, pons,  and  medulla  oblongata. 

The  cerebrum  comprises  about  seven-eighths  of  the  whole  brain 
and  extends  its  entire  length  and  breadth  above,  while  the  other  parts 

FIG.  367. 


BASE  OF  THE  BKAIN.  1,  frontal  lobes  of  the  cerebrum :  2,  temporal  lobes ;  3,  occipital  lobes ;  4, 
5,  anterior  and  posterior  extremities  of  the  great  longitudinal  fissure ;  6,  sylvian  fissure ;  7,  ante- 
rior perforated  space ;  8,  infundibulum ;  9,  mammillary  eminences ;  10,  posterior  perforated  space ; 
11,  crura  of  the  cerebrum;  12,  pons;  13,  oblongata ;  14,  pyramid ;  14*,  decussation  of  the  pyramids ; 
15,  olive;  16,  restiform  body;  17,  hemispheres  of  the  cerebellum;  18,  vermis  at  the  bottom  of 
the  valley  separating  the  latter ;  19,  middle  peduncle  of  the  cerebellum ;  20,  floccule ;  21,  fissure 
which  accommodates  the  olfactory  lobe,  22 ;  23,  bulb  of  the  olfactory  lobe ;  24,  optic  commissure ; 
25,  oculo-motor  nerve ;  26,  trochlear  nerve ;  27,  trifacial  nerve ;  28,  abducent  nerve ;  29,  facial 
nerve ;  30,  auditory  nerve ;  31,  glosso-pharyngeal  nerve ;  32,  vagus  nerve ;  33,  accessory  nerve ;  34, 
hypoglossal  nerve. 


lie  beneath  its  back  portion.  It  occupies  the  vault  of  the  cranium 
together  with  the  anterior  and  middle  fossae  of  its  base.  The  cere- 
bellum in  size  is  related  to  the  former  as  about  one  to  eight  and  a  half, 
and  occupies  the  posterior  fossae  of  the  base  of  the  cranium  beneath  the 
cerebrum.  The  pons,  third  in  size  of  the  divisions  of  the  brain,  occu- 
pies a  position  just  back  of  the  centre  beneath  the  cerebrum  and  in 
advance  of  the  cerebellum,  resting  on  the  upper  part  of  the  spheno- 


716  THE   NERVOUS  SYSTEM. 

basilar  groove.  The  oblongata,  the  smallest  division  of  the  brain, 
lies  on  the  lower  part  in  advance  of  the  cerebellum,  connected  with 
the  pons  above  and  continuous  with  the  spinal  cord  below. 

The  cerebrum  on  its  exterior  surface  is  everywhere  of  a  reddish- 
gray  color.  It  resembles  a  mass  of  small  intestines  or  of  worms,  due 
to  its  being  covered  with  tortuous  ridges,  the  convolutions,  or  gyri, 
which  are  separated  by  corresponding  fissures.  The  cerebellum  pre- 
sents the  same  color,  but  is  divided  by  horizontal  fissures  into  thinner 
parallel  layers,  so  as  to  exhibit  a  laminar  appearance.  The  pons  and 
oblongata  present  a  more  uniform  surface  and  are  white  like  the  spinal 
cord. 

THE   MEDULLA   OBLONGATA. 

The  medulla  oblongata1  above  joins  the  pons,  from  which  it  is 
defined  by  a  constriction.  It  is  continuous  below  with  the  spinal  cord, 
of  which  it  appears  to  be  the  upper  expanded  extremity,  but  is 
regarded  as  distinct,  on  a  level  with  the  lower  border  of  the  occipital 
foramen.  It  occupies  a  position  between  the  basilar  groove  of  the 
occipital  bone  in  front  and  the  valley  of  the  cerebellum  behind.  It  is 
pyriform,  for  the  most  part  white,  about  an  inch  long,  three-fourths  of 
an  inch  at  its  widest  part  above  and  little  more  than  half  an  inch  thick. 
It  is  partially  divided  fore  and  aft  by  median  fissures  continuous  with 
those  of  the  spinal  cord.  The  anterior  median  fissure  is  inter- 
rupted below  by  the  decussation  of  the  pyramids  and  ends  above  in 
a  little  triangular  pit2  next  the  pons.  The  posterior  median  fis- 
sure at  the  upper  half  of  the  oblongata  expands  into  the  floor  of  the 
fourth  ventricle  of  the  brain.  Each  half  of  the  oblongata  is  formed 
by  a  group  of  three  columns,  from  which  originate  the  posterior  seven 
nerves  of  the  brain. 

The  anterior  columns3  of  the  oblongata  are  named  the  pyramids,4 
are  apparently  continuous  below  with  those  of  the  spinal  cord,  but 
are  so  only  to  a  small  extent  and  are  mainly  continuous  with  its  lateral 
columns.  The  pyramids  are  trilateral  prismatic  bodies  placed  at  the 
sides  of  the  anterior  median  fissure  and  appear  superficially  as  pyri- 
form eminences  most  prominent  at  the  upper  extremity,  where  they 
are  rounded  and  separated  by  a  narrow  constriction  from  the  pons. 
They  are  almost  wholly  composed  of  white  matter  consisting  of  longi- 
tudinal nerve-fibres,  which  subsequently  ascend  in  divergent  bundles 
through  the  pons.  At  their  lower  extremity  they  also  divide  into  bun- 
dles, which,  for  the  most  part,  cross  one  another  at  the  anterior  median 


1  Bulbus  rachidicus;  metencephalon.      French,  Moelle   allonge;   German,  ver- 
langerte  Mark. 

2  Foramen  caecum.  3  Funiculi  pyramidales. 

4  Pyramis  ;  p.  anterior ;  corpus  pyramidale  ;  prepyramid  ;  ventripyramid  ;   py- 
ramidal body. 


THE   NERVOUS   SYSTEM. 


717 


FIG.  368. 


fissure  and  thus  produce  the  decussation  of  the  pyramids.1  In 
this  the  bundles  descend  from  the  pyramids,  cross  one  another  back- 
ward and  inward,  and  thence  continue  on  opposite  sides  backward  and 
outward  to  the  lateral  columns  of  the  cord,  in  which  they  descend  as 
the  lateral  pyramidal  tract.  As  the  bundles  proceed  from  the  decussa- 
tion to  the  latter  they  pass  through  the  gray  matter  continued  from 
the  cord  and  sever  the  cornua  from  the  rest  of  that  substance. 

The  extent  of  the  decussation 
of  the  pyramids,  which  is  visible 
in  different  cases,  is  variable,  for 
sometimes  the  bundles  pursue  a 
deeper  and  sometimes  a  more  su- 
perficial course.  In  some  cases, 
also,  a  larger  portion  of  the  fibres 
descends  directly  in  the  anterior 
columns  of  the  cord  and  a  propor- 
tionately smaller  quantity  through 
the  decussation  in  the  lateral  col- 
umns. Occasionally  nearly  or  quite 
all  of  the  fibres  of  the  pyramids 
enter  into  the  decussation,  in  which 
instances  it  becomes  most  obvious. 

The  lateral  columns2  of  the 
oblongata  seem  to  be  a  continua- 
tion of  those  of  the  spinal  cord,  and 
are  so  to  a  small  extent,  but  are 
mainly  continuous  with  the  ante- 
rior columns  of  the  cord,  which, 
in  their  ascent  in  the  oblongata, 
are  shifted  outwardly,  through  the 
decussation  of  the  pyramids  with 
the  lateral  columns  of  the  cord. 
Directed  upward  and  outward  ex- 
ternally and  behind  the  pyramids, 
they  are  composed  of  bundles  of 

fibres,  which  for  the  most  part  ascend  to  the  pons,  while  a  small  por- 
tion in  continuation  of  the  cerebellar  tract  from  the  lateral  column 
of  the  cord  turns  backward  in  the  restiform  body.  From  the  upper 
part  of  the  lateral  column  projects  the  olive,3  which  appears  as  a 
conspicuous,  longitudinal,  oval  eminence.  It  extends  about  half  the 
length  of  the  oblongata,  and  its  upper  extremity  is  separated  from  the 
pons  by  a  deep  recess.  Along  its  anterior  border,  between  it  and  the 
pyramid,  emerge  the  roots  of  the  hypoglossal  nerve,  and  at  its  pos- 


FORE  PAET  OF  THE  PONS  AND  OBLONGATA.  1. 

pons ;  2,  oblongata ;  3,  middle  peduncle  of  the 
cerebellum ;  4,  cms  of  the  cerebrum ;  5,  cinere- 
ous tuber;  6,  infundibulum ;  7,  mammillary 
eminences,  and  behind  them  the  posterior 
perforated  space ;  8,  optic  tract ;  9,  optic  com- 
missure ;  10,  oculc-motor  nerve ;  11,  trochlear 
nerve:  12,  trifacial  nerve,  the  small  or  motor 
root  internal ;  13,  abducent  nerve ;  14,  facial 
nerve ;  15,  intermediate  portion ;  16,  auditory 
nerve ;  17,  glosso-pharyngeal  nerve ;  18,  vagus 
nerve;  19,  accessory  nerve;  20,  hypoglossal 
nerve ;  21,  first  spinal  or  suboccipital  nerve. 


1  Decussatio  pyramidum. 

8  Oliva  ;  olivary  body  ;  corpus  olivare  ;  c.  semiovale. 


2  Funiculi  olivares. 


718 


THE   NERVOUS    SYSTEM. 


terior  border  is  a  groove  occupied  by  ascending  fibres  of  the  lateral 
column,  behind  which  emerge  the  roots  of  the  glosso-pharyngeal, 
vagus,  and  accessory  nerves.  The  olive  is  embraced  by  the  ascending 
fibres  of  the  lateral  column,  which  diverge  in  front  and  behind  it  as 
they  proceed  to  the  pons  and  restiform  body.  Superficially  it  is  formed 
by  a  layer  of  transversely  curving  or  arciform  fibres,1  which  proceed 
from  the  anterior  median  fissure  and  from  the  outer  side  of  the  pyramid, 
and  thence  turn  backward  and  upward  behind  the  olive  to  the  restiform 
body.  The  arciform  fibres  often  form  more  or  less  well-marked  loops, 
especially  on  the  lower  part  of  the  olive  and  frequently  below  it,  and 
to  a  variable  degree  they  obscure  the  subjacent  ascending  fibres.  The 
olive  encloses  a  lamina  of  gray  matter,  the  olivary  nucleus,2  which 
is  in  the  form  of  a  deeply- wrinkled  ovoid  pouch,  with  the  mouth  di- 
rected inward.  The  interior  of  the 
pouch  is  filled  with  white  matter, 
which  consists  of  fibres  passing 
from  the  pouch  through  its  mouth 
and  becoming  continuous  with  as- 
cending fibres  behind  the  pyra- 
mid.3 Bundles  of  the  fibres  also 
penetrate  the  pouch  and  form  part 
of  the  external  arciform  fibres  of 
the  olive.  Sections  of  the  nucleus 
have  a  toothed  appearance,  whence 
the  older  name  of  the  corpus 
dentatum. 

The  posterior  columns  of  the 
oblongata,  like  the  others,  appear 
to  be  a  continuation  of  those  of  the 
spinal  cord,  and  in  this  case  are  so 
in  great  measure.  They  ascend 
behind  the  lateral  columns  and  are 
divided  into  three  lesser  columns 
or  funicles,  which  gradually  en- 
large in  their  ascent  and  then 
taper  away  to  the  side  of  the  res- 


VlEW  BACK  OF  THE  PONS  AND  OBLONGATA;  the 

cerebellum  removed.  1,  pineal  body  turned 
forward,  showing  the  posterior  commissure,  2 ; 
3,  thalamus;  4,  quadrigeminal  body:  5,  in- 
ternal geniculate  body ;  6,  anterior  velum ;  7, 
fillet;  8,  lingule;  9,  oblongata;  10,  posterior 
pyramid ;  11,  restiform  body ;  12,  floor  of  fourth 
ventricle;  13,  superior  peduncle  of  the  cere- 
bellum cut  through ;  14,  middle  peduncle  of 
the  cerebellum  cut  through ;  15,  inferior  pedun- 
cle of  the  cerebellum  cut  through. 


tiform  body. 

The  gracile  funicle  *  lies  next 

the  posterior  median  fissure  and 
is  continuous  below  with  the  posterior  median  column  of  the  cord. 
Above,  as  the  posterior  pyramid6  or  clava,  it  appears  as  an  emi- 


1  Arcuate  fibres. 

*  Nucleus  olivaris  ;  n.  dentatus  ;  corpus  fimbriatum,  ciliare,  or  rhomboideum. 
3  Pedunculus  olivae. 

*  Funiculus  gracilis.  5  Pyramis  posticus. 


THE   NERVOUS   SYSTEM.  719 

nence1  just  below  the  inferior  angle  of  the  fourth  ventricle,  and  thence 
diverges  and  tapers  away  at  the  side  of  it  in  the  restiform  body.  It 
contains  a  tract  of  gray  matter,  the  gracile  nucleus,2  which  enlarges 
upward  and  is  thickest  in  the  eminence  of  the  clava. 

To  the  outer  side  of  the  gracile  funicle  are  the  internal  and  ex- 
ternal cuneate  funicles,3  continuous  below  with  the  lateral  posterior 
column  of  the  cord  and  above  with  the  restiform  body.  Between  them 
emerge  the  roots  of  the  glosso-pharyngeal,  vagus,  and  accessory  nerves. 
The  internal  funicle  is  slightly  swollen4  near  the  eminence  of  the  clava, 
and  it  contains  a  tract  of  gray  matter,  the  internal  cuneate  nucleus.5 
The  external  funicle  also  contains  a  tract  of  gray  matter,  the  ex- 
ternal cuneate  nucleus,6  which  enlarges  above  and  produces  at  the 
surface  a  slight  grayish  prominence,  the  external  cuneate  eminence.7 

The  bundles  of  white  fibres  of  the  three  funicles  composing  the 
posterior  column  of  the  oblongata  are  continued  below  as  those  of  the 
posterior  column  of  the  cord  and  above  partly  end  in  their  gray  nuclei 
and  partly  ascend  in  the  restiform  body. 

The  restiform  body8  appears  as  a  continuation  of  the  posterior 
column  of  the  oblongata  upward  and  outward  at  the  side  of  the  fourth 
ventricle  and  reflected  backward  to  the  corresponding  hemisphere  of 
the  cerebellum  as  its  inferior  peduncle.  It  appears  to  be  formed 
mainly  by  the  convergence  and  ascent  of  the  arciform  fibres  of  the 
oblongata,  joined  by  others  from  its  lateral  column  and  from  the  cere- 
bellar  tract  of  the  spinal  cord.  The  fibres  of  the  cerebellar  tract  in 
their  ascent  pass  superficially  behind  the  olive  and  obliquely  cross  the 
cuneate  funicles  and  the  line  of  emergence  of  the  adjacent  nerves  into 
the  restiform  body. 

FOURTH  VENTKICLE  OF  THE  BRAIN. 

The  fourth  ventricle  of  the  brain,9  which  may  now  be  conveni- 
ently examined,  is  situated  at  the  back  of  the  oblongata  and  pons 
in  front  of  the  central  portion  of  the  cerebellum.  Its  fore  part,  dis- 
tinguished as  the  floor,  is  a  lozenge-shaped  recess ;  its  back  part,  or 
roof,  is  formed  above  by  the  anterior  velum  and  below  by  the  poste- 
rior velum  and  choroid  tela.  The  superior  angle  of  the  ventricle  com- 
municates through  the  ventricular  aqueduct  with  the  third  ventricle, 
and  the  inferior  angle,  or  calamus  scriptorius,  with  the  central  canal 
of  the  oblongata  and  spinal  cord. 

1  Eminentia  gracilis.  2  N.  gracilis. 

8  Funiculus  cuneatus  internus  or  medius  and  externus,  lateralis,  or  Rolandi ; 
corpus  restiforme ;  pyramis  lateralis. 

*  Eminentia  cuneatus.  5  N.  cuneatus. 

6  N.  cuneatus  externus  ;  n.  of  Kolando. 

7  Tubercle  of  Rolando ;  tuberculum  cinereum. 

8  Corpus  restiforme ;  pyramis  lateralis  ;  funiculus  restiformis. 

9  Ventriculus  quartus  ;  v.  Arantii. 


720 


THE   NERVOUS   SYSTEM. 


FIG.  370. 


The  floor  of  the  fourth  ventricle l  slopes  gently  downward  and 
backward.  Its  inferior  triangle 2  is  formed  by  the  oblongata,  and  is 
produced  by  the  divergence  of  the  clavse  and  restiform  bodies.  The 

superior  triangle3  is  formed  by 
the  pons  and  is  produced  by  the 
divergence  from  above  of  the  supe- 
rior peduncles  of  the  cerebellum. 
The  lateral  triangles  are  pro- 
duced by  the  convergence  of  the 
superior  and  inferior  peduncles  of 
the  cerebellum  outward  and  back- 
ward behind  the  position  of  the 
middle  peduncles.  Each  is  pro- 
longed into  a  lateral  recess  or 
finger-like  pouch,  the  cornucopia, 
which  curves  outward  around  the 
restiform  body  to  the  floccule  of 
the  cerebellum. 

The  upper  part  of  the  roof  of 
the  fourth  ventricle  is  formed  by 
the  anterior  velum,4  a  lamina 
of  white  matter  which  descends 
in  a  slope  from  the  quadrigeminal 
body  to  the  stem  of  the  vermis 
and  laterally  connects  the  supe- 
rior peduncles  of  the  cerebellum. 
The  lower  part  of  the  roof  imme- 
diately succeeding  the  anterior 
velum  is  formed  by  the  fore  part 
of  the  nodule  of  the  vermis  and 
on  each  side  of  this  by  the  poste- 
rior velum,5  whence  the  choroid 
tela,6  an  extension  of  the  pia,  de- 
scends to  the  inferior  angle  of  the  ventricle  and  closes  the  lower  back 
part  of  this  cavity. 

The  floor  of  the  fourth  ventricle  is  chiefly  composed  of  gray  matter 
which  is  continuous  with  that  in  the  interior  of  the  oblongata  and  is 
divided  by  a  median  furrow.  On  each  side  of  this  is  a  slightly  promi- 
nent column,  the  terete  funicle,7  which  commences  in  the  inferior 

1  Fossa  or  sinus  rhomboidalis. 

2  Medullary  portion  of  the  fourth  ventricle.  3  Pontal  portion. 

4  V.  medullare  anterior  or  superior  ;   valve  of  the  brain  ;   valve  of  Vieussens  ; 
valvula  cerebri  or  cerebelli. 

5  V.  med.  post. 

6  T.  choroidea  inferior;  t.  ventriculi  quarti  or  cerebelli. 
'  Funiculus  or  corpus  teres;  pyramides  posteriores. 


POSTERIOR  PART  OF  OBLONGATA  AND  FLOOR 
OF  FOURTH  VENTRICLE:  magnified  one  and  a 
half  times.  1,  superior  peduncle  of  the  cere- 
bellum, cut  surface ;  2,  cut  surface  of  the  mid- 
dle and  inferior  peduncles  ;  3,  lingule  lying  on 
the  anterior  velum ;  4,  posterior  median  fissure ; 
5,  gracile  funicle ;  6,  clava  tapering  away  at  7 ; 
8,  internal  cuneate  funicle ;  9,  external  cuneate 
funicle;  10,  lateral  funicle;  11,  cuneate  emi- 
nence ;  12,  obex ;  13,  ponticulus ;  14,  inferior 
velum ;  15,  superior  fovea ;  16,  inferior  fovea ; 
17,  cinereous  eminence ;  18,  terete  funicle ;  19, 
auditory  eminence  crossed  by  the  auditory 
striae ;  20,  root  of  auditory  nerve. 


THE  NERVOUS  SYSTEM.  721 

angle  in  a  somewhat  lighter  point,  gradually  widens  to  about  the 
middle  of  the  venti*icle,  where  it  is  slightly  but  variably  thickened  as 
the  terete  eminence,1  and  thence  ascends  more  uniformly  to  the 
superior  angle  of  the  ventricle. 

External  to  the  lower  end  of  the  terete  funicle  is  an  angular  de- 
pression, the  inferior  fovea,2  which  includes  a  slight  elevation,  the 
cinereous  eminence.3  This  is  darker  than  the  adjacent  surface, 
but  is  continuous  with  the  gray  matter  of  the  terete  funicle  and  also 
that  within  the  oblongata.  Above  the  middle  of  the  floor,  external 
to  the  terete  eminence,  is  another  slight  angular  depression,  the  supe- 
rior fovea.*  The  more  prominent  portion  of  the  floor  to  the  outer  side 
between  the  latter  and  the  inferior  fovea  is  the  auditory  eminence.5 
This  is  crossed  transversely  by  several  variable  white  lines,  the  audi- 
tory striae,6  which  spring  from  the  floor  near  the  median  furrow 
and  thence  proceed  outward  round  the  restiform  body  to  the  auditory 
nerve.  Among  them  there  is  commonly  to  be  seen  a  variably  promi- 
nent gray  stria.7 

In  the  superior  triangle  of  the  ventricle  along  the  lateral  border  is 
a  variable  slate-blue  streak,  named  the  locus  caeruleus.  It  extends 
from  the  superior  fovea  to  the  ventricular  aqueduct,  and  is  due  to  a 
subjacent  tract  of  gray  matter  containing  large  and  unusually  dark 
pigmented  cells.  It  is  commonly  better  marked  after  adult  age. 

At  an  early  period  of  the  development  of  the  brain  the  fourth 
ventricle,  in  the  position  of  the  choroid  tela,  is  closed  by  a  thin  white 
lamina  which  subsequently  is  rendered  incomplete.  Remains  of  this 
plate,  somewhat  variable,  are  distinguished  as  the  inferior  velum,  obex, 
and  ponticulus. 

The  inferior  velum 8  is  a  thin  band  extending  from  the  restiform 
body,  below  the  auditory  striae,  outwardly  to  the  floccule,  where  it  is 
continuous  with  the  posterior  velum,  forming  together  an  oval  pouch, 
the  cornucopia,  which  is  open  below.  The  inferior  velum  lies  in 
front  against  the  roots  of  the  glosso-pharyngeal  and  vagus  nerves  and 
is  often  closely  adherent  to  them. 

The  obex 9  is  a  little  triangular  furcate  plate  inserted  in  the  inferior 
angle  of  the  fourth  ventricle,  between  the  clavse. 

The  ponticulus 10  consists  of  a  pair  of  little  bands,  above  the  obex, 
springing  from  the  respective  restiform  bodies  and  approaching  but 
not  usually  joining  each  other,  thus  forming  an  imperfect  bridge. 

Immediately  above  the  obex  the  choroid  tela  exhibits  a  slit-like 

1  Eminentia  teres  ;  colliculus  rotundus.  2  F.  posterior. 

3  Eminentia  cinerea  cuneiformis  ;  ala  cinerea.  *  F.  anterior. 

5  Eminentia  acustica. 

6  S.  medullares  ;  tsenise  acusticae.  7  Tseniola  cinerea. 

8  V.  medullare  inferius  ;  upper  part  of  the  tsenia  plexus  choroidei. 

9  Obex  sinus  rhomboidalis. 

10  Alse  pontis ;  ligulse ;  lower  part  of  the  tsenia  plexus  choroidei. 

46 


722 


THE   NERVOUS   SYSTEM. 


17 


opening,   the   foramen  of    Magendie,1   through   which   the    fourth 
ventricle  communicates  with  the  adjacent  subarachnoid  space. 

Projecting  into  the  fourth  ventricle  along  the  middle  of  the  choroid 
tela  are  two  narrow  vascular  appendages,  the  median  choroid  plex- 
uses.2 From  the  extension  of  the  tela  along  the  posterior  velum,  on 
each  side,  the  lateral  choroid  plexus3  projects  from  the  cornucopia. 

INTEKIOK  OF   THE   OBLONGATA. 

The  interior  arrangement  of  the  structure  of  the  oblongata  is  most 
readily  studied  by  the  examination  of  successive  horizontal  sections 

from  below  upward. 

The  gray  matter  of  the  spinal 
cord  is  continued  in  the  oblongata, 
but  is  much  altered  in  its  arrange- 
ment, besides  which  it  is  aug- 
mented by  additional  tracts  or 
nuclei. 

The  decussation  and  produc- 
tion of  the  pyramids  and  the  in- 
troduction of  the  olives  into  the 
oblongata  cause  the  recession  of 
the  ascending  gray  matter  of  the 
cord  and  other  displacements  of 
its  parts.  At  the  limit  of  the  cord 
the  posterior  cornua  are  reflected 
more  outward  and  are  more  nar- 
rowed at  their  neck  and  rounded 
at  their  head.  The  anterior  com- 
missure is  thicker  and  is  continu- 
ous above  with  the  decussation  of 
the  pyramids. 

In  sections  through  the  decus- 
sation the  bundles  of  fibres  are 
seen  to  pass  from  the  pyramids 
backward  and  inward,  cross  one 
another  through  the  anterior  me- 
dian fissure,  and  thence  pass  back- 
ward and  outward,  on  the  opposite 

sides  of  the  oblongata,  through  the  gray  matter  severing  the  cornua 
from  the  more  central  portion. 

In  tracing  the  bundles  of  fibres  from  the  pyramidal  tract  of  the 
lateral  column  of  the  spinal  cord  they  are  observed  to  cross  through 
the  decussation  of  the  pyramids  and  ascend  in  the  fore  part  of  that 


12  3 

HORIZONTAL  SECTION  OF  THE  OBLONGATA  AT 
THE  UPPER  PART  OF  THE  DECUSSATION  OF  THE 
PYRAMIDS,  right  half:  four  diameters.  1,  an- 
terior median  fissure ;  2,  pyramid ;  3,  arciform 
nucleus;  4,  arciform  fibres;  5,  decussation  of 
the  pyramids ;  6,  olivary  nucleus ;  7,  accessory 
nucleus;  8,  reticular  formation;  9,  central 
canal ;  10,  gray  matter  enclosing  central  canal ; 
11,  lateral  nucleus ;  12,  external  cuneate  funi- 
cle ;  13,  nucleus  of  gelatinosa  of  the  external 
cuneate  funicle ;  14,  ascending  root  of  trifacial 
nerve;  15, internal  cuneate  funicle;  16,  nucleus 
of  internal  cuneate  funicle ;  17,  accessory  nu- 
cleus of  the  internal  cuneate  funicle ;  18,  gracile 
funicle ;  19,  gracile  nucleus ;  20,  nucleus  of  ac- 
cessory nerve ;  21, nucleus  of  hypoglossal  nerve. 


1  F.  Magendii ;  f.  ventriculi  quarti. 

2  P.  choroidei  superior  or  medialis. 


3  P.  chor.  inferior  or  lateralis. 


THE   NERVOUS   SYSTEM. 


723 


22- 


of  the  opposite  side.  Those  from  the  pyramidal  tract  of  the  anterior 
column  of  the  cord  are  reflected  outwardly  and  ascend  in  the  pyramid 
of  the  same  side,  at  first  external  to  the  decussation  and  then  behind 
the  others. 

The  central  gray  matter  of  the  oblongata,  after  the  separation  of 
the  cornua,  in  section  appears  triangular  with  the  apex  directed  forward 
and   enclosing    the   central   canal 
continued  from  the  cord.     In  its 
ascent  it  gradually  recedes  to  the 
posterior  surface  of  the  oblongata, 
divides  behind  and  spreads  later- 
ally until  the  central  canal  is  laid 
open,  when  it  is  extended  on  the 
floor  of  the  fourth  ventricle. 

The  anterior  cornu  of  the  cord 
ascends  in  the  oblongata,  behind 
the  olive,  as  the  lateral  nucleus, 
which  gradually  decreases.  The 
posterior  cornu,  enlarged  and 
rounded,  ascends  behind  the  ante- 
rior, within  the  external  cuneate 
funicle,  as  its  nucleus.  This  in  its 
course  approaches  the  surface,  pro- 
duces the  slight  grayish  external 
cuneate  eminence,1  and  continues 
upward  into  the  pons.  A  con- 
spicuous bundle  of  fibres  embracing 
it  externally  forms  the  ascending 
root  of  the  trifacial  nerve. 

A  columnar  tract  of  gray  mat- 
ter in  the  gracile  funicle  is  the 
gracile  nucleus.  It  commences 
in  the  oblongata  below,  gradually 
enlarges  in  its  ascent,  and  at  its 
upper  extremity  produces  the  eminence  of  the  clava. 

A  similar  tract  in  the  internal  cuneate  funicle  is  the  cuneate  nu- 
cleus, which  springs  from  the  central  gray  matter  of  the  cord  and 
becomes  continuous  with  the  former  nucleus. 

A  section  of  the  olive  at  either  extremity  exhibits  the  olivary 
nucleus  as  a  bent  elliptical  ring  and  at  the  middle  as  a  deeply-folded 
loop. 

Behind  the  olive  is  the  accessory  olivary  nucleus,  which  is  a 
vertically  ovoid  gray  plate.  A  similar  smaller  plate  in  the  outer  side 
of  the  pyramid  is  also  indicated  as  an  accessory  olivary  nucleus. 


23 


124  3 

HORIZONTAL  SECTION  OF  THE  OBLONGATA, 
about  the  middle  of  the  olive,  right  half:  four 
diameters.  1,  anterior  median  fissure ;  2,  pyr- 
amid, interior  ascending  bundles ;  3,  arciform 
fibres ;  4.  arciform  nucleus ;  5,  arciform  fibres 
of  the  olive;  6,  olivary  nucleus;  7,  raph6;  8, 
reticular  formation ;  9,  10,  accessory  olivary 
nuclei ;  11,  nucleus  ambiguus ;  12,  lateral  nu- 
cleus ;  13,  nucleus  of  gelatinosa;  14,  ascending 
root  of  the  trifacial  nerve ;  15,  restiform  body ; 
16,  cuneate  nucleus:  17,  gracile  nucleus;  18, 
terete  funicle ;  19,  longitudinal  bundle  of  nerve- 
fibres;  20,  20,  two  portions  of  the  vagus  nu- 
cleus ;  21,  root  of  vagus  nerve ;  22,  hypoglossal 
nucleus ;  23,  root  of  hypoglossal  nerve. 


1  Tubercle  of  Kolando. 


724  THE   NERVOUS  SYSTEM. 

A  thin  tract  of  gray  matter  in  the  superficial  fore  part  of  the  pyra- 
mid is  the  arciform  nucleus,1  which  gives  origin  to  the  contiguous 
arciform  fibres. 

The  space  between  the  pyramids  and  olives  in  front  and  the  prin- 
cipal tracts  of  gray  matter  of  the  oblongata  behind  is  occupied  by  the 
reticular  formation,2  named  from  its  appearance.  It  is  chiefly  com- 
posed of  longitudinal  fibres  ascending  from  the  lateral  columns  of  the 
oblongata  intersected  by  transverse  fibres,  which  from  their  curving 
course  are  named  arciform  fibres.  The  reticular  formation  com- 
mences in  the  lower  part  of  the  oblongata  through  the  breaking  up  of 
some  of  the  gray  matter  by  the  decussating  bundles  of  fibres  of  the 
pyramids ;  thence  it  increases  upward  and  is  continued  into  the  back 
of  the  pons. 

A  decussation  of  the  fibres  of  the  reticular  formation  in  the  median 
line  forms  the  raphe.  It  is  mingled  with  some  gray  matter  contain- 
ing nerve-cells  and  extends  from  the  decussation  of  the  pyramids 
upward  into  the  pons.  The  nerve-fibres  pursue  different  directions 
and  appear  mainly  to  pertain  to  the  arciform  series.  Longitudinal 
ascending  fibres  from  either  side  cross  one  another  and  turn  outwardly 
in  the  reticular  formation  as  deep  arciform  fibres,  while  others  pass 
forward  and  emerge  at  the  anterior  median  fissure  as  superficial  arci- 
form fibres. 

The  longitudinal  fibres  of  the  reticular  formation  are  reinforced  in 
their  ascent  by  many  of  the  arciform  fibres,  which  proceed  from  the 
decussation  of  the  pyramids  and  raphe  and  from  the  gracile,  cuneate, 
and  olivary  nuclei. 

The  outer  area  of  the  reticular  formation  contains  gray  matter  with 
many  large  nerve-cells,  while  the  inner  area  is  devoid  of  them. 

The  arciform  fibres  are  in  general  distinguished  as  a  deep  and  a 
superficial  series.  The  deep  arciform  fibres  mainly  proceed  from  the 
decussation  of  the  pyramids  and  the  raphe  and  curve  outward  and 
backward,  partly  running  to  the  gracile  and  cuneate  nuclei  and  partly 
to  and  through  the  olivary  nucleus,  thence  into  the  restiform  body. 
Of  the  superficial  arciform  fibres  proceeding  from  the  same  source, 
a  portion  passes  forward  at  the  anterior  median  fissure,  turns  outward 
on  the  pyramid  and  olive,  thence  ascends  in  the  restiform  body,  while 
another  portion  passes  out  laterally  behind  the  pyramid  and  joins  the 
former  portion.  The  superficial  arciform  fibres  are  also  reinforced  by 
others  proceeding  directly  from  the  outer  part  of  the  pyramids,  in 
addition  to  some  deep  ones  issuing  from  the  olivary  nucleus. 

The  extension  of  the  posterior  cornu  of  the  cord  into  the  oblongata, 
where  it  forms  the  external  cuneate  nucleus,  is  an  accumulation  of 
gelatinosa  with  nerve-cells,  from  which  arise  the  fibres  of  the  ascending 
root  of  the  trifacial  nerve  embracing  the  outer  side  of  the  nucleus. 

1  Nucleus  of  the  pyramid.  2  Formatio  reticularis. 


THE   NERVOUS  SYSTEM.  725 

The  extension  of  the  anterior  cornu  as  the  lateral  nucleus  of  the 
oblongata  appears  to  become  diffused  as  the  gray  matter  of  the  lateral 
area  of  the  reticular  formation,  in  which  there  are  many  large  nerve- 
cells. 

The  olivary  nucleus  is  a  lamina  of  gelatinosa  with  numerous  medium- 
sized  multipolar  nerve-cells  and  nerve-fibres,  which  pass  through  the 
nucleus  and  continue  as  arciform  fibres. 

The  gracile  nucleus  contains  large  multipolar  cells  sparsely  dis- 
tributed. 

The  gray  matter  enclosing  the  central  canal  of  the  lower  part  of 
the  oblongata  and  thence  extending  upward  in  the  floor  of  the  fourth 
ventricle  is  chiefly  composed  of  gelatinosa.  Embedded  in  it  are  groups 
of  nerve-cells,  which  are  the  nuclei  or  centres  of  origin  of  some  of  the 
important  nerves  of  the  brain. 

The  hypoglossal  nucleus  consists  of  a  columnar  tract  of  large 
multipolar  nerve-cells,  which  give  origin  to  the  nerve-fibres  forming  the 
rootlets  of  the  hypoglossal  nerve.  It  is  embedded  in  the  gray  matter 
of  the  terete  funicle  in  the  inferior  triangle  of  the  fourth  ventricle,  ex- 
tending downward  into  that  enclosing  the  central  canal  of  the  oblongata. 

The  nucleus  of  the  glosso-pharyngeal,  vagus,  and  accessory 
nerves  is  a  continuous  columnar  tract  of  smaller  nerve-cells  than  The 
preceding,  embedded  in  the  gray  matter  of  the  cinereous  eminence, 
extending  downward  into  that  enclosing  the  central  canal  behind  the 
former  tract. 

Two  auditory  nuclei  are  distinguished  on  each  side  in  the  floor  of 
the  fourth  ventricle.  The  internal  or  principal  auditory  nucleus 
corresponds  in  position  with  the  auditory  eminence  crossed  by  the 
auditory  striae.  It  is  a  columnar  tract  of  small  multipolar  cells  em- 
bedded in  the  eminence,  and  is  widest  at  the  striae,  whence  it  narrows 
towards  the  extremities.  The  external  auditory  nucleus l  is  a  tract 
of  large  nerve-cells  situated  to  the  outer  side  of  the  former,  is  largest 
at  the  upper  extremity  in  the  superior  fovea,  and  tapers  below  to  the 
position  of  the  auditory  striae.  It  is  traversed  by  longitudinal  bundles 
of  nerve-fibres,  which  pass  to  or  from  the  cerebellum.  From  these 
bundles,  as  well  as  from  the  nucleus,  the  superior  root  of  the  auditory 
nerve  appears  to  have  its  origin,  proceeds  forward  and  outward,  and 
emerges  from  among  the  ascending  fibres  of  the  restiform  body  to  join 
the  inferior  root  in  front  of  that  body. 

The  auditory  striae  proceed  from  behind  the  principal  auditory 
nucleus  and  pass  outward  around  the  restiform  body  to  its  fore  part 
as  the  posterior  division  of  the  inferior  root  of  the  auditory  nerve. 
The  anterior  division  of  the  inferior  root  proceeds  from  the  deep 
part  of  the  nucleus  outward  to  the  inner  side  of  the  restiform  body 
and  there  joins  the  posterior  division. 

1  Superior  aud.  nucleus ;  nucleus  of  Deiters  or  of  Laura. 


726  THE   NERVOUS   SYSTEM. 

Some  gray  matter  situated  between  the  superior  root  of  the  audi- 
tory nerve  and  the  restiform  body,  thence  extending  into  the  angular 
interval  of  the  two  divisions  of  the  anterior  root,  contains  the  acces- 
sory auditory  nucleus.  This  is  a  group  of  small  multipolar  nerve- 
cells,  which  are  peculiar  among  those  of  the  brain  in  that  they  are 
provided  with  a  nucleated  sheath  like  the  nerve-cells  of  ganglia. 

THE   PONS. 

The  pons 1  appears  superficially  as  a  conspicuous  white  eminence 
situated  at  the  base  of  the  brain  behind  its  centre.  It  is  placed  above 
the  oblongata  with  which  it  is  connected  below,  in  front  of  the  cere- 
bellum with  which  it  is  connected  behind,  and  beneath  the  cerebrum 
with  which  it  is  connected  above.  It  is  quadrate,  with  the  prominent 
fore  part  convex  and  with  a  median  furrow 2  which  accommodates  the 
basilar  artery.  It  rests  in  front  against  the  spheno-basilar  groove  of 
the  cranium.  Laterally  it  is  contracted  and  prolonged  backward  and 
outward  into  the  middle  peduncles 3  of  the  cerebellum.  Its  back  part 
is  narrower  than  the  fore  part,  forms  the  upper  triangle  of  the  floor 
of  the  fourth  ventricle  extending  to  the  ventricular  aqueduct,  and  is 
flawed  above  and  below  by  the  superior  and  inferior  peduncles  of  the 
cerebellum.  The  upper  part  of  the  pons  is  transversely  arched,  but 
depressed  at  the  middle.  Laterally  it  is  extended  obliquely  outward 
and  backward  as  the  fore  part  of -the  middle  peduncles  of  the  cerebel- 
lum, and  from  its  sides  ascend  the  crura  of  the  cerebrum.  The 
lower  part  is  more  nearly  straight,  and  laterally  bends  outward  as  the 
back  part  of  the  middle  peduncles  of  the  cerebellum.  The  front  of 
the  pons  is  strongly  striate  transversely,  indicating  the  course  of  the 
fibres  which  compose  its  more  superficial  portion.  It  also  exhibits 
many  little  perforations  due  to  blood-vessels  from  the  investing  pia. 

As  in  the  case  of  the  oblongata,  the  interior  structure  of  the  pons 
is  best  studied  by  the  examination  of  horizontal  sections  in  succes- 
sion from  below  upward.  In  these  it  is  observed  that  the  pons  for 
more  than  half  its  thickness  from  the  front  is  mainly  composed  of 
transverse  bundles  of  nerve-fibres  crossed  in  their  course  by  longitu- 
dinal bundles  ascending  from  the  pyramids.  To  the  latter  bundles 
is  due  the  greater  prominence  on  each  side  of  the  front  of  the  pons. 
The  pyramidal  bundles  enter  the  pons  in  columns  which  separate 
the  superficial*  from  the  deeper  portion5  of  the  transverse  bundles. 

1  Pons  Varolii  or  cerebelli ;  commissura  cerebelli ;  nodus  encephali ;  eminentia 
or  protuberantia  annularis  ;  tuber  annulare. 

2  Sulcus  basilaris. 

3  Crura  cerebelli  ad  pontem ;  c.  media  or  lateralia ;  brachia  pontis ;  c.  cerebri ; 
cerebral  peduncles. 

4  Fasciculus  pontis  anterior  or  inferior. 

5  F.  p.  posterior  or  superior ;  trapezium. 


THE   NERVOUS   SYSTEM. 


727 


In  their  further  ascent  the  columns  break  up  into  smaller  bundles, 
which  spread  in  layers  separated  by  corresponding  divisions  of  the 
transverse  bundles  of  the  pons.  The  ascending  bundles  multiply  and 
become  smaller,  but  collectively  larger,  due  to  an  accession  of  fibres  in 
passing  through  the  pons.  In  the  upper  part  of  this  the  pyramidal 
bundles  collect  together  and  emerge  to  ascend  in  the  cerebral  crura. 
The  transverse  bundles  of  the  pons,  after  passing  the  crura  outwardly, 


FIG.  373. 


FIG.  374. 


11 


FORE  PART  OF  THE  PONS  AND  OBLONGATA.     1. 

pons ;  2,  oblongata ;  3,  middle  peduncle  of  the 
cerebellum ;  4,  crus  of  the  cerebrum ;  5,  cinere- 
ous tuber;  6,  infundibulum ;  7,  mammillary 
eminences,  and  behind  them  the  posterior 
perforated  space ;  8,  optic  tract ;  9,  optic  com- 
missure ;  10,  oculo-motor  nerve ;  11,  trochlear 
nerve;  12,  trifacial  nerve,  the  small  or  motor 
root  internal;  13,  abducent  nerve;  14,  facial 
nerve;  15,  intermediate  portion;  16,  auditory 
nerve ;  17,  glosso-pharyngeal  nerve ;  18,  vagus 
nerve;  19,  accessory  nerve;  20,  hypoglossal 
nerve ;  21,  first  spinal  or  suboccipital  nerve. 


SECTION  ACROSS  THE  PONS,  left  half,  near  the 
middle  of  the  fourth  ventricle :  magnified  two 
diameters.  1,  transverse  bundles  of  fibres  pass- 
ing to  the  middle  peduncle  of  the  cerebellum, 
2;  3,  anterior  velum;  4,  fourth  ventricle;  5, 
raph6;  6,  bundles  of  fibres  ascending  from  the 
pyramid ;  7,  others  separated  from  the  former ; 
8,  deep  transverse  bundles  forming  the  trape- 
zium ;  9,  reticular  formation ;  10,  terete  funi- 
cle ;  11,  superior  olivary  nucleus ;  12,  ascending 
root  of  the  trifacial  nerve ;  13,  abducent  nerve ; 
14,  its  nucleus ;  15,  facial  nerve ;  16,  intermedi- 
ate portion  of  the  facial  nerve ;  17,  nucleus  and 
commencement  of  the  facial  nerve ;  18,  upper 
root  of  the  auditory  nerve ;  19,  part  of  its  outer 
or  upper  nucleus. 


collect  together  to  form  the  middle  peduncles  of  the  cerebellum.  The 
intermediate  transverse  bundles  are  most  direct  in  their  course,  and 
on  each  side  turn  outward  and  backward  in  the  peduncles.  The  lower 
bundles  curve  forward  at  the  sides,  then  likewise  turn  outward  and 
backward  in  them ;  the  upper  bundles  laterally  curve  backward  super- 
ficially over  the  others  and  then  continue  in  the  same  course. 

The  intervals  in  the  bundles  of  fibres  of  the  ventral  portion  of  the 
pons  include  some  gray  matter l  containing  many  small  nerve-cells  from 


1  Nucleus  pontis. 


728 


THE   NERVOUS   SYSTEM. 


which  nerve-fibres  proceed  both  in  a  longitudinal  and  a  transverse 
direction.     At  the  upper  part  of  the  pons  a  narrow  bundle  of  fibres l 

emerges  from  the  recess  between 
the  cerebral  crura  and  runs  out- 
wardly around  each  crus  to  the 
groove  between  'the  superior  and 
middle  cerebellar  peduncles  and 
accompanies  them  into  the  cere- 
bellum. 

The  dorsal  portion  of  the  pons 
is  mainly  composed  of  an  upward 
extension  of  the  reticular  forma- 
tion of  the  oblongata,  covered  be- 
hind by  a  layer  of  gray  matter 
which  forms  the  corresponding 
portion  of  the  floor  of  the  fourth 
ventricle.  It  is  flanked  above  and 
below  by  the  superior  and  infe- 
rior peduncles  of  the  cerebellum. 
The  reticular  formation  on  each 
side  is  also  conjoined  by  an  up- 
ward extension  of  the  raphe,  which 
in  the  ventral  portion  of  the  pons 
is  in  a  great  measure  obsolete  or 
obscured  by  the  passage  of  the 
transverse  bundles  of  fibres.  Be- 
sides the  more  generally  diffused 
gray  matter  of  the  reticular  forma- 
tion, at  the  fore  part  of  its  lateral  area  it  encloses  a  small,  folded  gray 
lamina,  distinguished  as  the  superior  olivary  nucleus.2  The  stratum 
of  gray  matter  at  the  back  of  the  pons,  in  the  floor  of  the  fourth  ven- 
tricle, has  been  described  in  the  account  of  that  cavity. 


3  2 

SECTION  ACROSS  THE  UPPER  PABT  OP  THE  PONS  ; 
left  half:  one  and  a  half  diameters.  1,  pons; 
2,  transverse  bundle  of  fibres ;  3,  3,  3,  ascend- 
ing bundles  of  the  pyramids ;  4,  reticular  for- 
mation ;  5,  longitudinal  bundles  of  fibres  of  the 
fillet;  6,  superior  peduncle  of  the  cerebellum; 
7,  lingule ;  8,  anterior  velum ;  9,  fourth  ven- 
tricle; 10,  posterior  longitudinal  bundle  of 
fibres;  11,  descending  root  of  the  trifacial 
nerve  with  its  nucleus;  12,  substantia  ferru- 
ginea;  13,  nucleus  continued  upward  in  the 
floor  of  the  ventricular  aqueduct ;  14,  trifacial 
nerve. 


THE   CEKEBELLUM. 

The  cerebellum 3  is  the  lower  posterior  division  of  the  brain  and 
occupies  the  posterior  cranial  fossae  beneath  the  cerebrum,  from  which 
it  is  separated  by  the  tentorium.  It  is  connected  at  its  fore  part  above 
to  the  other  divisions  of  the  brain  by  means  of  its  peduncles,  which 
communicate  with  them  through  the  great  oval  foramen  of  the  dura. 
Its  widest  part  is  commonly  three  and  a  half  to  four  inches  trans- 
versely, about  two  to  two  and  a  half  inches  fore  and  aft,  and  about 
two  inches  in  depth.  It  consists  of  a  pair  of  solid,  half-spheroidal 


1  Taenia  pontis.  2  N.  olivarius  superior. 

3  Parencephalis  ;  cerebrum  parvum  or  posterior;  little  or  after  brain. 


THE   NERVOUS   SYSTEM.  729 

masses,  the  hemispheres,  joined  by  a  median  portion,  the  vermis.1 
The  fore  part  above  is  deeply  notched  at  the  middle  for  the  accom- 
modation of  the  cerebellar  peduncles,  likewise  below  for  the  reception 
of  the  oblongata.  Above,  the  hemispheres  are  continuous  in  a  median 
rounded  ridge,2  formed  by  the  upper  part  of  the  vermis,  but  they  are 
separated  at  the  posterior  border  by  a  wide  notch,3  which  receives  the 
cerebellar  falx.  The  anterior  border  is  nearly  straight,  and  is  directed 
obliquelyoutward  and  backward  from  the  peduncles,  which  enter  its 
inner  extremity.  The  posterior  rounded  border  curves  from  the  median 
notch  outward  and  forward  to  the  anterior  border.  The  upper  surface 
slants  from  the  vermis  outward  and  backward,  is  slightly  concave  in 
the  same  direction,  and  slightly  convex  from  the  front  backward  and 
inward.  Below  the  upper  surface,  the  hemispheres,  as  implied  by  the 
name,  are  nearly  hemispherical  and  are  separated  by  a  deep  interval, 
the  valley,4  which  extends  from  the  posterior  notch  downward  and 
forward.  Into  the  valley  projects  the  inferior  portion  of  the  vermis,5 
which  here  appears  as  a  worm-like  ridge,  whence  its  name. 

The  cerebellum  is  characterized  by  its  laminated  appearance,  the 
surface  being  everywhere  divided  into  plates  separated  by  narrow  fis- 
sures which  receive  folds  of  the  pia.  The  plates  are  in  general  of 
uniform  thickness,  nearly  parallel  and  for  the  most  part  disposed  hori- 
zontally. The  fissures  are  of  variable  length  and  depth  and  often  run 
into  one  another.  The  laminar  appearance  of  the  cerebellum  is  accom- 
panied by  a  corresponding  arrangement  of  its  structure. 

The  interior  white  matter  extends  from  the  cerebellar  peduncles 
within  each  hemisphere  as  a  conical  trunk,  which  is  continuous  with 
its  fellow  through  the  stem  of  the  vermis.  Both  the  trunk  and  the 
stem  divide  into  divergent  plates,  and  these  again  divide  two  or  three 
times  in  the  same  manner.  The  terminal  plates  are  short,  thin,  and 
uniform,  and  have  folded  around  them  a  comparatively  thick  layer 
of  gray  matter,  which  is  everywhere  continuous  as  the  cortex  of 
the  cerebellum.  In  consequence  of  the  arrangement  thus  described, 
sections  of  the  cerebellum  crossing  the  laminaa  exhibit  a  remarkable 
arborescent  appearance,  distinguished  as  the  arbor  vitse.  In  the  vermis 
the  appearance  is  the  more  striking  from  the  more  graceful  proportions 
of  the  stem  and  its  branches  than  in  the  hemispheres. 

The  deepest  fissures  of  the  cerebellum  are  usually  the  most  obvious 
on  the  surface,  and  serve  to  distinguish  the  principal  divisions  or  lobes, 
which  consist  of  groups  of  lamina?.  One  of  the  most  conspicuous 
is  the  great  horizontal  fissure,6  which  divides  each  hemisphere  near 

1  Worm  ;  lobus  medius  cerebelli. 

2  Vermis  superior ;  sup.  vermiform  process. 

3  Incisura  marginalis  posterior. 

*  Vallis  ;  vallecula  ;  scissura  longitudinalis. 

5  Vermis  inferior  ;  inf.  vermiform  process. 

6  Sulcus  magnus  horizontalis. 


730 


THE   NERVOUS  SYSTEM. 


FIG.  376. 


its  middle.     Starting  in  front  to  the  outer  side  of  the  middle  peduncle, 
it  passes  outward  and  backward,  turns  under  the  posterior  border 

of  the  hemisphere  and  then  up- 
ward and  inward  over  the  border 
to  the  bottom  of  the  notch  between 
the  hemispheres. 

The  lobes  of  the  cerebellum 
are  commonly  distinguished  as  fol- 
lows: 

The  superior  lobe1  includes 
all  the  visible  upper  part  of  the 
hemisphere,  except  the  posterior 
primary  division  and  the  lower 
secondary  portion  of  the  posterior 
primary  division  of  the  vermis. 
The  laminae  and  intervening  fis- 
sures, seen  on  the  surface  of  these 
lobes,  pass  obliquely  from  in  front 
on  each  side  inward  and  back- 
ward to  the  vermis,  on  which  they 
become  abruptly  bent  from  their 
previous  course  and  more  or  less 
interrupted.  A  more  distinct  por- 
tion of  these  lobes  behind  has  been  named  the  crescentic  lobe.2 

The  first  division  of  the  superior  lobe  corresponding  with  the  an- 
terior primary  division  of  the  vermis  is  the  central  lobe.3  It  is  con- 
cealed by  the  greater  portion  of  the  superior  lobes  behind  and  rests  in 
front  against  the  anterior  velum  and  superior  peduncles  of  the  cerebel- 
lum. From  its  lower  part  extends  upward  and  forward  on  the  velum 
the  lingule,*  which  is  a  tongue-like  process  of  gray  matter  consisting 
of  four  or  five  transverse  bars,  which  correspond  with  other  laminae  of 
the  cortex  of  the  cerebellum. 

The  posterior  lobe5  forms  the  thick  rounded  border  of  the  hemi- 
sphere back  of  the  superior  lobe,  from  which  it  is  separated  by  a 
deep  fissure  which  curves  from  the  outer  border  of  the  hemisphere 
backward  and  inward  to  the  bottom  of  the  posterior  median  notch. 
It  includes  the  greater  part  of  the  hemisphere  beneath,  where  it  is 
separated  from  the  inferior  lobe  by  a  shorter  fissure  pursuing  a  simi- 
lar course  from  the  outer  part  of  the  hemisphere  to  the  lower  part 
of  the  valley.  It  is  composed  of  the  three  posterior  inferior  primary 
divisions  of  the  hemisphere  and  is  divided  by  the  great  horizontal  fis- 
sure. The  portion  above  the  fissure,  the  posterior  superior  lobe,6 


-14 


RIGHT  HEMISPHERE  OF  THE  CEREBELLUM,  seen 
from  beneath:  two-thirds  size.  1,  great  hori- 
zontal fissure ;  2,  3,  posterior  superior  and  in- 
ferior lobes;  4,  gracile  lobe;  5,  inferior  or  bi- 
ventral  lobe ;  6,  cut  surface  from  removal  of  the 
tonsilla ;  7,  floccule ;  8-10,  vermis ;  8,  tuber ;  9, 
pyramid ;  10,  uvula ;  11,  posterior  velum ;  12, 
inferior  velum ;  13,  cornucopia ;  14,  pons ;  15, 
cut  surface  of  oblongata. 


1  Quadrate  lobe  ;  lobus  quadratus  or  quadrangularis  ;  antero-superior  lobe. 

2  Posterior  crescentic  lobe.  3  Lobus  centralis.  *  Lingula. 
5  Lobus  semilunaris.                               6  L.  semilunaris  superior. 


THE   NERVOUS   SYSTEM.  731 

is  thick  and  crescentic,  and  commonly  joins  its  fellow  through  the 
vermis  by  a  single  plate.1  The  posterior  inferior  lobe2  forms  the 
greater  part  of  the  inferior  surface  of  the  hemisphere.  It  presents 
several  more  conspicuous  fissures  besides  the  lesser  ones,  and  its  lowest 
division  has  been  regarded  as  distinct  under  the  name  of  the  gracile 
lobe.3  In  advance  of  the  latter  and  outwardly  embraced  by  it  is  the 
inferior  lobe,*  which  appears  prominently  at  the  fore  part  of  the 
hemisphere  to  the  outer  side  of  the  oblongata.  It  is  composed  of  the 
lower  largest  primary  division  of  the  hemisphere  divided  into  two  sec- 
ondary ones,  whence  the  name  of  biventral  lobe. 

The  tonsilla5  is  an  oval  lobe  situated  at  the  inner  side  of  the 
hemisphere,  occupying  a  recess  of  the  inferior  lobe  and  projecting  into 
the  valley  behind  the  lower  part  of  the  oblongata.  It  is  attached  by 
a  stern  which  springs  from  the  inner  part  beneath,  of  the  central  white 
trunk  of  the  hemisphere. 

The  floccule 6  is  a  little  elliptical  lobe,  which  occupies  the  outer  part 
of  the  angular  space  in  front  of  the  middle  peduncle  of  the  cerebellum, 
between  the  superior  and  inferior  lobes.  Its  stem  springs  from  the 
inner  side  below,  of  the  middle  peduncle.  It  is  sometimes  accompanied 
by  a  smaller  accessory  floccule,7  which  is  partially  concealed  by  the 
larger  one. 

The  inferior  more  distinct  portion  of  the  vermis  is  also  divided  into 
lobes.  Of  these,  the  tuber 8  is  an  eminence  composed  of  four  or  five 
plates  which  belong  to  the  lower  branch  of  the  posterior  primary  di- 
vision of  the  vermis  and  connect  the  posterior  lobes  of  the  cerebellum 
across  the  upper  part  of  the  valley. 

Immediately  below  the  tuber  a  more  conspicuous  portion  of  the 
vermis  is  distinguished  as  the  pyramid,9  which  occupies  a  recess  be- 
tween the  posterior  lobes  of  the  cerebellum.  Its  apex  is  directed  back- 
ward, while  the  base,  more  in  advance,  unites  the  inferior  lobes  of  the 
cerebellum. 

In  front  of  the  pyramid  is  the  uvula,10  a  lobe  formed  of  a  series 
of  transverse  plates  successively  decreasing  and  producing  together  a 
keel-like  ridge,  which  projects  forward  into  the  valley  between  the 
tonsillse  and  behind  the  fourth  ventricle.  Its  widest  part  behind  is 
extended  on  each  side  in  a  ridge11  which  joins  the  corresponding 
tonsilla. 

1  Folium  or  lamina  cacuminis  ;  commissura  tenuis  ;  c.  loborum  semilunarium. 

2  Lobus  semilunaris  inferior.'  3  Lobus  gracilis ;  1.  inferior  medius. 

4  Lobus  inferior  anterior ;  1.  cuneiformis. 

5  Amygdala ;  lobus  inferior  internus  ;  1.  med.  oblongatse. 

6  Flocculus  ;  lobus  nervi  pneumogastrici. 

7  F.  secundarius.  8  T.  valvulse ;  vermis  posterior. 
9  Pyramidal  lobe ;  pyramis  ;  lobus  inferior  anterior. 

10  Lobus  intertonsillaris. 

11  Ala  uvulae ;  commissura  transversa  sulcata ;  furrowed  band. 


732  THE   NERVOUS   SYSTEM. 

Surmounting  the  uvula  is  a  smaller  lobe,  the  nodule,1  which  is 
formed  by  the  first  primaiy  lower  branch  of  the  vermis,  projecting 
behind  the  fourth  ventricle. 

In  front  of  the  nodule  on  each  side  is  a  thin  white  crescentic 
lamina,  the  posterior  velum,2  which  forms  part  of  the  lower  slope 
of  the  roof  of  the  fourth  ventricle.  It  springs  from  the  central  stem 
of  the  vermis,  extending  outward  to  the  floccule,  and  arches  forward 
and  downward  over  the  corresponding  tonsilla  and  terminates  in  a 
sharp  concave  edge.  It  extends  along  the  posterior  border  of  the 
lateral  recess  of  the  fourth  ventricle,  and  near  the  floccule  joins  the 
inferior  velum  of  the  oblongata,  to  form  with  it  an  open  pouch,  the 
cornucopia. 

The  peduncles  of  the  cerebellum  consist  of  three  pairs  of  stout 
bundles  of  nerve-fibres,  which  connect  it  with  the  other  chief  divisions 
of  the  brain,  and  are  distinguished  from  their  relative  position  as  supe- 
rior, middle,  and  inferior. 

The  middle  peduncle,3  much  larger  than  the  others,  is  a  cylin- 
drical process  which  passes  from  each  side  of  the  pons  obliquely  out- 
ward and  backward  and  enters  the  inner  fore  part  of  the  corresponding 
hemisphere  of  the  cerebellum.  It  is  formed  by  the  convergence  of  the 
transverse  bundles  of  fibres  of  the  ventral  portion  of  the  pons. 

The  superior  peduncle  *  is  a  flattened,  cylindrical  process  which 
passes  from  behind  and  beneath  the  quadrigeminal  body  on  each  side, 
descends  obliquely  outward  and  backward,  and  enters  the  hemisphere 
of  the  cerebellum  behind  and  beneath  the  middle  and  inferior  peduncles. 

The  inferior  peduncle,5  about  the  size  of  the  former,  but  more 
cylindrical,  is  the  continuation  of  the  restiform  body  on  each  side  of 
the  oblongata.  Ascending  obliquely  outward  it  turns  abruptly  back- 
ward and  enters  the  hemisphere  of  the  cerebellum  between  the  superior 
and  middle  peduncles. 

The  superior  peduncles  descend  at  the  sides  of  the  upper  triangle 
of  the  fourth  ventricle,  connected  together  by  the  anterior  velum, 
while  the  inferior  peduncles  ascend  at  the  sides  of  the  lower  triangle 
of  the  ventricle.  By  the  convergence  of  the  three  peduncles  on  each 
side  the  lateral  angle  of  the  ventricle  is  produced.  In  its  descent  the 
superior  peduncle  crosses  and  enters  the  cerebellum  beneath  the  inferior 
peduncle,  which  enters  between  the  superior  and  middle  peduncles. 

The  anterior  velum,6  connecting  the  superior  peduncles,  is  a 
white  lamina  which  forms  the  upper  part  of  the  roof  of  the  fourth 
ventricle  and  descends  obliquely  from  the  quadrigeminal  body  to  the 
stem  of  the  vermis  of  the  cerebellum.  Its  upper  surface,  slightly  de- 
pressed, is  for  the  most  part  covered  by  the  lingule,7  a  process  of  the 

1  Nodulus.  2  V.  medullare  posticum  ;  v.  Tarini ;  v.  semilunaris. 

3  Cms  ad  pontem.          4  Crus  ad  cerebrum.  5  Crus  ad  medullam. 

6  V.  medullare  anterius  or  superius.  T  Lingula. 


THE   NERVOUS  SYSTEM.  733 

cerebellar  cortex.  Extended  from  the  velum  to  the  median  groove  of 
the  quadrigeminal  body  is  a  little  white  band,  the  frenule,  on  each 
side  of  which  the  trochlear  nerve  issues. 

To  the  outer  side  of  the  superior  peduncles  above,  is  a  prominent 
white  band,  the  fillet,1  which  emerges  from  the  groove  between  the 
middle  and  superior  peduncles  and  ascends  obliquely  forward  and 
inward  to  the  quadrigeminal  body. 

The  three  peduncles  of  the  cerebellum  on  entering  the  correspond- 
ing hemisphere  unite  in  a  large  compressed  conical  trunk,  which  sub- 
sequently divides  into  plates,  and  the  division  is  several  times  repeated, 
until  finally  the  thin  terminal  plates  reach  the  cortex.  The  trunk  and 
plates  consist  of  bundles  of  fibres,  which  emanate  from  the  peduncles 
and  radiate  in  all  directions  to  reach  the  interior  surface  of  the  folded 
gray  cortex  of  the  cerebellum.  The  stem  of  the  vermis  is  continuous 
with  the  anterior  velum  and  with  the  superior  peduncles,  and  in  a  similar 
manner  to  the  trunk  of  the  hemisphere  extends  to  the  cortex. 

Embedded  in  the  central  white  trunk  of  each  hemisphere  of  the 
cerebellum  is  a  wrinkled  gray  lamina,  named  from  its  appearance  in 
section  the  dentate  nucleus.2  It  is  in  the  form  of  an  oval  pouch 
and  has  the  mouth  directed  inward,  forward,  and  downward.  It  is 
filled  with  white  matter3  consisting  of  fibres  mainly  continuous  with 
those  of  the  superior  peduncle  and  anterior  velum.  In  structure  the 
dentate  resembles  the  olivary  nucleus  of  the  oblongata. 

Between  the  dentate  nucleus  and  the  median  line  of  the  vermis  in 
each  hemisphere  there  are  several  smaller  and  less  conspicuous  accu- 
mulations of  gray  matter,  which  are  not  completely  isolated,  but  are 
continuous  with  the  dentate  nuclei  and  with  one  another.  The  largest, 
the  fastigiate  nucleus,*  is  an  oval  plate  in  the  fore  part  of  the  vermis 
separated  from  its  fellow  by  a  narrow  strip  of  white  matter.  The 
second  in  size,  the  emboliform  nucleus,5  is  a  fore  and  aft  clavate 
streak  close  to  the  mouth  of  the  dentate  nucleus.  The  remaining 
one,  the  globose  nucleus,6  is  a  rounded  streak  lying  intermediate 
to  and  a  little  lower  than  the  others. 

The  emboliform  nucleus  in  structure  resembles  the  dentate  nucleus, 
but  the  others  have  larger  nerve-cells. 

The  cortex 7  of  the  cerebellum  consists  of  two  nearly  equally  thick 
strata  of  gray  matter  separated  by  a  thin  stratum  less  gray  or  nearly 
white. 

The  cortex  of  the  cerebellum  forms  a  pretty  uniform  layer,  but  is 
thicker  at  the  free  borders  and  sides  of  the  folds  than  at  the  bottom. 


1  Lemniscus  ;  laqueus ;  band  of  Keil. 

2  N.  dentatus  ;  corpus  dentatum,  fimbriatum,  lenticulatum,  or  ciliare ;  ganglion 
cerebelli. 

3  Medulla  centralis  or  ciliaris.  *  N.  fastigii. 

6  N.  emboliformis.  6  N.  globosus.  T  Cortical  gray  substance. 


734 


THE   NERVOUS   SYSTEM. 


FIG.  377. 


It   consists  of  two   principal   layers,  of  which   the   external   is  the 
thicker. 

The  internal  cortical  layer,1  of  a  yellowish  or  rust-brown  hue, 

is  composed  of  a  matrix  of  neu- 
roglia,  with  numerous  fine  capil- 
lary vessels,  densely  crowded  with 
small  rounded  nerve-cells  and  per- 
vaded by  fine  medullated  nerve- 
fibres.  The  nerve-cells  are  mostly 
bipolar  and  by  means  of  their 
nerve-fibres  are  continuous  with 
those  of  the  terminal  plates  of 
the  white  matter  enclosed  by  the 
cortex. 

Partially  embedded  in  the  outer 
surface  of  the  internal  cortical 
layer  is  a  single  stratum  of  large 
nerve-cells,2  many  of  which 
range  from  y^V^r to  TVT>  °f  an  'ncn 
in  diameter.  They  are  mostly  flask- 
shaped  and  are  generally  arranged 
vertically  with  their  neck-like  pro- 
cesses directed  towards  the  free 
surface  of  the  cortex  and  forking 
into  two  widely-diverging  branches 
which  ramify  through  the  external 
cortical  layer.  From  their  base  a 
single  smaller  process  becomes  the 
axis-fibre  of  a  medullated  nerve- 
fibre.  The  large  nerve-cells  par- 
tially lie  in  a  very  thin  whitish 
stratum  of  nerve-fibres  between  the 
two  principal  layers  of  the  cortex. 
The  external  cortical  layer,  of  a  clearer  gray  hue  than  the  former, 
consists  of  an  abundant  matrix  of  neuroglia  pervaded  by  the  branch- 
ing fibres  of  the  large  nerve-cells  beneath,  with  a  few  scattered  and 
small  rounded  nerve-cells  and  numerous  capillary  vessels. 

THE   CEKEBKUM. 

The  cerebrum,3  the  largest  principal  division  of  the  brain,  is  hori- 
zontally ovoid  or  oval,  with  the  length  fore  and  aft  and  the  greater 
breadth  opposite  the  parietal  eminences.  It  is  deeply  divided  in  the 


VERTICAL  SECTION  OF  THE  CORTEX  OF  THE 
CEREBELLUM:  highly  magnified.  1,  internal 
cortical  layer,  crowded  with  small  nerve-cells 
(only  a  few  represented) ;  2,  external  cortical 
layer  of  neuroglia  and  branching  processes  3, 
of  the  large  nerve-cells  4. 


1  Granular  layer. 

8  Fore-brain  ;  great  brain  ;  pro-encephalon. 


Cells  or  corpuscles  of  Purkinje. 


THE   NERVOUS   SYSTEM. 


735 


median  line  by   the   great   longitudinal   fissure1  into  two    hemi- 
spheres. 

Each  cerebral  hemisphere2  presents  an  outer  convex  surface  next 
the  cranial  vault,  an  inner,  vertical  flat  surface  which  forms  the  side 
of  the  longitudinal  fissure,  and  an  under  surface.  This  is  divided  at 
the  fore  part  by  a  deep  cleft,  the  sylvian  fissure,  into  two  prominent 
lobes,  which  closely  conform  to  the  anterior  and  middle  cranial  fossse, 
while  the  back  part  is  concave  and  rests  on  the  tentorium,  a  partition 
of  the  dura,  which  separates  it  from  the  cerebellum. 

FIG.  378. 


SECTION  OF  THE  BRAIN  ALONG  THE  GREAT  LONGITUDINAL  FISSURE.  1,  oblongata ;  2,  pons ;  3, 
cms  of  the  cerebrum ;  4,  arborescent  appearance  in  section  of  the  vermis  of  the  cerebellum ;  5, 
left  hemisphere  of  the  cerebellum  ;  6,  inner  surface  of  the  left  hemisphere  of  the  cerebrum ;  7, 
callosum  ;  8,  ventricular  septum ;  9,  fornix ;  10,  anterior  crus  of  the  fornix  descending  to  join  the 
corresponding  mammillary  eminence ;  11,  fissure  through  which  the  choroid  tela,  12,  is  intro- 
duced into  the  third  ventricle ;  13,  pineal  body ;  14.  its  peduncle ;  15,  rests  on  the  thalamus  within 
the  third  ventricle ;  16,  posterior  commissure  of  the  latter ;  17,  middle  commissure ;  18,  anterior 
commissure ;  19,  foramen  of  communication  between  the  third  and  lateral  ventricles ;  20,  optic 
nerve;  21,  pituitary  body  ;  22,  infundibulum ;  23,  mammillary  eminence ;  24,  oculo-motor  nerve ; 
25,  posterior  perforated  space ;  26,  fourth  ventricle  :  27,  anterior  velum ;  28,  quadrigeminal  body ; 
29,  ventricular  aqueduct;  30,  31,  32,  frontal,  temporal,  and  occipital  lobes  of  the  cerebrum. 

By  gently  pressing  apart  the  cerebral  hemispheres  they  are  ob- 
served to  be  conjoined  centrally  along  the  middle  of  the  longitudinal 
fissure  by  a  bridge  of  white  nerve-substance,  the  callosum,  corpus 
callosum,  or  great  cerebral  commissure.  In  advance  and  behind 
the  latter  the  fissure  extends  to  the  bottom  of  the  cerebrum  and  re- 
ceives a  partition  of  the  dura,  the  cerebral  falx,  which  reaches  the 
callosum  behind,  but  not  within  a  short  distance  in  front. 

The  cerebral  hemispheres  are  each  composed  of  a  central  mass  of 


1  Pissura  longitudinalis  ;  scissura  cerebri  longitudinalis. 

2  Hemisphseria  cerebri. 


736  THE   NERVOUS   SYSTEM. 

white  matter 1  enveloped  by  a  thick  and  nearly  uniform  layer  of 
gray  matter,  the  cortex.2  The  white  matter  consists  of  a  dense  aggre- 
gation of  nerve-fibres,  which  mainly  proceed  from  the  cerebral  crura 
and  callosum  and  thence  diverge  in  every  direction  to  the  cortex. 
Approaching  the  latter,  the  central  mass  of  white  matter  breaks  up 
into  short,  thick  plates,  which  pursue  a  tortuous  course,  intersect  one 
another,  and  are  enclosed  by  corresponding  thick  folds  of  the  cortex. 
The  arrangement  is  essentially  the  same  as  that  in  the  cerebellum,  in 
which  the  peripheral  divisions  lie  parallel  with  one  another  instead  of 
being  tortuous. 

The  convolutions,3  or  tortuous  divisions  of  the  surface  of  the 
cerebrum,  are  much  thicker  and  less  uniform  than  the  corresponding 
divisions  or  laminae  of  the  cerebellum.  Though  approximating  uni- 
formity in  size  they  vary  considerably  and  generally  are  thicker  about 
the  middle  than  at  the  anterior  and  posterior  extremities  of  the  hemi- 
spheres. They  are  mostly  of  greater  height  than  thickness  and  are 
slightly  thicker  at  the  top  than  at  the  bottom.  They  are  even  and 
smooth,  flat  at  the  sides,  slightly  flattened  along  the  top,  and  rounded 
at  the  opening  of  the  fissures  separating  them.  The  fissures4  are  of 
variable  length  and  depth,  accord  in  direction  with  the  convolutions, 
often  branch  and  run  into  one  another,  or  they  are  interrupted  and 
sometimes  are  short  and  isolated.  Commonly  from  half  an  inch  to 
an  inch  in  depth,  they  vary  in  this  respect  in  different  brains  and  in 
different  parts  of  the  same  brain.  The  convolutions  are  closely  and 
evenly  invested  with  the  pia,  from  which  processes  dip  between  them 
to  the  bottom  of  the  fissures. 

The  cerebral  convolutions  are  to  a  variable  degree  unlike  on  the 
two  sides  of  the  brain.  In  different  individuals  they  vary  consider- 
ably in  number,  size,  and  direction.  The  principal  ones  recognized  as 
most  constant  in  position,  though  more  or  less  modified  by  division  or 
union  and  deviation  of  course,  are  regarded  as  of  primary  importance, 
while  the  others  are  viewed  as  offsets  and  of  secondary  importance. 
Of  the  fissures,  equally  variable  in  their  course,  the  more  constant  serve 
to  define  the  principal  convolutions,  and  also  groups  of  these  distin- 
guished as  the  lobes  of  the  cerebrum. 

The  chief  divisions  of  the  cerebral  hemispheres,  with  their  prin- 
cipal convolutions  and  fissures,  may  now  be  conveniently  examined. 
The  former  are  distinguished  as  the  frontal,  parietal,  occipital,  tem- 
poral, and  central  lobes,  and  are  to  some  extent  defined  by  the  sylvian, 
central,  and  parieto-occipital  fissures.6  The  first  three  lobes  lie  in  con- 
tact with  the  corresponding  bones,  but  do  not  accord  with  their  limits ; 
the  fourth  occupies  the  middle  cranial  fossa,  and  the  fifth  is  enclosed 
by  the  others. 


1  S.  medullaris  or  alba.  2  Substantia  cinerea. 

*  Sulci ;  furrows.  5  Interlobar  sulci. 


THE   NERVOUS   SYSTEM.  737 

The  sylvian  fissure l  is  the  most  conspicuous  of  those  of  the  cere- 
brum. It  commences  at  the  base  of  the  latter,  in  the  depression 2  form- 
ing the  anterior  perforated  space,  thence  curves  outwardly  to  the  lateral 
surface  of  the  hemisphere  and  divides  into  a  short  anterior  and  a  long 
posterior  branch.  The  inner  lower  portion  of  the  fissure  separates 
the  frontal  and  temporal  lobes  and  is  occupied  by  the  small  wing  of 
the  sphenoid  bone. 

The  anterior  branch3  ascends  a  short  distance  into  the  frontal 
lobe  and  terminates  abruptly  or  opens  into  a  contiguous  fissure. 

The  posterior  branch4  runs  backward  and  a  little  upward  at 
about  the  middle  third  of  the  hemisphere  and  separates  the  parietal 

FIG.  379. 


T 

LEFT  HEMISPHERE  OF  THE  CEREBRUM  OF  A  WHITE  MAN,  outer  view:  one-fourth  size.  F, 
frontal  lobe ;  P.'parietal  lobe ;  0,  occipital  lobe ;  T,  temporal  lobe  ;  1,  sylvian  fissure ;  2,  anterior 
branch ;  3,  posterior  branch ;  4,  central  fissure ;  5,  6,  7,  superior,  inferior,  and  posterior  frontal 
fissures ;  8,  interparietal  fissure ;  9, 10,  superior  and  inferior  temporal  fissures;  11, 12,  superior  and 
inferior  occipital  fissures ;  13,  occipito-parietal  fissure ;  14,  calloso-marginal  fissure ;  a,  6,  c,  superior, 
middle,  and  inferior  frontal  convolutions ;  d,  e,  anterior  and  posterior  central  convolutions ;  /,  g, 
superior  and  inferior  parietal  convolutions ;  g,  h,  angular  convolution ;  i,  k,  I,  superior,  middle, 
and  inferior  temporal  convolutions ;  m,  n,  o,  superior,  middle,  and  inferior  occipital  convolutions ; 
x,  x,  x,  x,  annectant  convolutions. 

and  temporal  lobes.  Usually  it  turns  up  behind  and  ends  abruptly  in 
the  parietal  lobe,  or  occasionally  into  one  of  the  contiguous  fissures. 

The  group  of  convolutions  included  in  the  angle  between  the 
two  branches  of  the  sylvian  fissure  overlaps  and  conceals  from  view 
the  central  lobe.  From  its  lid-like  character  it  is  called  the  oper- 
culum.5 

The  fore  part  of  the  sylvian  fissure  outwardly  nearly  ascends  in 
position  with  the  summit  of  the  great  sphenoidal  wing.  Its  anterior 
branch  ascends  near  the  lower  extremity  of  the  fronto-parietal  suture, 
and  the  posterior  branch,  after  passing  back  over  the  fore  part  of  the 


1  Fissura  Sylvii ;  f.  inferior,  anterior,  or  transversa. 

2  Vallecula  Sylvii.  3  F.  lateralis  anticus  or  adscendens. 
4  F.  lateralis  posticus.                             5  O.  lobi  superioris. 

47 


738 


THE    NERVOUS    SYSTEM. 


temporo-parietal  suture,  ascends  obliquely  towards  the  centre  of  the 
parietal  bone. 

The  central  fissure,1  or  fissure  of  Rolando,  though  not  specially 
conspicuous,  is  one  of  the  most  constant  in  its  position  and  course. 
It  runs  obliquely  across  the  lateral  surface  of  the  hemisphere  near 
its  middle.  It  usually  commences  just  behind  the  vertex,  or  top  of 
the  hemisphere,  close  to  the  great  longitudinal  fissure,  and  descends 
obliquely  forward  to  and  near  the  sylvian  fissure,  into  which  it  occa- 
sionally opens.  It  defines  the  frontal  from  the  parietal  lobe,  and  runs 
nearly  parallel  with  the  coronal  suture,  but  is  situated  a  considerable 
distance  behind  it. 

FIG.  380. 


LEFT  HEMISPHERE  OF  THE  CEREBRUM  OF  A  NEGRO  MALE,  outer  view :  one-fourth  size.  Refer- 
ences as  in  the  preceding  figure.  3,  the  posterior  branch  of  the  sylvian  fissure,  continuous 
through  intermediate  fissures  with  the  parie to-occipital  fissure  13,  and  with  another  separating 
the  temporal  and  occipital  lobes,  p,  points  to  the  position  where  the  sylvian  fissure  forks,  in 
which  the  central  lobe  is  visible  externally. 

The  central  fissure  is  remarkably  constant  and  uniform  in  man  and 
the  higher  apes,  but  is  not  present  in  mammals  generally.  It  seems 
to  be  the  result  of  an  early  communication  in  its  position  between  the 
longitudinal  sinus  and  the  middle  cerebral  vein,  which  is  well  marked 
to  about  the  middle  of  foetal  life,  but  is  subsequently  obliterated. 

The  parieto-occipital  fissure 2  in  its  usually  greater  extent  is  seen 
on  the  median  surface  of  the  cerebral  hemisphere,  where  it  descends 
from  the  upper  margin,  some  distance  behind  the  callosum,  to  the  cal- 
carine  fissure,  which  runs  from  beneath  the  latter  to  near  the  posterior 
extremity  of  the  hemisphere.  Its  external  portion,3  usually  short,  turns 


1  F.  centralis ;  f.  transversa  anterior;  sulcus  parietalis  anterius  ;  scissura  perpen- 
dicularis. 

2  F.  parieto-occipitalis  internus ;  f.  occipitalis  perpendicularis  or  posticus ;  sinus 
parieto-occipitalis  ;  s.  opertus  minor. 

3  External  parieto-occipital  fissure. 


THE   NERVOUS   SYSTEM.  739 

outward  and  ends  abruptly  or  terminates  in  a  contiguous  fissure.  It 
partially  defines  the  parietal  and  occipital  lobes.  Occasionally  through 
one  or  more  of  the  intermediate  fissures  it  is  continuous  with  the  syl- 
vian  fissure  and  completely  separates  the  parietal  and  occipital  lobes, 
as  in  the  negro  brain  represented  in  Fig.  380. 

The  frontal  lobe l  of  the  cerebral  hemisphere  is  that  portion  in 
advance  of  the  central  fissure  laterally  and  the  sylvian  fissure  beneath. 
It  is  not  defined  on  the  inner  surface  of  the  hemisphere  behind,  but  is 
separated  from  the  fornicate  convolution  at  its  lower  part  by  the  cal- 
loso-marginal  fissure.  It  displays  four  principal  convolutions,2  variably 
modified  in  different  brains  by  division  into  secondary  convolutions  and 
by  difference  in  their  connections.  All  are  seen  on  the  outer  or  frontal 
surface  of  the  lobe,  and  they  extend  on  the  lower  or  orbital  surface 
and  partially  on  the  inner  surface.  They  are  the  superior,  middle, 
and  inferior  frontal  and  the  anterior  central  convolutions. 

The  anterior  central  convolution 3  descends  obliquely  in  advance 
of  the  central  fissure,  around  the  ends  of  which  it  is  commonly  con- 
tinuous with  the  posterior  central  convolution.  Its  upper  extremity  * 
reaches  the  inner  surface  of  the  frontal  lobe  bordering  the  longitudinal 
fissure,  where  it  is  continuous  with  the  superior  frontal  convolution. 
Its  lower  extremity,  at  the  sylvian  fissure,  is  usually  continuous  with 
the  inferior  frontal  convolution. 

The  superior  frontal  convolution5  borders  the  great  longitudinal 
fissure  and  is  displayed  on  all  three  surfaces  of  the  frontal  lobe.  Com- 
mencing behind  and  beneath  the  latter  in  union  with  the  fornicate 
convolution,  it  winds  forward,  upward,  and  backward  around  it  and 
joins  the  upper  extremity  of  the  anterior  central  convolution.  It  is 
variably  subdivided  on  both  the  inner  and  outer  surfaces,  and  on  the 
orbital  surface  forms  the  inner  convolution,6  which  is  divided  fore  and 
aft  by  the  olfactory  fissure 7  for  the  accommodation  of  the  olfactory 
lobe.8 

The  middle  frontal  convolution,9  variously  subdivided  and  con- 
nected with  the  adjacent  convolutions,  occupies  the  outer  surface  of 
the  frontal  lobe  in  an  intermediate  position  to  the  others  and  is  also 
continued  beneath  as  the  intermediate  convolution10  of  the  orbital 
surface. 

The  inferior  frontal  convolution,11  below  the  preceding  outwardly, 

1  Lobus  frontalis.  2  Gyri  frontales. 

3  Ascending  or  transverse  frontal  convolution  ;  gyrus  centralis  anticus  ;  tractus  pa- 
rietalis  anticus  ;  premier  pli  ascendant ;  circonvolution  transverse  parietale  anterieur. 
*  Lobus  paracentralis. 

5  Gyrus  frontalis  superius ;  first  frontal  convolution. 

6  Internal  orbital  convolution.  7  Sulcus  olfactorius  ;  s.  rectus. 

8  Olfactory  nerve.  9  Gyrus  frontalis  medius  ;  second  frontal  convolution. 

10  Anterior  orbital  convolution. 

11  Gyrus  frontalis  inferius  ;  third  frontal  convolution. 


740 


THE   NERVOUS   SYSTEM. 


FIG.  381. 


borders  the  sylvian  fissure,  arching  over  its  anterior  branch  to  join  the 
lower  extremity  of  the  anterior  central  convolution.  A  continuation1 
inwardly  forms  the  back  part  of  the  orbital  surface  bordering  the  syl- 
vian fissure. 

On  the  frontal  surface  of  the  frontal  lobe  the  anterior  central  con- 
volution is  separated  by  the  pos- 
terior frontal  fissure  from  the 
frontal  convolutions,  and  these  are 
separated  by  the  superior  and 
inferior  frontal  fissures.  The 
fissures  are  very  variable  and  more 
or  less  interrupted  or  bridged  by 
connecting  convolutions.  On  the 
orbital  surface  the  convolutions  are 
separated  by  a  variably-irregular 
triradiate  fissure.2 

The  parietal  lobe3  occupies 
the  outer  surface  of  the  cerebral 
hemisphere  behind  the  middle.  It 
is  defined  in  front  by  the  central 
fissure,  below  in  part  by  the  syl- 
vian fissure,  and  usually  in  a  less 
degree  behind  by  the  parieto-oc- 
cipital  fissure.  Commonly  behind 
and  below  it  is  continuous  with 

both  the  occipital  and  temporal  lobes.  Rarely,  as  seen  in  Fig.  380,  by 
an  extension  of  the  parieto-occipital  fissure  and  its  continuity  through 
intermediate  fissures  with  the  sylvian  fissure,  the  parietal  lobe  becomes 
completely  separated  from  the  occipital  and  temporal  lobes. 

Three  principal  convolutions  occupy  the  outer  surface  of  the  parie- 
tal lobe,  and  two  of  them  extend  to  the  inner  surface  of  the  hemisphere 
as  the  quadrate  lobule.  They  are  the  posterior  central  and  the  superior 
and  inferior  parietal  convolutions. 

The  posterior  central  convolution4  borders  the  central  fissure 
behind  and  parallel  with  the  anterior  central  convolution,  with  which 
it  is  ordinarily  continuous  at  both  extremities  around  the  ends  of  the 
central  fissure. 

The  superior  and  inferior  parietal  convolutions,  behind  the  former, 
are  separated  by  the  variable  fore  and  aft  interparietal  fissure,5 
which  is  sometimes  interrupted  and  sometimes  is  continuous  with  the 


UNDER  SURFACE  OF  THE  FRONTAL  LOBE  OF 

THE   LEFT  CEREBRAL   HEMISPHERE:    one-fourth 

size,  a,  a,  superior  frontal  convolution;  b, 
middle  frontal  convolution ;  c,  inferior  frontal 
convolution ;  d,  sylvian  fissure ;  g,  anterior  per- 
forated space;  e,  temporal  lobe;  /,  olfactory 
lobe. 


1  Posterior  orbital  convolution. 

2  Sulcus  triradiatus  ;  s.  orbitalis.  3  Lobus  parietalis  ;  1.  temporalis. 

4  Ascending  parietal  convolution ;  gyrus  centralis  posticus  ;  tractus  parietalis 
medius  ;  deuxieme  pli  ascendant ;  circonvolution  transverse  medio-parietale. 

5  Intraparietal  sulcus. 


THE   NERVOUS  SYSTEM.  741 

parieto-occipital  fissure,  or  more  rarely  with  the  sylvian  fissure  and 
occasionally  with  both. 

The  superior  parietal  convolution,1  variously  subdivided,  occu- 
pies the  upper  part  of  the  parietal  lobe,  and  is  commonly  continuous 
in  front  with  the  posterior  central  convolution.  Behind  it  is  the  parieto- 
occipital  fissure,  below  the  end  of  which  it  usually  joins  the  occipital 
lobe  by  a  narrow  bridge,  distinguished  as  the  first  annectant  con- 
volution. 

The  inferior  parietal  convolution,2  below  the  former  and  often 
united  with  it  across  the  interparietal  fissure,  is  tortuous  and  variably 
subdivided  and  connected.  Commonly  it  exhibits  two  chief  portions, 
distinguished  as  the  superior  marginal  and  angular  convolutions. 


1 

RIGHT  HEMISPHERE  OF  THE  CEREBRUM  OF  A  WHITE  MAN,  inner  view :  one-fourth  size.  1,  syl- 
vian fissure ;  2,  upper  end  of  the  central  fissure ;  3,  calloso-marginal  fissure ;  4,  parieto-occipital 
fissure ;  5,  calcarine  fissure ;  6,  hippocampal  fissure ;  7,  collateral  fissure,  a,  callosum ;  &,  thala- 
mus ;  c,  striatum ;  d,  section  of  cms ;  e,  fornicate  convolution ;  /,  hippocampal  convolution ;  g, 
hippocampal  hook ;  h,  cuneate  lobule ;  i,  quadrate  lobule ;  k,  superior  frontal  convolution ;  I, 
temporo-occipital  convolution ;  m,  olfactory  lobe ;  n,  optic  nerve. 

The  superior  marginal  convolution  is  usually  continuous  with 
the  lower  extremity  of  the  posterior  central  convolution  and  thence 
arches  over  the  posterior  extremity  of  the  sylvian  fissure,  behind 
which  it  joins  the  superior  temporal  convolution  of  the  temporal  lobe. 

The  angular  convolution,  behind  the  former,  in  like  manner 
usually  arches  over  the  turned-up  extremity  of  the  superior  temporal 
fissure,  running  below  and  nearly  parallel  with  the  sylvian  fissure,  and 
commonly  joins  the  middle  temporal  convolution  and  the  occipital  lobe. 
With  the  latter  it  is  commonly  connected  through  the  middle  occipital 
convolution  by  two  branches,  distinguished  as  the  second  and  third 
annectant  convolutions. 


1  Sup.  par.  lobule  ;  gyrus  parietalis  superius. 

2  Inf.  par.  lobule ;  gyrus  parietalis  inferius. 


742  THE   NERVOUS   SYSTEM. 

On  the  median  surface  of  the  cerebral  hemisphere  the  upper  ex- 
tremity of  the  posterior  central  convolution,  together  with  the  con- 
tiguous portion  of  the  superior  parietal  convolution,  forms  the  quad- 
rate lobule,1  which  is  variously  subdivided  and  is  defined  before  and 
behind  by  the  central  and  parieto-occipital  fissures  and  is  continuous 
inwardly  below  with  the  fornicate  convolution. 

The  occipital  lobe 2  of  the  cerebral  hemisphere  is  the  pyramidal 
portion  behind  the  parieto-occipital  fissure,  and  is  commonly  continu- 
ous by  its  convolutions  with  those  of  the  parietal  and  temporal  lobes. 
It  occupies  the  upper  fossa  of  the  occipital  bone  and  rests  on  the  ten- 
torium.  Its  outer  surface  exhibits  three  principal  convolutions,  as 
usual  variously  subdivided,  and  distinguished  from  their  relative  posi- 
tion as  the  superior,  middle,  and  inferior  occipital  convolutions.  These 

FIG.  383. 


i 

RIGHT  HEMISPHERE  OF  THE  CEREBRUM  OF  A  NEGRO  MALE.  From  the  same  brain  as  Fig.  380. 
References  as  in  Fig.  382. 

are  separated  by  the  equally  variable  superior  and  middle  occipital 
fissures,  of  which  the  former  is  often  continuous  with  the  parieto- 
occipital  fissure. 

The  superior  occipital  convolution3  commonly  joins  the  superior 
parietal  convolution  below  the  parieto-occipital  fissure  by  means  of  the 
first  annectant  convolution. 

The  middle  occipital  convolution4  ordinarily  joins  the  inferior 
parietal  convolution  by  two  branches,  the  second  and  third  annectant 
convolutions. 

The  inferior  occipital  convolution 5  usually  joins  both  the  middle 
and  the  inferior  temporal  convolution  by  a  fourth  annectant  con- 
volution. 

On  the  inner  surface  of  the  cerebral  hemisphere  the  superior  oc- 

1  Lobulus   quadrilateralis ;   1.   parietalis ;   prsecuneus  ;   lobule   du  deuxieme   pli 
ascendant. 

2  Lobus  occipitalis.  3  Gyrus  occipitalis  superius. 
4  G.  occipitalis  medius.                                              5  G.  occipitalis  inferius. 


THE   NEEVOUS   SYSTEM.  743 

cipital  convolution  occupies  a  triangular  area,  in  which  it  forms  the 
cuneate  lobule,1  variably  subdivided,  denned  in  front  by  the  parieto- 
occipital  fissure,  behind  and  below  by  the  calcarine  fissure. 

The  under  or  tentorial  surface  of  the  occipital  lobe  is  formed  by  two 
principal  convolutions,  which  extend  fore  and  aft  from  the  temporal 
lobe  separated  by  the  collateral  fissure  and  variously  subdivided.  The 
innermost  convolution  is  a  prolongation2  of  the  hippoeampal  convolu- 
tion from  the  inner  side  of  the  temporal  lobe  and  is  separated  from 
the  cuneate  lobule  by  the  calcarine  fissure.  The  outermost  lower  con- 
volution is  the  occipital  portion  of  the  occipito-temporal  convolu- 
tion,3 which  usually  runs  the  length  of  both  the  temporal  and  occipi- 
tal lobes,  and  is  separated  from  the  inferior  occipital  convolution  by 
the  inferior  occipital  fissure. 

The  temporal  lobe*  occupies  the  middle  cranial  fossa  and  is  sepa- 
rated by  the  sylvian  fissure  from  the  frontal  lobe  and  partially  from 
the  parietal  lobe.  It  is  continuous  behind  with  the  latter  and  the 
occipital  lobe,  while  its  anterior  rounded  apex  is  free.  Five  principal 
convolutions,  variable  as  usual,  occupy  its  surface.  Three  are  displayed 
outwardly,  distinguished  as  the  superior,  middle,  and  inferior  tem- 
poral convolutions,5  usually  pursuing  a  fore  and  aft  course,  separated 
from  one  another  and  from  the  remaining  pair  of  convolutions  by  cor- 
responding fissures. 

The  superior  and  middle  temporal  convolutions  commonly  turn  up 
behind  the  sylvian  fissure  and  join  the  inferior  parietal  convolution. 
The  superior  temporal  fissure,6  separating  them,  usually  runs  parallel 
with  the  sylvian  fissure  and  in  like  manner  turns  up  behind,  where  it 
is  ordinarily  embraced  by  the  angular  convolution.  The  inferior  tem- 
poral convolution  and  sometimes  the  middle  one  join  the  occipital  lobe 
by  an  annectant  convolution. 

Barely  the  temporal  convolutions  are  separated  from  the  parietal 
and  occipital  lobes  by  fissures  continuous  with  the  sylvian  fissure,  when 
the  temporal  lobe  appears  outwardly  distinct  from  the  others,  as  in  the 
case  of  the  negro  brain  represented  in  Fig.  380.  The  remaining  con- 
volutions of  the  temporal  lobe  occupy  its  lower  surface  and  are  thence 
commonly  continued  backward  on  the  under  surface  of  the  occipital 
lobe.  The  outer  convolution  succeeds  the  temporal  convolutions  and  is 
the  fore  part  of  the  occipito-temporal  convolution,7  which  variably 
subdivided  extends  the  length  of  both  the  temporal  and  occipital  lobes. 

Separated  from  the  occipito-temporal  convolution  by  the  collateral 

1  Cuneus  ;  lobulus  occipitalis  ;  1.  interparietalis  superius  ;    1.  falciformis  posticus 
or  minor. 

2  Lobulus  lingualis.  3  Gyrus  occipito-temporalis  inferius. 

4  Lobus  temporo-sphenoidalis,  temporalis,  or  sphenoidalis. 

5  Gyri  temporo-sphenoidales  ;  transverse  temporal  gyri. 

6  Sulcus  temporo-sphenoidalis  superius  ;  s.  temporalis  parallelus. 

7  Gyrus  occipito-temporalis  inferius  ;  lobulus  fusiformis. 


744  THE   NEKVOUS  SYSTEM. 

fissure  inwardly  is  the  hippocampal  convolution.1  This  commences 
near  the  apex  of  the  temporal  lobe,  winds  backward  round  the  outer 
side  of  the  cerebral  crus,  and,  after  giving  a  division2  behind  the  cal- 
losum  to  the  fornicate  convolution,  is  continued  beneath  the  occipital 
lobe  below  the  calcarine  fissure.  It  forms  the  floor  of  the  descending 
horn  of  the  lateral  ventricle,  and  its  lower  extremity  is  bent  upward 
and  backward  on  itself  in  the  hippocampal  hook,3  which  embraces 
the  lower  end  of  the  horn. 

The  hippocampal  convolution  is  separated  from  the  cerebral  crus 
by  the  hippocampal  fissure,4  which  dips  into  the  hippocampus  and 
extends  from  within  the  fornicate  convolution  behind  the  callosum 
downward  to  the  hippocampal  hook.  From  the  bottom  of  the  fis- 
sure projects  inwardly  the  dentate  band,5  an  indented  gray  ridge 
or  narrow  convolution,  which  descends  along  the  upper  border  of  the 
hippocampal  convolution. 

Above  the  position  of  the  dentate  band  the  pia  is  connected  with 
the  choroid  plexus  occupying  the  descending  horn  of  the  lateral 
ventricle. 

The  hippocampal  convolution  is  peculiar  in  the  fact  that  it  is 
invested  inwardly  with  a  thin  reticular  layer  of  white  nerve-matter.6 

The  collateral  fissure,7  named  from  its  penetrating  at  bottom 
the  collateral  eminence  of  the  descending  horn  of  the  lateral  ventricle, 
pursues  a  fore  and  aft  course,  variably  divided  and  separating  the 
hippocampal  and  occipito-ternporal  convolutions. 

The  calcarine  fissure,8  named  from  its  penetrating  at  bottom  into 
the  calcar  of  the  posterior  horn  of  the  lateral  ventricle,  commences  by 
dividing  the  hippocampal  convolution  beneath  the  back  part  of  the 
callosum,  whence  it  extends  backward  to  the  posterior  extremity  of  the 
hemisphere.  About  midway  it  is  joined  by  the  parieto-occipital  fissure, 
and  it  separates  the  occipital  portion  of  the  hippocampal  convolution 
from  the  fornicate  convolution  and  the  cuneate  lobule. 

The  central  lobe,9  or  island  of  Reil,  lies  within  the  cerebral  hemi- 
sphere, concealed  by  the  operculum.  It  is  a  triangular  eminence  com- 
posed of  five  or  six  convolutions 10  which  start  from  the  inner  extremity 
of  the  sylvian  fissure,  at  the  anterior  perforated  space,  and  thence 
diverge  upward,  enlarge  in  their  ascent,  and  become  continuous  with 
those  of  the  operculum.  In  front  it  is  defined  from  the  frontal  lobe  by 

1  G-.  hippocampus  or  uncinatus ;  g.  occipito-temporalis   superius   or  medialis ; 
subiculum  cornu  ammonis ;  pli  temporal  superieur  interne. 

2  Isthmus.  3  Processus  unciformis  ;  uncus. 
4  Dentate  fissure.                                               5  Fascia  dentata. 

6  Substantia  alba  reticularis.  T  Sulcus  occipito-temporalis. 

8  Fissura  calcarina ;  f.  hippocampi ;  f.  occipitalis  horizontalis  or  posticus. 

9  Lobus  centralis,  caudicus,  opertus,  or  medius  ;   insula ;   i.  Keilii ;  lobulus  cor- 
poris  striati ;  1.  fissurse  Sylvii. 

10  Gyri  operti,  unciformes,  or  breves. 


THE   NERVOUS   SYSTEM.  745 

a  fissure  proceeding  outwardly  into  the  anterior  branch  of  the  sylvian 
fissure,  and  behind  from  the  temporal  lobe  by  another  running  into  the 
posterior  branch  of  the  sylvian  fissure.  It  projects  below  and  to  the 
outer  side  of  the  position  of  the  striatum  and  thalamus.  It  is  earlier 
produced  in  the  embryo  than  the  other  lobes  of  the  hemisphere  which 
enclose  it.  Occasionally,  especially  in  the  negro  brain,  a  small  portion 
of  this  lobe  is  visible  immediately  below  the  point  of  division  of  the 
sylvian  fissure,  as  seen  in  Fig.  380. 

An  additional  portion  of  the  cerebral  hemisphere,  distinct  from  the 
lobes  above  described,  is  the  fornicate  convolution,1  situated  centrally 
on  the  median  surface.  It  commences  narrowly  beneath  the  fore  part 
of  the  callosum  where  it  joins  the  superior  frontal  convolution,  thence 
arches  round  and  over  the  former,  widening  and  variously  subdivided, 
and  continuous  behind  into  the  quadrate  lobule.  From  the  superior 
frontal  convolution,  continuous  with  the  upper  extremity  of  the  ante- 
rior central  convolution,  it  is  separated  by  the  calloso-marginal  fis- 
sure, which  pursues  nearly  the  same  course  and  ascends  behind,  in 
front  of  the  quadrate  lobule,  to  end  at  the  vertex  a  short  distance  back 
of  the  central  fissure.  From  the  callosum,  closely  embraced  by  it,  it  is 
separated  by  the  callosal  fissure,  at  the  bottom  of  which  outwardly 
the  gray  cortex  of  the  convolution  abruptly  ceases. 

The  superior  and  inferior  frontal  convolutions  beneath  the  frontal 
lobe  behind  conjoin  in  a  low  pyramidal  eminence,  the  olfactory  tuber,* 
from  which  the  olfactory  lobe  is  extended  forward  beneath  the  olfactory 
fissure.  Externally  the  tuber  is  continuous  with  the  lower  end  of  the 
central  lobe  of  the  cerebral  hemisphere  and  inwardly  with  the  com- 
mencement of  the  superior  frontal  and  fornicate  convolutions.  The 
gray  cortex  of  the  tuber  is  continuous  above  with  the  bottom  of  the 
lenticular  nucleus  and  claustrum  in  the  interior  of  the  hemisphere. 

Behind  the  olfactory  tuber  is  a  slightly  depressed  area,  the  anterior 
perforated  space,3  which  extends  outwardly  to  the  commencement 
of  the  sylvian  fissure  and  is  limited  behind  by  the  optic  tract.  It  is 
pierced  with  many  small  foramina  for  the  passage  of  blood-vessels, 
which  mainly  ascend  to  the  striatum.  It  is  chiefly  composed  of  gray 
matter4  continuous  above  with  the  nuclei  of  the  striatum,  but  is  crossed 
superficially  by  a  band  of  white  matter  continued  from  the  peduncle 
of  the  callosum  and  proceeding  from  the  longitudinal  fissure  outward 
to  the  sylvian  fissure. 

The  olfactory  lobe,5  which  has  been  usually  described  as  the  ol- 
factory nerve,  is  in  man  a  feebly-developed  part  of  the  brain  in  com- 


1  Gyrus  fornicatus ;   g.  supracallosus ;   fornix  periphericus ;  circumvolutio  cris- 
tata;  circon volution  de  1'ourlet;  grande  circonvolution  du  corps  calleux. 

2  Tuber  olfactorius.  s  Locus  perforatus  anticus. 
*  Substantia  perforata  anterior  ;  s.  cribrosa  lateralis ;  lamina  cribrosa. 

5  Lobus  olfactorius  ;  rhinencephalon. 


746  THE   NERVOUS    SYSTEM. 

parison  with  its  ordinary  condition  in  most  vertebrates.  It  is  a  long 
club-shaped  body  lying  along  the  olfactory  fissure  beneath  the  superior 
frontal  convolution  on  the  orbital  surface  of  the  frontal  lobe  of  the 
cerebrum.  The  narrow  portion,  or  olfactory  tract,1  is  three-sided, 
with  two  sides  slanting  laterally,  adapted  to  the  olfactory  fissure,  and 
the  remaining  side  directed  downward.  The  posterior  extremity  is 
expanded  and  continuous  with  the  olfactory  tuber.  The  anterior  ex- 
tremity swells  into  an  oval  mass,  the  olfactory  bulb,2  which  lies  in 
the  ethmoidal  gutter  and  from  beneath  gives  off  the  olfactory  nerves. 

The  lower  part  of  the  olfactory  tract  is  white  and  composed  of 
longitudinal  bundles  of  medullated  nerve-fibres,  which  diverge  at  the 
posterior  extremity  in  two  portions,  entering  the  olfactory  tuber  as  the 
external3  and  the  internal  root.4  The  upper  border  of  the  tract  ap- 
pears gray,  and  its  connection  with  the  olfactory  tuber  is  the  middle 
root.5  The  olfactory  bulb  is  softer  than  the  tract,  is  gray  below  and 
white  above. 

The  olfactory  tract  below  and  at  the  sides  is  mainly  composed 
of  longitudinal  bundles  of  medullated  nerve-fibres  enclosing  neuroglia, 
which  extends  to  the  upper  border  of  the  tract.  The  olfactory  bulb  is, 
for  the  most  part,  composed  of  gray  matter,  except  above,  where  it 
appears  white.  The  upper  portion,  nearly  a  third  of  the  thickness  of 
the  bulb,  is  chiefly  composed  of  bundles  of  medullated  fibres  proceeding 
from  those  of  the  tract  and  arranged  in  the  form  of  a  flattened  pouch, 
which  is  filled  with  neuroglia  containing  small  nerve-cells  sparsely  scat- 
tered. The  intermediate  portion  of  the  bulb,  more  than  a  third  of  its 
thickness,  is  composed  chiefly  of  neuroglia  with  numerous  nerve-cells 
more  or  less  scattered  and  in  groups.  In  the  upper  stratum6  of  this 
portion  the  cells  are  more  numerous  and  more  grouped  and  resemble 
those  in  the  deeper  layer  of  the  cortex  of  the  cerebellum.  In  the  lower 
stratum7  the  cells  are  generally  pyramidal,  the  largest  ones  above 
and  resembling  those  of  the  cortex  of  the  cerebrum.  The  lower 
portion8  of  the  bulb  is  mainly  composed  of  a  dense  plexus  of  bundles 
of  non-medullated  nerve-fibres,  descending  from  above  and  arranged 
horizontally  below.  Embedded  among  the  descending  bundles  of  fibres 
are  many  rounded  groups  of  nerve-cells,  the  olfactory  glomeruli, 
which  give  origin  to  nerve-fibres. 

The  olfactory  nerves  proper  appear  as  bundles  of  non-medullated 
fibres,  which  emerge  from  the  plexus  forming  the  lower  portion  of  the 
olfactory  bulb. 


1  Tractus  olfactorius  ;  crus  olfactorium  ;  c-  rhinencephalicum'. 

2  Bulbus  olfactorius  ;  b.  cinereus. 

3  Eadix  externus  or  longus.  4  K.  interims  or  brevis. 

5  Upper  or  gray  root ;  trigonum  olfactorium  ;  pyramis  grisea. 

6  Granule  layer.  7  Intermediate  or  nerve-cell  layer. 
8  Layer  of  olfactory  nerve-fibres. 


THE   NERVOUS   SYSTEM. 


747 


THE    CEKEBKAL   CKURA. 

The  crura  of  the  cerebrum 1  emerge  from  the  upper  part  of  the 
pons,  thence  ascend  obliquely  forward  and  outward  and  enter  the  hemi- 
spheres beneath  and  internally  about  their  centre.  They  are  robust, 
cylindrical  white  columns,  longitudinally  striated  and  expanded  in  their 
ascent.  Behind  them  is  the  quadrigeminal  body,  from  which  outwardly, 
as  they  enter  the  hemispheres,  they  are  embraced  by  the  geniculate 
bodies  and  optic  tracts.  From  their  divergence,  in  front  they  leave 
a  space,  the  intercrural  recess,2  which  is  lozenge-shaped  in  outline 
and  defined  in  front  by  the  convergence  of  the  optic  tracts  and  chiasm. 
The  recess  deepens  behind  into  an  angular  pit,3  from  the  sides  of  which, 
at  about  half  its  depth,  emerge  the  oculo-motor  nerves.  From  the 
position  of  the  nerves  the  bottom  of  the  pit  is  distinguished  as  the  pos- 
terior perforated  space,4  which  is  composed  of  gray  matter  traversed 


FIG.  384. 


10 


2  2 

SECTIONS  ACROSS  THE  CEREBRAL  CRURA  AND  QUADRIGEMINAL  BODY  :  size  of  nature.  A,  section 
through  the  lower  pair  of  tubercles  of  the  quadrigeminal  body ;  B,  through  the  upper  pair.  1, 
crusta ;  2,  posterior  perforated  space  and  raph6 ;  3,  reticular  formation  of  the  tegmentum ;  4, 
tegmental  nucleus;  5,  fillet;  6,  locus  niger;  7,  quadrigeminal  body;  8,  nucleus  of  the  quadri- 
geminal body:  9,  ventricular  aqueduct  surrounded  by  gray  matter;  10,  posterior  longitudinal 
bundle  of  nerve- fibres ;  11,  nucleus  of  the  oculo-motor  nerve  11* ;  12,  nucleus  and  descending 
root  of  the  trifacial  nerve. 

by  many  foramina  for  blood-vessels.  Behind  and  outward  the  crura 
are  defined  from  the  quadrigeminal  body  and  fillet  by  a  groove,  which 
together  with  the  line  of  emergence  of  the  oculo-motor  nerve  indicates 
the  position  of  division  of  the  crura  into  two  portions,  distinguished 
as  the  crusta  and  the  tegmentum. 

The  crusta 5  forms  the  anterior  portion  of  the  crus,  including  about 
half  its  thickness,  and  is  composed  of  bundles  of  fibres  mainly  pro- 
ceeding from  the  pyramidal  bundles  of  the  pons  and  ascending  to  the 
corresponding  cerebral  hemisphere.  Superficially  the  inner  fibres  of 


1  C.  cerebri ;  cerebral  peduncles  ;  pedunculi  cerebri. 

2  Interpeduncular  space.  3  Foramen  caecum  anterius. 

4  Locus  perforates  posterius  ;  pons  Tarini ;   substantia  or  lamina  posterior  perfo- 
rata;  1.  cribrosa. 

5  Basis ;  pes ;  proper  cerebral  peduncle. 


748  THE   NERVOUS   SYSTEM. 

the  crura  are  observed  to  diverge  with  an  outward  twist  and  ascend  to 
the  under  and  outer  part  of  the  thalami.  In  horizontal  sections  of  the 
crura,  the  crusta  is  seen  as  a  crescentic  area,  separated  by  an  interval 
corresponding  with  the  intercrural  recess. 

The  tegmentum  forms  the  back  part  of  each  cerebral  crus,  having 
the  crusta  in  front  and  outwardly  and  the  quadrigeminal  body  and 
ventricular  aqueduct  behind.  It  is  the  continuation  upward  of  the 
reticular  formation  of  fhe  pons,  associated  with  a  considerable  quan- 
tity of  gray  matter  which  between  the  crura  forms  the  posterior  per- 
forated space.  Its  longitudinal  bundles  of  fibres  partly  appear  as 
those  which  directly  ascend  from  the  anterior  columns  of  the  spinal 
cord  through  the  reticular  formation  of  the  oblongata  and  pons.  Others 
are  derived  from  the  superior  peduncles  of  the  cerebellum,  intersect 
one  another  through  the  raphe,  and  thence  ascend  to  the  thalami  of 
opposite  sides.  A  more  defined  band,  the  posterior  longitudinal 
bundle,  ascends  along  the  course  of  the  ventricular  aqueduct  just 
outside  the  position  of  the  gray  matter  of  its  floor.  In  sections  of  the 
cerebral  crura  the  tegmentum  appears  as  a  quadrate  area  embraced  in 
front  and  outwardly  by  a  white  band  formed  by  the  longitudinal  fibres 
of  the  fillet.  The  posterior  longitudinal  bundle  appears  as  a  pyriform 
white  islet  at  the  side  of  the  gray  matter  which  surrounds  the  ven- 
tricular aqueduct. 

Between  the  crusta  and  tegmentum  is  a  considerable  patch  of  un- 
usually dark  pigmented  gray  matter  distinguished  as  the  locus  niger.1 
Its  surface  next  the  tegmentum  is  concave  and  even,  while  that  di- 
rected towards  the  crusta  is  convex  and  gives  off  thin  tapering  Iamins9 
which  penetrate  among  the  fibrous  bundles  of  the  crusta.  In  cross- 
sections  of  the  crura  it  appears  like  a  crescentic  comb  with  the  teeth 
directed  from  the  convex  border. 

In  the  upper  part  of  the  cerebral  crura,  embedded  among  the 
ascending  fibres  of  the  tegmentum,  is  an  oval  accumulation  of  pale 
reddish-gray  matter,  named  the  tegmental  nucleus.2 

The  space  between  the  cerebral  crura,  or  the  intercrural  recess, 
defined  in  front  by  the  optic  tracts  and  commissure,  is  occupied  by 
a  lozenge-shaped  gray  eminence,  the  cinereous  tuber.3  Continuous 
behind  with  the  posterior  perforated  space,  it  forms  the  lower  part  of 
the  third  ventricle,  from  which  it  is  prolonged  in  the  infundibulum. 
This  is  a  hollow  conical  process  descending  from  the  third  ventricle 
behind  the  optic  commissure  and  ending  by  joining  the  pituitary  body. 

Embedded  in  the  outer  part  of  the  cinereous  tuber  is  a  small  group 
of  nerve-cells,*  which  give  origin  to  some  of  the  fibres  of  the  contiguous 
optic  tract. 

From  the  cinereous  tuber  beneath  and  behind  the  infundibulum, 

1  Substantia  nigra ;  stratum  nigrum.  2  N.  tegmenti ;  the  red  nucleus. 

3  T.  cinereum  ;  basis  infundibuli.  *  Basal  optic  ganglion. 


THE   NERVOUS   SYSTEM. 


749 


project  the  mammillary  eminences,1  a  pair  of  white  spherical  bodies 
lying  side  by  side.  Each  is  formed  by  the  conjunction  of  two  roots  or 
bundles  of  nerve-fibres,  which  descend  through  the  cinereous  tuber  and 
converge  in  a  twisted  fold  enclosing  a  gray  nucleus.  The  anterior 
root2  corresponds  with  the  anterior  pillar  of  the  fornix,  while  the 
posterior  root 3  is  derived  from  the  anterior  nucleus  of  the  thalamus. 

The  interior  of  the  cerebrum.  On  separating  the  hemispheres 
towards  the  bottom  of  the  great  longitudinal  fissure  the  callosum  *  is 
seen  extending  along  the  middle  for  nearly  half  its  length  and  passing 
laterally  beneath  the  calloso-mar- 
ginal  fissure  into  the  hemispheres. 
By  removing  the  upper  part  of 
these  on  a  line  with  the  fissure,  the 
callosum  is  observed  to  be  a  wide 
bridge  connecting  the  white  mass 
of  matter5  of  the  interior  of  the 
hemispheres.  Arching  over  it  on 
each  side  is  the  fornicate  convo- 
lution. It  approaches  nearer  the 
front  than  the  back  of  the  brain, 
is  strongly  arched  fore  and  aft 
and  is  concave  from  side  to  side, 
or  is  nearly  straight  at  the  middle 
and  curved  up  at  the  sides.  It  is  a 
thick  plate  of  white  matter  roofing 
over  a  pair  of  cavities,  the  lateral 
ventricles6  of  the  brain ;  it  is  thin- 
ner along  the  middle  and  thickest 
at  the  posterior  border,  where  it 
is  also  widest.  It  is  transversely 
striated  above  and  below,  and  is 
composed  of  flattened  bundles  of 
medullated  nerve-fibres  closely  ag- 
gregated and  passing  into  the 
white  matter  of  the  cerebral  hemi- 
spheres extending  in  every  direction  to  the  enveloping  cortex. 

The  posterior  thickened  rounded  border  of  the  callosum,  named  the 
splenium,  is  situated  at  the  bottom  of  the  interval  between  the  cere- 
brum and  the  cerebellum  just  above  the  transverse  cerebral  fissure, 

1  Eminentia  or  corpora  mammillaria,  albicantia,  candicantia,  or  papillaria ;  bulbs 
of  the  fornix. 

2  Kadix  adscendens  fornicis.  3  R.  descendens  fornicis. 
*  Corpus  callosum  ;  trabs  cerebri  or  medullaris  ;  commissura  cerebri  magna. 

5  Centrum  ovale  or  semiovale  Vieussenii ;  c.  medullare ;  c.  ovale  minus  and  majus  ; 
tegmentum  ventriculorum. 

6  Ventriculi  laterales  or  tricornes. 


TRANSVERSE  SECTION  OF  THE  HEMISPHERES  OP 
THE  CEREBRUM  ON  A  LEVEL  WITH  THE  CALLO- 
SUM. 1,  white  'substance  of  the  hemispheres, 
dotted  with  divided  blood-vessels ;  2,  gray  cor- 
tex of  the  convolutions ;  3,  callosum,  with  the 
direction  of  its  fibres  indicated  by  transverse 
striae;  4,  longitudinal  median  striae;  5,  ante- 
rior and  posterior  portions  of  the  great  longi- 
tudinal fissure. 


750  THE   NERVOUS    SYSTEM. 

which  communicates  between  that  interval  and  the  third  ventricle  of 
the  brain. 

In  front  the  callosum  folds  from  above  downward  and  backward 
in  the  knee,1  and  the  under  part  of  this  tapers  into  the  rostrum,2 
which  curves  downward  to  the  bottom  of  the  cerebrum.  At  the  sides 
the  rostrum  is  connected  with  the  frontal  lobes  and  below  with  the 
cinereous  lamina,  by  which  it  is  attached  to  the  optic  commissure. 

Crossing  the  middle  of  the  callosum  above,  fore  and  aft,  are  the 
median  longitudinal  striae,3  two  white  lines  separated  by  a  furrow* 
and  consisting  of  slender  bundles  of  nerve-fibres.  At  the  back  of  the 
callosum  they  diverge  and  enter  the  occipital  lobes.  On  the  knee 
they  also  diverge  and  join  the  callosal  peduncles.5  These  appear  as 
narrow  white  bands,  which  descend  at  the  sides  of  the  rostrum  close 
to  the  frontal  lobes,  from  which  they  also  receive  fibres  and  then 
widely  diverge  and  run  outwardly  across  the  anterior  perforated  space 
contiguous  to  the  optic  tract.  Below  the  rostrum  they  are  joined  by 
a  transverse  commissural  band.6 

At  the  sides  of  the  callosum  are  the  lateral  longitudinal  striae,7 
similar  to  the  former  and  connected  with  the  longitudinal  fibres  of  the 
contiguous  fornicate  convolution. 

Beneath  the  callosum  are  the  right  and  left  lateral  ventricles,8 
or  the  first  and  second  of  the  five  like-named  cavities  of  the  brain. 
They  ai'e  separated  by  a  median  vertical  partition,  the  ventricular 
septum,  and  each  is  extended  by  prolongations,  named  the  horns.9 
The  main  portion,  or  body,10  of  each  ventricle  is  a  fore  and  aft  cleft, 
lying  parallel  with  its  fellow  and  arching  from  in  front  upward  and 
backward  and  then  diverging  a  little  outward.  It  is  deepest  at  the 
fore  part,  where  it  is  trilateral,  and  it  gradually  becomes  shallower 
behind.  Its  roof  is  formed  by  the  callosum ;  its  inner  wall  by  the  ven- 
tricular septum  which  merges  behind  into  the  fornix.  Its  outer  wall 
gradually  passes  behind  into  the  floor  and  is  formed  in  succession  by 
the  striatum,  the  semicircular  band,  the  thalamus,  the  choroid  plexus, 
and  the  lateral  band  of  the  fornix. 

The  fore  part  of  the  lateral  ventricle  extends  a  little  way  into  the 
frontal  lobe  as  the  anterior  horn,11  into  which  projects  the  thick 
anterior  extremity  of  the  striatum,  and  is  enclosed  within  the  anterior 
folded  portion  of  the  callosum.  Its  posterior  extremity  is  continuous 
with  the  longer  and  more  conspicuous  prolongations,  the  posterior  and 
middle  horns. 


1  Genu  corporis  callosi.  2  K.  corporis  callosi. 

3  S.  longitudinales  mediales  or  internae  ;  nerves  of  Lancisi. 

4  Raphe.  5  Pedunculi  corporis  callosi.  6  Commissura  baseos  alba. 

7  S.  longitudinales  laterales  or  externse ;  ligamenta  tecta  or  obtecta. 

8  Ventriculi  laterales,  tricornes,  anteriores,  or  magni ;  procceliae. 

9  Cornua.  10  Corpus  ventriculi ;  aula.  ll  Cornu  anterius  ;  praecornu. 


THE   NERVOUS  SYSTEM. 


751 


FIG.  386. 


Near  the  middle  of  the  body  of  each  ventricle,  at  its  lowest  point, 
is  a  rounded  aperture,  the  foramen  of  Monro,  by  which  the  lateral 
ventricles  communicate  with  the 
third  ventricle. 

The  ventricular  septum,1  the 
median  partition  of  the  lateral 
ventricles,  is  deepest  in  front, 
where  it  is  included  in  the  knee 
of  the  callosum,  and  it  tapers  away 
behind  between  the  latter  and  the 
fornix.  It  is  also  thickest  in  front, 
thins  away  and  becomes  pellucid 
behind.  Its  outer  surfaces  are 
concave,  due  to  the  gradual  thick- 
ening of  the  septum  approaching 
the  contiguous  surfaces  of  the  ven- 
tricle. It  encloses  a  cleft,  the 
fifth  ventricle,2  widest  forward 
and  above  and  extending  the 
greater  part  of  the  depth  of  the 
septum,  but  everywhere  closed. 
Each  side  of  the  ventricle  com- 
posing the  septum  consists  of  an 
external  lamina  of  white  matter 
continuous  with  that  of  the  cal- 
losum and  interior  of  the  hemi- 
sphere, and  a  thinner  internal 
lamina  of  gray  matter,  which  is 
isolated  from  the  gray  matter  of 
the  cerebrum. 

In  the  development  of  the 
brain  the  fifth  ventricle  at  first  appears  as  a  part  of  the  great  longi- 
tudinal fissure  and  is  subsequently  closed  from  it  in  the  production  of 
the  callosum. 

The  striatum,  or  corpus  striatum,3  appears  in  the  body  of  the 
lateral  ventricle  as  a  smooth,  convex  gray  eminence  projecting  from 
its  outer  wall  into  the  anterior  horn  and  tapering  behind  outside  and 
above  the  thalamus,  where  it  disappears  from  view.  Its  fore  part  is 
directed  towards  its  fellow  and  is  separated  from  it  by  the  deeper  por- 
tion of  the  ventricular  septum.  It  is  chiefly  a  pyriform  mass  of  gray 
matter  embedded  in  the  white  matter  of  the  cerebral  hemisphere  with 


TRANSVERSE  SECTION  OF  THE  CEREBRAL  HEMI- 
SPHERES, THE  CALLOSUM  REMOVED,  AND  THE 
LATERAL  VENTRICLES  EXPOSED.  1,  white  SUD- 

stance  of  the  interior  of  the  cerebral  hemi- 
spheres ;  2,  gray  cortex  of  the  convolutions ;  3, 
4,  anterior  and  posterior  extremities  of  the  cal- 
losum ;  5,  anterior  horn  of  the  left  lateral  ven- 
tricle ;  6,  middle  or  descending  horn ;  7,  poste- 
rior horn;  8,  striatum;  9,  ventricular  septum; 
10,  fifth  ventricle  ;  11,  fornix ;  12,  posterior  crus 
of  the  fornix ;  13,  attachment  of  the  fornix  to 
the  under  part  of  the  callosum  ;  14,  hippocam- 
pus; 15,  fimbria;  16,  calcar;  17,  semicircular 
band ;  18,  choroid  plexus ;  19,  edge  of  the  thala- 
mus ;  20,  arrow  through  the  foramen  of  Monro. 


1  S.  ventriculorum,  lucidum  or  pellucidum,  medium,  or  medullare  triangulare. 

2  Ventriculus  quintus,  septi  lucidi,   or  Sylvii ;   incisura,  camera,  or  sinus  septi 
lucidi ;  pseudoccelia. 

3  Eminentia  striata  or  pyriformis  ;  ganglion  magnum  superior  cerebri. 


752  THE   NERVOUS   SYSTEM. 

its  free  surface  projecting  into  the  lateral  ventricle.  The  greater  part 
inwardly  is  of  uniform  structure,  but  its  outer  lower  part  is  streaked, 
due  to  the  entrance  of  laminae  from  the  contiguous  white  matter  of  the 
hemisphere ;  hence  the  name,  though  the  appearance  is  seen  only  in 
sections  of  it.  It  has  also  been  distinguished  as  the  caudate  nucleus,1 
from  the  posterior  tail-like  prolongation,2  which  from  the  back  of  the 
ventricle  descends  in  the  inner  part  of  the  roof  of  the  middle  horn  to 
the  amygdaloid  nucleus  at  the  bottom  of  the  cerebral  hemisphere. 

The  gray  substance  of  the  striatum  consists  of  a  matrix  of  neu- 
roglia  pervaded  by  medullated  nerve-fibres  ascending  from  the  cere- 
bral crus  and  others  communicating  with  the  cerebral  cortex,  with 
embedded  multipolar  nerve-cells,  moderately  large  and  small,  and  with 
other  spheroidal  cells  containing  several  nuclei.  The  ventricular  sur- 
face is  covered  with  a  layer  of  neuroglia  invested  with  an  ependyma  of 
ciliated  cells. 

The  fornix 3  is  a  triangular  white  plate  situated  at  the  back  part 
of  the  lateral  ventricles,  which  it  separates  from  the  third  ventricle. 
From  the  splenium  it  arches  forward  beneath  the  callosum  nearly  to 
the  rostrum,  is  continuous  with  the  former  behind,  is  connected  by  a 
median  triangular  portion  with  the  callosum  above,  and  is  connected 
in  front  with  the  posterior  inferior  border  of  the  ventricular  septum. 
The  sides  of  the  fornix  are  free  and  appear  as  a  pair  of  flat  cylindrical 
bands  projecting  from  beneath  the  callosum  into  the  lateral  ventricles 
and  resting  on  the  thalami.  In  front  they  conjoin  and  curve  forward 
and  downward  in  advance  of  the  thalami  and  become  the  anterior 
pillars  of  the  fornix,4  which  descend  as  cylindrical  cords,  at  first 
close  together  and  then  slightly  diverging,  and,  after  penetrating  the 
cinereous  tuber  on  each  side,  end  in  the  mammillary  eminences  at  the 
base  of  the  brain.  From  the  posterior  angles  of  the  fornix,  the  lateral 
bands,  as  the  posterior  pillars,5  enter  the  middle  horns  of  the  ventri- 
cles and  thence  descend  as  the  fimbriae.  The  under  part  of  the  fornix 
exhibits  a  median  triangular  depression  enclosed  by  the  lateral  bands 
and  the  splenium,  marked  by  longitudinal,  oblique,  and  transverse  strise 
and  distinguished  as  the  lyre.6 

The  lateral  bands  of  the  fornix,  extended  as  the  anterior  and 
posterior  pillars,  are  antero-posterior  commissures  composed  of  lon- 
gitudinal bundles  of  nerve-fibres. 

The  semicircular  band7  is  a  narrow,  semi-transparent  whitish 
streak  lying  along  the  groove  between  the  striatum  and  the  thala- 


1  Interventricular  portion  of  the  corpus  striatum.  2  Cauda ;  surcingle. 

3  F.  tricuspidalis  ;  trigonum  cerebris ;  corpus  cameratum. 

4  Crura  or  columnse  fornicis  anteriora. 

5  Crura  or  columnse  fornicis  posteriora. 

6  Lyra ;  psalterium  ;  corpus  psalloides. 

7  Stria  terminalis  or  cornea ;  tsenia  semicircularis  or  striata. 


THE    NERVOUS   SYSTEM. 


753 


mus,  having  beneath  it  a  vein  which  receives  its  branches  from  those 
bodies  and  ends  in  the  internal  cerebral  vein.  The  band  is  a  thin 
lamina  of  nerve-fibres  ascending  between  the  striatum  and  thalamus 
from  the  cerebral  crus.  Its  fore  part  is  continuous  with  the  anterior 
pillar  of  the  fornix,  and  its  back  part  is  prolonged  and  descends  in  the 
roof  of  the  middle  horn  of  the  ventricle  to  the  amygdaloid  nucleus. 

Between  the  semicircular  band  and  the  edge  of  the  fornix,  against 
which  lies  the  choroid  plexus,  a  narrow  strip  of  the  thalamus  is 
visible,  but  as  it  mainly  enters  into  the  construction  of  the  third 
ventricle  it  will  be  described  with  that  cavity. 

The  posterior  horn1  of  the  lateral  ventricle  is  a  conical  prolonga- 
tion from  the  body  curving  outward,  backward,  and  inward  into  the 
occipital  lobe.  From  its  bottom  inwardly  projects  a  claw-shaped  white 
eminence,  the  calcar,2  which  is  continuous  with  the  hippocampus  of 
the  middle  horn  of  the  ventricle 

and   is   produced    by  the   inward  FIG.  387. 

fold  of  the  contiguous  convolutions 
of  the  bottom  of  the  calcarine  fis- 
sure. A  less  conspicuous  promi- 
nence3 above  the  calcar  inwardly 
is  produced  by  the  bundles  of 
fibres  which  curve  from  the  sple- 
nium  backward  and  outward  into 
the  occipital  lobe.  The  roof  of 
the  horn  is  formed  by  the  fibres 
of  the  callosum  arching  above  the 
cavity  into  the  occipital  lobe. 

The  middle,  inferior,  or  de- 
scending horn4  of  the  lateral 
ventricle,  much  longer  than  the 
others,  joins  the  posterior  horn. 
It  curves  outward  around  the  back 
of  the  thalamus  and  beneath  it 
descends  forward  and  inward  to 
end  within  the  anterior  thickened 
extremity  of  the  hippocampal  con- 
volution. Internally  it  opens  along 
the  hippocampal  fissure,  but  is 
closed  by  the  lining  ependyma  and 

contiguous  pia.  It  is  curved  clavate,  widening  towards  the  bottom. 
Its  roof  is  formed  in  part  by  the  thalamus  and  partly  by  the  radiating 

1  Cornu  occipitale  or  ancyroide  ;  cavitas  digitata ;  postcornu  ;  posterior  cornu. 
?  C.  avis  ;  hippocampus  minor  ;  ergot ;  eminentia  unciformis  or  digitata. 

3  Bulbus  cornu  posterioris. 

4  Cornu  medium,  inferius,  descendens,  magnum,  laterale,  or  sphenoidale;  ven- 
triculus  or  sinus  inferior  hippocampi  or  cornu  Ammonis  ;  medicornu. 

48 


SECTION  OF  THE  LEFT  CF.REBRAL  HEMISPHERE, 
exposing  the  middle  and  posterior  horns  of  the 
lateral  ventricle.  1,  frontal  lobe;  2,  hippo- 
campal convolution  ;  3,  hippocampal  hook ;  4, 
lower  end  of  the  middle  horn  of  the  lateral 
ventricle ;  5,  posterior  horn  ;  6,  hippocampus ; 
7,  calcar:  8,  collateral  eminence;  9,  posterior 
crus  of  the  fornix;  10,  fimbria;  11,  dentate 
band ;  12,  posterior  extremity  of  the  callosum. 


754  THE   NEEVOUS   SYSTEM. 

bundles  of  fibres  of  the  callosum;  its  floor1  by  bundles  curving  from 
the  splenium  outward,  downward,  and  forward,  together  with  others 
extending  from  the  occipital  lobe  to  the  end  of  the  middle  horn  in 
the  temporal  lobe. 

Projecting  from  the  inner  side  of  the  horn,  lying  along  its  bottom 
is  a  conspicuous  rounded  ridge,  the  hippocampus,2  which  is  continuous 
above  with  the  posterior  lateral  angle  of  the  fornix  and  gradually  en- 
larges in  its  descent  to  the  lower  extremity.  This  outwardly  exhibits 
three  or  four  slight  indentations,  giving  it  the  appearance  of  a  paw, 
whence  the  name  of  pes  hippocampi,  conveniently  substituted  by 
that  of  hippocampus. 

The  hippocampus  is  formed  by  the  out  and  in  folding  of  the  upper 
border  of  the  hippocampal  convolution,  the  hook  of  which  encloses 
its  lower  end.  The  cavity  of  the  horn  curves  from  the  hippocampal 
fissure  outwardly  above  the  hippocampus,  then  downward  and  inward 
beneath  it  into  the  middle  of  the  hippocampal  convolution.  Beneath 
the  inner  border  of  the  hippocampus  projects  the  dentate  band,* 
which  is  composed  of  gray  matter  and  is  dentated  at  the  free  border 
directed  inwardly.  Above,  it  is  connected  with  the  hippocampal  con- 
volution at  the  outer  part  of  the  splenium,  and  ends  below  by  joining' 
the  end  of  the  hippocampal  hook.  It  is  separated  beneath  from  the 
hippocampal  convolution  by  the  dentate  fissure  opening  inwardly 
into  the  hippocampal  fissure. 

Extending  along  the  hippocampus,  reflected  outwardly  from  its 
inner  border,  is  the  fimbria,4  a  white  band  continuous  above  with 
the  posterior  pillar  of  the  fornix  and  ending  below  in  the  end  of  the 
hippocampal  hook. 

The  hippocampus  is  composed  of  two  white  layers  with  an  inter- 
vening gray  layer,  which  becomes  superficial  as  the  lower  part  of  the 
cortex  of  the  hippocampal  convolution.  The  revolute  white  layer,  or 
that  next  the  cavity  of  the  horn,  is  continuous  with  the  interior  white 
matter  of  the  floor  and  outer  wall,  and  along  the  inner  border  of  the 
hippocampus  is  reflected  outwardly  as  the  fimbria.  The  involute  white 
layer  extends  from  the  dentate  fissure  inwardly  upon  the  hippocampal 
convolution  and  at  the  bottom  of  the  fissure  embraces  the  dentate 
band.  This  is  a  flattened  cylindrical  tract  of  gray  matter  continuous 
with  that  of  the  hippocampus  beneath  the  upper  part  of  the  revolute 
white  layer. 

The  gray  layer  of  the  hippocampus  in  composition  resembles  the 
cerebral  cortex  and  consists  of  neuroglia  with  numerous  large  pyram- 
idal nerve-cells  mostly  embedded  next  the  revolute  white  layer,  while 


1  Tapetum. 

2  H.  major ;  cornu  Ammonis  or  arietis  ;  bombyx  ;  vermis  ;  appendix  bombycinus. 

3  Fascia  or  fasciola  dentata,  denticulata,  or  cinerea ;  margo  denticulatus  Tarini. 

4  Corpus  fimbriatum  ;  limbus  fimbriatus  ;  tsenia  hippocampi. 


THE   NERVOUS   SYSTEM. 


755 


numerous  smaller  cells  form  a  stratum  contiguous  to  the  involute  white 
layer. 

The  axial  portion  of  the  dentate  band  consists  of  neuroglia  with 
numerous  nerve-cells  like  those  of  the  hippocampal  gray  layer,  with 
which  it  is  continuous.  Below  and  inwardly  it  has  a  stratum  of  minute 
cells.  The  whole  is  enclosed  in  a  cortical  layer  of  vascular  neuroglia 
also  containing  many  minute  cells. 

From  the  conjunction  of  the  middle  with  the  posterior  cornu  a 
smooth  convex  white  ridge,  the  collateral  eminence,1  extends  along 
the  outer  part  of  the  inferior  horn  opposite  the  hippocampus.  It  is 
produced  by  the  fold  of  the  contiguous  convolutions  at  the  bottom  of 
the  collateral  fissure. 

Outside  of  the  position  of  the  lateral  ventricle,  embedded  in  the 
white  matter  of  the  central  lobe  of  the  cerebral  hemisphere,  is  a  mass 


FIG.  388. 


FIG.  389. 


TRANSVERSE  VERTICAL  SECTION  OF  THE  RIGHT 
HEMISPHERE  OF  THE  CEREBRUM  :  the  back  part 
viewed  from  behind.  1,  callosum ;  2,  ventricu- 
lar septum  with  the  fifth  ventricle ;  3,  lateral 
ventricle ;  4,  striatum ;  5,  lenticular  nucleus ;  6, 
claustrum;  7,  commissure  of  the  floor  of  the 
third  ventricle ;  8,  cinereous  lamina  closing  the 
fore  part  of  the  latter;  9,  temporal  lobe;  10, 
olfactory  nerve. 


12 


8    9 


TRANSVERSE  VERTICAL  SECTION  OF  THE  LEFT 
HEMISPHERE  OF  THE  CEREBRUM:  the  back  por- 
tion viewed  from  in  front.  1,  callosum ;  2,  ante- 
rior cms  of  the  fornix ;  3,  anterior  commissure 
of  the  third  ventricle ;  4,  extension  of  the  same 
into  the  hemisphere ;  5,  lateral  ventricle ;  6, 
bottom  of  the  third  ventricle;  7,  fifth  ventricle; 
8,  optic  tract ;  9,  cinereous  tuber :  10,  striatum ; 
11,  claustrum';  12,  three  zones  of  the  lenticular 
nucleus;  13,  amygdaloid  nucleus;  14,  central 
lobe  of  the  cerebrum. 


of  gray  matter,  named   from   its 
general  shape  the  lenticular  nu- 
cleus.2   It  occupies  an  angular  in- 
terval outwardly  from  the  striatum  and  thalamus,  from  both  of  which 
it  is  separated  by  a  considerable  white  layer,  distinguished  as  the  in- 
ternal capsule3  and  consisting  of  ascending  bundles  of  nerve-fibres 

1  Eminentia  collateralis  ;  pes  accessorius. 

2  N.  lentiformis  ;  corpus  striatum  externum ;  extra-ventricular  portion  of  the 
corpus  striatum.    It  is  common  to  include  the  lenticular  nucleus  with  the  corpus 
striatum,  while  the  latter,  as  ahove  described,  is  called  the  caudate  nucleus. 

3  Capsula  interna ;  triangulum  medullare. 


756  THE   NERVOUS   SYSTEM. 

diverging  from  the  cerebral  erus.  In  sections  of  the  fore  part  of  the 
striatum  it  is  observed  to  be  continuous  beneath  with  the  lenticular  nu- 
cleus, and  both  are  also  connected  by  many  tapering  gray  striae l  which 
cross  the  internal  capsule.  Similar  striae  from  the  inner  side  of  the  len- 
ticular nucleus  curve  through  the  capsule  towards  the  thalamus  and 
downward  among  the  ascending  bundles  of  nerve-fibres.  The  outer 
surface  of  the  lenticular  nucleus  gives  off  no  processes  and  is  evenly 
convex.  In  a  frontal  section  of  the  brain,  about  the  middle  of  the 
lenticular  nucleus,  it  is  observed  to  differ  from  the  shape  expressed  by 
the  name  and  to  exhibit  a  wedge-like  outline  with  the  apex  directed 
inward  and  downward  to  the  cinereous  tuber.  The  gray  area  further 
appears  divided  by  two  perpendicular  curved  white  lines  into  three 
nearly  equally  wide  bands,  of  which  the  external  is  the  largest,  darkest 
in  color,  and  inwardly  marked  with  radiant  white  striae.  The  other 
bands  are  paler  and  in  this  respect  resemble  the  tegmental  nucleus. 
As  the  divisions  from  within  outwardly  extend  fore  and  aft,  in  sections 
they  are  observed  successively  to  decrease  in  number. 

The  lenticular  nucleus  is  traversed  by  bundles  of  nerve-fibres  derived 
from  the  crusta  of  the  cerebral  crus,  conspicuous  as  they  enter  the 
outer  division  of  the  nucleus.  The  intermediate  lines  separating  its 
divisions  indicate  the  position  at  which  bundles  of  nerve-fibres  enter 
the  different  parts.  Bundles  of  nerve-fibres  also  connect  the  striatum 
and  lenticular  nucleus,  and  others  radiating  from  the  latter  diverge  in 
the  white  matter  of  the  cerebral  hemisphere.  The  gray  matter  of  the 
lenticular  nucleus  contains  many  yellowish  nerve-cells. 

Outside  the  position  of  the  lenticular  nucleus,  embedded  in  the 
white  substance  of  the  central  lobe  of  the  cerebrum  near  its  external 
convolutions,  is  a  thin,  gray  layer,  the  claustrum.2  It  is  of  greatest 
breadth  fore  and  aft  and  is  higher  than  the  lenticular  nucleus,  with 
which  it  is  continuous  at  its  fore  part  beneath  within  the  olfactory 
tuber  and  the  anterior  perforated  space.  Its  inner  surface  is  concave 
and  even  and  is  directed  towards  the  lenticular  nucleus,  but  the  outer 
surface  is  convex  and  somewhat  uneven. 

The  nerve-cells  of  the  claustrum  are  mostly  small  and  fusiform  and 
generally  arranged  parallel  with  the  surfaces  like  those  in  the  deep  part 
of  the  cerebral  cortex. 

The  white  layer  separating  the  claustrum  from  the  lenticular  nu- 
cleus is  the  external  capsule.3  It  consists  of  bundles  of  nerve-fibres 
derived  from  the  cerebral  crus  and  from  the  anterior  commissure  of  the 
third  ventricle. 

Beneath  the  fore  part  of  the  lenticular  nucleus,  situated  within  the 
anterior  extremity  of  the  hippocampal  convolution,  is  an  irregular 

1  Striae  grisese  communicantes. 

2  Stratum  cirjereum  ;  nucleus  taeniaeformis. 

3  Capsula  externa ;  c.  medullaris  nuclei  lentiformis. 


THE   NERVOUS   SYSTEM.  757 

rounded  gray  mass,  the  amygdaloid  nucleus.1  It  is  connected  with 
the  contiguous  cortex  of  the  convolution  and  is  similar  in  structure  to 
the  lenticular  nucleus. 

The  foramen  of  Monro2  is  a  short  Y-shaped  canal  situated  be- 
tween the  anterior  pillars  of  the  fornix  and  the  thalami,  of  which  the 
upper  branches  communicate  with  the  lateral  ventricles  and  the  lower 
one  with  the  fore  part  of  the  third  ventricle.  Through  it  the  veins  of 
the  striata  and  choroid  plexuses  reach  the  internal  cerebral  veins. 

The  third  ventricle 3  of  the  brain  is  a  median  cleft  of  the  cere- 
brum, situated  between  the  thalami  laterally,  roofed  over  by  the  fornix 
and  extending  downward  into  the  infundibulum  at  the  base  of  the  brain. 
1J  is  widest  above  and  behind,  narrows  below  to  a  vertical  fissure,*  and 
is  deepest  in  front.  The  bottom  is  formed  in  succession  from  before 
backward  by  the  chiasmal  recess,  the  infundibulum,  the  cinereous  tuber-, 
the  posterior  perforated  space,  and  the  groove  of  divergence  of  the 
tegmenta  of  the  cerebral  crura.  Beneath  the  splenium  it  communicates 
by  the  transverse  cerebral  fissure 5  with  the  interval  of  the  cere- 
brum and  cerebellum,  in  which  position  the  choroid  tela,6  a  process 
of  the  pia,  enters  and  the  internal  cerebral  veins  escape  from  it.  At 
the  lower  back  part  it  communicates  by  the  ventricular  aqueduct  with 
the  fourth  ventricle.  Its  fore  part  extends  forward  between  the  de- 
scending and  diverging  anterior  pillars  of  the  fornix  and  is  closed  in 
front  from  the  great  longitudinal  fissure  by  the  cinereous  lamina,7 
situated  immediately  in  advance  of  the  chiasmal  recess. 

The  third  ventricle  is  crossed  by  three  commissures,  named  from 
their  relative  position  anterior,  middle,  and  posterior.  The  bottom  is 
lined  with  gray  matter  which  forms  a  commissural  union  between  the 
cerebral  hemispheres. 

The  thalamus 8  appears  as  a  large  oval  eminence  which  projects 
from  the  corresponding  hemisphere  inwardly  into  the  third  ventricle 
and  along  its  upper  part  into  the  lateral  ventricle,  where  it  is  separated 
from  the  striatum  by  a  groove,  which  ascends  from  the  bottom  of  the 
fore  part  of  the  ventricle  and  winds  backward  and  outward  to  the 
middle  horn.  The  upper  part,  visible  in  the  lateral  ventricle,  is  de- 
fined from  that  of  the  third  ventricle  by  a  shallow  groove,  which 
accommodates  the  lateral  band  of  the  fornix,  to  the  outer  edge  of 
which  lies  the  choroid  plexus  of  the  lateral  ventricle.  The  anterior 
somewhat  prominent  extremity  of  the  thalamus  is  its  tubercle,9  and 

1  Amygdala;  nucleus  amygdalae. 

2  F.  Monroi  or  commune  anterius  ;  porta  ;  vulva. 

3  Ventriculus  tertius  or  medius  cerebri ;  diacoelia.  4  Sulcus  Monroi. 

5  Fissura  cerebri  transversa  anterior ;  rima  transversa  cerebri. 

6  Tela  choroidea ;  velum  interpositum.  7  L.  terrninalis  ;  1.  cinerea. 

8  T.  opticus  or  nervus  optici ;  ganglion  cerebri  medium,  posticum,  or  magnum 
inferius  ;  eminentia  magna  cerebri. 

9  Tuberculum  anterius  or  ant.  superius  ;  corpus  album  subrotundum. 


758 


THE    NERVOUS   SYSTEM. 


this  likewise  lies  to  the  outer  side  of  the  apex  of  the  fornix  within  the 
lateral  ventricle.  The  posterior  extremity  of  the  thalamus  forms  a 
wide,  transverse  bolster-like  process,  the  pulvinar,1  which  is  placed  to 
the  outer  side  of  the  quadrigeminal  body  and  overhangs  the  entrance 
of  the  middle  horn  of  the  lateral  ventricle. 

Within  the  third  ventricle  the  nearly  vertical  surface  of  the  thal- 
amus is  divided  by  a  prominent  white  line,  the  pineal  stria,2  which 

FIG.  390. 


STRIATA,  THALAMI,  QUADRIGEMINAL  BODY,  AND  CEREBELLUM.  1,  quadrigeminal  body;  2, 
anterior  velum ;  3,  superior  peduncle  of  the  cerebellum ;  4,  upper  portion  of  the  middle  peduncle ; 
5,  upper  portion  of  the  cms  of  the  cerebrum ;  6,  pulvinar  of  the  thalamus ;  7,  its  tubercle ;  8, 
verrnis  of  the  cerebellum ;  9,  lingule ;  10,  posterior  commissure  of  the  third  ventricle ;  11,  middle 
commissure ;  12,  anterior  commissure ;  13,  pineal  body  turned  forward ;  14,  its  peduncle ;  15,  thala- 
mus; 16,  hemispheres  of  the  cerebellum;  17,  dentate  nucleus;  18,  semicircular  band;  19,  vein 
of  the  striatum ;  20,  anterior  crura  of  the  fornix;  21,  striatum ;  22,  ventricular  septum. 

proceeds  from  the  peduncle  of  the  pineal  body  forward  to  the  inner  side 
of  the  tubercle.  From  the  latter  a  slightly  prominent  band,  produced 
by  the  anterior  pillar  of  the  fornix,  descends  in  a  curve,  convex  for- 
ward, to  the  bottom  of  the  ventricle  and  passes  through  the  cinereous 
tuber  to  end  in  the  corresponding  mammillary  eminence.  Near  their 
middle,  crossing  the  narrowest  part  of  the  third  ventricle,  the  thalami 


1  Tuberculum  posterius. 

'2  S.  pinealis  or  medullaris  thalami ;  taenia  fornicis  or  thalami. 


THE   NERVOUS   SYSTEM.  759 

are  conjoined  by  a  thin  oval  disk  of  gray  matter,  the  middle  com- 
missure.1 

The  anterior  commissure2  of  the  third  ventricle  is  a  rounded 
cord  crossing  the  fore  part  immediately  in  advance  of  the  anterior  pil- 
lars of  the  fornix  and  behind  the  cinereous  lamina  of  the  ventricle.  It 
is  a  cylindrical  bundle  of  white  nerve-fibres  which  enters  the  striatum 
on  each  side  and  extends  below  the  lenticular  nucleus,  thence  curving 
outward  and  backward,  somewhat  twisted  and  spreading  in  the  central 
lobe.  It  is  further  traceable  into  the  temporal  lobe  above  the  middle 
horn  of  the  lateral  ventricle  to  the  amygdaloid  nucleus. 

The  posterior  commissure 3  is  situated  at  the  back  of  the  third 
ventricle,  immediately  above  the  entrance  of  the  ventricular  aqueduct. 
It  is  a  white  plate  doubled  on  itself,  with  the  closed  part  of  the  fold  di- 
rected forward  and  the  open  part  backward  and  transversely  wrinkled. 
It  is  extended  between  the  thalami  laterally,  while  its  upper  part  joins 
the  pineal  body  and  its  lower  part  behind  the  quadrigeminal  body.  It 
is  composed  of  transverse  bundles  of  nerve-fibres  which  pass  between 
the  thalami  and  partly  through  them  into  the  white  matter  of  the 
cerebral  hemispheres. 

Beneath  the  pulvinar  of  the  thalamus  are  two  elliptical  white 
eminences,  the  geniculate  bodies.4  Of  these  the  internal5  is  the 
more  prominent  and  better  defined,  and  is  situated  transversely  be- 
tween the  pulvinar,  the  quadrigeminal  body,  and  the  cerebral  crus. 
The  external,6  somewhat  larger,  is  situated  fore  and  aft  to  the  outer 
side  of  the  former,  at  the  outer  fore  part  of  the  pulvinar.  From  the 
geniculate  bodies  proceed  a  pair  of  bands  uniting  in  the  optic  tract,7 
which  also  receives  less  conspicuous  bundles  of  nerve-fibres  from 
the  anterior  tubercles  of  the  quadrigeminal  body  and  from  the  pul- 
vinar. 

The  optic  tract  appears  as  a  flattened  cord  proceeding  in  two  con- 
spicuous bands  from  the  geniculate  bodies,  winding  from  the  outer  side 
of  the  cerebral  crus,  as  this  is  about  to  enter  the  cerebral  hemisphere, 
downward,  forward,  and  inward.  Gradually  becoming  more  defined 
as  a  flattened  cylindrical  cord  it  proceeds  downward  and  inward  in 
front  of  the  cinereous  tuber  at  the  base  of  the  brain  and  joins  its  fel- 
low to  form  the  optic  commissure.  The  optic  tract  in  its  descent 

1  Commissura  media  or  mollis  ;  soft  commissure ;  medicommissura. 

2  Commissura  anterior  cerebri ;  praecommissura. 

3  Commissura  posterior  cerebri,  parva  posterior,  or  posterior  ventriculi  tertii ; 
trigonum  molle,  fluctuans,  or  pensile  ;  postcommissura. 

4  Corpora  geniculata. 

5  Corpus   geniculatum  internum   or  mediale ;    tuberculum  posticum   medium  ; 
postgeniculatum. 

6  C.  g.  externum  or  laterale ;   tub.  post,  inferius  or  laterale ;  optical  nucleus  ; 
prsegen  iculatum . 

7  Tractus  opticus. 


760 


THE   NERVOUS   SYSTEM. 


FIG.  391. 


is  closely  connected  with  the  cerebral  crus  and  cinereous  tuber,  from 
both  of  which  it  derives  nerve-fibres. 

The  optic  commissure,  or  chiasm,1  is  formed  by  the  conjunction 
of  the  optic  tracts  in  front  of  the  cinereous  tuber,  and  from  it  proceed 
the  optic  nerves.  In  the  commissure  most  of  the  nerve-fibres  of  one 
tract  diagonally  cross  those  of  the  other  tract  and  enter  the  optic  nerve 
of  the  opposite  side,  a  few  fibres  passing  into  the  nerve  of  the  same  side. 
A  small  arching  bundle  of  fibres  at  the  back  of  the  commissure  passes 
from  one  tract  to  the  other.  A  similar  bundle  has  been  stated  to  pass 
between  the  two  optic  nerves. 

The  thalamus  chiefly  consists  of  an  accumulation  of  gray  matter, 
covered  on  its  ventricular  surface  with  a  thin  layer  of  white  matter,2 
and  is  embedded  outwardly  and  beneath  in  the  white  matter  of  the 

cerebral  hemisphere.  The  white 
matter  externally  forms  the  inner 
capsule,  consisting  of  bundles  of 
nerve-fibres  ascending  and  diverg- 
ing from  the  crusta  of  the  cere- 
bral crus.  Beneath  is  the  exten- 
sion of  the  tegmentum  of  the 
crus,  chiefly  composed  of  nerve- 
fibres  ascending  into  the  inner 
capsule  and  the  outer  part  of  the 
thalamus.  Between  the  subthal- 
amic  tegmentum  and  the  crusta, 
as  this  ascends  outwardly  to  the 
inner  capsule  and  externally  to 
the  locus  niger,  is  some  gray  mat- 
ter, the  subthalamic  nucleus.3 

The  gray  matter  of  the  thal- 
amus is  partially  separated  by 
thin  white  laminse  into  three  por- 
tions or  nuclei.  Of  these  the 
anterior  nucleus  occupies  the 
tubercle  of  the  thalamus,  and  be- 
hind it  is  the  internal  nucleus, 
joined  to  that  of  the  opposite  side 
by  the  middle  commissure  of  the 

third  ventricle.  The  external  nucleus,  larger  than  the  others,  is 
situated  to  their  outer  side  and  is  separated  from  them  by  a  sigmoid 
lamina  slanting  from  without  downward  and  inward.  It  also  extends 
beneath  them  and  into  the  pulvinar.  The  geniculate  bodies  also  contain 
gray  nuclei  continuous  with  the  external  nucleus  of  the  thalamus. 
Numerous  nerve-cells  are  scattered  through  the  gray  matter  of  the 


HORIZONTAL  SECTION  THROUGH  THE  RIGHT 

HEMISPHERE    OF    THE    CEREBRUM.       1,    frontal 

Icfoe ;  2,  parietal  lobe ;  3,  central  lobe ;  4,  oc- 
cipital lobe ;  5,  6,  fore  and  back  parts  of  the 
callosum ;  7,  ventricular  septum ;  8,  anterior 
pillar  of  the  fornix ;  9,  striatum ;  10,  lenticular 
nucleus;  11,  12,  13,  three  nuclei  of  the  thal- 
amus ;  14,  nucleus  of  the  external  geuiculate 
body ;  15,  claustrum. 


1  Chiasma  opticum. 


2  Stratum  zonale. 


Corpus  subthalamicum. 


THE   NERVOUS   SYSTEM.  761 

thalamus,  and  they  are  largest  in  the  anterior  nucleus.  The  darker 
gray  nucleus  of  the  external  geniculate  body  also  contains  many 
yellow  pigmented,  mostly  fusiform  nerve-cells.  The  external  nucleus 
of  the  thalamus  at  its  outer  part  is  streaked  with  white,  due  to  bundles 
of  nerve-fibres  passing  thence  into  the  contiguous  inner  capsule.  The 
subthalamic  nucleus  is  a  lenticular  layer  of  gray  matter  with  many 
pigmented  nerve-cells. 

From  the  outer  part  of  the  thalamus  and  the  striatum,  bundles  of 
nerve-fibres  radiate  in  all  directions  to  the  cerebral  cortex. 

The  bottom  or  floor  of  the  third  ventricle  extends  as  a  groove, 
curving  from  the  entrance  of  the  ventricular  aqueduct  forward  and 
downward  to  the  position  of  the  optic  commissure,  in  front  and  above 
which  the  ventricle  is  closed  from  the  fore  part  of  the  great  longitu- 
dinal fissure  by  the  cinereous  lamina.  The  floor  is  formed  of  gray 
matter  ascending  a  short  distance  on  the  sides  and  connecting  the 
cerebral  hemispheres,  whence  it  has  been  named  the  gray  commis- 
sure of  the  floor.  Below  the  position  of  the  thalami  the  basis  of  the 
floor  is  formed  by  the  tegmenta  of  the  cerebral  crura  as  they  diverge 
and  proceed  upward  and  outward  beneath  the  thalami.  In  advance 
of  the  tegmenta  the  gray  matter  of  the  floor  increases  and  reaches  the 
base  of  the  brain  between  the  cerebral  crura.  where  it  forms  the  pos- 
terior perforated  space,  the  cinereous  tuber,  and  the  infundibulum. 

The  third  ventricle  is  prolonged  in  the  infundibulum  in  a  conical 
pit  to  its  termination. 

In  advance  of  the  infundibulum  is  another  conical  pit,  the  chiasmal 
recess,1  which  is  bounded  behind  by  the  optic  chiasm  and  in  front  by 
the  cinereous  lamina. 

The  cinereous  lamina2  of  the  third  ventricle  is  a  thin  gray  band 
which  descends  from  the  rostrum  of  the  callosum  to  the  front  of  the 
anterior  commissure,  thence  to  the  anterior  upper  border  of  the  optic 
chiasm,  connected  on  each  side  with  the  corresponding  anterior  perfo- 
rated space.  In  front  of  it  at  the  sides  descend  the  callosal  peduncles, 
between  which  the  lamina  is  visible  at  the  bottom  of  the  great  longi- 
tudinal fissure. 

The  quadrigeminal  body3  is  a  quadrate  plate  divided  on  its  upper 
surface  by  a  crucial  groove  into  four  rounded  white  tubercles.  It  is 
situated  in  the  interval  of  the  cerebrum  and  cerebellum  beneath  the 
splenium.  It  is  connected  in  front  with  the  thalami,  from  which  it 
inclines  downward  and  backward  to  the  superior  cerebellar  peduncles 
and  anterior  velum  and  on  each  side  joins  the  tegmentum  of  the  cere- 
bral crus.  With  its  tubercles  directed  upward  and  backward,  beneath 
it  in  the  median  line,  is  the  ventricular  aqueduct.  The  anterior  pair 


1  Kecessus  chiasmatis.  2  L.  cinerea  terminalis  ;  terma. 

3  Corpora,  tubercula,  eminentia,  or  lamina  quadrigemina,  or  bigemina ;  protu- 
berantiae  or  prominentiae  orbiculares  or  encephali ;  optic  lobes. 


762  THE   NERVOUS   SYSTEM. 

of  tubercles1  is  the  larger,  but  the  posterior  pair2  is  slightly  more 
prominent.  Laterally  they  are  prolonged  obliquely  forward  and  out- 
ward in  slightly  less  prominent  arms.3  The  median  groove  as  it 
widens  in  front  supports  the  pineal  body,  and  from  its  back  part  a 
little  ridge,  the  frenule,4  extends  to  the  anterior  velum.  The  tubercles 
are  composed  superficially  of  a  layer  of  white  matter8  mainly  consisting 
of  transverse  fibres  which  pass  into  the  arms.  The  layer  is  thicker 
on  the  anterior  tubercles  and  in  front  is  connected  with  the  posterior 
commissure  of  the  third  ventricle.  Beneath  it  is  a  gray  layer,6  which  is 
thickest  where  the  tubercles  are  most  prominent  and  contains  numer- 
ous small  nerve-cells.  A  third  layer,'  also  of  gray  matter  with  small 
nerve-cells,  is  traversed  by  longitudinal  fibres,  which  diverge  laterally 
and  pass  into  the  arms  and  optic  tract.  A  fourth  layer8  consists  of 
fibres  from  the  fillet,  passing  between  the  former  layer  and  the  wall  of 
the  aqueduct  to  the  opposite  side  and  thence  to  the  layer  above.  The 
posterior  tubercles  next  their  thinner  white  layer  are  mainly  composed 
of  gray  matter  with  many  small  and  a  few  large  nerve-cells.  It  is 
separated  from  the  wall  of  the  aqueduct  by  a  thin  layer  of  fibres  from 
the  fillet. 

The  ventricular  aqueduct,9  a  canal  communicating  between  the 
third  and  fourth  ventricles,  is  enclosed  between  the  tegmenta  of  the 
cerebral  crura  beneath  the  median  line  of  the  quadrigeminal  body.  It 
is  a  narrow  passage,  little  more  than  half  an  inch  long,  and  is  enclosed 
in  a  thick  wall  of  gray  matter  lined  with  an  ependyma  of  ciliated 
columnar  cells.  The  gray  matter  contains  many  scattered  nerve-cells 
of  varied  form  and  size,  besides  which  it  includes  several  important 
accumulations  as  nuclei  of  several  of  the  cerebral  nerves. 

The  pineal  body 10  is  a  little  ovoid,  conical,  reddish  organ  situated 
in  the  posterior  part  of  the  third  ventricle,  immediately  above  the  pos- 
terior commissure,  to  which  it  is  attached  by  its  base,  and  thence  rests 
obliquely  backward  and  downward  between  the  anterior  pair  of  tuber- 
cles of  the  quadrigeminal  body.  From  its  base  on  each  side  a  narrow 
white  band,  the  peduncle,11  curves  outward  and  forward  and  is  con- 
tinued as  the  pineal  stria  of  the  thalamus.  The  peduncle  extends 
outwardly  to  the  thalamus  in  a  narrow  triangular  shelf12  directed  back- 

1  Corpora,  eminentiae,  or  prominentise  anteriores,  superiores,  inajores,  or  nati- 
formes  ;  nates  ;  prseoptici  ;  anterior  lobes  of  the  mesencephalon. 

2  C.,  e.,  or  p.  posteriores,  inferiores,  minores,  or  testiformes ;  testes ;  postoptici ; 
posterior  lobes  of  the  mesencephalon. 

3  Brachia  conjunctiva.  *  Frenulum  ;  f.  veli  medullare  antici. 
5  Stratum  zonale.  6  S.  cinereum. 

7  S.  opticum.  8  S.  lemnisci. 

9  Aquseductus  Sylvii ;  iter  e  tertio  ad  quartum  ventriculum  ;  ventriculus  opticus 
or  mesencephali  ;  mesoccelia  ;  mesial  part  of  mesocele  ;  vulva ;  fistula  sacra. 

10  Pineal  gland ;  glandula  pinealis  ;  conarium  ;  pinus  ;  epiphysis  cerebri. 

11  Pedunculus  or  habenula  conarii  or  pinealis. 

12  Trigonum  habenulse. 


THE   NERVOUS   SYSTEM.  763 

ward  in  a  groove  beneath  the  pulvinar.  The  peduncles  conjoin,  and 
between  their  conjunction  and  the  posterior  commissure  is  a  little 
conical  recess l  opening  forward  into  the  third  ventricle. 

The  pineal  body  is  smooth,  or  sometimes  more  or  less  uneven.  It 
consists  of  a  matrix  of  soft  connective  tissue  with  follicles  filled  with 
cells,  which  are  generally  regarded  as  being  of  the  character  of  epi- 
thelial cells,  though  they  are  also  looked  upon  as  nerve-cells.  It  also 
commonly  contains  more  or  less  sand-like  grains,2  of  variable  size  and 
resembling  bone-earth  in  composition,  with  a  small  proportion  of 
organic  matter. 

The  pituitary  body 3  is  enclosed  in  the  sella  of  the  sphenoid  bone 
attached  by  a  narrow  stem4  to  the  infundibulum  of  the  brain.  It 
is  solid,  of  a  pale-reddish  color,  is  surrounded  by  vascular  connective 
tissue  continuous  with  the  pia,  and  is  enclosed  in  a  sac  of  the  dura, 
perforated  for  the  connection  of  its  stem  with  the  infundibulum.  It 
consists  of  an  anterior,  larger,  transverse  reniform  lobe,  with  a  smaller 
rounded  lobe  closely  connected  with  the  recess  of  the  other  behind. 
It  is  very  enigmatic  in  character,  very  unlike  the  rest  of  the  brain  in 
structure,  though  a  constant  accessory  to  it  in  vertebrate  animals.  The 
anterior  lobe,  of  darker  color,  is  composed  of  a  matrix  of  connective 
tissue  with  convoluted  follicles  of  the  same  material  filled  with  nucleated 
cells  of  varied  size  resembling  those  of  glandular  epithelium.  The 
posterior  lobe  contains  in  its  connective-tissue  matrix  numerous  spindle- 
shaped  and  branching  cells,  together  with  a  few  larger  pigmented  cells. 

The  anterior  lobe  of  the  pituitary  body  is  developed  as  a  tubular 
prolongation  from  the  ectoderm  of  the  buccal  cavity  of  the  embryo. 
The  posterior  lobe  is  a  development  extending  from  the  third  ventricle 
of  the  brain,  subsequently  becoming  solidified.  In  fishes  it  remains 
hollow  in  conjunction  with  the  infundibulum. 

The  gray  cortex 5  of  the  cerebral  hemispheres,  in  each,  is  continu- 
ous throughout,  and  is  a  much-folded  pouch  with  the  mouth  directed 
centrally  inward  and  downward.  The  pouch  is  filled  with  white 
matter6  which  is  continuous  through  the  mouth  with  that  of  the 
opposite  hemisphere  and  of  the  isthmus  connecting  the  cerebrum  with 
the  other  chief  divisions  of  the  brain.  The  white  matter  consists  of 
a  dense  aggregation  of  flattened  bundles  of  medullated  nerve-fibres, 
which  for  the  most  part  extend  from  the  isthmus  and  callosum  and 
spread  in  every  direction  within  each  hemisphere  to  the  cortex.  Em- 
bedded in  the  white  matter  are  accumulations  of  nuclei  of  gray  matter, 
from  which  emanate  additional  bundles  of  fibres  to  reinforce  the  for- 
mer. Separations  in  the  direction  of  the  main  trunks  of  white  matter 
proceeding  from  the  callosum  and  isthmus  form  the  lateral  and  third 

1  Ventriculus  conarii.  2  Acervulus  cerebri ;  brain-sand. 

3  P.  gland  ;  glandula  pituitaria  ;  hypophysis  cerebri. 

4  Pedunculus  hypophyseos.  5  Substantia  cinerea. 
6  Substantia  medullaria. 


764 


THE   NERVOUS    SYSTEM. 


FIG.  392. 


O, 


ventricles  of  the  cerebrum.  The  white  mat- 
ter of  the  cerebral  convolutions  consists  of 
bundles  which  enter  them  along  their  mid- 
dle, perpendicular  to  their  summit,  and  then 
spread  out  in  curves  to  the  cortex.  Accord- 
ing to  Henle,  the  extension  of  fine  bundles 
of  fibres  from  the  white  matter  of  the  con- 
volutions into  the  cortex  for  about  half  its 
thickness  divides  it  into  an  outer  pure  gray 
layer  and  an  inner  more  whitish  layer.  At 
the  bottom  of  contiguous  convolutions,  bun- 
dles of  fibres  curve  from  one  to  the  other 
around  the  cortex  at  the  bottom  of  the  inter- 
vening fissure. 

Vertical  sections  across  the  cerebral  cor- 
tex exhibit  to  the  naked  eye  the  appearance 
ot  several  strata  slightly  differing  in  color 
and    translucency.      Though    not    uniform, 
throughout  its  greater  extent  a  half-dozen 
layers  are  distinguishable,  as  follows:    1,  a 
thin  external  layer  of  whitish  neuroglia,  vari- 
able in  thickness  in  different  positions,  and 
especially  well  marked  on  the  inner  surface 
of  the   lower    part   of 
the  hippocampal  convo- 
lution ;    2,  a    layer    of 
reddish-gray  matter ;  3, 
a  white  layer,1  which  is 
especially  well  marked 
on  the  convolutions  of 
the  occipital  lobe  bound- 
ing   the    calcarine    fis- 
sure;   4,  a  second  and 
lighter  gray  layer;    5, 

a  second  thin  white  layer;2  6,  a  yellowish- 
gray  layer. 

The  cerebral  cortex  is  composed  of  an 
abundant  neuroglia  matrix,  with  variable 
proportions  of  nerve-cells  and  nerve-fibres  in 
its  different  strata.  The  nerve-cells  are  of 
various  sizes  and  shapes  and  in  a  measure  are 
disposed  in  strata  and  columns  not  sharply 
defined.  The  largest  and  longest  cells,  regarded  as  characteristic,  are 


FIG.  392. — VERTICAL  SEC- 
TION THROUGH  THE  DEEPER 
PORTION  OF  THE  CEREBRAL 

CORTEX  :  highly  magnified. 
1 , 2,  small  pyramidal  nerve- 
cells  below  the  neuroglia 
layer  containing  few  or  no 
cells;  3,  4,  intermediate 
layer  of  large  pyramidal 
cells;  5,  6,  deep  layer  of 
small  cells,  and  groups  of 
ascending  fibres;  6,  7, 
white  matter  with  fusiform 
nerve-cells. 


1  Line  of  Vicq  d'Azyr ;  outer  line  of  Baillarger. 

2  Inner  line  of  Baillarger. 


THE   NERVOUS   SYSTEM.  765 

mostly  pyramidal,  with  the  apex  directed  to  the  surface  of  the  convo- 
lution and  prolonged  into  a  branching  process.  From  the  angles  of 
the  base  fine  processes  proceed  in  the  opposite  direction,  mostly  branch 
and  anastomose  and  form  a  net-work  in  the  surrounding  neuroglia. 
From  each  cell  an  undivided  branch  may  be  traced  into  a  medullated 
nerve-fibre  as  its  axis-fibre.  The  cells  appear  to  be  contained  in  clearer 
areas,  which  are  regarded  as  lymphatic  spaces.  With  the  more  charac- 
teristic nerve-cells  are  mingled  others,  which  are  smaller  and  angular 
and  provided  with  branches  radiating  in  various  directions.  In  the 
deeper  stratum  of  the  cortex  there  are  also  small  spindle-shaped  cells 
with  processes  proceeding  in  opposite  directions.  Mingled  with  the 
others  there  occur  many  small  cells,  which  resemble  ordinary  colorless 
blood-corpuscles. 

The  external  neuroglia  layer  of  the  cortex  contains  only  a  few  small 
branching  cells  and  next  the  pia  a  few  medullated  nerve-fibres.  In  the 
next  layer  the  pyramidal  nerve-cells  are  more  abundant  and  crowded 
than  elsewhere  and  generally  smaller.  In  the  succeeding  layers  they 
are  more  widely  separated,  generally  larger  and  with  the  deeper  ones 
largest.  In  the  deepest  layers  they  are  fewest  and  mingled  with 
numerous  smaller  and  less  characteristic  forms.  From  the  white 
matter  beneath  the  cortex,  bundles  of  fibres  ascend  through  its  deeper 
layers,  separating  the  cells  into  columns,  and  become  more  diffused  in 
the  upper  layers. 

The  interior  white  matter,  or  medullary  centre,  of  the  cerebral 
hemispheres,  which  in  the  fresh  condition  appears  homogeneous,  is 
composed  of  flattened  bundles  of  medullated  nerve-fibres  densely  ag- 
gregated and  united  together  by  neuroglia.  When  a  brain  is  hardened 
in  alcohol,  on  tearing  it  apart  the  general  course  of  the  bundles  of 
nerve-fibres  becomes  quite  obvious.  In  each  hemisphere  they  for  the 
most  part  radiate  from  the  cerebral  crus,  thalamus,  striatum,  and  callo- 
sum  to  the  cerebral  cortex.  The  fibres  are  referable  to  three  systems, 
distinguished  according  to  the  general  direction  they  pursue,  as  the 
ascending,  transverse,  and  longitudinal. 

The  ascending  fibres  of  each  hemisphere  partly  proceed  from  the 
crusta  and  partly  from  the  tegmentum  of  the  corresponding  cerebral 
crus.  Those  from  the  crusta  chiefly  enter  the  inner  capsule,  separating 
the  thalamus  and  striatum  from  the  lenticular  nucleus,  in  their  course 
give  fibres  to  these  and  receive  others  from  them  and  thence  diverge 
in  all  directions  to  the  cerebral  cortex,  producing  an  arrangement  which 
is  called  the  corona  radiata.  While  many  of  the  fibres  of  the  crusta 
appear  directly  to  pass  through  the  inner  capsule  into  the  medullary 
centre  continuing  to  the  cortex,  only  a  portion  of  them  have  been  defi- 
nitely traced  throughout  their  entire  course.  Thus  the  pyramidal 
tract  from  the  oblongata  has  been  followed  through  the  crusta  and 
inner  capsule  to  the  ascending  frontal  and  parietal  convolutions  and 
contiguous  parts  of  the  cerebral  hemisphere.  The  fact  is  of  interest 


766  THE    NERVOUS   SYSTEM. 

from  the  circumstance  that  experiment  indicates  the  gray  matter  of 
these  convolutions  to  be  concerned  in  the  movements  of  the  principal 
groups  of  muscles  of  the  body.  Another  portion  of  the  crusta  out- 
wardly, as  the  direct  sensory  tract,  has  been  traced  into  the  white 
matter  of  the  occipital  lobe  of  the  hemisphere.  A  small  portion  of 
the  crusta  inwardly  does  not  enter  the  inner  capsule,  but  its  fibres 
collected  in  a  bundle1  pass  outward  beneath  the  thalanms  and  enter 
the  lenticular  nucleus. 

The  fibres  proceeding  from  the  tegmentum  of  the  cerebral  crus 
derived  from  the  reticular  formation  of  the  oblongata,  reinforced,  by 
others  from  the  superior  peduncle  of  the  cerebellum  and  probably  also 
from  the  middle  peduncle,  the  quadrigeminal  body,  and  the  gray  nuclei 
in  their  course,  mostly  appear  to  terminate  in  the  subthalamic  region 
and  in  the  thalamus.  Further,  numerous  fibres  emerge  from  the  outer 
side  of  the  thalamus  and  join  those  of  the  corona  radiata  in  their  dis- 
tribution, but  particularly  proceed  to  the  temporal  and  occipital  lobes ; 
which  experiments  appear  to  indicate  as  being  concerned  with  the 
functions  of  the  special  sense-organs.  Some  of  the  fibres  from  the 
back  of  the  thalamus  enter  the  optic  tract,  and  others  from  the  lower 
part  in  front  form  a  bundle,2  which  curves  below  around  the  lenticular 
nucleus  and  enters  the  white  matter  of  the  cerebral  hemisphere. 

The  transverse  fibres 3  of  the  cerebrum  are  chiefly  those  of  the 
callosum,  which  radiate  in  all  directions  within  the  hemispheres,  where 
they  intersect  the  fibres  of  the  corona  radiata.  The  fibres  proceeding 
into  the  parietal  lobe  and  the  back  part  of  the  frontal  lobe  are  nearly 
transverse  in  their  course,  but  those  from  the  callosal  knee  curve  round 
into  the  anterior  part  of  the  frontal  lobe.  From  the  splenium  they 
mostly  arch  round  the  posterior  and  middle  horns  of  the  lateral  ven- 
tricle into  the  temporal  and  lower  part  of  the  occipital  lobe ;  while 
others  from  beneath  proceed  in  a  curve*  into  the  back  and  upper 
parts  of  the  occipital  lobe. 

To  the  transverse  fibres  of  the  cerebrum  also  belong  those  of  the 
anterior  commissure  of  the  third  ventricle. 

To  the  longitudinal  fibres5  of  the  cerebral  hemispheres  belong 
the  following : 

1.  The  fornicate  fascicle.6  This  forms  the  white  matter  of  the 
fornicate  convolution,  in  which  the  fibres  pursue  a  longitudinal  course 
and  give  offsets  upward  and  backward  into  its  secondary  convolutions. 
In  front  the  fibres  turn  down  in  the  convolution  to  the  anterior  perfo- 
rated space ;  behind  they  turn  round  the  splenium  and  descend  to  the 
end  of  the  temporal  lobe. 


1  Ansa  lenticularis.  2  Inferior  peduncle  of  the  thalamus. 

3  Commissural  fibres  of  the  corpus  callosum. 

4  Forceps  major.  5  Collateral  or  association  fibres. 
6  Fillet  of  the  corpus  callosum. 


THE   NERVOUS   SYSTEM.  767 

2.  The  uncinate  fascicle.1    A  bundle  which  crosses  the  bottom  of 
the  sylvian  fissure  and  connects  the  frontal  and  temporal  lobes. 

3.  The  inferior  longitudinal  fascicle.     A  bundle  which  lies  close 
to  the  outer  wall  of  the  posterior  and  middle  horns  of  the  lateral  ven- 
tricle and  connects  the  occipital  and  temporal  lobes. 

4.  The  gyral  fascicles.2     These  are  fibres  which  connect  the  adja- 
cent convolutions  arching  across  the  bottom  of  the  intervening  fissure 
and  situated  close  to  the  cortex.    Deeper  and  longer  fibres  also  connect 
convolutions  more  widely  separated. 

5.  Other  longitudinal  fibres  of  the  cerebrum  are  the  longitudinal 
striae  of  the  callosum,  the  semicircular  band  of  the  lateral  ventricles,  and 
the  lateral  bands  of  the  fornix,  with  its  anterior  pillars  and  its  posterior 
pillars  prolonged  as  the  fimbrise. 

BKAIN   OP   THE   EMBKYO. 

In  the  development  of  the  cerebro-spinal  axis,  it  early  makes  its 
appearance  in  the  embryo  as  a  simple  tube,  which  is  expanded  at  the 
anterior  or  cephalic  extremity.  The  expanded  portion  becomes  con- 
stricted into  two  and  then  three  successive  portions,  distinguished  as 
the  cerebral  vesicles,3  which  represent  the  future  brain  or  enceph- 
alon,  while  the  remaining  portion  of  the  tube  represents  the  spinal 
cord.  The  continuous  cavity  of  the  cerebral  vesicles  and  spinal  portion 
of  the  tube  subsequently  become  the  ventricles  of  the  brain  and  the 
central  canal  of  the  spinal  cord.  The  cerebral  vesicles  by  further 
development  form  five  fundamental  divisions,  which  correspond  with  as 
many  parts  of  the  mature  brain.  The  first,  or  anterior  cerebral 
vesicle,4  forms  two  divisions,  of  which  the  anterior,  named  the  pros- 
encephalon,5  consists  of  the  cerebral  hemispheres  together  with  the 
callosum,  striata,  fornix,  and  lateral  ventricles.  The  posterior  division, 
named  the  thalamencephalon,6  consists  of  the  thalajni,  the  third 
ventricle,  the  pituitary  and  pineal  bodies.  The  second,  or  middle 
cerebral  vesicle,7  forms  the  mesencephalon,8  which  consists  of  the 
quadrigeminal  body,  the  cerebral  crura,  and  the  ventricular  aqueduct. 
The  third,  or  posterior  cerebral  vesicle,9  forms  two  divisions,  of 
which  one,  the  epencephalon,10  consists  of  the  cerebellum  and  pons, 
with  the  upper  portion  of  the  fourth  ventricle ;  while  the  other  divi- 
sion, the  metencephalon,11  consists  of  the  oblongata12  and  the  lower 
portion  of  the  fourth  ventricle. 


1  Arcuate  fasciculus.  2  Association  fibres. 

3  Primary  vesicles.  4  Anterior  primary  vesicle. 

5  Fore-brain.  6  Inter-brain  ;  di-encephalon. 

7  Middle  primary  vesicle.  8  Mid-brain. 

9  Posterior  primary  vesicle.  10  Hind-brain. 

11  After-brain.  12  Myelencephalon. 


768  THE   NERVOUS   SYSTEM. 

CHOEOID   TEL^E   AND   PLEXUSES. 

The  choroid  tela1  of  the  third  ventricle  is  a  process  of  the 
pia  extending  into  that  cavity  through  the  transverse  cerebral  fissure, 
beneath  the  callosum  and  above  the  quadrigeminal  body.  It  occupies 
the  roof  of  the  ventricle  adherent  to  the  under  surface  of  the  fornix 
and  below  to  the  quadrigeminal  and  pineal  bodies  and  to  the  thalami 
above  the  position  of  the  pineal  striae.  It  thins  away  to  the  foramen  of 
Monro  and  at  the  sides,  where  it  is  connected  with  the  choroid  plexuses 
of  the  lateral  ventricles. 

Beneath  the  tela  are  the  choroid  plexuses2  of  the  third  ven- 
tricle, narrow,  vascular,  villous  appendages,  similar  to  those  of  the 
lateral  ventricles.  They  extend  from  the  foramen  of  Monro  along  the 
tela,  one  on  each  side  of  the  median  line,  to  its  back  part.  Eunning  near 
the  plexuses  from  the  same  point  are  the  two  internal  cerebral  veins, 
derived  from  branches  of  the  lateral  and  third  ventricles  and  from 
their  choroid  plexuses  and  terminating  at  the  transverse  cerebral  fis- 
sure in  the  vein  of  Galen,  which  opens  into  the  straight  sinus  of  the 
dura. 

The  choroid  plexuses3  of  the  lateral  ventricles  are  two  highly- 
vascular,  curly-looking,  dark-red  appendages  of  the  choroid  tela  of  the 
third  ventricle,  though  contained  within  the  lateral  ventricles.  Each 
lies  along  the  outer  edge  of  the  fornix  and  then  on  the  hippocampus 
and  fimbria.  They  commence  in  a  pointed  manner  at  the  foramen  of 
Monro,  through  which  they  conjoin,  thence  pass  backward  in  the  lat- 
eral ventricles,  gradually  enlarging,  and  descend  in  the  middle  horns 
to  near  their  lower  extremity,  where  they  taper  away.  At  the  entrance 
of  the  middle  horn  they  are  often  thickened,  apparently  the  result  of 
disease.  Along  the  fornix  they  are  continuous  with  the  choroid  tela 
beneath  the  edge  of  that  body,  and  in  the  middle  horn  of  the  ventri- 
cle are  connected  with  the  pia  of  the  hippocampal  fissure.  They  are 
more  or  less  lobulated,  and  the  lobules  are  composed  of  bunches  of 
rounded  villous  processes.  They  contain  numerous  blood-vessels,  which 
form  looped  capillaries  within  the  villi.  The  arteries  are  furnished  by 
the  anterior  choroid  artery  on  each  side,  entering  the  lower  part  of 
the  plexus  through  the  hippocampal  fissure,  and  behind  by  the  posterior 
choroid  artery  entering  the  transverse  cerebral  fissure.  The  veins 
partly  run  forward  in  the  plexus  and  join  the  vein  of  the  striatum 
to  end  in  the  internal  cerebral  vein,  and  partly  inward  through  the 
choroid  tela  to  end  in  the  same  vein. 

The  choroid  tela  of  the  fourth  ventricle  *  is  an  extension  of  the 
pia  closing  the  lower  back  part  of  that  cavity.  Above,  it  is  attached 

1  T.  choroidea ;  t.  c.  superior  or  cerebri ;  velum  interpositum  ;  v.  triangulare. 

2  P.  choroidei  ventriculi  tertii ;  p.  choroideus  tertius. 

3  P.  choroideus.  4  T.  choroidea  ventriculi  quarti  or  inferior. 


THE   NERVOUS  SYSTEM. 


769 


to  the  nodule  of  the  vermis  extending  laterally  to  the  posterior  and 
then  the  inferior  velum.  In  its  descent  it  is  attached  to  the  restiform 
bodies  and  clavae,  extending  to  the  obex  at  the  inferior  angle  of  the 
ventricle.  Immediately  above  the  obex  it  presents  an  opening,  the 
foramen  of  Magendie,1  through  which  the  fourth  ventricle  communi- 
cates with  the  adjacent  subarachnoid  space.  Two  other  openings  exist 
in  the  tela,  one  on  each  side,  communicating  between  the  cornucopise 
and  the  subarachnoid  space. 

From  the  under  surface  of  the  tela  project  into  the  ventricle  the 
median  choroid  plexuses.2  These  are  two  long,  narrow,  vascular, 
villous  appendages,  which  lie  side  by  side  along  the  tela  and  extend 
through  its  opening  on  the  under  part  of  the  vermis.  Lateral  cho- 
roid plexuses3  also  occupy  the  fourth  ventricle,  one  on  each  side,  ex- 
tending from  the  lateral  recess  along  the  cornucopia  to  the  floccule 
and  projecting  from  the  adjacent  aperture. 

EPENDYMA. 

The  ventricles  of  the  brain,  except  that  of  the  ventricular  septum, 
and  the  central  spinal  canal  are  lined  throughout  with  an  endo- 
thelial  membrane,  the  epen- 

dyma.4     On  the  nerve-structures  FIG.  393. 

it  is  closely  adherent  to  a  variably- 
thick  stratum  of  neuroglia,5  and 
is  thence  reflected  on  and  closely 
invests  the  choroid  telse  and  plex- 
uses where  these  exist.  It  closes 
the  lateral  ventricles  at  the  sides 
from  the  third  ventricle,  so  that 
they  only  communicate  through 
the  foramen  of  Monro,  and  it  also 
shuts  off  the  inferior  horns  of  the 
lateral  ventricles  at  the  hippo- 
campal  fissure.  The  endothelium 
chiefly  consists  of  short  columnar, 

ciliated  cells,  though  the  cilia  mostly  disappear  by  adult  age,  except  in 
the  ventricular  aqueduct.  On  the  choroid  plexuses  the  endothelium 
consists  of  larger  pavement  cells,  and  in  the  adult,  besides  the  nucleus, 
each  commonly  contains  a  yellowish  or  reddish  corpuscle. 

MEMBRANES   OF  THE   CEREBRO-SPINAL   AXIS. 

The  cerebro-spinal  axis  is  provided  with  three  membranous  enve- 
lopes, the  dura,  the  pia,  and  the  arachnoid. 

1  F.  Magendii.  2  Plexus  choroideus  medialis  or  superior. 

3  P.  choroideus  lateralis,  inferior,  or  nervi  vagi. 

4  Henle's  Anatomy,  1871.  5  Ependyma.     Quain's  Anatomy,  1882. 

49 


EPENDYMA  OF  THE  VENTRICLES:  350  diame- 
ters. A,  from  the  striatum  of  the  lateral  ven- 
tricle. 1,  viewed  on  the  free  surface ;  2,  through 
the  thickness ;  a,  endothelial  cells ;  b,  neurog- 
lia. B,  endothelial  cells,  free  surface,  from  the 
middle  commissure  of  the  third  ventricle. 


770  THE   NERVOUS  SYSTEM. 


MEMBKANES   OF   THE    BKAIN.1 

The  dura,  or  dura  mater,2  is  a  thick,  dense,  white,  inelastic  fibrous 
membrane  which  lines  the  interior  of  the  cranium  and  gives  off  several 
partitions  which  separate  the  chief  divisions  of  the  brain.  Its  exterior 
portion  next  the  cranium  is  the  periosteum  of  the  adjacent  bones,  to 
which  it  closely  adheres  in  the  usual  manner  by  small  blood-vessels  and 
fibrous  processes  passing  between  them.  The  adhesion  is  not  so  firm 
as  on  the  exterior  of  the  bones  of  the  skeleton,  as  exemplified  in  the 
ready  detachment  of  the  dura  in  ordinary  post-mortem  examinations 
of  the  brain.  It  adheres  more  intimately  along  the  sutures  and  at  the 
base  of  the  cranium,  which  is  perforated  by  numerous  foramina,  through 
which  the  dura  is  prolonged  and  becomes  continuous  with  the  pericramal 
periosteum.  It  also  becomes  continuous  with  the  fibrous  sheaths  of 
the  nerves  and  blood-vessels  which  pass  out  and  in  the  cranium. 

The  processes  of  the  dura  which  form  membranous  partitions  to  the 
brain  are  the  cerebral  falx,  the  tentorium,  and  the  cerebellar  falx. 

The  cerebral  falx3  is  a  large  sickle-shaped  process  of  the  dura 
which  extends  as  a  median  partition  in  the  great  longitudinal  fissure 
between  the  hemispheres  of  the  cerebrum.  Narrow  in  front  where  it 
is  attached  to  the  ethmoidal  crest,  it  gradually  widens  backward  to  the 
tentorium,  with  which  it  is  continuous  in  the  median  line.  Its  upper 
convex  border  is  attached  to  the  cranium  from  the  fore  part  of  th& 
frontal  crest  backward  to  the  internal  occipital  protuberance,  in  which 
position  it  gradually  widens  in  the  same  direction  and  contains  the  su- 
perior longitudinal  sinus.  Its  lower  concave  border  is  free  and  sharp 
and  reaches  to  within  a  little  distance  of  the  callosum,  nearer  behind 
than  in  front.  Within  this  border  the  inferior  longitudinal  sinus  runs 
backward. 

The  tentorium  *  is  a  broad  membrane  stretched  over  the  cerebellar 
fossae,  slanting  down  from  the  attachment  of  the  cerebral  falx  to  its 
circumference  and  separating  the  occipital  lobes  of  the  cerebrum,  which 
rest  upon  it,  from  the  hemispheres  of  the  cerebellum  beneath.  It  is 
attached  along  its  convex  border  on  each  side  from  the  internal 
occipital  protuberance  to  the  horizontal  limb  of  the  occipital  cross 
and  thence  along  the  upper  margin  of  the  temporal  pyramid  to  the 
apex,  where  it  divides  into  two  short  folds,  of  which  one  extends  in- 
ward to  the  posterior  clinoid  process  and  the  other  forward  to  the 
anterior  clinoid  process.  Its  anterior  free  border  encircles  a  large  oval 
aperture,  through  which  the  cerebral  crura  ascend  from  the  pons  to- 
the  cerebral  hemispheres.  Within  its  posterior  border  on  each  side 
runs  the  lateral  sinus ;  within  its  attachment  to  the  temporal  pyramid 

1  Meninges.  2  Dura  meninx. 

8  F.  cerebri  or  major  ;  processus  falciformis  ;  mediastinum  cerebri. 

4  T.  cerebelli ;  septum  encephali. 


THE   NERVOUS  SYSTEM.  771 

runs  the  superior  petrosal  sinus,  and  along  its  attachment  to  the 
tentorium  runs  the  straight  sinus. 

The  cerebellar  falx l  is  a  small  triangular  process  of  the  dura  at- 
tached behind  to  the  occipital  bone,  descending  to  the  occipital  foramen 
and  projecting  forward  into  the  notch  separating  the  hemispheres  of 
the  cerebellum.  Its  lower  extremity  diverges  in  two  smaller  processes 
which  subside  at  the  sides  of  the  occipital  foramen.  It  contains  the 
posterior  occipital  sinus  or  sinuses. 

The  dura  is  separable  into  two  layers,  which  are  composed  of  bands 
and  lamina?  of  fibre-connective  tissue,  with  some  elastic  tissue,  obliquely 
intersecting  one  another  in  the  two  layers.  By  the  separation  of  the 
two  layers  the  venous  sinuses  of  the  dura  are  formed,  lined  by  the 
common  internal  tunic  of  the  veins.  The  interior  surface  of  the  dura, 
smooth  and  shining,  is  invested  with  a  pavement  endothelium  of  clear, 
nucleated  cells. 

The  blood-vessels  of  the  dura  are  numerous,  the  arteries  being 
branches  of  the  meningeals  and  mainly  destined  to  supply  the  adja- 
cent bones.  The  corresponding  veins  communicate  with  the  diploic 
veins  and  the  sinuses,  but  mostly  accompany  the  meningeal  arteries, 
of  which  notably  the  great  meningeal  artery  has  two  companion  veins. 
The  nerves  of  the  dura  are  small  and  are  derived  from  the  trifacial, 
hypoglossal,  and  sympathetic  nerves. 

The  pia,  or  pia  mater,  is  a  highly-vascular  membrane,  mainly  con- 
sisting of  an  intricate  plexus  of  blood-vessels  formed  by  the  chief 
arteries  and  veins  of  the  brain  and  finally  giving  off  a  multitude  of 
the  finest  vessels,  which  alone  directly  enter  the  brain-substance.  It 
is  associated  with  an  intertexture  of  delicate  connective  tissue  with 
elastic  fibres,  and  the  same  tissue  forms  tubular  sheaths  to  the  vessels. 
The  sheaths  accompany  the  finer  vessels  into  the  brain  and  serve  as 
lymphatic  channels. 

The  pia  closely  invests  the  cortical  substance  of  the  cerebral  con- 
volutions, penetrating  all  the  intervening  fissures,  in  which  it  forms  a 
double  layer.  In  the  same  manner  it  closely  invests  the  cerebellum, 
but  on  this  the  membrane  is  finer  and  it  only  forms  a  double  fold  in 
the  principal  fissures.  As  the  choroid  tela  it  extends  through  the 
transverse  cerebral  fissure  into  the  third  ventricle,  connected  with  the 
choroid  plexuses  of  that  and  the  lateral  ventricles.  It  also  forms  the 
choroid  tela  of  the  floor  of  the  fourth  ventricle,  likewise  connected 
with  its  choroid  plexuses.  Investing  the  cerebral  crura,  the  pons,  and 
the  oblongata,  it  is  less  vascular  and  is  of  a  more  fibrous  and  dense 
character.  From  the  inner  surface  its  finest  vessels  everywhere  perpen- 
dicularly penetrate  the  substance  of  the  brain,  and  at  the  base  groups 
of  long  vessels  from  the  pia  produce  the  anterior  and  posterior  per- 
forated spaces. 

1  F.  cerebelli  or  minor. 


772  THE   NERVOUS   SYSTEM. 

Nerves  to  the  pia,  destined  to  its  numerous  vessels,  are  probably 
derived  from  the  sympathetic  and  from  all  of  those  of  the  brain,  except 
the  nerves  of  special  sense  and  the  hypoglossal. 

The  arachnoid *  is  a  delicate  and  mostly  transparent  membrane, 
which  is  attached  to  the  pia  by  loose  areolar  tissue  or  by  thin  bands 
and  laminae,  leaving  between  the  membranes  an  interval,  the  sub- 
arachnoid  space,  filled  with  a  clear  liquid,  the  cerebro-spinal  fluid. 
It  is  free  from  the  dura,  from  which  it  is  separated  by  the  subdural 
space,  occupied  also  by  a  small  portion  of  liquid.  On  the  surface  of 
the  hemispheres  of  the  cerebrum  and  cerebellum  it  passes  over  the 
convolutions  and  ridges  without  dipping  into  the  fissures  between 
them.  At  the  base  of  the  brain  it  is  thicker  and  towards  the  centre 
is  less  transparent  and  whitish. 

The  subarachnoid  space  for  the  most  part  over  the  surface  of  the 
hemispheres  of  the  cerebrum  and  cerebellum  is  a  narrow  interval,  but 
at  the  base  of  the  brain  in  several  positions  forms  considerable  inter- 
spaces. One 2  of  these  extends  from  the  fore  part  of  the  oblongata  over 
the  front  of  the  pons  and  intercrural  recess  to  the  optic  commissure 
and  laterally  between  the  temporal  lobes,  and  another3  between  the 
lower  part  of  the  hemispheres  of  the  cerebellum  and  the  back  of  the 
oblongata.  With  the  latter  space  the  ventricles  of  the  brain  communi- 
cate through  the  openings  of  the  choroid  tela  of  the  fourth  ventricle. 

The  arachnoid  is  composed  of  an  intertexture  of  bands  of  fibro- 
connective  tissue  laminated ;  the  subarachnoid  tissue  of  more  delicate 
bundles  of  the  same  material.  The  free  surface  of  the  membrane  is 
covered  with  a  pavement  endothelium ;  the  subarachnoid  space  is  like- 
wise lined  throughout  in  the  same  manner.  The  blood-vessels  are 
comparatively  few,  and  its  nerves  are  derived  from  the  fifth,  seventh, 
and  eleventh. 

The  cerebro-spinal  fluid,  filling  the  ventricles  and  subarachnoid 
space  of  the  brain,  is  a  limpid  liquid  with  a  salty  taste  and  a  slightly 
alkaline  reaction.  It  consists  of  98.5  per  cent,  of  water  and  1.5  per 
cent,  of  animal  and  saline  matters. 

Pacchionian  bodies.  Commonly  there  are  found  attached  to  the 
outer  surface  of  the  dura  along  the  superior  longitudinal  sinus,  whitish, 
granular  bodies,  often  in  clusters,  and  when  large  received  into  pits  on 
the  inner  surface  of  the  cranial  vault.  They  are  also  found  in  the  same 
position  on  the  inner  surface  of  the  dura  and  likewise  projecting  from 
the  latter  into  the  longitudinal  sinus  and  further,  on  the  pia  at  the 
margins  of  the  cerebral  hemispheres.  Less  frequently  these  bodies 
are  found  in  other  positions  of  the  brain.  They  are  known  as  the 
glands  or  bodies  of  Pacchioni.4  They  are  enlarged  villi  of  the 


1  Tunica  arachnoidea.  2  Anterior  subarachnoid  space. 

3  Posterior  subarachnoid  space. 

4  Glandulae  Pacchioni ;  cerebral  granulations. 


THE   NERVOUS   SYSTEM.  773 

arachnoid  normally  existing  in  the  same  position.  In  their  growth 
they  perforate  the  dura  and  by  further  enlargement  cause  absorption 
of  the  contiguous  portion  of  the  skull.  They  do  not  exist  in  early 
infancy,  but  usually  appear  after  seven  years  and  are  disposed  to 
increase  with  the  advance  of  age.  Occasionally  they  are  absent. 

MEMBKANES   OF   THE   SPINAL   COED. 

The  dura1  of  the  spinal  cord  is  continuous  with  that  of  the  brain, 
but,  unlike  it,  consists  of  a  single  layer  which  is  independent  of  the 
periosteum.  It  is  tightly  attached  around  the  occipital  foramen  and 
thence  envelops  the  cord  and  roots  of  the  spinal  nerves  in  a  capacious 
sheath,  which  is  separated  from  the  walls  of  the  spinal  canal  by  loose 
areolar  tissue  with  fat  and  the  spinal  plexus  of  veins.  It  is  widest  in 
the  cervical  and  lumbar  regions,  narrower  in  the  thoracic  region,  and 
tapers  away  in  the  sacral  canal,  ending  in  a  slender  solid  string  which 
is  attached  to  the  back  of  the  coccyx.  In  the  sheath  near  the  inter- 
vertebral  and  sacral  foramina  is  a  pair  of  apertures  close  together  for 
the  passage  of  the  corresponding  roots  of  a  spinal  nerve,  which  are 
then  together  enclosed  in  a  tubular  prolongation  of  the  dura,  fixed  to 
the  intervertebral  or  sacral  foramen,  and  becoming  continuous  with 
the  nerve-sheath. 

Unlike  that  of  the  brain,  the  spinal  dura  is  moderately  elastic.  It 
is  thicker  behind  than  in  front,  and  is  composed  of  bands  of  fibro- 
connective  tissue,  with  elastic  fibres,  for  the  most  part,  arranged  longi- 
tudinally. The  interior  smooth  surface  is  lined  by  a  simple  pavement 
endothelium,  and  such  is  likewise  the  case  with  the  outer  surface.  The 
spinal  dura  is  supplied  by  the  meningeal  branches  of  the  spinal  arteries. 
Its  veins  terminate  in  the  plexus  of  spinal  veins.  Nerves  have  been 
traced  into  it. 

The  pia2  of  the  spinal  cord  is  a  thicker,  denser,  and  less  vascular 
membrane  than  that  of  the  brain,  with  which  it  is  continuous  and 
corresponds  in  general  anatomical  and  physiological  character.  It  is 
closely  adherent  to  the  subjacent  nerve-substance  of  the  cord  and  gives 
a  fold  into  the  anterior  median  fissure  and  a  delicate  partition  into 
the  posterior  median  fissure.  It  gives  a  sheath  to  each  of  the  threads 
or  rootlets  of  the  spinal  nerve-roots,  subsequently  continuous  with  the 
connective-tissue  sheath  of  the  nerves.  From  the  lower  end  of  the 
cord  it  is  continued  as  a  long  slender  thread,  the  terminal  filum,3 
which  descends  in  the  centre  of  the  bunch  of  nerves  forming  the  cauda 
equina  to  the  end  of  the  dural  sheath,  which  it  joins. 

In  front  the  pia  is  thickened  by  a  glistening,  white,  longitudinal, 
fibrous  band,  the  splendid  line.4 


1  Dura  mater.  2  Pia  mater. 

3  Filum  terminate ;  nervus  impar.  *  Linea  splendens  Halleri. 


774  THE   NERVOUS   SYSTEM. 

From  each  side  of  the  pial  sheath  extends  the  denticulate  liga- 
ment,1 a  narrow,  translucent,  fibrous  band  directed  outward  in  the 
subarachnoid  space  and  forming  a  partial  partition  between  the  an- 
terior and  posterior  roots  of  the  spinal  nerves.  Its  inner  border  is 
continuous  with  the  pial  sheath  of  the  cord ;  its  outer  border  is  divided 
by  wide  festooned  notches  into  angular  points,  which  are  fixed  at  their 
end  to  the  inside  of  the  dural  sheath.  There  are  about  twenty  of  the 
points,  of  which  the  first  is  fixed  to  the  dura  opposite  the  occipital 
foramen  between  the  hypoglossal  nerve  and  the  vertebral  artery ;  the 
others  alternate  in  position  with  the  roots  of  the  spinal  nerves.  At 
the  lower  end  of  the  cord  the  ligament  is  continuous  with  the  terminal 
filum,  which  may  be  regarded  as  its  last  point. 

The  pia  is  composed  of  fibro-connective-tissue  bundles  with  elastic 
fibres,  mostly  arranged  longitudinally,  includes  an  intricate  plexus  of 
blood-vessels  formed  by  the  numerous  spinal  arteries  and  veins,  and 
finally  gives  off  from  its  interior  surface  multitudes  of  fine  vessels 
which  penetrate  the  substance  of  the  cord.  The  denticulate  ligament 
is  also  composed  of  connective  tissue  with  elastic  fibres.  The  exterior 
surface  of  the  pia  and  of  the  denticulate  ligaments,  corresponding  with 
the  subarachnoid  space,  is  invested  with  a  simple  pavement  endothe- 
lium,  and  such  likewise  is  the  case  with  the  surface  next  the  cord. 
The  spinal  pia  is  supplied  with  nerves  from  the  sympathetic  pursuing 
the  course  of  the  blood-vessels. 

The  spinal  arachnoid2  is  a  delicate,  translucent,  whitish  membrane 
continuous  with  that  of  the  brain  and  holding  the  same  relative  position 
with  the  cord.  It  is  loosely  attached  to  the  pia  and  cauda  equina,  with 
a  large  intervening  subarachnoid  space  filled  with  the  cerebro-spinal 
fluid,3  and  is  in  contact  by  its  free  surface  with  the  inner  surface  of  the 
dural  sheath ;  the  subdural  space  being  occupied  by  a  small  quantity  of 
liquid.  The  arachnoid  is  connected  with  the  pia  by  threads  and  slender 
bands  of  fibro-connective  tissue  and  at  the  back  of  the  cord  by  a  thin 
median  partition,  most  complete  in  the  cervical  region  but  imperfect 
and  cribriform  below.  Through  the  subarachnoid  space  laterally  ex- 
tend the  roots  of  the  spinal  nerves  and  the  points  of  the  denticulate 
ligament  enclosed  in  funnel-like  prolongations  of  the  arachnoid. 

The  arachnoid  is  composed  of  fibro-connective  tissue  mostly  arranged 
longitudinally,  and  is  covered  on  the  free  surface  by  a  pavement  endo- 
thelium,  which  likewise  lines  the  subarachnoid  space  throughout. 

The  spinal  subarachnoid  space  is  continuous  with  that  of  the  brain 
and  its  ventricles  through  the  openings  of  the  choroid  tela  of  the  fourth 
ventricle. 

The  spinal  cord  within  its  capacious  dural  sheath  maintains  its 
central  position,  bathed  in  the  cerebro-spinal  fluid  of  the  subarachnoid 


1  Ligaraentum  denticulatum  ;  1.  serratum. 

2  Tunica  arachnoidea.  8  Cephalo-rachidian  fluid. 


THE   NERVOUS   SYSTEM. 


775 


FIG.  394. 


space,  through  its  connection  with  the  brain  above,  through  the  roots 
of  the  spinal  nerves  and  denticulate  ligaments  laterally  with  the  dural 
sheath,  and  below  through  the  terminal  filum  with  the  sheath. 

BLOOD-VESSELS   OF   THE   CEREBKO-SPINAL   AXIS. 

The  brain  and  spinal  cord  are  highly  vascular,  though  no  conspicu- 
ously large  blood-vessels  enter  them  to  be  distributed  to  their  struc- 
ture. Their  many  large  arteries  derived  from  the  internal  carotids 
and  vertebrals  first  ramify  throughout  the  pia,  forming  a  wide-spread 
plexus,  from  which  a  multitude  of  arterioles  directly  penetrate  and  are 
distributed  to  the  nervous  substance. 

In  the  spinal  cord,  numerous  arterioles  form  the  anterior  spinal 
artery  in  the  pia  of  the  anterior  median  fissure,  enter  the  anterior 
commissure  and  divide  each  into  a  right  and  left  branch,  which  anasto- 
mose with  the  corresponding  ones  above  and  below  and  proceed  to  the 
base  of  the  anterior  gray  cornua  in  which  they  are  distributed.  Other 
fine  arterioles  in  the  posterior  median  fissure  penetrate  the  gray  com- 
missure, and  give  branches  to 
the  posterior  white  columns 
and  to  the  posterior  gangli- 
onic  tracts.1  Arterioles  also 
enter  with  the  spinal  nerve- 
roots  and  follotf  them  to  the 
corresponding  gray  cornua  in 
which  they  are  distributed. 
A  number  also  radially  pene- 
trate the  white  columns  to 
which  some  are  distributed, 
while  others  continue  to  the 
central  gray  matter,  where 
they  anastomose  with  those 
entering  the  cornua.  The 
veins  pursue  the  course  of  the 
arterioles,  and  among  them 
is  a  longitudinal  vein,  on  each 
side  of  the  central  canal,  ac- 
companying the  correspond- 
ing anastomotic  arteries. 

At  the  base  of  the  brain, 
from  the  cerebral  arteries 
spring  half  a  dozen  groups 
of  arterioles,  which  ascend  to 
supply  the  central  ganglia  or  accumulations  of  gray  matter  in  the 
cerebral  hemispheres  and  are  named  from  their  relative  position. 


— 10 


HORIZONTAL  SECTION  OF  THE  SPINAL  CORD,  SHOWING 
THE  GENERAL  MODE  OF  DISTRIBUTION  OF  THE  ARTERIES : 
magnified.  1,  anterior"  median  fissure  ;  2,  posterior 
median  fissure ;  3,  anterior  column ;  4,  lateral  column  ; 
5,  posterior  lateral  column ;  6,  posterior  median  col- 
umn ;  7,  anterior  rootlets  of  a  spinal  nerve ;  8,  posterior 
rootlet ;  9,  anterior  gray  column  or  cornu ;  10,  posterior 
cornu;  11,  intermedio-lateral  tract;  12,  posterior  gan- 
glionic  tract;  13,  gray  commissure ;  14,  anterior  com- 
missure. 


1  Clarke's  column. 


776 


THE    NERVOUS   SYSTEM. 


The  antero-median  group  spring  from  the  lower  part  of  the 
anterior  cerebral  arteries  and  their  communicating  artery  and  pene- 
trate the  contiguous  part  of  the  cerebrum  to  supply  the  fore  part  of 
the  striatum. 

The  antero-lateral  group,  on  each  side,  spring  from  the  middle 
cerebral  artery  and  thence  ascend  through  the  anterior  perforated 
space  to  supply  the  striatum  and  fore  part  of  the  thalamus.  A  branch, 
named  the  lenticulo-striate  artery,1  to  the  outer  part  of  the  len- 
ticular nucleus  and  striatum,  is  said  to  be  a  frequent  source  of  hemor- 
rhage of  the  brain. 

The  postero-median  group  spring  from  the  commencement  of 
the  posterior  cerebral  arteries  and  ascend  in  the  posterior  perforated 
space  to  supply  the  walls  of  the  third  ventricle. 

The  postero-lateral  group,  on  each  side,  come  from  the  posterior 
cerebral  artery  after  turning  round  the  cerebral  crus,  which  it  partly 
supplies,  together  with  the  back  of  the  thalamus  and  the  geniculate 
and  quadrigeminal  bodies. 

In  the  further  course  and  distribution  of  the  cerebral  arteries  in 
the  pia,  the  terminal  branches  or  arterioles  penetrate  the  subjacent 
cortex  of  the  cerebral  convolutions. 

The  anterior  cerebral  artery  supplies  the  superior  and  the  fore  part 

of  the  middle  frontal  convolu- 
tions, the  upper  part  of  the 
anterior  central  convolution,  the 
lower  part  of  the  frontal  lobe 
outside  the  olfactory  fissure,  the 
fornicate  convolution,  the  quad- 
rate lobule,  and  the  callosum. 

The  middle  cerebral  artery, 
most  extensive  of  the  three, 
supplies  the  inferior  and  the 
posterior  part  of  the  middle 
frontal  convolutions,  the  lower 
part  of  the  anterior  central  con- 
volution, those  of  the  central 
and  parietal  lobes,  and  the  supe- 
rior and  upper  lateral  part  of 
the  temporal  lobe. 

The  posterior  cerebral  artery 
supplies  the  lower  part  of  the 
temporal  lobe,  including  the  hip- 
pocampal  convolution,  the  cune- 
ate  lobule,  and  the  convolutions  of  the  occipital  lobe. 

In  the  final  distribution  of  the  cerebral  arteries  from  the  pia  a  pro- 


SECTION  ACROSS  A  CEREBRAL  CONVOLUTION,  EX- 
HIBITING THE   ARTERIAL   ARRANGEMENT.       1,  the 

gray  cortex ;  2,  interior  white  matter ;  3,  medul- 
lary arteries  penetrating  the  cortex  to  the  white 
matter;  4,  cortical  arteries  distributed  to  the 
cortex. 


Artery  of  cerebral  hemorrhage. 


THE   NERVOUS  SYSTEM. 


777 


15 


fusion  of  distinct  thread-like  arterioles  leave  the  under  surface  of  the 
membrane  and  penetrate  the  surface  of  the  subjacent  convolutions. 
Those  at  the  summit  enter  perpendicularly,  at  the  sides  in  the  inter- 
vening fissures  obliquely,  and  at  the  bottom  less  so.  Of  the  entering 
vessels  the  more  numerous,  finer,  and  shorter  cortical  branches  are 
distributed  in  the  gray  cortex;  while  the  fewer,  larger,  and  longer 
medullary  branches  pass 
into  the  white  substance,  in 
which  they  continue  some 
distance  and  end  in  a  delicate 
capillary  plexus.  The  two 
systems  of  vessels,  those  en- 
tering from  the  convolutions 
and  those  from  the  base  of 
the  brain  to  the  central  gan- 
glia, have  little  or  no  com- 
munication through  anasto- 
mosis. 

The  central  white  matter 
of  the  cerebral  hemispheres 
is  much  less  vascular  than 
the  cortical  gray  substance, 
and  of  this  the  intermediate 
layer  is  most  abundantly  sup- 
plied with  capillaries. 

The  cerebellar  arteries  in 
their  ramification  and  for- 
mation of  a  wide-expanded 
plexus  in  the  pia  investing 
the  cerebellum  and  in  their 
final  distribution  to  it  con- 
form to  the  cerebral  arteries. 

The  oblongata  and  pons 
are  supplied  by  the  anterior 
spinal,  vertebrals,  basilar. 
and  posterior  cerebral  ar- 
teries. In  their  final  distri- 
bution from  the  pia  many  of  the  chief  arterioles  enter  and  follow  the 
course  of  the  nerve-roots.  In  the  oblongata  others  enter  the  anterior 
median  fissure  and  between  its  different  columns,  supplying  them  with 
branches  and  converging  to  the  gray  matter  in  the  floor  of  the  fourth 
ventricle. 

While  the  chief  arteries  of  the  brain  are  distributed  from  its  base 
upward  in  the  pia,  the  chief  veins  in  general  pursue  a  reverse  course ; 
the  larger  cerebral  veins  ascending  and  ending  in  the  superior  longi- 
tudinal sinus,  while  the  internal  cerebral  veins  from  the  lateral  and 


2          3  1 

HORIZONTAL  SECTION  OF  THE  OBLONGATA  ,  SHOWING  THE 
DISTRIBUTION  OF  THE  ARTERIES.  1,  artery  entering  the 
median  fissure  and  raph6 :  2,  pyramid  ;  3,  arciform  nu- 
cleus; 4,  olive;  5,  olivary  nucleus;  6,  arciform  fibres; 
7,  reticular  formation ;  8,  accessory  olivary  nucleus ;  9, 
lateral  nuclei ;  10,  11,  arciform  fibres  of  the  restiform 
body ;  12,  gelatinosa  nucleus ;  13,  ascending  root  of  the 
trifacial  nerve ;  14,  longitudinal  bundle  of  nerve-fibres ; 
15,  facial  nucleus  in  th<^  terete  funicle ;  16,  external 
facial  nucleus ;  17,  inferior  portion  of  the  auditory  nu- 
cleus ;  18,  vagus  nucleus ;  19,  20,  hypoglossal  nuclei ; 
21,  vagus  nerve ;  22,  hypoglossal  nerve.  The  black 
branching  lines  represent  the  chief  arteries. 


778  THE   NERVOUS  SYSTEM. 

third  ventricles  run  backward  and  unite  in  the  vein  of  Galen,  which 
ends  in  the  straight  sinus. 

The  lymphatics  of  the  brain  and  spinal  cord  appear  to  originate  in 
perivascular  spaces  of  the  blood-vessels  in  the  nerve-substance,  and 
these  communicate  with  lymphatic  spaces  of  the  pia  and  with  the 
subarachnoid  space. 

THE  NERVES  OF  THE  BRAIN. 

The  nerves  of  the  brain,  or  cerebral  nerves,  are  commonly 
numbered  as  twelve  pairs,  are  named  numerically  and  also  from  their 
function  and  distribution.  As  they  proceed  from  the  brain,  in  succes- 
sion from  before  backward  they  are  as  follows : 

1st,  or  olfactory  nerves,  7th,  or  facial  nerves, 

2d,  or  optic  nerves,  8th,  or  auditory  nerves. 

3d,  or  oculo-motor  nerves,  9th,  or  glosso-pharyngeal  nerves, 

4th,  or  pathetic  nerves,  10th,  or  vagus  nerves, 

5th,  or  trifacial  nerves,  llth,  or  accessory  nerves, 

6th,  or  abducent  nerves,  12th,  or  hypoglossal  nerves. 

ORIGIN  OF   THE   CEREBRAL   NERVES. 

All  the  cerebral  nerves  make  their  appearance  at  some  part  of  the 
surface  of  the  brain,  and  this  is  distinguished  as  their  superficial  or 
apparent  origin,  but  their  fibres  or  roots  may  be  traced  more  or  less 
deeply  into  the  substance  of  the  brain,  where  they  appear  to  be  con- 
nected with  nuclei  of  gray  matter,  and  this  is  regarded  as  their  deep 
or  true  origin. 

The  first,  or  olfactory  nerve,1  as  commonly  named,  is  not  a  nerve 
in  the  sense  of  the  rest  of  the  series,  but  is  really  one  of  the  divisions 
of  the  brain,  the  olfactory  lobe,  as  described  on  page  745. 

The  olfactory  lobes  of  man  are  relatively  very  small  compared  with 
their  condition  in  other  animals  of  his  class,  and  in  fishes  especially 
they  appear  as  conspicuous  divisions  of  the  brain. 

The  second,  or  optic  nerve,2  one  of  the  largest  of  those  of  the 
brain  in  its  origin  from  the  optic  tract,  has  been  described  on  page  760. 

The  third,  or  oculo-motor  nerve,3  much  smaller  than  the  pre- 
ceding, is  of  considerable  size.  It  springs  from  a  nucleus  of  large 
pigmented  cells  embedded  in  the  gray  matter  at  the  side  of  the  floor 
of  the  ventricular  aqueduct,  beneath  the  quadrigeminal  body,  whence 
it  proceeds  through  the  tegmentum  and  locus  niger  and  emerges  from 
the  inner  side  of  the  cerebral  crus,  between  the  tegmentum  and  crusta, 
in  from  nine  to  twelve  filaments  or  slender  bundles,  which  speedily 


1  N.  olfactorius ;  tractus  olfactorius.  2  N.  opticus. 

3  N.  oculo-motorius  ;  n.  oculo-muscularis  communis. 


THE    NERVOUS   SYSTEM.  779 

unite  in  a  rounded  cord.  Not  unfrequently  one  of  the  filaments  is 
separated  from  the  rest  and  issues  from  the  crus  in  advance. 

The  fourth,  or  trochlear  nerve,1  the  smallest  of  those  of  the  brain, 
springs  from  a  nucleus  of  large  nerve-cells  situated  immediately  below 
that  of  the  third  nerve  in  the  gray  matter  of  the  floor  of  the  ventricular 
aqueduct.  Thence  it  turns  upward  and  inward  above  the  aqueduct  and 
enters  the  anterior  velum,  in  which  it  partially  decussates  with  its 
fellow  and  emerges  on  the  opposite  side  near  the  median  line,  just  below 
the  quadrigeminal  body. 

The  fifth,  or  trifacial  nerve,2  is  the  largest  of  those  of  the  brain 
and  in  several  points  resembles  the  spinal  nerves.  It  arises  by  two 
roots,  of  which  the  smaller  is  motor  in  function  and  the  larger  is 
sensory.  Each  root  also  originates  in  two  chief  portions  which  pro- 
ceed from  diiferent  nuclei,  distinguished  as  motor  and  sensory.  In  the 
small,  motor  root,  one  portion  comes  from  a  nucleus  of  large  multipolar 
cells  situated  just  below  the  lateral  angle  of  the  fourth  ventricle,  thence 
proceeds  forward  and  outward  in  the  pons,  joined  by  the  other  portion, 
which  descends  from  a  nucleus  of  large  cells  embedded  in  the  gray 
matter  at  the  side  of  the  ventricular  aqueduct.  In  the  large,  sensory 
root,  one  portion  comes  from  a  nucleus  of  small  nerve-cells  lying  to 
the  outer  side  of  the  lower  motor  nucleus  and  is  joined  by  the  other 
portion,  which  ascends  from  the  gelatinosa  prolonged  upward  from  the 
cuneate  eminence.3  The  roots  proceed  together  through  the  pons  to 
emerge  from  the  side,  separated  by  a  few  of  its  transverse  fibres.4 

The  sixth,  or  abducent  nerve,5  arises  from  a  nucleus  in  the  terete 
funicle  of  the  fourth  ventricle,  in  advance  of  the  medullary  striae, 
whence  it  proceeds  outward  and  downward  through  the  pons  to  emerge 
between  its  lower  border  and  the  top  of  the  pyramid  of  the  oblongata. 

The  seventh,  or  facial  nerve,6  has  its  origin  in  the  facial  nucleus 
of  the  reticular  formation  at  the  back  of  the  pons.  The  upper  end  of 
the  nucleus  is  close  to  the  motor  nucleus,  of  the  fifth  nerve  and  its 
lower  end  near  an  accumulation  of  gray  matter  of  the  oblongata 
named  the  ambiguous  nucleus.7  The  fibres  of  the  nerve-root  pass 
backward  from  the  nucleus  and  collect  into  a  compact  bundle,  which 
turns  up  in  the  terete  funicle,  then  outward  and  forward  around  the 
nucleus  of  the  sixth  nerve  and  passes  through  the  pons  to  emerge  from 
the  oblongata  in  the  interval  of  the  olive  and  restiform  body.  Close 
to  the  emerging  nerve  on  the  outer  side  is  the  auditory  nerve,  and 
between  them  lies  a  filament,  the  intermediate  portion,8  which  is 
commonly  connected  with  both  nerves. 


1  N.  patheticus  or  trochlearis  ;  n.  oculo-muscularis  superior. 

2  N.  quintus,  trifacialis,  or  trigeminus. 

3  Tubercle  of  Kolando.  *  Lingula  Wrisbergii.  5  N.  abducens. 

6  N.  facialis  ;  n.  communicans  faciei ;  portio  dura  of  the  seventh  nerve  of  Willis. 

7  N".  ambiguus.  8  Pars  intermedia. 


780  THE   NERVOUS   SYSTEM. 

The  eighth,  or  auditory  nerve,1  arises  by  two  principal  roots  from 
the  auditory  nuclei  of  the  floor  of  the  fourth  ventricle.  (See  page  725.) 
The  superior  root  springs  from  the  external  auditory  nucleus,  in- 
cluding fibres  from  within  it  traceable  to  the  cerebellum.  The  inferior 
root  arises  from  the  internal  auditory  nucleus  and  is  reinforced  by 
the  auditory  striae  of  the  fourth  ventricle.  Both  roots  from  their  origin 
proceed  outward  and  unite  in  a  common  trunk,  which  turns  around  the 
restiform  body  at  the  lower  border  of  the  pons,  to  the  outer  side  of  the 
facial  nerve. 

The  ninth,  or  glosso-pharyngeal  nerve,2  arises  from  the  glosso- 
pharyngeal  nucleus,  which  occupies  the  cinereous  eminence  in  the  floor 
of  the  fourth  ventricle.  The  fibres  of  the  nerve  pass  outward  and 
forward  through  the  oblongata  and  emerge  in  a  series  of  five  or  six 
rootlets,  in  the  furrow  between  the  olive  and  restiform  body  immedi- 
ately below  the  auditory  nerve. 

The  tenth,  vagus,  or  pneumogastric  nerve,3  arises  from  the 
vagal  nucleus,  which  is  continuous  above  with  that  of  the  glosso- 
pharyngeal  nerve  and  is  extended  below  as  the  accessory  nucleus. 
The  fibres  of  the  nerve  proceed  through  the  oblongata  in  the  same 
direction  as  those  of  the  ninth  nerve  and  emerge  below  in  from  ten 
to  fifteen  rootlets,  from  the  same  furrow. 

The  eleventh,  or  accessory  nerve,4  has  its  origin  in  part  from 
the  oblongata  in  the  downward  extension  of  the  vagal  nucleus,  but  in 
greater  part  from  the  cervical  portion  of  the  spinal  cord  in  the  inter- 
medio-lateral  tract  and  in  the  adjacent  part  below  of  the  anterior  cornu, 
and  above  in  the  reticular  formation  and  base  of  the  posterior  cornu. 
The  smaller  portion  emerges  from  the  oblongata  in  a  series  of  four 
or  five  rootlets  immediately  below  and  in  the  same  line  as  the  vagus 
nerve;  while  the  larger  spinal  portion  emerges  through  the  lateral 
column  of  the  spinal  cord  in  five  or  six  rootlets,  which  successively 
unite  in  a  trunk  ascending  from  the  spinal  canal  through  the  occipital 
foramen,  where  the  two  portions  conjoin  in  a  common  trunk. 

The  twelfth,  or  hypoglossal  nerve,5  arises  from  the  hypoglossal 
nucleus,  a  column  of  large,  multipolar  nerve-cells,  which  extends  from 
within  the  lower  part  of  the  terete  funicle  of  the  fourth  ventricle 
downward  at  the  side  of  the  central  canal  in  the  lower  part  of  the 
oblongata.  From  the  nucleus  spring  numerous  nerve-fibres,  which 
pass  outward  and  forward  in  the  oblongata  and  emerge  in  from  ten  to 
fifteen  rootlets,  from  the  furrow  between  the  pyramid  and  olive. 

1  N.  auditorius  or  acusticus ;  acoustic  nerve ;  portio  mollis  of  the  seventh  nerve 
of  Willis. 

2  N.  glosso-pharyngeus ;  part  of  the  eighth  nerve  of  Willis. 

3  N.  vagus  ;  n.  pneumogastricus ;  part  of  the  eighth  nerve  of  Willis. 

4  N.  accessorius ;  spinal  accessory  nerve ;  part  of  the  eighth  nerve  of  Willis. 

5  N.  hypoglossus  ;  ninth  nerve  of  Willis. 


THE   NERVOUS   SYSTEM. 


781 


DISTRIBUTION   OF  THE   NEKVES   OF  THE   BEAIN. 

I.     OLFACTORY   NERVES. 
The  first,  or  olfactory  nerve,  is  described  with  the  nose. 

II.     OPTIC   NERVES. 
The  second,  or  optic  nerve,  is  described  with  the  eye. 

III.     OCULO-MOTOR   NERVES. 
The  third,  or  oculo-motor  nerve,1  of  medium  size  among  those 


of  the  brain,  makes  its  appearance 
at  the  base  in  the  intercrural  re- 
cess, where  it  emerges  from  the 
side  of  the  cerebral  crus  in  slender 
bundles  of  fibres,  which  unite  in  a 
firm,  rounded  trunk.  Proceeding 
forward  between  the  posterior 
cerebral  and  superior  cerebellar 
arteries  to  the  outer  side  of  the 
posterior  clinoid  process,  it  passes 
through  an  aperture  of  the  dura 
and  runs  through  the  outer  wall 
of  the  cavernous  sinus  to  the  sphe- 
noidal  foramen.  Here  it  divides 
into  two  branches,  which  enter  the 
orbit  between  the  heads  of  the 
external  rectus  muscle  and  are 
separated  by  the  nasal  branch  of 
the  ophthalmic  nerve. 

The  superior  branch,  smaller, 
runs  inward  above  the  optic  nerve 
to  the  superior  rectus  and  palpe- 
bral  elevator  muscles. 

The  inferior  branch  divides 
into  three,  which  run  to  the  in- 


FIG.  397. 


OCULO-MOTOR  AND  ABDUCENT  NEKVE,  the 
upper  part  of  the  right  orbit  removed.  1,  oculo- 
motor nerve ;  2,  3,  branch  to  the  superior  rectus 
and  palpebral  elevator  muscles ;  4,  5,  branches 
to  the  internal  and  inferior  recti  muscles;  6, 
branch  to  the  inferior  oblique  muscle ;  7,  branch 
from  the  latter  to  the  ophthalmic  ganglion ;  8, 
abducent  nerve  to  the  external  rectus  muscle ; 
9,  communicating  filaments  between  the  ab- 
ducent nerve  and  the  carotid  plexus  of  the 
sympathetic.  To  their  outer  side  is  the  tri- 
facial  nerve.  10,  ciliary  nerves  perforating  the 
sclerotica  and  passing  forward  between  it  and 
the  choroidea  to  the  ciliary  muscle  and  iris. 


ferior  and  internal  recti  and  infe- 
rior oblique  muscles.     The  branch 

to  the  last  muscle  gives  off  a  short,  thick  one  to  the  ophthalmic  gan- 
glion, forming  its  inferior  or  short  root. 

The  branches  to  the  recti  and  palpebral  elevator  muscles  enter  in 
diverging  twigs  on  the  surface  directed  towards  the  eyeball,  while  that 
to  the  inferior  oblique  muscle  enters  its  back  border.  The  name  indi- 
cates the  function  of  the  oculo-motor  nerve. 


1  N.  oculo-motorius ;  common  motor  nerve  of  the  eyeball. 


782  THE   NERVOUS    SYSTEM. 


IV.     TKOCHLEAE  NERVES. 

The  fourth,  or  trochlear  nerve,1  the  smallest  of  those  of  the 
brain,  pursues  the  longest  course  within  the  cavity  of  the  cranium. 
From  its  superficial  origin  in  the  anterior  velum,  immediately  behind 
the  quadrigeminal  body,  it  turns  outward  across  the  superior  cerebellar 
peduncle,  thence  forward  round  the  outer  side  of  the  cerebral  crus. 
Lying  between  and  parallel  to  the  posterior  cerebral  and  superior  cere- 
bellar arteries,  it  passes  through  an  aperture  of  the  dura,  just  below 
the  free  edge  of  the  tentorium  a  little  behind  the  posterior  clinoid 
process,  and  runs  through  the  outer  wall  of  the  cavernous  sinus  to  the 
inner  extremity  of  the  sphenoidal  foramen.  Entering  the  orbit  above 
the  external  rectus,  it  proceeds  inward  over  the  palpebral  elevator  to 
the  trochlear  muscle,  which  it  enters  at  the  outer  part  of  its  upper 
surface.  In  its  course  through  the  cavernous  sinus  it  lies  on  the  oph- 
thalmic nerve,  crosses  the  oculo-motor  nerve  from  the  outer  side  below 
upward,  and  is  connected  by  filaments  with  the  ophthalmic  and  sym- 
pathetic nerves.  The  trochlear  is  a  purely  motor  nerve. 

V.     TKIFACIAL   NERVES. 

The  fifth,  or  trifacial  nerve,2  the  largest  of  those  of  the  brain, 
resembles  the  spinal  nerves  in  that  it  has  a  sensory  and  a  motor  root 
and  the  former  is  provided  with  a  ganglion.  Of  the  two  roots  which 
appear  at  the  side  of  the  pons,  the  small,  or  motor  root,3  emerges 
above  the  large,  or  sensory  root,4  and  both  together  are  directed 
forward  beneath  the  anterior  extremity  of  the  tentorium,  where  they 
pass  through  an  elliptical  aperture  of  the  dura  above  the  apex  of  the 
temporal  pyramid.  Here  the  larger  root  expands,  its  bundles  of  fibres 
assume  a  plexiform  arrangement,5  and  in  this  condition  ends  in  the 
semilunar  or  trifacial  ganglion.  The  small  root  inclines  forward  on 
the  inner  side  of  the  large  root,  then  passes  beneath  it  and  the  gan- 
glion, but  withaut  forming  any  connection  with  it. 

The  semilunar  ganglion 6  is  a  flattened,  oval,  somewhat  crescentic 
body  lying  in  the  depression  in  front  of  the  apex  of  the  temporal 
pyramid  attached  to  the  subjacent  periosteum,  but  more  intimately 
adherent  to  the  dura  which  covers  it.  Its  surface  is  striate,  and  on 
the  inner  side  it  is  joined  by  filaments  of  the  contiguous  carotid  plexus 
of  the  sympathetic  nerve.  Its  upper  concave  border  receives  the  large 
root  of  the  trifacial  nerve  and  its  forward  convex  border  gives  off  three 
nerves.  Of  these  the  inner  uppermost  and  smallest,  the  ophthalmic 

1  N.  trochlearis ;  n.  patheticus,  quartus,  or  oculo-muscularis  superior. 

2  N.  trifacialis ;  n.  trigeminus,  trimellus,  quintus,  or  mixtus. 

3  Radix  minor,  superior,  or  anterior. 

4  R.  major,  inferior,  posterior,  or  longior.  5  Plexus  triangularis. 
6  G.  semilunare  ;  g.  Gasseri ;  Gasserian  ganglion. 


THE   NERVOUS   SYSTEM. 


783 


FIG.  398. 


nerve,  proceeds  forward  through  the  sphenoidal  ibramen  into  the 
orbit ;  the  second,  intermediate  in  position  and  size,  the  superior  max- 
illary nerve,  proceeds  for- 
ward from  the  cranial  cavity 
through  the  rotund  foramen. 
The  third,  outermost  and 
largest,  descends  through 
the  oval  foramen  in  com- 
pany with  the  small  root 
and  then  unites  with  it  to 
form  the  inferior  maxillary 
nerve.  Thus  the  first  two 
nerves  proceeding  from  the 
ganglion  are  purely  sensory 
nerves,  while  the  third,  de- 
rived from  the  ganglion,  has 
associated  with  it  the  mo- 
tor root  of  the  trifacial  and 
is  therefore  a  sensory  motor 
nerve. 

OPHTHALMIC    NERVE. 

The  ophthalmic  nerve,1 

the  first  and  smallest  branch 
from  the  semilunar  ganglion 
of  the  fifth,  is  flattened  and 
about  an  inch  long.  It  runs 
forward  in  the  outer  wall  of 
the  cavernous  sinus,  in  com- 
pany with  and  below  the 
third  and  fourth  nerves, 
to  the  sphenoidal  foramen, 
where  it  divides  into  three 
branches,  the  lachrymal, 
frontal,  and  nasal  nerves. 
At  its  commencement  it 
gives  off  a  small  recurrent 

branch2  to  the  tentorium,  and  in  its  further  course  is  connected  by 
filaments  with  the  cavernous  plexus  of  the  sympathetic  and  with  the 
third,  fourth,  and  sixth  nerves. 

The  lachrymal  nerve3  runs  along  the  outer  part  of  the  orbit  above 
the  external  rectus  muscle  to  the  lachrymal  gland  and  upper  eyelid, 
to  which  it  is  distributed.  In  its  course  it  gives  off  a  branch4  which 


TBIFACIAL  NERVE,  the  upper  part  of  the  orbit  and  tem- 
poral fossa  removed.  1,  semilunar  ganglion  ;  2,  ophthal- 
mic nerve ;  3,  lachrymal  nerve ;  4,  frontal  nerve ;  5,  6, 
its  supraorbital  branches ;  7,  supratrochlear  branch ;  8, 
nasal  nerve ;  9,  its  infratrochlear  branch ;  10,  course  of 
the  nasal  nerve  from  the  orbit  into  the  cranium  and 
nose ;  11, 12, 13,  deep  temporal  branches  of  the  inferior 
maxillary  nerve;  14,  commencement  of  the  auriculo- 
temporal  nerve;  15,  superficial  petrosal  nerve;  I, olfac- 
tory nerve ;  II,  optic  nerves ;  III,  oculo-motor  nerve ;  IV, 
trochlear  nerve  to  the  trochlear  muscle  of  the  eye ;  V, 
trifacial  nerve ;  its  small  root  visible  beneath  the  cut 
end  of  the  large  root,  which  ends  in  the  semilunar  gan- 
glion giving  off  three  divisions;  VI,  abducent  nerve; 

VII,  facial,  included  in  a  groove  of  the  auditory  nerve, 

VIII,  both  entering  the  auditory  meatus ;  IX.  glosso- 
pharyngeal ;  X,  vagus,  and  XI,  accessory  nerves  emerg- 
ing at  the  jugular  foramen  ;  XII,  hypoglossal  nerve. 


1  N.  ophthalmicus ;  n.  orbitalis. 

8  N.  lachrymalis ;  n.  lachrymo-palpebralis. 


2  N.  recurrens  ;  n.  tentorii. 
*  Kamus  temporo-malaris. 


784  THE   NERVOUS   SYSTEM. 

joins  the  temporo-malar  branch  of  the  superior  maxillary  nerve,  and  its 
terminal  filaments  anastomose  with  the  facial  nerve. 

The  frontal  nerve,1  the  largest  division  of  the  ophthalmic,  runs 
along  the  roof  of  the  orbit  above  the  palpebral  elevator  and  divides 
into  the  supratrochlear  and  supraorbital  nerves.  The  supratrochlear 
nerve,2  a  small  branch,  after  sending  a  filament  to  join  the  infratroch- 
lear  nerve  leaves  the  orbit  external  to  the  pulley  of  the  trochlear  mus- 
cle and  ascends  to  the  forehead  close  to  the  bone.  It  gives  twigs  to 
the  skin  and  conjunctiva  of  the  upper  eyelid ;  its  terminal  branches 
perforate  the  palpebral  orbicular  and  frontal  muscles  to  be  distributed 
to  the  skin  of  the  forehead.  The  supraorbital  nerve,3  the  main 
branch  of  the  frontal,  passes  from  the  orbit  through  the  supraorbital 
foramen  and  divides  into  two  branches,  which  ascend  beneath  the 
frontal  muscle  to  be  distributed  in  many  slender  filaments  to  the  skin 
of  the  forehead  and  upper  part  of  the  scalp.  The  outer  larger  branch  * 
extends  far  back  over  the  scalp,  the  inner  one5  but  little  beyond  the 
frontal  bone.  The  nerve  also  gives  twigs  to  the  pericranium  and  as  it 
emerges  from  the  orbit  to  the  upper  eyelid. 

The  supraorbital  nerve  often  divides  before  leaving  the  orbit,  when 
the  larger  branch  passes  through  the  supraorbital  foramen  and  the 
smaller  one  passes  from  the  orbit  inwardly  and  sometimes  through  a 
notch  or  foramen. 

The  nasal  nerve 6  enters  the  orbit  between  the  two  heads  of  the  ex- 
ternal rectus  and  the  two  branches  of  the  third  nerve,  proceeds  inward 
beneath  the  upper  muscles  and  over  the  optic  nerve  to  the  anterior 
ethmoidal  foramen.  Through  this  it  reaches  the  cranial  cavity,  runs 
forward  in  a  groove  of  the  ethmoidal  cribriform  plate  and  through  a 
foramen  at  its  fore  part  descends  to  the  nasal  cavity,  where  it  divides 
into  two  branches.  Of  these  the  internal  branch7  is  distributed  to 
the  mucous  membrane  at  the  fore  part  of  the  nasal  partition,  while 
the  external  branch8  descends  in  a  groove  behind  the  nasal  bone,  sup- 
plies the  mucous  membrane  at  the  fore  part  of  the  outer  wall  of  the 
nose,  then  leaves  the  cavity  between  the  nasal  bone  and  nasal  cartilage 
and  is  distributed  to  the  skin  of  the  tip  and  wing  of  the  nose. 

In  its  course  the  nasal  nerve  gives  off  the  following :  a  branch  to 
the  ophthalmic  ganglion,  constituting  its  long  root,  a  slender  fila- 
ment which  runs  forward  on  -the  outer  side  of  the  optic  nerve  and 
enters  the  ganglion  at  its  upper  back  angle.  The  long  ciliary  nerves,9 
usually  two,  sometimes  three  slender  filaments,  which  proceed  to  the 
eyeball  and  pierce  the  back  of  the  sclerotica  and  run  forward  between 
it  and  the  choroidea  to  supply  the  ciliary  muscle  and  iris.  The  infra- 


1  N.  frontalis  ;  n.  supraorbitalis.  2  N.  supratrochlearis. 

3  N.  supraorbitalis.  *  External  frontal  nerve.  5  Internal  frontal  nerve. 

6  N.  nasalis ;  n.  oculo-nasalis  ;  internal  nasal  nerve  ;  n.  nasalis  internus. 

7  N.  anterior  septi.          8  N.  nasalis  extern  us  or  anterior.  9  N.  ciliares  longi. 


THE   NERVOUS   SYSTEM. 


785 


trochlear  nerve l  is  given  from  the  nasal  as  it  is  about  to  enter  the 
anterior  ethmoidal  foramen.  It  proceeds  beneath  the  pulley  of  the 
trochlear  muscle,  is  joined  by  a  filament  from  the  supratrochlear  nerve, 
then  leaves  the  orbit  at  the  inner  corner  of  the  eye  and  is  distributed 
to  the  lachrymal  sac  and  caruncle,  the  conjunctiva,  and  the  skin  of  the 
eyelids  and  root  of  the  nose. 

The  ophthalmic  nerve  is  altogether  sensory  in  function  and  supplies 
the  eyeball,  the  lachrymal  gland,  the  mucous  membrane  of  the  nose 
and  eyelids,  the  skin  of  the  nose,  upper  eyelid,  forehead,  and  scalp. 
It  communicates  with  the  sympathetic,  the  third,  fourth,  sixth,  and 
seventh  nerves. 

OPHTHALMIC    GANGLION. 


FIG.  399. 


Connected  with  the  main  divisions  of  the  trifacial  nerve  are  several 
ganglia,  which,  though  re- 
garded as  more  directly  per- 
taining to  the  sympathetic 
system,  are  conveniently  de- 
scribed with  the  trifacial. 

Within  the  orbit  is  the  oph- 
thalmic ganglion,2  placed  be- 
tween the  optic  nerve  and 
external  rectus  muscle,  em- 
bedded in  areolar  tissue  and 
fat  and  usually  lying  in  con- 
tact with  the  ophthalmic  ar- 
tery. It  is  a  little,  reddish, 
quadrangular  body,  joined  be- 
hind by  branches  from  the 
oculo-motor,  ophthalmic,  and 
sympathetic  nerves,  and  giv- 
ing off  in  front  the  short  cili- 
ary nerves.  Its  communica- 
tion with  the  oculo-motor 
nerve  is  its  short,  or  motor 
root,  a  short,  thick  branch 
from  the  inferior  division  of  that  nerve  joining  the  ganglion  at  its  lower 
back  angle.  The  communication  with  the  ophthalmic  nerve  is  its  long, 
or  sensory  root,  a  slender  filament  from  the  nasal  branch,  joining  the 
upper  back  angle  of  the  ganglion.  The  median,  or  sympathetic 
root,  is  another  slender  filament  from  the  cavernous  plexus  of  the 
sympathetic,  often  joining  the  long  root. 

The  short  ciliary  nerves,8  from  six  to  nine,  come  from  the  front 


8  7    10        4 
OPHTHALMIC  GANGLION — THE  OUTER  PAKT  OF  THE 

EIGHT  ORBIT  REMOVED.     1,  Optic  nefVC  ;  2,  OCUlo-motOF 

nerve ;  3,  branch  to  the  superior  rectus  and  palpebral 
elevator  muscles;  4,  branch  to  the  inferior  oblique 
muscle ;  5,  abducent  nerve  to  the  external  rectus 
muscle;  6,  trifacial  nerve,  its  ganglion  and  three 
principal  branches;  7,  ophthalmic  nerve;  8,  nasal 
nerve ;  9,  ophthalmic  ganglion ;  10,  its  communicating 
branch  with  the  oculo-motor  nerve;  11,  communi- 
cating branch  with  the  ophthalmic  nerve  ;  12,  com- 
municating branch  with  the  cavernous  plexus  of  the 
sympathetic ;  13,  the  ciliary  nerves ;  14,  supraorbital 
nerve. 


1  N.  infratrochlearis  ;  n.  nasalis  externus. 
1  G.  ophthalmicum,  lenticulare,  or  ciliare. 

50 


8  N.  ciliares  breves. 


786  THE   NERVOUS   SYSTEM. 

of  the  ganglion,  usually  in  two  groups  from  the  upper  and  lower 
angles,  thence  proceed  along  the  optic  nerve  above  and  below  and 
divide  into  from  a  dozen  to  twenty  slender  filaments.  The  lower  larger 
bundle  is  joined  by  the  long  ciliary  nerves  from  the  nasal  branch  of  the 
ophthalmic,  and  all  enter  the  back  of  the  eyeball  by  apertures  of  the 
sclerotica  around  the  entrance  of  the  optic  nerve,  whence  they  run  for- 
ward between  the  sclerotica  and  choroidea  to  be  distributed  to  the 
ciliary  muscle,  iris,  and  cornea. 

SUPERIOR    MAXILLARY    NERVE. 

The  superior  maxillary  nerve,1  the  second  branch  of  the  semi- 
lunar  ganglion  of  the  fifth,  intermediate  in  size  and  position  to  the 
others,  runs  forward  and  leaves  the  cranial  cavity  through  the  sphe- 
noidal  rotund  foramen,  thence  crosses  the  upper  part  of  the  spheno- 
maxillary  fossa,  enters  the  infraorbital  canal,2  and  continues  to  the  face. 
In  the  spheno-maxillary  fossa  it  gives  off  the  temporo-malar  and  spheno- 
palatine  nerves. 

The  temporo-malar  nerve,3  a  small  cutaneous  branch,  enters  the 
orbit  through  the  spheno-maxillary  foramen  and  divides  into  two 
branches.  Of  these  the  temporal  branch,4  after  receiving  one  from 
the  lachrymal  nerve,  passes  through  a  foramen  of  the  malar  bone  to 
the  temporal  fossa,  where  it  ascends  beneath  the  temporal  muscle,  per- 
forates it  and  the  temporal  fascia,  and  is  distributed  to  the  skin  at  the 
fore  part  of  the  temple.  The  malar  branch 5  likewise  passes  through 
a  foramen  of  the  malar  bone  to  be  distributed  to  the  cheek.  Both 
branches  anastomose  with  filaments  of  the  facial  nerve. 

The  spheno-palatine  nerves  are  two  short  branches  descending 
to  the  spheno-palatine  ganglion,  which  is  situated  below  the  trunk  of 
the  superior  maxillary  nerve  in  the  spheno-maxillary  fossa. 

In  the  further  part  of  its  course  the  superior  maxillary  nerve  gives 
off  the  dental  nerves,6  which  supply  the  upper  teeth,  the  gum,  and 
the  maxillary  antrum. 

The  posterior  dental  nerve 7  conies  from  the  superior  maxillary 
as  it  is  about  to  enter  the  infraorbital  canal,  and  immediately  divides 
into  two  branches,  which  frequently  also  come  off  separately  from  the 
trunk.  Descending  on  the  maxilla  in  company  with  the  corresponding 
artery,  one  branch  is  distributed  to  the  mucous  membrane  of  the  cheek 
and  gum  and  the  other  branch  enters  the  posterior  dental  canal  and  its 
divisions  to  supply  the  back  teeth  and  maxillary  antrum. 

1  N.  maxillaris  superior. 

2  Infraorbital  nerve,  passing  through  the  canal. 

3  N.  temporo-malaris  ;  n.  orbitalis  ;  n.  suhcutaneus  malse. 
*  Kamus  temporalis.  5  R.  malaris  or  facialis. 

6  Nervi  dentales;  n.  alveolo-dentales. 

7  Post,  superior  dental  nerve ;  n.  alveolaris  sup.  posticus. 


THE   NERVOUS   SYSTEM.  787 

The  anterior  dental  nerve  l  comes  from  the  superior  maxillary  at 
the  fore  part  of  the  infraorbital  canal  and  descends  in  the  corresponding 
dental  canal  of  the  maxilla  to  supply  the  front  teeth  and  contiguous 
part  of  the  antrum. 

Sometimes  there  is  a  middle  dental  nerve,  variable  in  its  origin 
between  the  others  and  supplying  the  intermediate  teeth. 

The  dental  arteries  anastomose2  and  together  form  the  superior 

FIG.  400. 


11 

SUPERIOR  MAXILLARY  NERVE — THE  EXTERNAL  WALL  OF  THE  LEFT  ORBIT  AND  OF  THE  MAXILLA 
REMOVED.  1,  superior  maxillary  nerve  in  its  course  through  the  infraorbital  canal ;  2,  posterior 
dental  nerves ;  3,  middle  dental  nerve ;  4,  anterior  dental  nerve ;  5,  superior  dental  plexus ;  6, 
spheno-palatine  ganglion ;  the  branch  from  the  superior  maxillary  nerve  above  is  the  commence- 
ment of  the  temporo-malar  nerve;  7,  vidian  nerve;  8,  superficial  petrosal  nerve  joining  the 
facial  nerve ;  9,  deep  petrosal  nerve  joining  the  carotid  plexus  of  the  sympathetic ;  10,  abducent 
nerve  and  its  communicating  branches  with  the  latter  plexus ;  11,  superior  cervical  ganglion ;  12, 
ascending  branches  to  the  carotid  plexus;  13,  facial  nerve;  14,  glosso-pharyngeal  nerve;  15,  the 
tympanic  nerve ;  16,  branch  to  the  carotid  plexus ;  17, 18, 19,  branches  to  the  round  and  oval  win- 
dows and  eustachian  tube ;  20,  communicating  branch  of  the  small  petrosal  nerve,  21. 

dental  plexus,  which  occupies  corresponding  canals  of  the  alveolar 
border  and  gives  off  branches  to  the  teeth  and  gum. 

The  superior  maxillary  nerve  finally  emerges  at  the  infraorbital 
foramen  and  breaks  up  into  a  group  of  palpebral,  nasal,  and  labial 
branches. 

The  palpebral  branches,  commonly  an  inner  and  an  outer,  ascend 
to  supply  the  skin  and  conjunctiva  of  the  lower  eyelid. 

The  nasal  branches,  two  or  three,  are  directed  inward  between 
the  fibres  of  the  naso-labial  elevator  to  the"  skin  of  the  nose. 

The  labial  branches,  the  largest  and  three  or  four  in  number, 
descend  between  the  supralabial  and  oral  angle  elevators  and  supply 
the  skin  and  mucous  membrane  of  the  upper  lip  and  contiguous  part 
of  the  cheek. 


1  Ant.  sup.  dental  nerve ;  n.  alveolaris  sup.  anterior. 

2  Forming  the  ansa  supramaxillaris. 


788  THE   NERVOUS   SYSTEM. 

The  terminal  branches  of  the  superior  maxillary  nerve  are  connected 
with  branches  of  the  facial  nerve  and  together  form  the  infraorbital 
plexus. 

SPHENO-PALATINE    GANGLION. 

The  spheno-palatine  ganglion1  is  a  reddish-gray,  ovoid  body, 
about  a  fifth  of  an  inch  in  diameter,  situated  in  the  spheno-maxil- 
lary  fossa  just  below  the  superior  maxillary  nerve,  with  which  it 
is  connected  by  the  two  spheno-palatine  nerves.  Its  nerve-cells  mainly 
occupy  the  back  part  of  the  ganglion  and  involve  but  few  of  the  fibres 
descending  from  the  spheno-palatine  nerves,  which  for  the  most  part 
continue  into  the  nasal  and  palatine  branches.  From  the  ganglion 
proceed  the  palatine,  nasal,  and  vidian  nerves. 


VIEW  OF  THE  SPHENO-PALATINE  GANGLION,  THE  OUTER  WALL  OF  THE  LEFT  NASAL  CAVITY,  AND 

THE  OLFACTORY  NERVE.  1,  external  olfactory  nerves ;  2,  nasal  branch  of  the  ophthalmic  nerve ; 
3,  spheno-palatine  ganglion ;  4,  5,  6,  palatine  nerves ;  7,  inferior  nasal  nerve ;  8,  superior  nasal 
nerves;  9,  naso-palatine  nerve;  10,  vidian  nerve;  11,  facial  nerve;  12,  deep  petrosal  nerve  joining 
the  carotid  plexus,  13 ;  the  other  branch  of  the  vidian  is  the  superficial  petrosal  nerve,  which 
joins  the  facial. 

The  palatine  nerves,2  of  which  there  are  three,  descend  through 
the  posterior  palatine  canal  and  its  divisions  to  the  palate. 

The  large,  or  anterior  palatine  nerve,3  is  directed  forward  from 
the  canal  in  a  groove  of  the  hard  palate,  the  mucous  membrane  and 
glands  of  which  it  supplies.  In  its  course  through  the  canal  it  gives 
off  the  inferior  nasal  nerves,*  two  branches  which  pass  through  small 
foramina  in  the  outer  wall  of  the  nasal  cavity  to  supply  the  mucous 
membrane  on  the  middle  and  lower  turbinals  and  in  the  middle  meatus. 

1  G.  spheno-palatinum  ;  Meckel's  ganglion  ;  g.  nasale. 

2  N.  palatini  descendentes. 

3  N.  palatinus  major  or  anticus.  *  N.  nasales  posteriores  inferiores. 


THE   NERVOUS   SYSTEM.  789 

The  small  palatine  nerves 1  pass  through  the  canals  of  the  pyram- 
idal process  of  the  palate  bone  and  supply  the  soft  palate,  uvula,  and 
tonsil,  including  the  palatal  elevator  and  uvular  muscles. 

The  superior  nasal  nerves  are  two  or  three  small  ones  which 
proceed  from  the  inner  side  of  the  ganglion  through  the  spheno-palatine 
foramen  into  the  nasal  cavity,  where  they  are  distributed  to  the  mucous 
membrane  of  the  back  part  of  the  roof,  of  the  superior  and  middle 
turbinals,  and  of  the  adjacent  part  of  the  nasal  partition. 

The  naso-palatine  nerve,2  a  long  slender  branch,  comes  from  the 
inner  side  of  the  ganglion  and  accompanies  the  superior  nasal  nerves 
into  the  nasal  cavity,  where  it  descends  obliquely  forward  on  the 
partition,  beneath  the 'mucous  membrane,  to  the  naso-palatine  canal. 
Passing  through  this  and  the  incisive  foramen,  it  terminates  in  the 
mucous  membrane  of  the  hard  palate  behind  the  position  of  the  incisor 
teeth. 

The  vidian  nerve,3  from  the  spheno-palatine  ganglion  runs  back- 
ward through  the  vidian  canal  and  divides  into  the  deep  and  super- 
ficial petrosal  nerves.  The  vidian  gives  some  small  nasal  branches  to 
the  contiguous  mucous  membrane  and  a  small  pharyngeal  branch, 
through  the  pterygo-palatine  canal,  to  the  roof  of  the  pharynx. 

The  deep  petrosal  nerve,4  of  a  reddish  color  and  comparatively 
soft  texture,  is  directed  backward  and  joins  the  carotid  plexus  of  the 
sympathetic  nerve. 

The  superficial  petrosal  nerve5  perforates  the  fibro-cartilage 
occupying  the  middle  lacerate  foramen,  enters  the  cranium  to  the  outer 
side  of  the  carotid  artery  and  beneath  the  semilunar  ganglion,  is  thence 
directed  outward  and  backward  in  a  groove  of  the  temporal  pyramid, 
and  enters  the  hiatus 6  of  the  facial  canal 7  to  join  the  geniculate  gan- 
glion of  the  facial  nerve. 

The  spheno-palatine  nerves  may  be  regarded  as  the  sensory  roots 
of  the  spheno-palatine  ganglion,  the  superficial  petrosal  as  its  motor 
root,  and  the  deep  petrosal  as  its  sympathetic  root. 

The  superior  maxillary  nerve  is  sensory  in  function.  It  supplies 
the  skin  of  the  upper  lip,  side  of  the  nose,  cheek  and  lower  eyelid,  the 
mucous  membrane  of  the  back  part  of  the  nasal  cavity,  posterior  eth- 
moidal  sinuses  and  maxillary  antrum,  the  upper  teeth,  the  hard  and 
soft  palate,  the  uvula,  and  the  tonsil. 

1  N.  palatinus  minus  or  posticus  and  n.  p.  minimus  or  externus. 

2  N.  naso-palatinus ;  n.  septi  narium ;  n.  spheno-palatinus  internus ;  nerve  of 
Scarpa;  nerve  of  Cotunnius. 

3  N.  Vidianus  ;  n.  pterygoideus  ;  n.  anastomoticus  ;  n.  quinti  recurrens. 

4  N.  petrosus  profundus  major ;  greater  deep  petrosal  nerve. 

5  N.  petrosus  superficial  major ;  greater  superficial  petrosal  nerve. 
8  H.  Fallopii.  T  Canalis  Fallopii. 


790 


THE    NERVOUS   SYSTEM. 


INFERIOR   MAXILLARY    NERVE. 

The  inferior  maxillary  nerve,1  the  third  and  largest  branch  of 
the  trifacial,  is  formed  by  the  union  of  the  small  motor  root  with  the 
largest  branch  from  the  semilunar  ganglion.  The  two  parts  of  the 
nerve  descend  together  from  the  cranium  through  the  sphenoidal  oval 
foramen  and  immediately  at  their  exit  unite  in  a  short,  flat,  plexiform 

FIG.  402. 


DISTRIBUTION  OF  THE  INFERIOR  MAXILLARY  NERVE.  1,  muscular  branch  to  the  masseter 
muscle ;  2, 3,  7,  branches  to  the  temporal  muscle ;  5,  branch  to  the  buccinator,  anastomosing  with 
one  from  the  facial  at  4;  6,  external  pterygoid  muscle ;  8,  auriculo-temporal  nerve ;  9,  superficial 
temporal  branch ;  10,  branches  to  the  ear ;  11,  its  anastomosis  with  the  facial ;  12,  lingual  nerve ; 
13,  branch  to  the  mylo-hyoid  muscle  from  the  inferior  dental  nerve,  14 ;  15,  branches  to  the  teeth ; 
16,  mental  nerve  to  the  lower  lip  and  chin ;  17,  anastomosis  with  the  facial  nerve. 

trunk,  which  lies  between  the  pterygoid  muscles.  The  trunk  separates 
into  a  small  and  a  large  division,  each  of  which  at  once  breaks  up  into 
two  groups  of  branches.  The  small  division  receives  most  of  the  fibres 
of  the  small  root  of  the  nerve  and  is  mainly  distributed  to  the  muscles 
of  mastication,  while  the  large  division  is  chiefly  sensory. 

The  trunk  of  the  inferior  maxillary  nerve  gives  off  a  little  recur- 


N.  maxillaris  inferior ;  n.  inframaxillaris. 


THE   NERVOUS   SYSTEM.  791 

rent  branch,1  which  passes  through  the  adjacent  spinous  foramen  to 
the  great  meningeal  artery.  It  also  commonly  gives  off  the  internal 
pterygoid  nerve,  which  descends  and  enters  the  inner  surface  of  the 
corresponding  muscle. 

The  small  division  of  the  inferior  maxillary  nerve  divides  into  deep 
temporal,  masseteric,  external  pterygoid,  and  buccal  branches. 

The  deep  temporal  nerves,  usually  an  anterior  and  a  posterior, 
ascend  beneath  the  temporal  muscle,  to  which  they  are  distributed,  enter- 
ing its  inner  surface.  The  anterior  not  unfrequently  arises  together 
with  the  buccal  and  the  posterior  with  the  masseteric  nerve ;  sometimes 
there  is  a  third  or  middle  temporal  branch. 

The  masseteric  nerve  is  directed  outward,  behind  the  temporal 
and  over  the  external  pterygoid  muscle,  through  the  mandibular  notch 
to  the  back  part  of  the  inner  surface  of  the  masseter  muscle,  to  which 
it  is  distributed.  It  also  gives  a  filament  to  the  articulation  of  the 
jaw. 

The  external  pterygoid  nerve  enters  the  inner  surface  of  the 
corresponding  muscle. 

The  buccal  nerve,  usually  arising  together  with  the  external 
pterygoid  and  the  anterior  deep  temporal  nerve,  runs  forward  between 
the  heads  of  the  external  pterygoid  muscle  and  descends  to  the  out- 
side of  the  buccinator,  on  which  it  forms  a  plexus  with  branches  of 
the  facial  nerve,  and  is  finally  distributed  to  the  skin  and  mucous 
membrane  of  the  cheek.  The  destination  of  the  nerve  indicates  its 
sensory  character. 

The  internal  pterygoid  nerve,  as  before  mentioned,  is  commonly 
a  branch  of  the  main  trunk  of  the  trifacial.  At  its  commencement  it 
is  closely  connected  with  the  otic  ganglion. 

The  large  division  of  the  inferior  maxillary  nerve  gives  off  the 
auriculo-temporal,  inferior  dental,  and  lingual  nerves. 

The  auriculo-temporal  nerve,2  the  smallest  of  the  three  just  in- 
dicated, commonly  arises  by  two  branches,  which  pass  backward,  unite, 
and  enclose  the  great  meningeal  artery.  Thence  it  turns  outward  and 
backward  around  the  articulation  of  the  jaw  and  upwards  in  company 
with  and  behind  the  temporal  artery  to  the  temple.  The  branches  of 
origin  are  connected  by  filaments  with  the  otic  ganglion,  and  as  the 
nerve  turns  up  to  the  temple  it  sends  forward  around  the  temporal 
artery  one  or  two  considerable  branches,  which  join  the  temporo-facial 
division  of  the  facial  nerve.  In  its  course  the  nerve  gives  branches 
to  the  articulation  of  the  jaw,  the  auditory  meatus  and  pinna,  and 
the  parotid  gland.  The  ascending  portion,  or  superficial  temporal 
nerve,3  is  distributed  to  the  skin  of  the  temporal  region,  its  anterior  fil- 
aments communicating  with  the  temporal  branches  of  the  facial  nerve. 

1  N.  recurrens.  2  N.  auriculo-temporalis. 

s  N.  temporalis  superficialis  or  cutaneus. 


792  THE   NERVOUS  SYSTEM. 

The  inferior  dental  nerve,1  the  largest  of  the  branches  of  the 
fifth,  descends  between  the  pterygoid  muscles  behind  and  to  the  outer 
side  of  the  lingual  nerve  and  passes  between  the  stylo-maxillary  liga- 
ment and  ramus  of  the  mandible  to  the  inferior  dental  canal.  In 
company  with  the  dental  artery  it  runs  through  the  canal,  supplies 
branches  to  the  teeth,  and  near  the  mental  foramen  divides  into  the 
incisor  branch  for  the  corresponding  teeth  and  the  mental  branch, 
which  emerges  at  the  mental  foramen.  The  dental  branches  together 
form  a  plexus  like  that  of  the  upper  jaw.  Before  entering  the  dental 
canal  the  inferior  dental  nerve  gives  off  the  mylo-hyoid  branch,2 
which  descends  on  the  inner  side  of  the  mandible  beneath  the  mylo- 
hyoid  muscle,  to  which  and  the  anterior  belly  of  the  digastric  muscle 
it  is  distributed.  The  fibres  of  this  branch  are  traceable  within  the 
sheath  of  the  inferior  dental  nerve  to  the  motor  division  of  the  in- 
ferior  maxillary. 

The  mental  branch,3  proceeding  from  the  inferior  dental  nerve 
through  the  mental  foramen,  breaks  up  into  branches  beneath  the  oral 
angle  depressor,  distributed  to  the  skin  and  mucous  membrane  of  the 
lower  lip  and  chin  and  communicating  with  the  adjacent  branches  of 
the  facial  nerve. 

The  lingual,  or  gustatory  nerve,4  descends  between  the  pterygoid 
muscles  in  advance  of  the  dental  nerve,  curves  forward  between  the 
internal  pterygoid  muscle  and  the  ramus  of  the  mandible  and  to  the 
outer  side  of  the  superior  pharyngeal  constrictor.  Passing  between 
the  stylo-glossal  muscle  and  the  submaxillary  gland,  it  proceeds  below 
across  the  duct  of  the  gland  and  along  the  side  of  the  tongue  to  its 
tip  immediately  beneath  the  mucous  membrane. 

Near  its  commencement  the  lingual  nerve  is  commonly  joined  by 
a  branch  from  the  inferior  dental.  It  also  receives  at  an  acute  angle 
the  tympanic  branch 6  of  the  facial  nerve,  which  descends  from  the 
tympanum  through  the  glenoid  foramen  behind  the  articulation  of  the 
jaw. 

Contiguous  to  the  submaxillary  gland  the  lingual  nerve  gives  off 
several  small  branches  to  the  submaxillary  ganglion  and  subsequently 
several  filaments  which  anastomose  with  others  of  the  hypoglossal 
nerve.  At  the  side  of  the  tongue  it  gives  branches  to  the  mucous  mem- 
brane and  to  the  sublingual  gland  and  gum.  The  terminal  branches 
ascend  through  the  muscular  structure  of  the  tongue  and  are  dis- 
tributed in  the  mucous  membrane  of  the  anterior  two-thirds,  mainly 
in  the  conical  and  fungiform  papillae. 

1  N.  alveolaris  inf. ;  n.  mandibularis.  2  N.  mylo-hyoideus. 

3  N.  mentalis.  *  N.  lingualis  ;  n.  gustatorius.          5  Chorda  tympani. 


THE   NERVOUS   SYSTEM. 


793 


FIG.  403. 
15  1412    1124  23 


'21 


2U 


OTIC   GANGLION. 

The  otic  ganglion l  is  an  oval,  reddish-gray  body,  about  the  sixth 
of  an  inch  in  its  longer, 
fore  and  aft  diameter.  It 
is  situated  on  the  inner  side 
of  the  trunk  of  the  infe- 
rior maxillary  nerve,  from 
which  it  receives  a  little 
bundle  of  fibres,  regarded 
as  the  sensory  root'2  of 
the  ganglion.  It  commonly 
encloses  the  internal  ptery- 
goid  nerve  and  likewise 
includes  the  branch  to  the 
palatal  tensor,  from  both  of 
which  it  derives  filaments 
apparently  representing 
the  motor  root  of  the  gan- 
glion. The  sympathetic 
root3  is  a  filament  ascend- 
ing from  the  contiguous 
sympathetic  plexus  of  the 
great  meningeal  artery. 

The  nerves  of  the  otic 
ganglion,  besides  its  sev- 
eral roots,  consist  of  com- 
municating filaments  with 
the  two  branches  of  ori- 
gin of  the  auriculo  -  tem- 
poral nerve,  two  muscular 
branches,  and  the  small  pe- 
trosal  nerve.  Of  the  mus- 
cular branches  one  runs  forward  and  downward  to  the  palatal  tensor 
and  the  other  backward  and  upward  to  the  tympanic  tensor. 

The  small  petrosal  nerve*  ascends  through  a  fine  canal  of  the 
sphenoidal  angular  process,  close  to  the  spinous  foramen,  into  the  cra- 
nial cavity,  whence  it  runs  through  another  fine  canal  of  the  tympanic 
tegmen  into  the  facial  canal.  Here  it  communicates  by  a  filament5 
with  the  facial  nerve  a  little  beyond  the  geniculate  ganglion  and  then 
descends  into  the  tympanum  to  join  the  tympanic  branch6  of  the  glosso- 
pharyngeal  nerve. 


THE  OTIC  GANGLION  AND  ITS  CONNECTIONS  :  view  from 
within.  1,  internal  pterygoid  muscle;  2,  palatal  tensor 
muscle ;  3,  its  tendon  passing  round  the  hook,  4,  of  the 
internal  pterygoid  process ;  5,  condyle  of  the  jaw ;  6,  tym- 
panic tensor  muscle;  7,  malleus:  8,  tympanic  membrane; 
9,  external  carotid  artery  dividing  into  the  temporal  and 
internal  maxillary  arteries ;  10,  tympanic  branch ;  11,  great 
meningeal  artery ;  12,  small  meningeal  artery ;  13,  inferior 
dental  artery ;  14,  third  division  of  the  semilunar  gan- 
glion of  the  trifacial  nerve ;  15,  motor  root  of  the  latter ; 
16,  lingual  nerve ;  17,  inferior  dental  nerve ;  18,  auriculo- 
temporal  nerve ;  19,  tympanic  branch  of  the  facial  nerve 
joining  the  lingual  nerve ;  20,  otic  ganglion ;  21,  nerve  to 
palatal  tensor;  22,  nerve  to  internal  pterygoid  muscle; 
23,  branch  to  tympanic  tensor;  24,  small  petrosal  nerve; 
25,  communicating  branch  with  the  sympathetic  nerve. 


1  G.  oticum ;  g.  Arnold! ;  g.  auriculare.          2  Radix  brevis. 

3  R.  sympathica  or  trophica.  *  N.  petrosus  superficialis  minor. 

5  Ramus  communicans  cum  plexu  tympanico.  6  N.  Jacobsonii. 


794  THE    NERVOUS   SYSTEM. 


STJBMAXILLARY    GANGLION. 

The  submaxillary  ganglion *  is  a  little  fusiform  body  lying  on  the 
submaxillary  salivary  gland  below  the  trunk  of  the  lingual  nerve,  with 
which  it  is  connected  by  several  filaments  converging  fore  and  aft  from 
the  nerve.  These  filaments  are  regarded  as  the  sensory  and  motor 
roots  of  the  ganglion  traceable  to  the  proper  fibres  of  the  lingual  nerve 
and  to  the  tympanic  branch  of  the  facial  associated  with  it.  The 
sympathetic  root  is  an  additional  filament  derived  from  the  contiguous 
sympathetic  plexus  of  the  facial  artery.  From  the  ganglion  about 
half  a  dozen  filaments  are  distributed  to  the  submaxillary  gland  and 
its  duct.  • 

The  sensory  portion  of  the  inferior  maxillary  nerve  supplies  the 
skin  of  the  temporal  region,  of  the  external  ear,  of  the  cheek,  and  of  the 
chin  and  lower  lip,  the  mucous  membrane  and  papilla  of  the  greater 
part  of  the  tongue,  the  mucous  membrane  of  the  cheek,  lower  lip  and 
gum,  the  teeth,  the  salivary  glands,  and  the  articulation  of  the  jaw. 
The  motor  portion  supplies  the  muscles  of  mastication,  the  mylo-hyoid 
and  anterior  belly  of  the  digastric  muscles,  and  the  palatal  and  tym- 
panic tensors. 

VI.     ABDUCENT  NERVES. 

The  sixth,  or  abducent  nerve,2  appears  as  a  band  of  filaments 
springing  from  the  groove  between  the  pons  and  the  upper  extremity 
of  the  pyramid  of  the  oblongata.  Advancing  beneath  the  pons,  it 
speedily  becomes  a  rounded  cord  and  proceeds  to  an  aperture  of  the 
dura  below  and  to  the  outer  side  of  the  clivus  of  the  sphenoid  bone. 
Thence  it  runs  through  the  floor  of  the  cavernous  sinus,  at  the  outer 
side  of  the  internal  carotid  artery,  to  the  sphenoidal  foramen,  and  enters 
the  orbit  between  the  heads  of  the  external  rectus  muscle,  to  which 
the  nerve  is  distributed,  entering  its  inner  surface.  The  nerve  passes 
through  the  sphenoidal  foramen  below  the  ophthalmic  vein  and  below 
all  the  other  nerves  accompanying  it.  In  its  course  through  the  cav- 
ernous sinus  it  is  connected  by  filaments  with  the  contiguous  plexus 
of  the  sympathetic,  and  on  entering  the  orbit  it  receives  a  filament 
from  the  ophthalmic  nerve. 

The  destination  of  the  abducent  indicates  its  character  as  a  motor 
nerve. 

VII.     FACIAL   NEEVES. 

The  seventh,  or  facial  nerve,3  makes  its  appearance  in  the  de- 
pression between  the  olive  and  restiform  body  of  the  oblongata  im- 
mediately below  the  pons.  Close  to  its  outer  side  lies  the  auditory 

1  G.  submaxillare  Merkelii ;  g.  linguale. 

2  N.  abducens  ;  n.  oculomotor! us  externus. 

8  N.  facialis  ;  n.  communicans  facei ;  portio  dura  of  the  seventh  nerve. 


THE    NERVOUS   SYSTEM.  795 

nerve,  and  between  them  is  a  filament,  the  intermediate  portion,1 
connected  with  both  nerves,  which  pass  together  forward  and  outward 
to  the  internal  auditory  meatus.  In  this  they  proceed  to  the  bottom, 
the  facial  nerve  lying  in  a  groove  in  the  upper  fore  part  of  the  audi- 
tory nerve,  with  the  intermediate  portion  still  retaining  its  position 
between  them.  At  the  bottom  of  the  meatus  the  facial  nerve  leaves 
the  auditory  nerve  and  enters  the  facial  canal,  the  winding  course  of 
which  it  follows  to  the  exit,  the  stylo-mastoid  foramen.  The  facial 
nerve  at  first  runs  a  short  distance  forward  and  outward  to  near  the 
hiatus  of  the  canal, 'When  it  abruptly  turns  backward  in  the  supra- 
promontory  of  the  tympanum  and  then  curves  downward  in  its  pos- 
terior wall  to  emerge  at  the  stylo-mastoid  foramen.  From  this  the 
nerve  runs  downward  and  forward  in  the  parotid  gland  and  separates 
in  the  temporo-facial  and  cervico-facial  divisions.  These  split  up  into 
eight  or  ten  principal  branches,  subdividing  and  anastomosing  in  loops 
arid  forming  together  the  parotid  plexus,2  which  spreads  over  the  side 
of  the  face  and  temple  and  extends  to  the  upper  part  of  the  neck  and 
freely  communicates  with  the  terminal  branches  of  the  three  divisions 
of  the  trifacial  nerve. 

In  the  facial  canal  where  the  facial  nerve  bends  backward  in  a 
knee,3  it  presents  an  enlargement,  the  geniculate  ganglion,4  which 
is  reddish  gray  and  contains  an  accumulation  of  nerve-cells. 

With  the  geniculate  ganglion  are  connected  the  following  nerves: 
a  filament  from  the  auditory  nerve  at  the  bottom  of  the  internal  audi- 
tory meatus,  the  superficial  petrosal  nerve 5  through  the  hiatus  of  the 
facial  canal,  and  a  filament6  connected  with  the  sympathetic  on  the 
great  meningeal  artery.  Just  beyond  the  ganglion  the  facial  nerve  is 
joined  by  a  filament,7  opposite  to  its  course,  from  the  small  petrosal 
nerve.8 

The  facial  nerve  in  its  descent  in  the  back  part  of  the  facial  canal 
gives  off  a  small  branch  to  the  stapedial  muscle,  a  tympanic  branch, 
and  a  filament 9  communicating  with  the  auricular  branch  of  the  vagus 
nerve. 

The  tympanic  branch,10  from  the  facial  nerve,  ascends  forward 
through  a  canal  and  enters  the  back  part  of  the  tympanum  close  to 
the  border  of  the  tympanic  membrane,  arches  across  its  upper  part, 
to  the  inner  side  of  the  handle  of  the  malleus,  covered  by  the  lining 

1  Pars  or  portio  media  "Wrisbergii ;  nervus  medius. 

2  Plexus  parotideus  ;  plexus  or  pes  anserinus.  3  Genu  n.  facialis. 

4  G.  geniculatum  ;  intumescentia  gangliformis. 

5  N.  petrosus  superficialis  major. 

6  N.  petrosus  superficialis  minimus  or  externus. 

7  Kamus  communicans  cum  plexu  tympanico. 

8  N.  petrosus  superficialis  minor. 

9  N.  communicans  cum  ramo  auriculari  nervi  vagi. 

10  Chorda  tympani ;  n.  tympano-lingualis. 


796 


THE    NERVOUS    SYSTEM. 


membrane  of  the  tympanum,  and  leaves  the  cavity  through  the  glenoid 
foramen.  It  then  descends  obliquely  forward  to  the  inner  side  of  the 
stylo-maxillary  ligament  and  at  an  acute  angle  joins  the  lingual  nerve. 
Within  the  sheath  of  the  latter  its  fibres  are  traceable,  partly  continu- 


FIG.  404 


THE  FACIAL  NERVE.  1,  trunk  of  the  nerve  after  emerging  at  the  stylo-mastoid  foramen ;  2,  its 
posterior  auricular  branch ;  3,  anastomosis  of  the  latter  with  the  great  auricular  nerve  of  the 
cervical  plexus ;  4,  5,  6,  branches  to  the  contiguous  muscles ;  7,  8,  branches  of  the  facial  to  the 
digastric  and  stylo-hyoid  muscles ;  9,  temporo- facial  division  of  the  nerve ;  10,  branch  to  the  tem- 
ple, anastomosing  with  the  auriculo-temporal  nerve;  11,  temporal  branches;  12, 13,  infraorbital 
branches;  14, 15,  cervico-facial  division  of  the  facial  nerve  ;  14,  buccal  branches;  16,  mandibular 
branches ;  17,  cervical  branches ;  18,  auriculo-temporal  nerve ;  19,  20,  supraorbital  nerves ;  21,  ter- 
minal branch  of  the  lachrymal  nerve;  22,  infratrochlear  nerve;  23,  branch  of  the  temporo-malar 
nerve ;  24,  external  branch  of  the  nasal  nerve ;  25,  infraorbital  nerves  ;  26,  anastomosis  between 
the  buccal  branch  of  the  inferior  maxillary  nerve  and  the  buccal  branches  of  the  facial  nerve ; 
27,  mental  branches  of  the  inferior  dental  nerve;  28,  great  occipital  nerve;  29,  31,  branches  of  the 
great  auricular  nerve;  30,  small  occipital  nerve;  32,  superficial  cervical  nerve,  anastomosing 
with  the  facial  nerve. 

ous  with  those  of  the  lingual  nerve  and  partly  leaving  it  to  form  the 
motor  root  of  the  submaxillary  ganglion. 

After  its  exit  from  the  cranium,  the  facial  nerve  gives  off  the  pos- 
terior auricular  nerve,1  which  turns  upward  between  the  ear  and 

1  N.  auricularis  posterior  profundus. 


THE   NERVOUS   SYSTEM.  797 

the  mastoid  process  and  after  anastomosing  with  the  great  auricular 
and  small  occipital  nerves  of  the  cervical  plexus  is  distributed  to  the 
postauricular  and  occipital  muscles,  and  to  the  transversalis  muscle  on 
the  back  of  the  pinna. 

Closely  succeeding  the  posterior  auricular  nerve  is  a  branch 1  which 
supplies  the  stylo-hyoid  and  the  posterior  belly  of  the  digastric  muscle 
and  is  connected  by  a  filament 2  with  the  glosso-pharyngeal  nerve. 

The  facial  nerve  then  communicates  by  anastomotic  branches,3 
usually  two,  with  the  auriculo-temporal  branch  of  the  fifth  nerve. 

The  temporo-facial  division  of  the  facial  nerve,  the  larger  of  the 
two,  is  directed  forward  through  the  upper  part  of  the  parotid  gland, 
across  the  external  carotid  artery  and  temporo-maxillary  vein,  and  is 
distributed  in  temporo-frontal,  infraorbital,  and  buccal  branches  over 
the  side  of  the  face,  extending  from  the  fore  part  of  the  temple  to  the 
cheek  on  a  line  with  the  angle  of  the  mouth. 

The  temporo-frontal  branches,4  of  which  there  are  two  or  three, 
ascend  over  the  zygoma  and  are  distributed  to  the  supra-  and  pre- 
auricular  muscles,  to  those  of  the  outer  surface  of  the  pinna,  and  to  the 
frontal,  superciliary,  and  palpebral  orbicular  muscles.  They  anasto- 
mose with  the  auriculo-temporal  nerve,  the  temporal  branch  of  the 
superior  maxillary  nerve,  and  the  lachrymal  and  supraorbital  branches 
of  the  ophthalmic  nerve. 

The  infraorbital  branches,5  of  which  there  are  three  or  four,  are 
directed  forward  over  the  malar  bone,  supply  the  palpebral  orbicular 
muscle,  the  zygomatic  and  other  muscles  of  the  upper  lip  and  those  of 
the  nose,  and  anastomose  with  the  lachrymal  branch  of  the  ophthalmic 
nerve  and  the  malar  and  infraorbital  branches  of  the  superior  maxillary 
nerve. 

The  buccal  branches,6  of  which  there  are  two  or  three,  are 
directed  forward  towards  the  angle  of  the  mouth,  supply  the  bucci- 
nator muscle,  those  of  the  upper  lip  and  nose  and  the  oral  sphincter, 
and  anastomose  with  the  buccal  branch  of  the  inferior  maxillary,  the 
infraorbital  branches  of  the  superior  maxillary  and  those  of  the  next 
division  of  the  facial  nerve. 

The  cervico-facial  division  of  the  facial  nerve  descends  obliquely 
through  the  parotid  gland  towards  the  angle  of  the  lower  jaw  and 
divides  into  mandibular  and  cervical  branches. 

The  mandibular  branch 7  runs  over  the  masSeter  muscle,  divides 
into  two,  and  is  distributed  to  the  imiscles  of  the  lower  lip,  anastomosing 
with  the  buccal  branch  of  the  inferior  maxillary  as  well  as  those  of 


1  N.  styloideus  ;  n.  stylo-hyoideus  and  digastricus. 

2  N.  communicans  glosso-pharyngei.  3  Kami  anastomotici. 
4  Kami  temporo-frontales  ;  r.  temporales. 

8  R.  zygomatici ;  malar  and  infraorbital  branches.  6  R.  buccales. 

7  R.  subcutaneus  mandibulae ;  r.  s.  maxillae  inferioris ;  supramaxillary  branches. 


798  THE   NERVOUS   SYSTEM. 

the  temporo-facial  division  of  the  facial  and  with  the  branches  of  the 
mental  nerve. 

The  cervical  branch l  descends  below  the  mandible,  anastomoses 
with  the  superficial  cervical  nerve,  and  is  distributed  to  the  platysma 
muscle. 

The  facial  is  the  principal  motor  nerve  of  the  head,  supplying  all 
the  superficial  and  some  of  the  deep  muscles.  Besides  those  of  the 
scalp,  temple,  auricle,  eyelids  (except  the  palpebral  elevator),  nose, 
and  mouth,  it  likewise  supplies  the  stapedial  muscle,  the  stylo-hyoid, 
the  posterior  belly  of  the  digastric,  and  the  platysma  muscle.  It  anas- 
tomoses with  the  three  divisions  of  the  trifacial  nerve,  is  connected 
with  all  their  ganglia,  and  also  communicates  with  the  auditory,  glosso- 
pharyngeal,  vagus,  sympathetic,  and  spinal  nerves. 

VIII.     AUDITORY   NERVES. 
The  eighth,  or  auditory  nerve,  is  described  with  the  ear. 

IX.     GLOSSO-PHARYNGEAL   NERVES. 

The  ninth,  or  glosso-pharyngeal  nerve,2  makes  its  appearance 
at  the  side  of  the  oblongata  in  the  groove  between  the  olive  and  resti- 
form  body,  immediately  below  the  facial  and  auditory  nerves.  Its  five 
or  six  rootlets  unite  in  a  pair  of  bundles  which  pass  outward  to  the 
jugular  foramen,  descend  through  its  middle  passage,  and  conjoin  in  a 
single  trunk.  On  this  is  an  enlargement,  the  petrous  ganglion,  from 
which  the  nerve  passes  between  the  internal  carotid  artery  and  jugular 
vein  outwardly  and  then  across  the  former  beneath  the  styloid  process 
and  its  muscles.  It  then  curves  forward  from  behind  the  stylo-pharyn- 
geal  and  beneath  the  hyo-glossal  muscle  to  be  distributed  to  the  root 
of  the  tongue. 

In  the  jugular  foramen  the  glosso-pharyngeal  nerve  is  accompanied 
by  the  vagus  and  accessory  nerves,  but  occupies  a  separate  tube  of 
the  dura.  It  lies  in  front  of  its  companions,  and  in  this  position  its 
posterior  bundle  commonly  exhibits  a  little  enlargement,  the  jugular 
ganglion.3 

The  petrous  ganglion,4  situated  on  the  nerve  at  the  exit  of  the 
jugular  foramen,  is  an  elliptical  body,  two  or  three  lines  long,  occupy- 
ing a  recess  in  the  jugular  groove  of  the  petrosal.  It  is  connected  by 
a  filament  with  the  first  cervical  ganglion  of  the  sympathetic  and  by 
a  second  filament  with  the  auricular  branch  of  the  vagus  nerve.  It 
gives  off  an  important  branch,  the  tympanic  nerve. 

The  tympanic  nerve 5  passes  up  a  canal  of  the  temporal  bone,  in 

1  R.  subcutaneus  colli  superior ;  inframaxillary  branch. 

2  N.  glosso-pharyngeus  ;  first  division  of  the  eighth  nerve  of  Willis. 

3  G.  jugulare  ;  g.  Ehrenritteri.  *  G.  petrosum  ;  g.  Anderschii. 
5  N.  tympanicus  ;  Jacobson's  nerve  ;  n.  Jacobsonii  or  Anderschii. 


THE    NERVOUS   SYSTEM. 


799 


FIG.  405. 


the  partition  between  the  jugular  foramen  and  carotid  canal,  into  the 
tympanum,  ascends  in  a  groove  on  the  promontory  and  leaves  the 
cavity  through  a  canal  behind  the  receptacle  of  the  tympanic  tensor, 
opening  on  the  upper 
surface  of  the  inner  end 
of  the  tympanic  tegmen, 
where  the  nerve  is  con- 
tinued as  the  small  pe- 
trosal  nerve  to  the  otic 
ganglion.  In  its  course 
it  is  connected  with  the 
cavernous  plexus  of  the 
sympathetic  by  a  couple 
of  filaments1  through 
foramina  in  the  wall  of 
the  carotid  canal,  and  by 
another  filament2  run- 
ning through  a  minute 
canal  in  the  receptacle 
of  the  tympanic  tensor. 
In  the  canal  by  which 
it  leaves  the  tympanum 
it  gives  a  small  com- 
municating branch3 
to  the  facial  nerve  just 
beyond  the  geniculate 
ganglion  in  a  direction 
opposite  to  the  course  of 
that  nerve.  On  the  pro- 
montory the  tympanic 
nerve  gives  branches  to 
the  lining  membrane  of 
the  cavity,  especially 
one*  to  the  commence- 
ment of  the  eustachian 


THE  LAST  POUR  CEREBRAL  NERVES,  THE  FACIAL  NERVE,  THE 
SYMPATHETIC,  AND  THE  UPPER  TWO  CERVICAL  NERVES.     1,  facial 

nerve ;  2,  glosso-pharyngeal ;  2',  anastomosis  between  a  branch 
of  the  facial  and  the  glosso-pharyngeal ;  3,  vagus ;  4,  acces- 
sory; 5,  hypoglossal;  6,  first  cervical  ganglion  of  the  sympa- 
thetic ;  7,  first  and  second  cervical  nerves :  8,  cavernous  plexus 
of  the  sympathetic  on  the  internal  carotid  artery :  9,  tympanic 
nerve  from  the  petrous  ganglion  of  the  glosso-pharyngeal ;  10, 
its  connection  with  the  carotid  plexus ;  11,  branch  to  the  eusta- 
chian tube ;  12, 13,  branches  to  the  oval  and  round  windows 
of  the  ear ;  14, 15,  branches  joining  the  small  and  superficial 


petrosal  nerves ;  16,  otic  ganglion  ;  17,  auricular  branch  from 
the  jugular  ganglion,  connected  by  filaments  with  the  petrous 
ganglion  and  the  facial  nerve ;  18,  anastomosis  of  the  acces- 
sory with  the  vagus ;  19,  anastomosis  of  the  first  cervical  nerve 
with  the  hypoglossal :  20,  anastomosis  of  the  second  cervical 
nerve  with  a  branch  of  the  accessory ;  21,  pharyngeal  plexus ; 
22,  superior  laryngeal  nerve ;  23,  its  external  branch ;  24,  second 
cervical  ganglion  of  the  sympathetic. 


tube  and  others  to  the 
oval  and  round  windows 
of  the  labyrinth. 

In     the     neck     the 
glosso-pharyngeal  nerve 
communicates      by      a 
couple  of  filaments  with  the  trunk  of  the  vagus  nerve  and  with  the 
branch  of  the  facial  nerve  to  the  stylo-hyoid  and  digastric  muscles. 


1  Nervi  carotico-tympanici. 
3  Ramus  communicans. 


2  N".  petrosus  profundus  minor. 
4  N.  tubae. 


800  THE   NERVOUS   SYSTEM. 

It  also  gives  off  several  pharyngeal  branches  to  the  side  of  the 
pharynx,  of  which  the  largest  joins  the  pharyngeal  branch  of  the 
vagus  to  form  the  pharyngeal  plexus,  supplying  the  superior  and 
middle  constrictors  and  contiguous  mucous  membrane  of  the  pharynx. 

It  subsequently  sends  a  muscular  branch1  to  the  stylo-pharyngeal 
muscle. 

Finally  reaching  the  root  of  the  tongue  beneath  the  tonsil,  the 
glosso-pharyngeal  nerve  gives  to  the  latter  the  tonsillitic  nerves,2 
which  supply  the  tonsil  and  the  mucous  membrane  of  the  side  of  the 
fauces. 

The  remainder  of  the  nerve,  the  lingual  branch,3  passing  beneath 
the  hyo-glossal  muscle,  is  distributed  to  the  mucous  membrane  of  the 
posterior  third  of  the  root  of  the  tongue,  including  the  circumvallate 
papillae  and  extending  to  the  epiglottis. 

X.     VAGUS   NERVES. 

The  tenth,  vagus,  or  pneumo-gastric  nerve,4  the  longest  and 
most  widely  distributed  of  the  nerves  of  the  brain,  at  the  side  of  the  ob- 
longata  immediately  succeeds  the  glosso-pharyngeal  nerve,  than  which 
it  is  much  larger.  Springing  in  the  same  line  below  it,  from  the  groove 
between  the  olive  and  restiform  body,  in  a  close  series  of  from  ten  to 
fifteen  rootlets,  these  unite  in  a  band  which  becomes  the  rounded  trunk 
of  the  nerve.  This  descends  through  the  middle  passage  of  the  ju- 
gular foramen  in  company  with  the  glosso-pharyngeal  and  accessory 
nerves,  separated  from  the  former  and  enclosed  in  the  same  tube  of 
the  dura  with  the  latter. 

In  the  foramen  the  vagus  presents  a  fusiform  enlargement,  the 
jugular  ganglion,6  about  the  sixth  of  an  inch  long.  Immediately 
below  the  foramen  is  a  second  enlargement,  the  gangliform  plexus,6 
flattened  cylindrical,  about  two-thirds  of  an  inch  long,  composed  of  a 
loose  intertexture  of  the  bundles  of  nerve-fibres  of  the  trunk  of  the 
vagus. 

The  vagus  from  the  gangliform  plexus  descends  the  neck  between 
the  jugular  vein  and  internal  carotid  artery,  then  between  the  vein 
and  the  common  carotid  artery,  in  the  interval  behind  and  all  together 
enclosed  in  the  same  sheath  of  the  cervical  fascia.  From  the  neck  the 
vagus  passes  into  the  thorax,  differently  on  the  two  sides. 

The  right  vagus  crosses  over  the  commencement  of  the  right  sub- 
clavian  artery  behind  the  innominate  vein  and  descends  on  the  side  of 
the  trachea  to  the  back  of  the  root  of  the  right  lung,  where  it  expands 
in  the  posterior  pulmonary  plexus.  Thence  the  nerve  emerges  in  two 

1  N.  stylo-pharyngeus.  2  N.  tonsillares.  3  R.  lingualis. 

4  N.  vagus  or  pneumo-gastricus  ;  second  division  of  the  eighth  nerve  of  Willis. 

5  G.  jugulare  ;  g.  superius. 

6  P.  gangliformis  ;  p.  nodosus  ;  ganglion  trunci  nervi  vagi. 


THE   NERVOUS   SYSTEM. 


801 


portions  which  apply  themselves  to  the  oesophagus  and  by  their  division 
and  union  with  similar  branches  of  the  left  vagus  form  the  oasophageal 
plexus.  At  the  lower  part  of  the  oesophagus  the  branches  for  the  most 


FIG.  406. 


THE  VAGUS  NERVE.  1,  trunk  of  the  vagus;  2,  gangliform  plexus ;  3,  its  anastomosis  with  the 
accessory  nerve ;  4,  anastomosis  with  the  hypoglossal ;  5,  pharyngeal  nerve ;  6,  superior  laryngeal 
nerve ;  7,  its  external  branch ;  8,  pharyngeal  plexus ;  9,  inferior  laryngeal  nerve ;  10.  superior  car- 
diac nerve;  11,  middle  cardiac  nerve;  12,  commencement  of  the  oasophageal  plexus:  13,  poste- 
rior pulmonary  plexus ;  14,  lingual  nerve ;  15,  lower  part  of  the  hypoglossal  nerve ;  16,  glosso- 
pharyngeal  nerve ;  17,  accessory  nerve;  18,  19,  20,  second,  third,  and  fourth  cervical  nerves;  21, 
commencement  of  the  phrenic  nerve;  22,  23,  the  lower  four  cervical  nerves  which  with  the  first 
thoracic  nerve  form  the  brachial  plexus;  24,  25,  first  and  second  cervical  ganglia  of  the  sympa- 
thetic ;  26,  third  cervical  united  with  the  first  thoracic  ganglion ;  27-30,  second  to  fifth  thoracic 
ganglia. 

part  collect  again  in  a  principal  trunk  which  descends  behind  the 
oesophagus,  through  the  oasophageal  orifice  of  the  diaphragm,  to  be 
distributed  on  the  posterior  surface  of  the  stomach. 

The  left  vagus  enters  the  thorax  between  the  left  common  carotid 

51 


802  THE   NERVOUS   SYSTEM. 

and  subclavian  arteries  and  behind  the  innominate  vein,  crosses  over 
the  arch  of  the  aorta,  and  runs  behind  the  root  of  the  left  lung,  where 
it  forms  the  corresponding  posterior  pulmonary  plexus.  Thence  the 
nerve  passes  to  the  oesophagus,  where  it  contributes  to  form  the 
ossophageal  plexus,  from  which  the  branches  for  the  most  part  again 
collect  in  a  principal  trunk  descending  in  front  of  the  oesophagus, 
through  the  orifice  of  the  diaphragm,  to  be  distributed  on  the  anterior 
surface  of  the  stomach. 

The  jugular  ganglion  is  connected  by  filaments  with  the  first  cer- 
vical ganglion  of  the  sympathetic,  the  petrous  ganglion  of  the  glosso- 
pharyngeal  nerve,  and  the  contiguous  trunk  of  the  accessory  nerve. 
It  gives  off  meningeal  and  auricular  branches. 

The  meningeal  branch  l  runs  backward  from  the  jugular  foramen 
and  is  distributed  to  the  dura  of  the  cerebellar  fossa  of  the  cranium. 

The  auricular  branch 2  receives  a  filament  from  the  glosso-pharyn- 
geal  nerve,  runs  outward  from  the  jugular  foramen  through  a  fine 
canal  of  the  temporal  pyramid,  and  crosses  the  lower  part  of  the  facial 
canal,  where  it  is  connected  by  a  couple  of  filaments  with  the  facial 
nerve.  Emerging  from  the  fissure  between  the  mastoid  process  and 
auditory  meatus  it  divides  into  two  branches,  of  which  one  joins  the 
posterior  auricular  branch  of  the  facial  nerve  and  the  other  is  dis- 
tributed to  the  skin  of  the  ear. 

The  gangliform  plexus  of  the  vagus  is  joined  by  a  considerable 
portion  of  the  accessory  nerve,  which  also  receives  filaments  in  return 
from  it.  In  addition  the  gangliform  plexus,  or  the  trunk  of  the 
nerve  above  or  below,  is  connected  by  filaments  with  the  hypoglossal 
and  sympathetic  nerves,  sometimes  also  with  the  upper  two  cervical 
nerves. 

The  division  of  the  accessory  nerve  joining  the  gangliform  plexus 
gives  to  the  vagus  its  motor  fibres,  most  of  which  pass  in  front  of  the 
plexus  and  are  continued  into  the  pharyngeal  and  superior  laryngeal 
branches,  while  a  few  descend  in  the  main  trunk  and  enter  the  inferior 
laryngeal  and  cardiac  branches. 

The  branches  of  the  vagus  nerve,  succeeding  those  above  described, 
are  the  pharyngeal,  superior  and  inferior  laryngeal  nerves,  and  the 
cardiac,  pulmonary,  oesophageal,  and  gastric  branches. 

The  pharyngeal  nerve,3  or  several  branches  in  its  place,  proceeds 
from  the  upper  part  of  the  gangliform  plexus  inward  over  the  internal 
carotid  artery  to  the  middle  constrictor  of  the  pharynx,  on  which  it 
divides  into  branches.  These,  together  with  the  pharyngeal  branches 
of  the  glosso-pharyngeal  nerve  and  a  filament  or  two  from  the  first 
cervical  ganglion  of  the  sympathetic,  form  the  pharyngeal  plexus, 
which  supplies  the  constrictors  and  mucous  membrane  of  the  pharynx. 

1  Ramus  meningeus ;  r.  recurrens. 

2  R.  auricularis  Arnold!;  nervus  fossae  jugularis.  s  N.  pharyngeus. 


THE   NERVOUS   SYSTEM.  803 

A  filament l  from  the  plexus  joins  the  hypoglossal  nerve  as  it  crosses 
the  external  carotid  artery  below  the  occipital  artery. 

The  superior  laryngeal  nerve,2  a  larger  branch  than  the  pharyn- 
geal,  proceeds  from  the  lower  part  of  the  gangliform  plexus  of  the 
vagus  downward  and  forward  to  the  inner  side  of  the  internal  carotid 
artery  and  to  the  upper  part  of  the  larynx.  It  is  joined  by  filaments 
from  the  pharyngeal  plexus  and  first  cervical  ganglion  of  the  sympa- 
thetic and  divides  into  the  external  and  internal  laryngeal  branches. 

The  external  laryngeal  branch3 runs  beneath  the  depressor  mus- 
cles of  the  hyoid  bone  and  is  distributed  to  the  crico-thyroid  muscle 
and  the  inferior  constrictor  of  the  pharynx.  It  commonly  gives  off  a 
cardiac  branch,  which  is  joined  by  the  superior  cardiac  nerve  from  the 
first  cervical  ganglion  and  descends  on  the  common  carotid  artery  into 
the  thorax,  where  it  contributes  to  form  the  cardiac  plexus.  From  the 
influence  of  this  branch  on  the  heart  it  has  been  called  the  inhibitory 
or  depressor  nerve.  It  is  sometimes  reinforced  by  a  filament  from  the 
internal  laryngeal  branch. 

The  internal  laryngeal  branch,*  considerably  larger  than  the 
external,  runs  to  the  interval  between  the  hyoid  bone  and  thyroid  carti- 
lage and  divides  into  branches  which  perforate  the  thyro-hyoid  mem- 
brane to  be  distributed  to  the  mucous  membrane  of  the -larynx,  from 
the  epiglottis  to  the  glottis.  A  descending  branch  along  the  inner  side 
of  the  thyroid  cartilage  joins  one  from  the  inferior  laryngeal  nerve. 

The  cardiac  branches 5  of  the  vagus  are  variable  in  number  and 
size,  even  on  the  two  sides,  and  are  generally  in  greater  number  on  the 
right,  Commonly  several  long  slender  filaments  proceed  from  the 
cervical  portion  of  the  trunk,  descend  in  front  and  behind  the  com- 
mon carotid  artery,  partly  join  the  cardiac  nerves  of  the  sympathetic 
and  partly  end  in  the  cardiac  plexus.  At  the  bottom  of  the  neck  a 
larger  filament  on  the  right  runs  along  the  innominate  artery  to  the 
deep  cardiac  plexus,  and  on  the  left  crosses  the  aorta  to  the  superficial 
cardiac  plexus.  In  the  thorax  several  cardiac  branches  proceed  from 
the  right  vagus  at  the  side  of  the  trachea  to  the  deep  cardiac  plexus. 
The  corresponding  branches  of  the  left  vagus  proceed  from  the  inferior 
laryngeal  nerve. 

The  inferior,  or  recurrent  laryngeal  nerve,6  larger  than  the 
superior,  on  the  right  side  comes  from  the  vagus  at  the  bottom  of 
the  neck,  thence  turns  backward  around  and  below  the  subclavian 
artery.  That  of  the  left  side  comes  from  the  vagus  in  the  chest  and 
turns  backward  around  and  below  the  transverse  portion  of  the  aortic 
arch.  Each  nerve  ascends  in  the  neck  "behind  the  common  carotid 
and  inferior  thyroid  arteries,  continues  up  in  the  groove  between  the 

1  Ramus  pharyngeus  vagi.  2  N.  laryngeus  superior. 

3  K.  laryngeus  externus.  *  K.  laryngeus  internus. 

5  Kami  cardiaci ;  nervi  molles.  6  N.  laryngeus  inferior  or  recurrens. 


804  THE   NERVOUS  SYSTEM. 

trachea  and  oesophagus  to  the  larynx,  which  it  enters  between  the 
cricoid  cartilage  and  inferior  constrictor  of  the  pharynx  and  ends  in 
branches  which  supply  all  the  muscles  of  the  larynx  except  the  erico- 
thyroid.  It  also  supplies  the  mucous  membrane  of  the  larynx  below 
the  glottis  and  gives  a  branch  of  communication  with  the  superior 
laryngeal  nerve. 

Where  the  recurrent  nerve  turns  up  it  gives  branches  to  the  cardiac 
plexus  and  is  connected  by  filaments  with  the  inferior  cervical  gan- 
glion of  the  sympathetic.  In  its  further  ascent  it  gives  branches  to 
the  trachea  and  oesophagus  and  finally  to  the  inferior  constrictor  of  the 
pharynx. 

The  pulmonary  branches  of  the  vagus  proceed  from  the  trunk 
of  the  nerve,  in  the  thorax  at  the  side  of  the  trachea,  in  two  divisions, 
one  to  the  fore  and  the  other  to  the  back  part  of  the  root  of  the  lung. 
The  anterior  pulmonary  branches1  consist  of  two  or  three  fila- 
ments, which  join  with  others  from  the  sympathetic  and  proceed  in 
front  of  the  bronchus,  where  they  form  the  anterior  pulmonary 
plexus,2  whence  branches  are  distributed  through  the  lung.  Behind 
the  root  of  the  lung  the  trunk  of  the  vagus  becomes  flattened  and 
gives  off  several  posterior  pulmonary  branches,3  much  larger  than 
the  anterior.  They  conjoin  with  filaments  from  the  second  to  the 
fourth  thoracic  •  ganglia  of  the  sympathetic  to  form  the  posterior 
pulmonary  plexus4  at  the  back  of  the  bronchus,  whence  branches 
are  distributed  throughout  the  lung. 

The  pulmonary  plexuses  of  both  vagi  intercommunicate  across  the 
lower  extremity  of  the  trachea  in  a  loose  plexus,  whence  branches  of 
each  nerve  proceed  to  the  opposite  lung. 

From  the  position  of  the  pulmonary  plexus  the  vagus  descends  on 
the  oesophagus,  divides  and  subdivides,  and  with  that  of  the  opposite 
side  forms  the  oesophageal  plexus,5  from  which  the  branches  supply 
the  oesophagus.  Other  oesophageal  branches  which  come  from  the 
vagus  above  the  pulmonary  branches  supply  the  contiguous  portion  of 
the  oesophagus. 

The  terminal,  or  gastric  branches,6  of  the  vagus  are  mainly  dis- 
tributed to  the  stomach.  The  left  vagus  runs  in  front  of  the  lower 
part  of  the  oesophagus  and  at  the  cardiac  orifice  of  the  stomach  breaks 
up  into  numerous  branches,  which  form  the  anterior  gastric  plexus 7 
in  the  anterior  wall  of  the  organ  and  partly  run  along  its  lesser  curva- 
ture, where  they  communicate  with  branches  of  the  right  vagus  and 
sympathetic,  some  of  the  filaments  being  continued  in  the  small  omen- 
turn  to  the  hepatic  plexus.  The  right  vagus  proceeding  from  behind 
the  oesophagus  is  mainly  distributed  in  the  posterior  gastric  plexus8 

1  Nervi  bronchiales  anteriores.  2  P.  pulmonalis  ant. 

3  N.  bronchiales  posteriores.         4  P.  pulmonalis  post.         5  P.  cesophageus. 

6  Kami  gastrici.  T  P.  gastricus  anterior.      8  P.  gastricus  posterior. 


THE   NERVOUS  SYSTEM.  805 

to  the  posterior  wall  of  the  stomach,  but  many  of  its  branches  run  to 
the  coeliac,  rnesenteric,  splenic,  and  renal  plexuses  of  the  sympathetic. 
The  vagus  nerves  are  sensory-motor.  They  supply  the  pharynx, 
O3sophagus,  and  stomach,  the  larynx,  trachea,  and  lungs,  and  through 
their  connection  with  the  sympathetic  nerves  the  heart  and  great 
blood-vessels,  the  liver,  pancreas,  spleen,  and  to  a  less  extent  the  kid- 
neys and  small  intestine.  They  also  give  branches  to  the  dura  and 
the  external  ear. 

XI.     ACCESSOKY   NERVE. 

The  eleventh,  or  accessory  nerve,1  consists  of  a  portion  arising 
from  the  oblongata  accessory  to  the  vagus  nerve,  and  a  larger  spinal 
portion  from  the  spinal  cord  destined  to  supply  the  sterno-mastoid  and 
trapezius  muscles.  The  accessory  portion2  is  directed  outward  in 
company  with  and  below  the  vagus  nerve.  The  spinal  portion  ascends 
from  the  dural  sheath  of  the  spinal  cord  between  the  denticulate  liga- 
ment and  the  posterior  roots  of  the  cervical  nerves,  enters  the  cranium 
through  the  occipital  foramen,  where  it  joins  the  small  portion  of  the 
nerve,  and  they  proceed  together  to  the  jugular  foramen.  Through 
this  they  descend  in  company  with  the  vagus  nerve  contained  in  the 
same  dural  tube,  which  separates  them  from  the  glosso-pharyngeal 
nerve.  The  two  portions  of  the  eleventh  nerve  quickly  separate,  and 
the  small  or  accessory  portion,  after  communicating  by  one  or  several 
short  filaments  with  the  jugular  ganglion  of  the  vagus,  joins  the  gan- 
gliform  plexus,  whence  most  of  the  fibres  pass  into  the  pharyngeal 
and  superior  laryngeal  nerves  and  the  rest  into  the  trunk  of  the  vagus 
below. 

The  larger,  or  spinal  portion,3  of  the  accessory  nerve  runs  to  the 
outer  side  of  the  internal  jugular  vein  backward  and  downward  and 
perforates  the  sterno-mastoid  muscle,  which  it  supplies  with  branches. 
Joined  by  a  branch  of  the  cervical  plexus  to  the  same  muscle,  the 
nerve  then  descends  across  the  triangular  space  behind,  passes  beneath 
the  trapezius  muscle,  where  it  communicates  with  branches  of  the  third 
and  fourth  cervical  nerves,  and  is  distributed  to  the  trapezius. 

XII.     HYPOGLOSSAL   NERVE. 

The  twelfth,  or  hypoglossal  nerve,*  in  its  origin  from  the  oblon- 
gata emerges  from  the  groove  between  the  pyramid  and  olive  in  a 
series  of  rootlets,  which  converge  into  a  pair  of  bundles.  These  pass 
through  separate  apertures  of  the  dura  opposite  the  condylar  foramen 
and  unite  in  a  single  trunk  in  their  course  through  it.  As  the  nerve 


1  N.  accessorius ;    n.  recurrens ;    spinal  accessory  nerve ;    third  portion  of  the 
eighth  nerve  of  Willis. 

2  Ramus  internus  ;  r.  anastomoticus.  3  R.  externus  ;   r.  muscularis. 
*  N.  hypoglossus  ;  n.  motorius  linguae  ;  n.  loquens  ;  ninth  nerve  of  Willis. 


806  THE   NEKVOUS    SYSTEM. 

leaves  the  foramen  it  is  situated  to  the  inner  side  of  those  passing 
through  the  jugular  foramen  and  turns  outwardly  between  the  acces- 
sory and  vagus  nerves.  It  then  passes  between  the  internal  jugular 
vein  and  internal  carotid  artery,  winding  forward  to  the  outer  side 
of  the  artery  and  sweeping  in  a  curve  with  the  convexity  downward 
to  the  under  part  of  the  tongue.  In  its  course  it  crosses  the  outside  of 
the  external  carotid  artery  at  the  origin  of  the  occipital  artery,  thence 
crosses  the  facial  artery  beneath  the  digastric  tendon  and  ascends  on 
the  outer  side  of  the  hyo-glossal  and  through  the  genio-glossal  muscle 
to  the  tip  of  the  tongue.  The  terminal  branches  are  distributed  to 
the  genio-,  hyo-,  and  stylo-glossal,  genio-hyoid  and  other  muscles  of  the 
tongue.  A  separate  branch  from  the  hypoglossal  nerve  as  it  approaches 
the  hyoid  bone  is  given  to  the  thyro-hyoid  muscle. 

Below  the  condylar  foramen  the  hypoglossal  nerve  is  connected  by 
a  filament  with  the  first  cervical  ganglion  of  the  sympathetic,  by  one  or 
several  filaments  with  the  loop  of  the  first  and  second  cervical  nerves 
and  with  the  gangliform  plexus  of  the  vagus  nerve.  It  also  receives 
a  filament1  from  the  pharyngeal  plexus  as  it  passes  below  the  occipital 
artery.  In  the  submaxillary  region  filaments  join  others  of  the  lingual 
nerve  in  one  or  two  loops  on  the  fore  part  of  the  hyo-glossal  muscle. 

As  the  hypoglossal  nerve  crosses  the  external  carotid  artery  it  gives 
off  a  descending  cervical  branch.2  This  runs  down  the  neck  on 
the  sheath  of  the  common  carotid  artery  and  communicates  with  a 
couple  of  filaments3  descending  from  the  second  and  third  cervical 
nerves,  which  interlace  and  together  form  a  loop,*  whence  branches 
are  distributed  to  the  omo-  and  sterno-hyoid  and  the  sterno-thyroid 
muscles.  Commonly,  also,  a  filament  from  the  loop  runs  down  on  the 
common  carotid  artery  to  the  cardiac  plexus  of  the  sympathetic 
nerve. 

The  hypoglossal  nerve,  motor  in  function,  supplies  the  muscles  of 
the  tongue,  including  the  genio-hyoid  and  thyro-hyoid,  and  reinforces 
branches  of  the  second  and  third  cervical  nerves  in  supplying  the  infra- 
hyoid  muscles.  It  anastomoses  with  the  vagus,  lingual,  upper  three 
cervical,  and  sympathetic  nerves. 

DISTRIBUTION   OF   THE   SPINAL   NEKVES. 

The  spinal  nerves  are  divided,  according  to  the  region  in  which 
they  issue  from  the  spinal  canal,  into  eight  pairs  of  cervical,  twelve 
thoracic,  five  lumbar,  five  sacral,  and  one  of  coccygeal  nerves. 
The  first  pair  of  cervical  nerves  emerge  from  the  intervertebral  foramina 
between  the  occiput  and  atlas,  and  the  eighth  pair  between  the  last 
cervical  and  first  thoracic  vertebrae ;  the  others  emerge  in  succession 

1  Lingual  branch  of  the  vagus ;  ramus  pharyngeus  vagi. 

2  Ramus  cervicalis  descendens ;  r.  descendens  noni. 

3  Ansa  hypoglossi.  *  Eami  communicantes  noni. 


THE   NERVOUS   SYSTEM.  807 

from  the  intervertebral  foramina  corresponding  in  number  and  posi- 
tion ;  the  coccygeal  nerve  emerges  from  the  end  of  the  sacral  canal 
and  the  intervertebral  foramen  between  the  first  and  second  coccygeal 
vertebrae. 

The  short  trunk  of  each  spinal  nerve  at  once  divides  into  two 
branches,  distinguished  as  the  posterior  and  anterior  spinal  nerves, 
the  former  distributed  to  the  back  of  the  body,  the  latter  to  the  front 
of  the  body  and  to  the  limbs. 

The  spinal  nerves,  which  are  sensory-motor,  supply  the  muscles  and 
skin  of  the  trunk  of  the  body  and  limbs.  The  anterior  roots  are  purely 
sensory,  the  posterior  roots  purely  motor,  and  by  their  union  the  short 
trunk  becomes  of  mixed  quality,  which  is  continued  in  its  branches. 

POSTEKIOK   SPINAL   NERVES. 

The  posterior  spinal  nerves  are  generally  much  smaller  than  the 
anterior.  They  spring  from  the  trunk,  immediately  after  the  conjunc- 
tion of  the  roots  succeeding  the  ganglion  on  the  posterior  root,  gener- 
ally in  the  intervertebral  foramen,  frequently  by  separate  bundles  from 
the  two  roots.  Each  nerve  turns  •  backward  between  the  transverse 
processes  of  the  vertebrae  and  generally  divides  into  an  external  and 
an  internal  branch,  which  are  distributed  to  the  muscles  and  skin 
behind  the  body.  Those  which  do  not  divide  are  the  first  posterior 
cervical,  fifth  and  sixth  posterior  sacral,  and  coccygeal  nerves. 

The  first  cervical  nerve,  emerging  between  the  occiput  and  atlas, 
is  distinguished  as  the  suboccipital  nerve.  Its  posterior  branch, 
slightly  larger  than  the  anterior,  emerges  over  the  arch  of  the  atlas, 
between  it  and  the  vertebral  artery,  and  runs  into  the  interval  between 
the  recti  and  oblique  muscles,  to  which  and  the  complexus  it  is  dis- 
tributed. 

Of  the  succeeding  posterior  cervical  nerves,  the  external 
branches  are  distributed  to  the  cervical  ascending  and  transversalis 
and  splenius  muscles.  Of  the  internal  branches,  that  from  the 
second  cervical  nerve,  from  its  size  and  destination,  is  named  the  great 
occipital  nerve.  It  passes  over  the  inferior  oblique  muscle,  per- 
forates the  complexus  and  trapezius,  giving  branches  to  the  former 
ascends  in  company  with  the  occipital  artery  to  the  scalp,  to  which  it 
is  distributed,  and  anastomoses  with  the  small  occipital  nerve.  The 
internal  branches  from  the  third  to  the  fifth  cervical  nerve  pass  over 
the  semispinalis  muscle  beneath  the  complexus,  supply  them  and  the 
multifidus  muscle,  then  near  the  spinous  processes  of  the  vertebras 
turn  outward  to  supply  the  skin  of  the  neck  over  the  trapezius.  The 
internal  branches  from  the  lower  three  cervical  nerves  run  beneath  the 
semispinalis  and  are  distributed  to  it  and  the  contiguous  muscles. 

Of  the  posterior  thoracic  nerves,  the  external  branches  in- 
crease in  size  from  above  downward  and  pass  through  or  beneath  the 
longissimus  muscle  to  the  interval  between  it  and  the  ilio-costalis  and 


808  THE   NERVOUS   SYSTEM. 

accessory  muscles,  which  they  supply.  The  lower  five  or  six  give 
cutaneous  branches  outward  to  the  skin  in  a  line  with  the  angle  of 
the  ribs.  Of  the  internal  branches,  the  upper  six  or  seven  appear 
between  the  multifidus  and  semispinalis  muscles,  supply  them  and 
others  contiguous,  then  turn  outward  from  the  vicinity  of  the  spinous 
process  of  the  vertebrae  to  be  distributed  to  the  skin.  The  internal 
branches  of  the  lower  nerves  are  for  the  most  part  distributed  to  the 
multifidus  muscle. 

Of  the  posterior  lumbar  nerves,  the  external  branches  supply 
the  contiguous  part  of  the  dorsal  extensor  and  intertrans verse  mus- 
cles. Cutaneous  branches  from  the  upper  three  pierce  the  ilio-costalis 
and  aponeurosis  of  the  longissimus^and  descend  outward  and  forward 
over  the  iliac  crest  to  the  skin  of  the  gluteal  region.  An  anastomotic 
branch  from  the  last  nerve  descends  to  join  the  corresponding  branch 
of  the  first  sacral  nerve.  The  internal  branches  turn  round  the 
contiguous  articular  processes  of  the  vertebrae  to  be  distributed  to  the 
multifidus  muscle. 

The  posterior  sacral  nerves  emerge  from  the  posterior  sacral 
foramina  and  the  corresponding  one  below.  The  first  three  as  usual 
divide  into  external  and  internal  branches,  while  the  others  remain 
undivided. 

The  internal  branches  of  the  first  three  posterior  sacral  nerves 
terminate  in  the  contiguous  portion  of  the  multifidus  muscle.  The 
external  branches  anastomose  with  one  another,  with  the  last  lumbar 
nerve,  and  with  the  fourth  sacral  nerve,  which  in  like  manner  anasto- 
moses with  the  fifth  sacral,  and  this  with  the  posterior  coccygeal 
nerve.  Thus  on  the  back  of  the  sacrum  and  coccyx  is  formed  a  series 
of  loops,  the  posterior  sacro-coccygeal  plexus. 

The  coccygeal  nerve  divides  in  the  sacral  canal  and  its  posterior 
branch  emerges  from  the  end  of  the  canal  and  through  the  foramen 
between  the  first  two  coccygeal  vertebra?  to  join  the  plexus  just  named. 

From  the  upper  part  of  the  posterior  sacro-coccygeal  plexus  two 
or  three  cutaneous  branches,  of  the  corresponding  sacral  nerves,  pene- 
trate the  origin  of  the  great  gluteal  muscle  in  a  line  from  the  posterior 
superior  iliac  spine  to  the  end  of  the  coccyx  and  turn  outwardly  to  be 
distributed  to  the  skin  over  that  muscle.  From  the  lower  part  of  the 
plexus  cutaneous  branches  are  distributed  on  the  back  of  the  coccyx. 

ANTERIOR   SPINAL   NERVES. 

The  anterior  spinal  nerves  are  distributed  to  the  trunk  of  the 
body  in  advance  of  the  vertebral  column  and  to  the  limbs,  supplying 
the  muscles  and  skin  of  those  parts.  Each  as  it  passes  outward  and 
forward  from  the  intervertebral  foramen  communicates  by  filaments 
with  the  adjacent  ganglion  of  the  sympathetic  nerve. 

The  anterior  cervical,  lumbar,  and  sacral  nerves  branch  and  anasto- 


THE   NERVOUS  SYSTEM.  809 

mose  and  form  plexuses,  but  the  thoracic  nerves  for  the  most  part 
remain  independent. 

The  upper  four  anterior  cervical  nerves  make  their  appearance  at 
the  side  of  the  neck  between  the  greater  pre-rectus  and  anterior  sca- 
lenus  muscles,  and  by  division  and  anastomosis  form  the  cervical 
plexus.  Each  nerve  at  its  commencement  is  connected  by  a  filament 
with  the  first  cervical  ganglion  of  the  sympathetic  or  with  the  trunk 
of  this  nerve  below.  The  first  anterior  cervical  nerve  is  the  smallest 
of  the  series,  the  second  and  third  successively  increase  in  size,  and 
the  fourth  is  about  as  large  as  the  third. 

THE   CEKVICAL   PLEXUS. 

The  cervical  plexus,1  formed  by  the  upper  four  anterior  cervical 
nerves,  is  situated  opposite  the  corresponding  vertebrae  and  rests  on  the 
middle  scalenus  and  scapular  elevator  muscles  covered  by  the  sterno- 
mastoid  muscle.  In  the  construction  of  the  plexus  the  first  cervical 
nerve  turns  downward,  the  others  each  divide  into  an  ascending  and 
a  descending  branch,  and  the  contiguous  branches  and  first  nerve  of 
the  series  conjoin  in  a  series  of  loops. 

The  first  anterior  cervical  nerve  runs  forward  to  the  outer  side 
of  the  prearticular  process  of  the  atlas  beneath  the  vertebral  artery 
and  turns  down  in  front  of  the  costo-trans verse  process  to  join  the 
second  cervical.  In  its  course  it  supplies  the  lateral  rectus  and  pre- 
recti  muscles,  and  is  connected  by  filaments  with  the  vagus,  hypo- 
glossal,  and  sympathetic  nerves. 

The  second  anterior  cervical  nerve  passes  forward  between  the 
costo-transverse  processes  of  the  atlas  and  axis  to  the  outer  side  of 
the  vertebral  artery  and  divides  into  an  ascending  branch  to  the  first 
cervical  and  a  descending  branch  to  the  third  cervical  nerve. 

The  nerves  of  the  cervical  plexus  consist  of  a  deep  set  principally 
distributed  to  the  muscles  and  a  superficial  set  which  perforate  the 
cervical  fasciae  and  are  distributed  to  the  skin. 

Deep  branches  of  the  cervical  plexus.  Besides  the  communi- 
cating branches 2  between  the  loop  of  the  first  and  second  cervical 
nerves  and  the  vagus,  hypoglossal,  and  sympathetic  nerves,  the  fourth 
cervical  is  connected  by  a  branch  with  the  fifth  cervical  nerve. 
Branches  also  descend  from  the  second  and  third  cervical  nerves  to 
anastomose  with  the  descending  cervical  branch  of  the  hypoglossal 
nerve  distributed  to  the  depressor  muscles  of  the  hyoid  bone. 

Muscular  branches  from  the  cervical  nerves  close  to  the  verte- 
brae supply  the  prevertebral  muscles.  Others  go  to  the  scapular  ele- 
vator and  middle  scalenus  muscles.  Branches  from  the  second  and 
third  cervicals  communicate  with  the  accessory  nerve  and  are  dis- 
tributed to  the  sterno-mastoid  and  trapezius  muscles. 

1  P.  cervicalis.  2  Kami  communicantes  noni. 


810 


THE    NERVOUS    SYSTEM. 


The  phrenic  nerve1  springs  from  the  third  and  fourth  cervical 
nerves  and  commonly  also  receives  a  contribution  from  the  fifth.  De- 
scending the  neck  on  the  anterior  scalenus  muscle,  it  enters  the  thorax 
between  the  subclavian  artery  and  vein  and  crosses  the  mammary 
artery  near  its  commencement.  Continuing  downward  in  front  of 
the  root  of  the  lung,  enclosed  between  the  pericardium  and  medias- 

FIG.  407. 


19 
21 

22 

'•-•-  16  .-•-''  15  24  11  10 
CERVICAL  AND  BRACHIAL  PLEXUSES  OF  NERVES,  a-h.  cervical  nerves;  i,  first  thoracic  nerve ; 
a-d,  cervical  plexus ;  e-i,  brachial  plexus.  1,  branch  to  pre-recti  muscles;  2,  auastomotic  branch, 
with  vagus,  hypoglossal,  and  sympathetic  nerves;  3,  small  occipital  nerve;  4,  great  auricular 
nerve ;  5,  superficial  cervical  nerve ;  6,  anastomotic  branch  with  the  accessory  nerve ;  7,  anasto- 
motic  branch  with  the  descending  cervical  branch  of  the  hypoglossal  nerve ;  8,  supraclavicular 
nerves ;  9,  branch  to  scaleni  muscles ;  10,  phrenic  nerve ;  11,  posterior  thoracic  nerve ;  12,  branch 
to  rhomboid  muscles;  13,  branch  to  subclavius;  14,  suprascapular  nerve;  15,  anterior  thoracic 
nerves;  16,  three  subscapular  nerves;  17,  musculo-cutaneous  nerve;  18,  median  nerve;  19, 
musculo-spiral  nerve ;  20,  circumflex  nerve  ;  21,  ulnar  nerve ;  22,  internal  cutaneous  nerve ;  23, 
small  cutaneous  nerve ;  24,  first  intercostal  nerve ;  25,  upper  cord  of  the  brachial  plexus ;  26, 
posterior  cord ;  27,  lower  cord. 

tinal  pleura,  it  approaches  the  diaphragm  and  divides  into  branches, 
which  perforate  the  muscle  to  be  divergently  distributed  on  its  lower 
eui'face.  The  right  nerve  is  more  deeply  placed  than  the  left,  is  more 
vertical,  and  enters  the  chest  along  the  outer  side  of  the  right  innominate 
vein  and  superior  cava.  The  left  nerve  is  somewhat  longer,  and  on 
entering  the  chest  crosses  in  front  of  the  arch  of  the  aorta  to  the  side 

1  N.  phrenicus  ;  internal  respiratory  nerve  of  Bell. 


THE   NERVOUS   SYSTEM.  811 

of  the  pericardium.  In  its  course  near  the  chest  it  is  joined  by  a  fila- 
ment from  the  sympathetic  and  usually  by  another  from  the  branch 
of  the  fifth  and  sixth  cervical  nerves  to  the  subclavian  muscle.  It 
also  gives  filaments  to  the  pericardium  and  pleura. 

Superficial  branches  of  the  cervical  plexus.  These  consist 
of  the  superficial  cervical,  great  auricular,  small  occipital,  and  supra- 
scapular  nerves. 

The  superficial  cervical  nerve,1  derived  from  the  second  and 
third  cervicals,  turns  from  behind  forward  across  the  outer  side  of  the 
stern o-mastoid  muscle,  about  its  middle,  beneath  the  external  jugular 
vein,  to  the  anterior  border  of  the  muscle.  Here  it  perforates  the 
cervical  fascia  and  divides  into  diverging  branches,  commonly  two 
principal  ones,2  which  penetrate  the  platysma  and  are  distributed  to 
the  skin  of  the  fore  part  of  the  neck  extending  from  the  face  to  the 
breast.  The  upper  larger  branch  anastomoses  with  the  cervico-facial 
division  of  the  facial  nerve. 

The  great  auricular  nerve,3  from  the  same  source  as  the  preceding, 
winds  from  behind  and  ascends  obliquely  upward  across  the  sterno- 
mastoid  muscle  to  the  back  of  the  ear,  to  which  it  is  distributed,  giving 
branches  to  the  skin  over  the  mastoid  process  and  to  the  face  over  the 
parotid  gland.4  It  anastomoses  with  the  posterior  auricular  branch  of 
the  facial  and  with  some  of  its  filaments  to  the  face. 

The  small  occipital  nerve,5  from  the  third  cervical,  ascends  along 
the  posterior  border  of  the  sterno-mastoid  muscle  to  the  scalp  in  the 
position  between  the  great  auricular  and  occipital  nerves,  with  both 
of  which  its  contiguous  filaments  anastomose  and  also  with  the  pos- 
terior auricular  branch  of  the  facial  nerve. 

The  least  occipital  nerve,6  derived  from  the  plexus  in  common 
with  one  of  the  former  nerves,  gives  a  branch  to  the  skin  at  the 
back  of  the  neck  and  then  ascends  between  the  great  auricular  and 
email  occipital  nerves  to  the  skin  over  the  mastoid  process. 

The  supraclavicular  nerves,7  usually  three  or  four  branches8  from 
the  third  and  fourth  cervicals,  descend  in  the  interval  of  the  sterno- 
mastbid  and  trapezius  muscles  and  diverge  over  the  clavicle  and  acro- 
mion  to  be  distributed  to  the  skin  of  the  upper  part  of  the  breast,  ex- 
tending as  far  as  the  position  of  the  fourth  rib  and  over  the  shoulder. 

The  cervical  plexus  supplies  cutaneous  branches  to  the  side  of  the 
head  behind  the  ear,  to  part  of  the  auricle,  face,  the  neck,  and  to  the 
upper  part  of  the  breast  and  shoulder.  It  furnishes  muscular  branches 
to  the  pre-recti,  the  scapular  elevator,  the  middle  scalenus,  the  infra- 

1  N.  superficialis  or  subcutaneus  colli. 

2  Upper  or  ascending  and  lower  or  descending  branches  ;  n.  subcutaneus  colli 
medius  and  inferior. 

3  N.  auricularis  magnus.  4  Kamus  facialis,  auricularis,  and  mastoideus. 

5  N.  occipitalis  minor.        6  N.  occipitalis  minimus.  7  N.  supraclaviculares. 

8  Internal,  middle,  and  external ;  sternal,  clavicular,  and  acromial. 


812  THE   NERVOUS   SYSTEM. 

hyoid,  the  sterno-mastoid  muscles,  the  trapezius,  and  the  diaphragm. 
It  anastomoses  with  the  facial,  vagus,  accessory,  hypoglossal,  and  sym- 
pathetic nerves. 

THE   BKACHIAL   PLEXUS. 

The  brachial  plexus l  is  formed  by  the  lower  four  anterior  cer- 
vical and  greater  part  of  the  first  anterior  thoracic  nerves,  which  are 
remarkable  for  their  large  size,  all  being  nearly  equal  and  much  larger 
than  the  preceding  nerves.  It  extends  from  the  lower  part  of  the  side 
of  the  neck  beneath  the  clavicle  into  the  axilla  and  is  accompanied  by 
the  great  blood-vessels  of  the  upper  limb.  It  is  broad  and  plexiform  at 
its  commencement,  narrows  opposite  the  clavicle,  forms  an  intricate  inter- 
lacement in  the  axilla,  and  finally  separates  into  many  long  branches 
distributed  to  the  upper  limb. 

The  arrangement  of  the  brachial  plexus  is  very  variable.  Com- 
monly the  fifth  and  sixth  cervical  nerves  converge  and  unite  in  a  short 
trunk ;  the  first  thoracic  nerve  ascends  over  the  neck  of  the  first  rib 
and  joins  the  eighth  cervical  nerve  to  form  a  second  trunk,  while  the 
seventh  cervical  nerve  continues  as  a  middle  trunk.  Each  trunk 
divides  into  an  anterior  and  a  posterior  branch,  and  the  posterior 
branches  converge  behind  the  axillary  blood-vessels  into  the  posterior 
cord  of  the  plexus ;  the  anterior  branches  of  the  upper  and  middle 
trunks  converge  and  unite  in  the  outer  cord  of  the  plexus ;  the  anterior 
branch  of  the  lower  trunk  continues  as  the  inner  cord  of  the  plexus. 
The  posterior  cord  of  the  plexus  divides  into  the  circumflex  and  mus- 
culo-spiral  nerves.  The  outer  and  inner  cords  divide,  their  contiguous 
branches  converge  above  and  below  the  axillary  vessels  and  in  front  of 
them  conjoin  in  the  median  nerve,  while  the  remaining  branch  of  the 
outer  or  upper  cord  is  continued  as  the  musculo-cutaneous  nerve,  and 
that  of  the  inner  or  lower  cord  as  the  ulnar  and  internal  cutaneous 
nerves. 

Sometimes  the  fifth,  sixth,  and  seventh  cervical  nerves  successively 
conjoin  in  the  upper  trunk,  while  the  other  nerves  unite  as  usual  in  the 
lower  trunk.  Branches  from  the  two  trunks  conjoin  to  form  the  pos- 
terior cord  of  the  plexus,  while  the  remainder  of  the  trunks  form  the 
upper  and  lower  cords.  In  some  instances  before  the  union  of  the 
upper  two  nerves  of  the  plexus  each  gives  off  a  branch  which  joins  the 
other  and  that  of  the  lower  trunk  to  form  the  posterior  cord. 

Besides  the  common  variations  in  the  disposition  of  the  chief  nerves 
of  the  brachial  plexus,  others,  in  the  mode  of  origin  of  its  different 
branches,  are  frequent. 

The  brachial  plexus  in  the  neck  is  situated  between  the  anterior 
and  middle  scalenus  muscles  and  extends  outward  and  downward 
under  the  clavicle  and  subclavian  muscle,  with  the  subclavian  artery 

1  P.  brachialis  ;  p.  axillaris. 


THE   NERVOUS   SYSTEM. 


813 


in  advance  of  its  lower  part  as  they  pass  together  over  the  first  rib. 
In  the  axilla  it  rests  on  the  upper  head  of  the  great  serratus  and  the 
subscapular  muscles,  to  the  outer  side  of  the  axillary  vessels.  It  then 
surrounds  the  vessels,  one  cord  to  the  outer  side,  one  to  the  inner  side, 
and  the  other  behind. 

At  their  commencement  the  nerves  of  the  brachial  plexus  are  con- 

FIG.  408. 


THE  BRACHIAL  PLEXUS.  1,  anastomosis  between  the  descending  cervical  branch  of  the  hypo- 
glossal  and  a  branch  of  the  cervical  plexus ;  2,  vagus  nerve ;  3,  phrenic  nerve ;  4-8,  the  lower  four 
cervical  and  the  first  thoracic  nerves,  forming  the  brachial  plexus ;  9,  branch  to  the  subclavian 
muscle  giving  a  filament  to  the  phrenic  nerve ;  10,  posterior  thoracic  nerve ;  11, 13,  anterior  tho- 
racic nerves ;  14,  anastomosis  between  the  latter ;  12,  suprascapular  nerve ;  15-17,  subscapular 
nerves ;  18,  small  cutaneous  nerve ;  19,  anastomosis  of  a  branch  of  the  latter  with  the  intercosto- 
humeral  nerve,  20 ;  21,  continuation  of  the  small  cutaneous  nerve  in  company  with  the  internal 
cutaneous,  22 ;  23,  ulnar  nerve ;  24,  median ;  25,  musculo-cutaneous ;  26,  musculo-spiral  nerve. 

nected  with  the  first  and  second  cervical  ganglia  of  the  sympathetic. 
The  fifth  nerve  receives  a  communicating  branch  from  the  fourth  cer- 
vical and  gives  a  filament  to  the  phrenic  nerve  as  it  lies  on  the  anterior 
scalenus  muscle. 

The  branches  of  the  brachial  plexus  are  the  following:  muscular, 
thoracic,  subscapular,  circumflex,  musculo-cutaneous,  cutaneous,  median, 
ulnar,  and  musculo-spiral  nerves. 

Muscular  branches.     Of  these  several  small  ones  go  to  the  long 


814  THE   NERVOUS   SYSTEM. 

cervical  and  scaleni  muscles.  Another  from  the  fifth  nerve  passes 
backward  through  the  middle  scalenus  to  the  rhomboid  muscles,  to 
which  it  is  distributed.  A  small  one  also  goes  to  the  subclavian 
muscle,  frequently  connected  by  a  filament  with  the  phrenic  nerve. 

The  posterior  thoracic  nerve l  springs  from  near  the  commence- 
ment of  the  upper  two  or  three  cervical  nerves  of  the  brachial  plexus, 
by  as  many  roots,  which  descend  and  conjoin  within  the  middle  sca- 
lenus muscle,  behind  the  plexus,  whence  the  nerve  runs  down  on  the 
outer  side  of  the  great  serratus  muscle  to  its  lower  border  distributed 
in  branches  to  it. 

Anterior  thoracic  nerves.2  Of  these  there  are  two,  distributed 
to  the  pectoral  muscles.  The  more  superficial  external  branch  comes 
from  the  outer  cord  of  the  brachial  plexus  and  crosses  over  the  axillary 
blood-vessels  to  supply  the  greater  pectoral  muscle.  The  deep,  or  in- 
ternal branch,  springs  from  the  inner  cord  of  the  plexus,  passes  for- 
ward between  the  axillary  artery  and  vein,  and,  after  anastomosing 
and  interlacing  with  the  former  branch,  is  distributed  to  both  pectoral 
muscles. 

Subscapular  nerves.3  Of  these  there  are  commonly  three,  spring- 
ing from  the  corresponding  upper  nerves  of  the  plexus  or  from  the 
posterior  cord  formed  by  them.  The  upper  branch  enters  the  upper 
part  of  the  subscapular  muscle,  which  it  supplies ;  the  lower  branch, 
larger  than  the  former,  enters  the  axillary  border  of  the  same  muscle 
and  ends  in  the  greater  teres  muscle,  both  of  which  it  supplies ;  the 
middle  branch,  largest  and  longest,  descends  in  company  with  the 
subscapular  artery  and  enters  the  inner  surface  of  the  latissimus 
muscle,  to  which  it  is  distributed. 

The  suprascapular  nerve4  springs  from  the  fifth  cervical  or  the 
cord  formed  by  its  union  with  the  sixth,  runs  outward  and  backward 
under  the  trapezius  to  the  upper  border  of  the  scapula,  and  passes 
through  the  coracoid  foramen  into  the  supraspinous  fossa.  Here,  after 
supplying  the  supraspinatus  muscle,  it  passes  through  the  scapular 
notch  to  be  distributed  to  the  infraspinatus  muscle,  in  its  course  giving 
filaments  to  the  shoulder-joint. 

The  circumflex  nerve,5  a  terminal  branch  of  the  posterior  cord 
of  the  brachial  plexus,  from  behind  the  axillary  blood-vessels,  winds 
backward  around  the  inner  side  of  the  humerus  below  its  head  in 
company  with  the  posterior  circumflex  artery,  in  the  interval  between 
the  teres  muscles  and  the  long  head  of  the  triceps,  and  divides  into 
two  branches.  Of  these  the  upper  branch  winds  outward  around 
the  humerus  beneath  the  deltoid,  nearly  to  the  anterior  border  of  the 


1  N.  thoracicus  posterior  or  longus  ;  external  respiratory  nerve  of  Bell. 

2  Nervi  thoracici  anteriores.  8  N.  subscapulares. 

4  N.  suprascapularis  ;  n.  scapularis. 

5  N.  circumflexus  ;  n.  axillaris  ;  n.  scapulo-humeralis. 


THE   NERVOUS   SYSTEM.  815 

muscle,  to  which  it  is  distributed,  one  or  two  of  its  filaments  pene- 
trating between  the  fleshy  fascicles  and  supplying  the  skin  over  the 
lower  part  of  the  muscle.  The  lower  branch  gives  filaments  to  the 
back  part  of  the  deltoid  and  supplies  the  small  teres  muscle,  and 
finally  penetrating  the  deep  fascia  is  distributed  to  the  skin  over 
the  lower  part  of  the  deltoid  and  adjacent  part  of  the  triceps  muscle. 
An  articular  filament  from  the  nerve  before  its  division  supplies 
the  capsular  ligament  of  the  shoulder-joint. 

The  musculo-cutaneous  nerve,1  the  smaller  of  the  terminal 
branches  of  the  outer  cord  of  the  brachial  plexus,  is  directed  down- 
ward, perforates  the  coraco-brachialis  muscle  and  passes  obliquely  out- 
ward between  the  biceps  and  brachialis  muscles  to  near  the  elbow, 
where  it  pierces  the  deep  brachial  fascia  and  becomes  cutaneous.  In 
its  course  it  supplies  the  muscles  just  named  and  gives  filaments  to 
the  humerus  and  elbow-joint. 

The  cutaneous  portion  of  the  nerve  passes  along  the  outer  side  of 
the  cephalic  vein  and  divides  into  two  branches.  Of  these  the  an- 
terior branch  passes  over  the  median  cephalic  vein  and  descends  in 
front  of  the  radial  side  of  the  forearm  to  the  ball  of  the  thumb,  dis- 
tributing branches  to  the  skin  in  its  course.  Near  the  wrist  it  lies  in 
front  of  the  radial  vessels  and  is  connected  with  a  branch  of  the  radial 
nerve.  The  posterior  branch  is  directed  outward  to  the  back  of 
the  forearm,  on  which  it  descends  to  the  wrist,  supplying  the  skin  in 
its  course  and  communicating  by  filaments  with  the  radial  and  lower 
cutaneous  branch  of  the  musculo-spiral  nerve. 

The  internal  cutaneous  nerve,2  smaller  than  the  preceding,  is 
derived  from  the  inner  cord  of  the  brachial  plexus  and  is  situated  in- 
ternally to  the  axillary  vessels.  Piercing  the  brachial  fascia  about 
the  middle  of  the  arm,  it  descends  along  the  basilic  vein  and  divides 
into  two  principal  branches.  Of  these  the  anterior  branch  usually 
passes  over,  sometimes  under,  the  median  basilic  vein  and  descends 
along  the  fore  part  of  the  ulnar  side  of  the  forearm  to  the  wrist,  sup- 
plying the  skin  in  its  course  and  communicating  with  cutaneous 
branches  of  the  ulnar  nerve.  The  posterior  branch  passes  down  on 
the  inner  side  of  the  basilic  vein,  thence  behind  the  inner  epicondyle 
and  along  the  back  part  of  the  ulnar  side  of  the  forearm  to  the  wrist, 
supplying  the  contiguous  skin  and  communicating  with  the  dorsal 
branch  of  the  ulnar  nerve.  In  the  arm  some  filaments  from  the  in- 
ternal cutaneous  nerve  supply  the  skin  over  the  biceps  muscle. 

The  small  cutaneous  nerve3  usually  comes  from  the  inner  cord 


1  N.  musculo-cutaneus ;  n.  cutaneus  externus  or  brachii  externus ;  n.  perforans 
Casserii. 

2  N.  cutaneus  interims  ;  n.  c.  brachii  medius. 

3  Small  internal  cutaneous  nerve ;  n.  cutaneus  minor  or  interims  minor  ;  n.  cut. 
brachii  internus. 


816 


THE   NERVOUS   SYSTEM. 


of  the  brachial  plexus  or  arises  together  with  the  former  nerve.  In  the 
axilla  it  lies  close  to  the  axillary  vein  and  descends  along  the  inner 
side  of  the  brachial  vessels  to  near  the  middle  of  the  arm,  where  it 
pierces  the  fascia  and  descends  to  the  interval  between  the  olecranon 


FIG.  410. 


12 


CUTANEOUS  NERVES  OF  THE  UPPER  EXTREMITY.  1,  supraclavicular  nerves  of  the  cervical 
plexus ;  2,  cutaneous  branches  of  the  circumflex  nerve ;  3,  branch  of  the  internal  cutaneous 
nerve ;  4,  small  cutaneous  nerve,  and  its  anastomosis  with  the  intercosto-humeral ;  5,  cutaneous 
branch  of  the  musculo-spiral  nerve  ;  6,  internal  cutaneous  nerve  piercing  the  brachial  fascia;  7, 
posterior  branch  anastomosing  with  8,  the  ulnar  nerve  and  9,  the  anterior  branch ;  10,  the  in- 
ternal cutaneous  dividing  into  branches,  some  passing  over  and  others  under  the  median  basilic 
vein ;  11,  musculo-cutaneous  nerve ;  12,  cutaneous  branch  of  the  musculo-spiral  nerve ;  13, 
branches  of  the  internal  cutaneous  to  the  front  of  the  forearm ;  14,  anastomosis  of  one  of  the 
latter  branches  with  one  from  the  ulnar  nerve ;  15,  terminal  branches  of  the  musculo-cutaneous 
nerve ;  16, 17,  anastomosis  between  the  latter  and  the  radial  nerve ;  18,  superficial  palmar  branch 
of  the  median  nerve ;  19-25,  digital  nerves. 

and  internal  epicondyle.     It  anastomoses  with  the  intercosto-humeral 
nerve  and  supplies  the  contiguous  skin. 

The  ulnar  nerve,1  the  larger  branch  of  the  inner  cord  and  one  of 
the  largest  nerves  of  the  brachial  plexus,  passes  along  the  inner  side 


1  N.  ulnaris  ;  n.  cubitalis. 


THE   NERVOUS   SYSTEM.  817 

of  the  axillary  and  brachial  vessels  to  near  the  middle  of  the  arm, 
where  it  gradually  diverges  behind  the  internal  intermuscular  septum 
on  the  triceps  muscle  to  the  interval  between  the  olecranon  and  inner 
epicondyle.  Prom  the  elbow,  it  passes  between  the  heads  of  the 
ulno-carpal  flexor,  beneath  which  it  descends  the  forearm,  resting  on 
the  deep  digital  flexor  and  covered  at  the, lower  part  by  the  fasciae 
and  skin.  From  the  wrist,  it  crosses  the  anterior  annular  ligament 
close  to  the  pisiform  bone,  below  which  it  divides  into  a  superficial 
and  a  deep  palmar  branch.  From  the  upper  third  of  its  course  in  the 
forearm  it  is  accompanied  by  the  ulnar  blood-vessels,  which  lie  to  its 
outer  side. 

In  the  arm  the  ulnar  nerve  gives  off  no  branches.  At  the  elbow  it 
gives  a  couple  of  small  articular  branches  to  the  elbow-joint,  and 
below  it  supplies  muscular  branches  to  the  ulno-carpal  and  deep 
digital  flexors. 

A  small  cutaneous  branch  comes  from  the  ulnar  nerve  about 
the  middle  of  the  forearm,  sometimes  communicating  by  a  filament 
with  the  internal  cutaneous  nerve,  and  accompanies  the  ulnar  artery 
to  the  hand,  where  it  is  distributed  to  the  skin. 

The  dorsal  cutaneous  branch,1  larger  than  the  former,  comes 
from  the  ulnar  nerve  a  couple  of  inches  above  the  wrist.  Turning 
backward  beneath  the  tendon  of  the  ulno-carpal  flexor  it  descends  on 
the  ulnar  side  of  the  back  of  the  wrist  and  hand,  to  which  it  is  dis- 
tributed. It  gives  a  dorsal  digital  branch  to  the  inner  side  of  the 
little  finger,  other  branches  dividing  into  the  collateral  dorsal  digi- 
tals 2  of  the  adjoining  sides  of  the  little,  ring,  and  middle  fingers,  and 
a  communicating  branch  or  two  to  the  radial  nerve,  which  in  like 
manner  supplies  the  other  fingers. 

The  superficial  palmar  branch,3  one  of  the  terminal  divisions  of 
the  ulnar,  gives  filaments  to  the  short  palmar  muscle  and  adjacent  part 
of  the  skin  and  divides  into  two  digital  branches.  One  of  these  runs 
along  the  inner  side  of  the  little  finger,  to  which  it  is  distributed ;  the 
other  is  connected  in  the  palm  of  the  hand  with  a  digital  branch  of  the 
median  nerve,  and  afterwards  divides  into  collateral  digital  branches 
which  supply  the  adjoining  sides  of  the  little  and  ring  fingers. 

The  deep  palmar  branch 4  of  the  ulnar  nerve  accompanies  the 
ulnar  artery  between  the  abductor  and  short  flexor  of  the  little  finger 
and  subsequently  the  deep  palmar  arch  beneath  the  flexor  tendons  in 
the  palm  of  the  hand.  It  supplies  the  short  muscles  of  the  little  finger, 
the  interosseous  and  two  inner  lumbrical  muscles,  and  ends  in  the 
adductor  and  inner  head  of  the  short  flexor  muscles  of  the  thumb. 
Filaments  also  ascend  to  the  articulations  of  the  wrist  and  others  to 
the  metacarpo-phalangeal  articulations. 

1  N.  dorsalis  ulnaris.  2  Nervi  digitorum  dorsales. 

3  N.  palmaris  superficialis.  *  N.  palmaris  profundus. 

52 


818 


THE   NERVOUS   SYSTEM. 


The  median  nerve,1  larger  than  the  ulnar,  springs  from  the  outer 
and  inner  cords  of  the  brachial  plexus  by  two  roots  which  unite  at 
an  acute  angle  in  front,  or  on  the  outer  side  of  the  axillary  blood- 


FIQ.  411. 


FIG.  412. 


12 


10 


MtTSCTJLO-CUTANEOUS,  MEDIAN,  ULNAR,  AND  MTJSCULO-SPIRAL  NERVES.      1,  ULUSCUlO-CUtaneOUS 

nerve ;  2,  3,  4,  muscular  branches ;  5,  anastomotic  filament  from  the  median  ;  6,  division  of  the 
musculo-cutaneous  nerve  into  branches  to  the  forearm ;  7,  musculo-spiral  nerve ;  8,  cutaneous 
branch;  9,  internal  cutaneous  nerve;  10,  its  branches  to  the  forearm;  11,  median  and  ulnar 
nerves ;  12,  median  nerve ;  13-16,  muscular  branches ;  17,  anterior  interosseous  nerve ;  18,  super- 
ficial palmar  branch ;  19,  branch  to  the  muscles  of  the  ball  of  the  thumb ;  20-24,  digital  nerves  of 
the  thumb,  index,  middle,  and  one  side  of  the  ring  finger ;  25,  ulnar  nerve ;  26,  muscular  branches ; 
27,  28,  cutaneous  and  dorsal  cutaneous  branches;  30, 31,  digitals  to  the  little  and  ring  fingers ;  32, 
deep  palmar  branch ;  33-36,  muscular  branches ;  37,  musculo-spiral  nerve ;  38,  posterior  inter- 
osseous  nerve ;  39,  a  muscular  branch ;  40,  radial  nerve. 

vessels.  The  nerve  descends  in  company  with  the  brachial  vessels, 
gradually  passing  inward  over  them,  and  near  the  elbow  lies  at  their 
inner  side.  Passing  over  the  bend  of  the  elbow  in  front,  it  runs  be- 
neath the  terete  pronator,  separated  by  the  deeper  portion  of  the 
muscle  from  the  ulnar  vessels,  and  continues  down  the  forearm  be- 


1  N.  medianus. 


THE   NERVOUS   SYSTEM.  819 

tween  the  superficial  and  deep  digital  flexors  to  near  the  wrist,  where 
it  lies  between  the  tendons  of  the  radio-carpal  and  superficial  digital 
flexors,  covered  by  the  fascia.  It  then  enters  the  palm  of  the  hand 
under  the  annular  ligament,  resting  on  the  flexor  tendons,  where  it 
becomes  somewhat  expanded  and  divides  into  two  portions,  of  which 
one  supplies  the  thumb  and  part  of  the  index  finger,  and  the  other 
supplies  the  remaining  part  of  the  index,  the  middle,  and  part  of  the 
ring  finger. 

The  median  nerve  gives  off  no  branches  in  the  arm.  It  gives  an 
articular  filament  to  the  front  of  the  elbow-joint. 

Muscular  branches  arise  separately  or  together  near  the  elbow 
and  proceed  to  supply  the  terete  pronator,  the  radio-carpal  and 
superficial  digital  flexors,  and  the  long  palmar  muscle. 

The  anterior  interosseous  nerve  1  arises  from  the  median  below 
the  elbow  and  accompanies  the  corresponding  vessels  in  front  of  the 
interosseous  membrane  to  the  quadrate  pronator,  in  the  deep  surface 
of  which  it  terminates.  It  supplies  the  long  pollical  and  outer  half  of 
the  deep  digital  flexors,  between  which  it  lies.  It  also  gives  filaments 
to  the  interosseous  membrane,  bones  of  the  forearm  and  the  wrist-joint. 

A  cutaneous  branch2  near  the  middle  of  the  forearm  pierces  the 
fascia  and  descends  in  the  direction  of  the  tendon  of  the  long  palmar 
muscle  to  the  skin  of  the  palm  of  the  hand. 

In  the  hand  the  median  nerve  gives  off  a  short  muscular  branch, 
which  is  distributed  to  the  abductor,  opponent,  and  outer  head  of  the 
short  flexor  muscles  of  the  thumb,  and  then  divides  into  three  common 
digital  nerves.3  Of  these  the  first  divides  into  three  collateral  digi- 
tal nerves,  of  which  one  runs  along  the  outer  side  of  the  thumb  to 
the  end,  while  the  others  in  the  same  manner  run  along  the  adjacent 
sides  of  the  thumb  and  the  index  finger ;  the  others  each  divide  in  a 
pair  of  collateral  digital  nerves,  which,  like  the  former,  run  along  the 
adjacent  sides  of  the  index,  ring,  and  middle  fingers.  The  branch  of 
the  first  common  digital  to  the  index  finger  and  the  second  give 
branches  to  the  first  and  second  lumbrical  muscles.  The  outer  branch 
of  the  first  common  digital  communicates  with  the  radial  nerve,  and 
the  third  common  digital  is  connected  by  a  branch  with  the  contiguous 
digital  of  the  ulnar  nerve. 

The  collateral  or  terminal  digitals  of  both  the  ulnar  and  median 
nerves  are  distributed  to  the  digits  in  the  same  manner.  In  their 
course  they  send  branches  forward  and  backward  to  the  skin,  those 
passing  behind  anastomosing  with  the  dorsal  digital  nerves.  At  the 
ends  of  the  fingers  each  digital  nerve  divides  into  two  branches,  of 
which  one  supplies  the  soft  tip  of  the  finger,  while  the  other  is  dis- 
tributed beneath  the  nail. 


1  N.  int.  anterior,  internus,  or  profundus. 

2  N.  cutaneus  antibrachii  palmaris.  3  N.  digitorum  volares. 


820  THE   NERVOUS   SYSTEM. 

The  musculo-spiral  nerve,1  the  largest  branch  of  the  brachial 
plexus,  springs  from  its  upper  cord  in  conjunction  with  the  circumflex 
nerve.  From  behind  the  position  of  the  axillary  blood-vessels  it  turns 
backward  and  outward  and  descends  in  the  musculo-spiral  groove  of 
the  humerus,  between  it  and  the  triceps  muscle,  accompanied  by  the 
superior  profunda  artery.  Piercing  the  external  intermuscular  septum 
it  descends  between  the  long  supinator  and  the  brachialis  muscle  to 
near  the  outer  condyle  of  the  humerus,  where  it  divides  into  the  pos- 
terior interosseous  and  radial  nerves. 

In  its  course  through  the  arm  the  musculo-spiral  nerve  gives  numer- 
ous muscular  branches  to  the  triceps  and  a  long  one  wThich  descends 
to  the  anconeus.  It  also  gives  others  to  the  long  supinator  and  the 
longer  radio-carpal  extensor. 

It  also  gives  off  several  cutaneous  branches,  of  which  the  in- 
ternal descends  from  the  axilla  along  the  inner  and  back  part  of  the 
arm  to  the  olecranon,  supplying  filaments  to  the  contiguous  skin.  Of 
two  which  are  external  and  perforate  the  external  intermuscular  sep- 
tum, an  upper  branch  accompanies  the  cephalic  vein  to  the  elbow, 
distributed  to  the  skin  on  the  lower  outer  part  of  the  arm,  while  a 
lower  branch  runs  along  the  outer  side  of  the  arm  and  the  back  of 
the  radial  side  of  the  forearm  to  the  wrist,  supplying  the  skin  in  its 
course  and  connected  near  the  wrist  with  a  branch  of  the  external 
cutaneous  nerve. 

The  posterior  interosseous  nerve,2  the  larger  of  the  terminal 
branches  of  the  musculo-spiral,  turns  backward  and  penetrates  the 
short  supinator,  descends  between  the  superficial  and  deep  portion  of 
the  extensors  to  about  the  middle  of  the  forearm,  where  it  runs  under 
the  second  pollical  extensor  to  the  lower  part  of  the  interosseous  mem- 
brane. Passing  to  the  back  of  the  carpus,  it  expands  in  a  small  gan- 
gliform  enlargement  which  distributes  filaments  to  the  contiguous 
articulations.  In  its  course  it  supplies  the  short  supinator  and  all 
the  extensors  of  the  forearm,  except  the  longer  radio-carpal  extensor, 
which  is  furnished  by  a  branch  from  the  trunk  of  the  musculo-spiral 
nerve. 

The  radial  nerve3  passes  down  the  forearm  beneath  the  long  su- 
pinator and  lies  a  short  distance  to  the  outer  side  of  the  radial  blood- 
vessels. Near  the  lower  end  of  the  radius  it  turns  backward  under  the 
tendon  of  the  long  supinator  and  divides  into  two  branches,  which  are 
distributed  to  the  skin  on  the  back  of  the  radial  side  of  the  hand.  The 
external  branch,  joined  by  a  branch  from  the  musculo-cutaneous 
nerve,  runs  along  the  radial  side  of  the  thumb  as  its  dorsal  digital 
nerve,  giving  filaments  to  the  ball  of  the  thumb.  The  internal 
branch,  larger  than  the  external,  communicates  with  the  musculo- 

1  N.  musculo-spiralis  ;  n.  radialis. 

2  N.  interosseus  posterior  or  externus.  3  N.  radialis ;  n.  spiralis. 


THE   NERVOUS   SYSTEM.  821 

cutaneous  nerve,  divides  into  two  common  dorsal  digital  nerves, 
and  by  a  communicating  branch  joins  the  contiguous  digital  of  the 
dorsal  cutaneous  branch  of  the  ulnar  nerve.  The  common  digital 
nerves  fork  into  collateral  digitals  supplying  the  adjacent  sides  of 
the  thumb,  index  and  middle  fingers. 

The  radial  nerve  and  the  dorsal  cutaneous  branch  of  the  ulnar 
nerve  are  variable  and  proportioned  to  each  other;  sometimes  each 
supplies  digital  branches  to  the  digits  equally,  and  at  other  times  the 
radial  supplies  all  except  the  little  finger  and  one  side  of  the  ring  finger, 
which  are  supplied  by  the  ulnar. 

ANTEKIOK  THOKACIC  NEKVES. 

The  twelve  anterior  thoracic  nerves1  are  almost  entirely  dis- 
tributed to  the  walls  of  the  thorax  and  abdomen,  the  exceptions  being 
the  great  part  of  the  first  one,  which  forms  one  of  the  trunks  of  the 
brachial  plexus,  and  the  second  and  twelfth,  which  give  branches 
respectively  to  the  arm  and  the  hip.  Near  their  commencement  each 
communicates  by  a  pair  of  filaments  with  the  adjacent  ganglion  of  the 
sympathetic  nerve. 

The  small  part  of  the  first  thoracic  nerve  and  the  succeeding  ten 
nerves  run  outward  and  forward  in  the  intercostal  spaces  and  are 
thence  called  intercostal  nerves.1'  The  first  six,  mainly  confined  to 
the  wall  of  the  thorax,  are  distinguished  as  the  upper  or  pectoral 
intercostal  nerves,  and  the  succeeding  five,  partly  distributed  to  the 
wall  of  the  abdomen,  as  the  lower  or  abdominal  intercostal  nerves, 
while  the  twelfth  nerve  runs  below  the  last  rib  in  the  abdominal 
wall. 

The  upper  intercostal  nerves  run  outward  and  forward  in  the 
intercostal  spaces  below  and  in  company  with  the  corresponding  ves- 
sels ;  at  first  situated  next  the  pleura  on  the  external  intercostal  mus- 
cle and  then  between  it  and  the  internal  muscle  to  about  the  middle 
of  the  rib,  where  they  each  give  off  a  lateral  cutaneous  nerve  of  the 
thorax.  Reduced  in  size,  they  proceed  forward  through  the  internal 
intercostal  muscle  and  then  between  it  and  the  pleura  towards  the 
sternum,  crossing  the  sternal  triangular  muscle  and  mammary  vessels. 
Finally  they  perforate  the  internal  intercostal  and  greater  pectoral 
muscles  and  then  continue  as  the  anterior  cutaneous  nerves  of  the 
thorax.  In  their  Course  they  supply  the  intercostal,  costal  elevators, 
great  serratus,  and  sternal  triangular  muscles. 

The  lateral  cutaneous  nerves  of  the  thorax 3  pierce  the  external 
intercostal  and  great  serratus  muscles  near  the  axillary  border  and 
divide  into  anterior  and  posterior  branches  which  are  distributed  to  the 
skin.  The  first  intercostal  commonly  gives  off  no  lateral  cutaneous 

1  Nervi  thoracici ;  dorsal  nerves. 

2  N.  intercostales.  3  N.  cutanei  pectoris  laterales. 


822  THE   NERVOUS   SYSTEM. 

nerve,  and  that  from  the  second  intercostal,  under  the  name  of  the 
intercosto-humeral  nerve,  goes  to  the  arm. 

The  anterior  branches  of  the  lateral  cutaneous  nerves  run  forward 
over  the  outer  border  of  the  greater  pectoral  muscle  to  be  distributed 
to  the  skin  of  the  breast  and  the  mammary  gland,  a  few  filaments 
from  the  lower  nerves  supplying  the  upper  digitations  of  the  external 
oblique  muscle  of  the  abdomen.  The  posterior  branches  run  back- 
ward to  be  distributed  to  the  skin  over  the  scapula  and  the  latissimus 
muscle  ;  that  from  the  third  nerve  ramifying  in  the  axilla  and  giving 
filaments  to  the  arm. 

The  intercosto-humeral  nerve,1  the  lateral  cutaneous  branch  of 
the  second  intercostal,  corresponding  with  the  posterior  branch  of  the 
succeeding  lateral  cutaneous  nerves,  runs  across  the  axilla  to  the  arm 
to  be  distributed  to  the  skin  on  the  inner  and  back  surface  nearly  to  its 
middle.  In  its  course  in  the  axilla  it  communicates  by  a  branch  with 
the  small  cutaneous  nerve  and  subsequently  with  the  internal  cutaneous 
branch  of  the  musculo-spiral  nerve.  It  varies  in  size  and  extent  of 
distribution  proportionately  with  the  small  cutaneous  nerve  and  other 
cutaneous  branches  of  the  arm. 

The  anterior  cutaneous  nerves  of  the  thorax,2  the  terminal 
branches  of  the  upper  intercostal  nerves,  turn  outward  to  be  distrib- 
uted to  the  skin  over  the  greater  pectoral  muscle  and  mamma. 

The  lower  intercostal  nerves  in  their  course  between  the  ribs 
accord  with  the  upper  ones,  and  like  them  give  off  lateral  cutaneous 
nerves.  From  the  fore  part  of  the  intercostal  spaces  they  continue 
forward  across  the  costal  cartilages  inwardly  and  between  the  internal 
oblique  and  transversalis  muscles  of  the  abdomen  to  the  edge  of  the 
rectus  muscle.  Piercing  the  sheath  of  the  rectus  they  pass  through 
it  and  end  as  the  anterior  cutaneous  nerves  of  the  abdomen.  They 
supply  the  corresponding  intercostal  muscles,  the  infraserratus,  and 
the  abdominal  muscles  through  which  they  pass. 

The  lateral  cutaneous  nerves  of  the  abdomen3  pass  through 
the  external  intercostal  and  oblique  muscles  in  a  line  with  those  above, 
and  like  them  divide  into  anterior  and  posterior  branches. 

The  anterior  branches,  the  larger,  run  inward  in  the  superficial 
fascia  of  the  abdomen  nearly  to  the  rectus  muscle,  supplying  the  con- 
tiguous skin.  The  posterior  branches  run  backward  to  the  skin 
over  the  latissimus  muscle. 

The  anterior  cutaneous  nerves  of  the  abdomen,4  small  and 
variable  in  number  and  position,  usually  two  or  three  twigs  for  each 
nerve,  perforate  the  sheath  of  the  rectus  near  its  outer  edge  and  near 
the  linea  alba  to  be  distributed  to  the  contiguous  skin. 

1  N.  intercosto-humeralis  ;  n.  cutaneus  brachii  interims. 

2  N.  cutanei  pectoris  anteriores. 

3  N.  cut.  pectoris  laterales.  *  N.  cutanei  abdominis  anteriores. 


THE   NERVOUS   SYSTEM.  823 

The  last  thoracic  nerve  runs  along  the  lower  border  of  the  last 
rib  and  in  company  with  the  first  lumbar  artery  crosses  the  inner  sur- 
face of  the  quadrate  lumbar  muscle,  then  passes  between  the  internal 
oblique  and  transversalis  muscles  of  the  abdomen  and  pursues  a  similar 
course  to  the  lower  intercostal  nerves.  From  near  its  commencement  a 
small  communicating  branch  descends  to  the  first  lumbar  nerve.  Its 
branches  are  the  same  as  those  of  the  lower  intercostal  nerves ;  the 
anterior  cutaneous  twigs  being  distributed  to  the  skin  about  midway 
between  the  umbilicus  and  the  pubis. 

The  lateral  cutaneous  branch  of  the  last  thoracic  nerve,  passing 
through  both  oblique  muscles  of  the  abdomen,  descends  over  the  iliac 
crest  to  be  distributed  to  the  skin  at  the  fore  part  of  the  gluteal  region, 
extending  to  the  position  of  the  great  trochanter. 

ANTERIOR   LUMBAR,   SACRAL,   AND   COCCYGEAL   NERVES. 

The  anterior  lumbar,  sacral,  and  coccygeal  nerves  unite  in  a  con- 
tinuous plexus  which  is  conveniently  divided  into  the  lumbar,  sacral, 
and  coccygeal  plexuses.  All  are  connected  near  their  commencement 
by  filaments  with  the  adjacent  ganglia  of  the  sympathetic  nerve. 

LUMBAR   PLEXUS. 

The  five  lumbar  nerves*  successively  increase  in  size,  and  the 
upper  three  with  part  of  the  fourth  form  the  lumbar  plexus,2  which 
is  joined  by  a  descending  branch  from  the  twelfth  thoracic  nerve. 
The  plexus  occupies  the  interior  of  the  psoas  muscle  and  is  arranged 
as  follows :  The  first  nerve  gives  off  two  branches,  the  ilio-hypogastric 
and  ilio-inguinal  nerves  and  a  communicating  branch  with  the  second 
nerve,  and  this  gives  off  part  of  the  genito-crural  and  external  cuta- 
neous nerves  and  a  communicating  branch  with  the  third  nerve.  The 
latter  unites  with  the  greater  portion  of  the  upper  division  of  the 
fourth  nerve  to  form  the  largest  branch  of  the  plexus,  the  anterior 
crural  nerve,  while  branches  from  the  second,  third,  and  fourth  nerves 
unite  to  form  the  obturator  nerve. 

The  ilio-hypogastric  nerve 3  from  the  first  lumbar  emerges  from 
the  upper  outer  part  of  the  psoas  muscle,  runs  obliquely  across  the 
quadrate  lumbar  muscle  to  the  iliac  crest,  perforates  the  transversalis 
muscle  and  between  it  and  the  internal  oblique  muscle  divides  into 
the  iliac  and  hypogastric  branches. 

The  iliac  branch  pierces  both  oblique  muscles  and  descends  over 
the  iliac  crest  to  be  distributed  to  the  skin  of  the  gluteal  region  be- 
hind the  position  supplied  by  the  lateral  cutaneous  branch  of  the  last 
thoracic  nerve.  The  hypogastric  branch  continues  between  the  trans- 

1  Nervi  lumbales  or  lumbares. 

2  P.  lumbalis.  3  N.  ilio-hypogastricus. 


824 


THE   NEEVOUS   SYSTEM. 


FIG.  413. 


LUMBAR,  SACRAL,  AND  COCCYGEAL  PLEXUSES. 
a,  last  thoracic  nerve;  b-f,  lumbar  nerves;  g-k, 
sacral  nerves ;  I,  coccygeal  nerve ;  3,  b-e,  lumbar 
plexus ;  12,  f-j,  sacral  plexus ;  26,  k,  I,  coccygeal 
plexus.  1,  anterior  branch  of  the  last  thoracic 
nerve ;  2,  lateral  cutaneous  branch ;  3,  thoracico- 
lumbar  nerve ;  4,  ilio-hypogastric  nerve ;  5,  ilio- 
inguinal  nerve ;  6,  genito-crural  nerve  ;  7,  ex- 
ternal cutaneous  nerve ;  8,  crural  nerve ;  9, 
psoas  branches;  10,  iliac  branches ;  11,  obturator 
nerve ;  12,  connecting  branch  from  the  fourth 
lumbar  nerve  with  the  sacral  plexus ;  13,  lumbo- 
sacral  cord ;  14,  great  sciatic  nerve ;  15,  superior 
gluteal  nerve;  16,  inferior  gluteal  nerve;  17, 
small  sciatic  nerve;  18,  gluteal  branches;  19, 
pudendal  nerve ;  20,  femoral  cutaneous  nerve ; 
21,  pudic  nerve ;  22,  branch  to  pyriform  muscle ; 
23,  visceral  branches;  24,  muscular  branches! 
25,  perforating  cutaneous  branch ;  26,  descend- 
ing branch  to  the  fifth  sacral  nerve;  27,  de- 
scending branch  to  the  coccygeal  nerve ;  28, 
coccygeal  branch. 


versalis  and  internal  oblique  mus- 
cles, to  both  of  which  it  gives  fila- 
ments and  anastomoses  with  the 
ilio-inguinal  nerve,  then  perforates 
the  external  oblique  aponeurosis 
just  above  the  external  abdominal 
ring  and  is  distributed  to  the  skin 
above  the  pubis. 

The  ilio-inguinal  nerve l 
crosses  the  quadrate  lumbar  mus- 
cle below  the  preceding  nerve 
and  at  the  iliac  crest  perforates 
the  transversalis  muscle  in  ad- 
vance of  the  ilio-hypogastric 
nerve,  with  which  it  anastomoses. 
Piercing  the  internal  oblique 
muscle,  it  descends  through  the 
inguinal  canal,  emerges  at  the 
external  abdominal  ring  and  is 
distributed  to  the  skin  of  the 
inner  part  of  the  groin,  of  the  penis 
and  scrotum,  or  in  the  female  to 
that  of  the  labium. 

The  ilio-hypogastric  and  ilio- 
inguinal  nerves  are  variable  in 
size  proportioned  to  one  another 
and  their  extent  of  distribution. 

The  genito-crural  nerve,2  de- 
rived from  the  second  lumbar  and 
the  connecting  cord  between  that 
and  the  first  nerve,  passes  through 
and  descends  in  front  of  the  psoas 
muscle  towards  the  groin  and  di- 
vides into  the  genital  and  the  crural 
branch. 

The  genital  branch 3  lies  near 
the  external  iliac  artery,  to  which 
it  gives  a  filament,  and  descends  in 
the  inguinal  canal  to  the  cremaster 
muscle,  which  it  supplies.  The 
crural  branch 4  passes  under  the 
femoral  arch  and  pierces  the  fascia 
lata  to  be  distributed  to  the  skin 
below  the  groin ;  some  of  its  fila- 


1  N.  ilio-inguinalis. 

3  N.  spermaticus  or  pudendus  externus. 


2  N.  genito-cruralis. 
*  N.  lumbo-inguinalis. 


THE   NERVOUS   SYSTEM. 


825 


merits  passing  to  the  femoral  artery  as  it  passes  beneath  Poupart's 
ligament. 

The  external  cutaneous  nerve,1  derived  from  the  second  arid 


FIG.  414. 


FIG.  415. 


Fig.  414. — CUTANEOUS  NERVES  OF  THE  FRONT  OF  THE  THIGH.  1,  external  cutaneous  nerve;  2, 
middle  cutaneous  nerve ;  3,  4,  5,  6,  7,  internal  cutaneous  nerve  and  its  branches ;  8,  cutaneous 
filaments  to  the  inner  part  of  the  thigh ;  9, 10,  branches  of  the  long  saphenous  nerve. 

Fig.  415.— LUMBAR  PLEXUS  AND  ITS  BRANCHES.  1,  crural  nerve ;  2,  3,  branches  to  the  iliac  and 
psoas  muscles ;  4,  commencement  of  the  cutaneous  nerves ;  5, 6,  muscular  filaments  to  the  pectineal 
and  adductor  muscles ;  7,  origin  of  the  cutaneous  filaments  seen  in  the  preceding  figure  on  the 
inner  part  of  the  thigh ;  8,  cutaneous  filament  descending  to  the  inner  part  of  the  knee ;  9, 10, 11, 
muscular  branches  of  the  crural  to  the  quadriceps  extensor ;  12,  long  saphenous  nerve ;  13,  branch 
to  the  knee ;  14,  branch  descending  the  leg  in  company  with  the  saphenous  vein ;  15,  obturator 
nerve;  16,  17,  18,  19,  branches  to  the  adductor  and  gracilis  muscles;  20,  branch  of  the  fourth 
lumbar  nerve,  with  the  fifth  lumbar  nerve  descending  to  join  the  first  sacral  nerve,  21 ;  22,  lumbar 
and  sacral  ganglia  of  the  sympathetic ;  23,  external  cutaneous  nerve. 

third  lumbar  nerves,  passes  from  the  outer  border  of  the  psoas  and 
across  the  iliac  muscle,  parallel  with  and  below  the  ilio-inguinal  nerve, 


1  1ST.  cutaneus  anterior  externus. 


826  THE   NERVOUS   SYSTEM. 

then  descends  under  the  femoral  arch  and  appears  on  the  thigh  below 
the  anterior  superior  iliac  spine,  where  it  divides  into  anterior  and 
posterior  branches. 

The  anterior  branch  passes  obliquely  through  the  fascia  lata 
below  the  groin  and  is  distributed  to  the  skin  on  the  outer  fore  part 
of  the  thigh  extending  to  the  knee.  The  posterior  branch,  smaller 
than  the  former,  perforates  the  fascia  lata  and  supplies  the  skin  on  the 
outer  part  of  the  thigh  to  about  its  middle. 

The  obturator  nerve1  springs  usually  by  three  roots  from  the 
second,  third,  and  fourth  lumbar  nerves  near  their  commencement,  but 
sometimes  the  uppermost  root  is  absent.  Passing  from  the  inner  side 
of  the  psoas  muscle  near  the  entrance  of  the  pelvis,  it  runs  along  its 
side  in  company  with  and  above  the  obturator  vessels  and  with  them 
passes  through  the  obturator  foramen  into  the  thigh,  where  it  divides 
into  anterior  and  posterior  branches. 

The  anterior  branch  descends  in  front  of  the  short  adductor, 
covered  by  the  pectineus  and  long  adductor  muscles,  to  all  of  which 
it  supplies  filaments.  In  its  course  it  gives  a  filament  to  the  hip-joint, 
a  terminal  one  to  the  femoral  artery,  and  anastomoses  with  the  internal 
cutaneous  and  a  branch  of  the  internal  saphenous  nerve.  The  pos- 
terior branch  pierces  the  external  obturator,  which  it  supplies,  and 
passes  behind  the  short  adductor  on  the  great  adductor,  in  which  it  is 
mainly  distributed.  It  gives  off  an  articular  filament  which  descends 
through  the  great  adductor  and  follows  the  popliteal  vessels  to  the 
back  of  the  knee-joint. 

An  accessory  obturator  nerve,2  a  small  branch,  not  unfrequently 
springs  from  the  trunk  of  the  obturator  nerve  or  from  the  third  and 
fourth  lumbar  nerves,  and  descends  along  the  inner  border  of  the 
psoas.  Passing  beneath  the  pectineus  muscle,  it  divides  into  branches, 
of  which  one  is  distributed  to  the  muscle,  another  to  the  hip-joint,  and 
a  third  communicates  with  the  anterior  branch  of  the  obturator  nerve. 

The  crural,  or  anterior  crural  nerve,3  the  largest  branch  of  the 
lumbar  plexus,  is  mainly  formed  by  the  third  and  fourth  nerves,  but 
also  receives  a  reinforcement  from  the  second.  Descending  through 
the  psoas  muscle,  it  emerges  at  its  outer  border  and  passes  down  be- 
tween it  and  the  iliac  muscle  and  under  the  femoral  arch  into  the  thigh, 
where  it  becomes  somewhat  expanded  and  divides  into  an  anterior 
and  a  posterior  portion.  In  the  thigh  it  is  separated  from  the  femoral 
blood-vessels  by  the  psoas  muscle,  covered  by  the  iliac  portion  of  the 
fascia  lata. 

Within  the  pelvis  the  crural  nerve  gives  small  branches  to  the  iliac 
muscle  and  a  filament  which  descends  on  the  femoral  artery. 

The  anterior  or  superficial  division  of  the  crural  nerve  gives  off  the 
middle  and  internal  cutaneous  nerves. 

1  N.  obturatorius.  2  N.  obt.  accessorius.  3  N.  cruralis  ;  n.  femoralis. 


THE   NERVOUS   SYSTEM.  827 

The  middle  cutaneous  nerve1  pierces  the  fascia  lata  several 
inches  below  the  groin  and  is  distributed  in  numerous  filaments  to 
the  skin  along  the  fore  part  of  the  thigh  to  the  knee,  where  it  com- 
municates with  others  of  the  long  saphenous  nerve.  Its  outer  fila- 
ments also  communicate  with  the  crural  branch  of  the  genito-crural 
nerve,  and  its  inner  ones  with  the  internal  cutaneous  nerve.  This  or 
the  following  nerve  supplies  the  sartorius  muscle. 

The  internal  cutaneous  nerve2  turns  inward  across  the  sheath 
of  the  femoral  blood-vessels  and  divides  into  internal  and  anterior 
branches.  The  internal  branch  descends  along  the  inner  border  of 
the  sartorius  muscle  to  the  knee,  where  it  pierces  the  fascia  lata,  com- 
municates with  the  long  saphenous  nerve,  gives  cutaneous  branches  to 
the  knee,  and  then  runs  down  on  the  inner  side  of  the  leg  distributed 
to  the  contiguous  skin.  In  the  thigh  it  gives  oif  filaments  on  the 
inner  side  along  the  course  of  the  long  saphenous  vein.  The  anterior 
branch  perforates  the  fascia  lata  at  the  lower  third  of  the  thigh,  is 
distributed  to  the  skin  along  the  front  and  inner  side  to  the  knee,  and 
communicates  with  the  long  saphenous  nerve. 

The  posterior  or  deep  division  of  the  crural  nerve  is  expended 
principally  in  muscular  branches  to  the  extensors  of  the  thigh.  It 
gives  off  a  considerable  cutaneous  branch,  the  long  saphenous  nerve. 

The  muscular  branches  supply  all  the  muscles  of  the  front  of 
the  thigh  except  the  fascial  tensor,  which  is  supplied  by  the  superior 
gluteal  nerve  and  the  sartorius,  which  is  supplied  by  branches  coming 
off  with  the  internal  or  middle  cutaneous  nerve.  A  branch  or  two 
pass  behind  the  femoral  vessels  to  the  pectineus  muscle  ;  that  to  the 
femoral  rectus  enters  the  posterior  surface ;  the  branches  to  the  cru- 
reus  and  internal  vastus  enter  about  their  middle  in  front ;  that  of  the 
external  vastus  accompanies  the  descending  branch  of  the  external 
circumflex  artery  to  the  lower  part  of  the  muscle. 

Of  articular  branches,  a  slender  filament  from  the  branch  to  the 
external  vastus  muscle  descends  to  the  knee-joint  and  another  from  the 
branch  to  the  internal  vastus  accompanies  the  deep  branch  of  the  anas- 
tomotic  artery  to  the  inner  side  of  the  joint. 

The  long,  or  internal  saphenous  nerve,3  the  largest  branch  of  the 
anterior  crural,  accompanies  the  femoral  blood-vessels,  at  first  lying 
to  their  outer  side,  gradually  crossing  to  .their  front  and  descending 
with  them  in  the  canal  of  the  great  adductor  tendon.  Leaving  the 
vessels,  by  piercing  the  canal,  it  continues  down  beneath  the  sartorius 
to  the  inner  side  of  the  knee.  Here  giving  off  the  patellar  branch,  it 
pierces  the  fascia  at  the  lower  border  of  the  sartorius  and  accompanies 
the  long  saphenous  vein  down  the  inner  side  of  the  leg  and  divides  into 
two  branches.  Of  these  one  runs  along  the  tibia  to  the  inner  ankle 

1  N.  cutaneus  medius ;  n.  perforans. 

2  N.  cut.  interims ;  n.  saphenus  minor.  3  N.  saphenus  major. 


828  THE   NERVOUS   SYSTEM. 

and  the  other  passes  in  front  of  it  and  runs  along  the  inner  side  of  the 
foot  to  the  great  toe. 

In  its  course  the  long  saphenous  nerve,  about  the  middle  of  the 
thigh,  gives  off  a  communicating  branch,  which  interlaces  with  fila- 
ments of  the  obturator  and  internal  cutaneous  nerves  beneath  the 
sartorius  muscle.  The  patellar  branch  pierces  the  sartorius  and 
fascia  lata  and  is  distributed  to  the  skin  over  the  front  of  the  knee, 
where  with  filaments  of  the  cutaneous  nerves  it  forms  a  reticular 
plexus.1 

To  the  skin  of  the  leg  and  inner  part  of  the  foot  the  long  saphe- 
nous nerve  distributes  many  branches,  communicating  with  those  of 
the  internal  cutaneous  and  musculo-cutaneous  nerves. 

SACRAL   PLEXUS. 

Of  the  five  anterior  sacral  nerves  the  upper  four  issue  from  the 
anterior  sacral  foramina,  the  last  one  from  the  intervertebral  fora- 
men between  the  sacrum  and  coccyx.  The  first  two  sacral  nerves  are 
large  and  of  nearly  equal  size,  the  others  are  small  and  successively 
decrease,  the  last  being  a  short  thread. 

A  division  of  the  fourth  lumbar  nerve  descends  obliquely  and  joins 
the  fifth  to  form  the  lumbo-sacral  cord,  which  together  with  the  upper 
three  and  part  of  the  fourth  sacral  nerves  forms  the  sacral  plexus.2 
This  does  not  present  the  usual  appearance  of  plexuses,  for  the  prin- 
cipal nerves  converge  and  for  the  most  part  conjoin  in  a  single  large 
band,  which  is  continued  as  the  great  sciatic  nerve,  while  a  small,  more 
plexiform  portion,  derived  partly  from  the  third  and  partly  from  the 
fourth  nerve,  is  continued  into  the  pudic  nerve.  The  upper  nerves 
in  their  convergence  to  the  plexus  descend  obliquely,  while  the  lower 
ones  become  more  horizontal,  thus  all  becoming  successively  shorter. 

The  plexus  is  vertically  flat  and  triangular  and  rests  in  front  of  the 
pyriform  muscle,  separated  from  the  sciatic  and  pudic  branches  of  the 
internal  iliac  vessels  and  from  the  pelvic  viscera  by  the  pelvic  fascia. 
It  converges  and  passes  from  the  pelvis  through  the  great  sciatic  fora- 
men below  the  pyriform  muscle  and  ends  in  the  great  sciatic  and 
pudic  nerves.  In  addition  it  gives  origin  to  some  small  muscular 
branches,  the  superior  and  inferior  gluteal,  small  sciatic,  and  perfo- 
rating cutaneous  nerves. 

The  small  muscular  branches  are  two  from  the  upper  nerves 
of  the  plexus  to  the  pyriform  muscle;  a  third  which  passes  below 
the  latter  around  the  ischial  spine  in  company  with  the  pudic  vessels 
and  passes  through  the  small  sciatic  foramen  to  the  internal  obturator 
muscle,  in  its  course  supplying  the  upper  division  of  the  geminus 
muscle ;  a  fourth  which  passes  from  the  plexus  under  the  geminus 

1  Patellar  plexus.  2  P.  ischiadicus. 


THE   NERVOUS   SYSTEM.  829 

muscle  to  the  femoral  quadrate  muscle,  giving  the  lower  division  of  the 
geminus  a  filament,  as  well  as  one  to  the  hip-joint. 

The  superior  gluteal  nerve l  springs  from  the  lumbo-sacral  cord 
and  first  sacral  nerve,  leaves  the  pelvis  in  company  with  the  gluteal 
vessels  through  the  great  sciatic  foramen  above  the  pyriform  muscle, 
and  divides  into  an  upper  and  a  lower  branch,  which  proceed  for- 
ward between  the  middle  and  small  gluteal  muscles  and  supply  them 
and  the  fascial  tensor. 

The  inferior  gluteal  nerve,2  from  the  back  of  the  plexus,  springs 
from  the  lumbo-sacral  cord  and  the  first  and  second  sacral  nerves,  turns 
backward  below  the  pyriform  muscle,  and  enters  the  lower  part  of  the 
great  gluteal  muscle  in  diverging  branches. 

The  small  sciatic  nerve,3  receiving  a  branch  from  the  former,  also 
derives  its  roots  from  the  second  and  third  sacral  nerves.  Emerging 
from  below  the  pyriform  muscle,  it  descends  beneath  the  great  glu- 
teal muscle,  behind  the  great  sciatic  nerve,  and  continues  down  the 
back  of  the  thigh,  covered  by  the  fascia  lata,  to  below  the  knee.  Here 
perforating  the  fascia,  it  follows  the  short  saphenous  vein  below  the 
middle  of  the  leg  and  is  connected  with  filaments  of  the  short  saphe- 
nous nerve. 

The  small  sciatic  is  a  cutaneous  nerve  and  supplies  the  lower  part 
of  the  buttock,  perineum,  back  of  the  thigh,  and  upper  back  part  of 
the  leg.  In  the  thigh  it  gives  off  the  gluteal  and  femoral  cutaneous 
branches  and  the  inferior  pudendal  nerve. 

The  gluteal  cutaneous  branches,4  of  which  there  are  several, 
turn  up  round  the  lower  border  of  the  great  gluteal  muscle  to  be  dis- 
tributed to  the  skin  of  the  lower  and  outer  part  of  the  buttock.  The 
inferior  pudendal  nerve 5  turns  inward  below  the  ischial  tuberosity, 
gives  branches  to  the  skin  of  the  upper  and  inner  part  of  the  thigh  and 
its  terminal  ones  to  the  outer  surface  of  the  scrotum ;  in  the  female  to 
the  labium.  The  femoral  cutaneous  branches  are  numerous  and 
are  distributed  to  the  skin  of  the  back  of  the  thigh,  the  greater  number 
to  the  inner  side. 

The  perforating  cutaneous  nerve,  a  small  branch  derived  from 
the  fourth  sacral  nerve,  passes  backward  through  the  great  sacro- 
sciatic  ligament  and  turns  up  round  the  lower  border  of  the  great 
gluteal  muscle  to  the  skin. 

The  pudic  nerve,6  the  smaller  terminal  division  of  the  sacral 
plexus,  is  derived  from  the  third  and  fourth  sacral  nerves,  with  occa- 

1  N.  glutseus  superior. 

2  N.  glutseus  inferior ;  n.  ischiadicus  minor ;    inf.  gluteal  branch  of  the  small 
sciatic  nerve. 

3  N.    ischiadicus   minor;   n.    cutaneus  posterior  or  post,  medius,  magnus,  or 
communis;  n.  cut.  n.  glutei  inf. 

4  N.  subcutanei  glutei  inf.  5  j^  pudendus  longus  inferior. 

6  N.  pudendalis  communis ;  plexus  pudendalis ;  p.  pudendo-hsemorrhoidalis. 


830  THE    NERVOUS   SYSTEM. 

sional  reinforcements  from  those  above.  Issuing  from  the  pelvis 
below  the  pyriform  muscle,  in  company  with  the  pudic  vessels  at  their 
inner  side,  it  turns  round  behind  the  ischial  spine  and  through  the 
small  sciatic  foramen  re-enters  the  pelvis.  Here  it  runs  forward  and 
upward  along  the  outer  side  of  the  ischio-rectal  fossa  enclosed  in  the 
obturator  fascia  and  ends  in  the  perineal  nerve  and  dorsal  nerve  of  the 
penis. 

Near  its  commencement  the  pudic  gives  off  the  hemorrhoidal 
nerve,1  which  after  anastomosis  with  filaments  of  the  hemorrhoidal 
plexus  of  the  sympathetic  is  distributed  to  the  anal  elevator  and 
sphincters,  the  neck  of  the  bladder  and  skin  of  the  anus  ;  in  the  female 
to  the  lower  part  of  the  vagina. 

The  perineal  nerve,2  the  larger  terminal  branch  of  the  pudic,  runs 
forward  along  the  outer  side  of  the  ischio-rectal  fossa  below  the  pudic 
vessels  and  divides  into  superficial  and  deep  branches.  The  super- 
ficial perineal  branch 3  is  distributed  to  the  skin  of  the  perineum ; 
the  deep  perineal  branch  *  to  the  muscles  of  the  perineum  and  to 
the  skin  of  the  back  of  the  scrotum  ;5  in  the  female  to  the  labium,  the 
nympha,  and  the  vestibule.6 

The  dorsal  nerve  of  the  penis  7  accompanies  the  pudic  artery 
along  the  ramus  of  the  ischium,  passes  through  the  deep  perineal 
fascia,  then  in  company  with  the ,  corresponding  artery  runs  along  the 
dorsum  of  the  penis  to  the  glans,  to  which  its  terminal  branches 8  are 
distributed.  In  its  course  it  gives  filaments  to  the  ischio-cavernous 
and  urethro-bulbar  muscles,  others  to  the  cavernous  body  anastomosing 
with  filaments  of  the  sympathetic,  and  numerous  filaments  to  the  skin 
of  the  penis  and  prepuce.  In  the  female  the  corresponding  dorsal 
nerve  of  the  clitoris  has  a  similar  distribution  and  ends  in  branches 
to  the  glans,  the  prepuce,  and  the  nympha. 

The  great  sciatic  nerve,9  remarkable  as  the  largest  nerve  of  the 
body,  the  continuation  in  great  part  of  the  sacral  plexus,  appears  as  a 
flattened  cylindrical  cord,  about  two-thirds  of  an  inch  broad.  It  issues 
from  the  pelvis  through  the  great  sciatic  foramen  below  the  pyriform 
muscle  and  descends  vertically  behind  the  thigh,  commonly  below  the 
middle,  where  it  forks  acutely  into  the  popliteal  and  peroneal  nerves. 
In  its  descent  it  first  rests  on  the  small  rotator  muscles  between  the 
ischial  tuberosity  and  great  trochanter,  in  company  with  the  small 
sciatic  nerve  and  artery,  covered  by  the  great  gluteal  muscle,  after- 
wards on  the  great  adductor  covered  by  the  long  head  of  the  femoral 

1  Inferior  hemorrhoidal  nerve  ;  nervus  hsemorrhoidalis  externus  or  medius  and 
inferior. 

2  N.  perinealis  or  perineus  ;  n.  pudendus  inf.  or  int. 

3  Sup.  perin.  nerves,  external  or  posterior  and  internal  or  anterior. 

4  N.  profundus  ;  n.  musculo-  or  bulbo-uretralis. 

5  Nervi  scrotales  posteriores.  6  N.  labiales  posteriores. 

7  N.  penis  dorsalis.  8  Kami  glandis.  9  N.  ischiadicus  magnus  or  major. 


THE   NERVOUS   SYSTEM. 


831 


biceps  muscle.     The  position  of  division  is  variable  and  may  occur  at 

any  point  from  near  the  plexus  to  the  upper  part  of  the  popliteal  space. 

Before  division  the  great  sciatic  nerve  gives  articular  filaments 


FIG.  416. 


FIG.  417. 


15 


Fig.  416.— PEEONEAL  NERVE  AND  ITS  BRANCHES.  1,  peroneal  nerve ;  2,  cutaneous  branch  to  the 
outer  part  of  the  leg ;  3,  peroneal  communicating  branch  anastomosing  with  the  short  saphenous 
nerve  4,  5 ;  6,  7,  8,  terminal  branches  of  the  latter  to  the  outer  part  of  the  foot ;  9,  musculo-cutane- 
ous  nerve ;  10, 11, 12,  terminal  branches  to  the  back  of  the  foot ;  13,  anterior  tibial  nerve ;  14,  ter- 
minal branch  of  the  latter  anastomosing  with  branches  of  the  musculo-cutaneous  nerve;  15, 
muscular  branches. 

Kg,  417.— POPLITEAL  NERVE.  1,  popliteal  nerve ;  2,  3, 4,  muscular  branches ;  5,  short  saphenous 
nerve;  6,  peroneal  nerve;  7,  cutaneous  branch;  8,  peroneal  communicating  branch  joining  the 
short  saphenous  nerve ;  9,  common  trunk  of  the  peroneal  communicating  and  saphenous  nerves 
to  the  outer  part  of  the  foot ;  10,  branch  to  the  heel ;  11,  cutaneous  branch  from  the  posterior 
tibial  nerve;  12, 13,  branches  of  the  long  saphenous  nerve. 

to  the  hip-joint  and  in  the  thigh  muscular  branches  to  the  biceps, 
semi-tendinosus,  semi-membranosus,  and  great  adductor  muscles. 

The   peroneal   nerve,1  the  smaller  division  of  the  great  sciatic, 


1  N.  peroneus  ;  external  popliteal  nerve  ;  n.  popliteus  externus  ;  n.  fibularis. 


832  THE   NERVOUS   SYSTEM. 

descends  obliquely  along  the  outer  side  of  the  popliteal  space  close 
to  the  biceps  muscle,  then  between  it  and  the  gastrocnemius.  Below 
the  head  of  the  fibula,  it  turns  forward  round  the  bone  beneath  the 
long  peroneal  muscle  and  divides  into  the  anterior  tibial  and  musculo- 
cutaneous  nerves. 

Before  division  the  peroneal  nerve  gives  off  articular  filaments 
which  accompany  the  external  articular  arteries  to  the  knee-joint,  and 
a  recurrent  branch l  follows  the  recurrent  tibial  artery  through  the 
anterior  tibialis  muscle  to  the  front  of  the  joint. 

Two  cutaneous  branches  from  the  peroneal  nerve  supply  the  skin 
on  the  outer  and  back  part  of  the  leg.  One  of  them,  the  peroneal 
communicating  branch,2  usually  joins  the  short  saphenous  nerve 
below  the  middle  back  part  of  the  leg,  but  sometimes  continues 
separate  and  is  distributed  as  low  as  the  heel  and  outer  side  of  the 
foot. 

The  musculo-cutaneous  nerve s  descends  between  the  peroneal 
muscles  and  long  digital  extensor  and  perforates  the  fascia  at  the  lower 
fore  part  of  the  leg,  where  it  divides  into  internal  and  external  branches. 
In  its  course  it  gives  branches  to  the  peroneal  muscles  and  filaments 
which  are  distributed  to  the  skin  at  the  lower  part  of  the  leg. 

The  internal  branch  *  descends  and  is  distributed  to  the  inner  part 
of  the  dorsum  of  the  foot  and  gives  branches  to  the  inner  ankle  and 
side  of  the  foot,  communicating  with  filaments  of  the  long  saphenous 
nerve.  It  furnishes  a  dorsal  digital  branch  to  the  inner  side  of  the 
great  toe  and  another  which  divides  into  collateral  digitals  for  the 
adjoining  sides  of  the  second  and  third  toes.  It  further  gives  a  com- 
municating branch  which  reinforces  the  digital  nerve  from  the  anterior 
tibial  nerve  in  the  interval  of  the  first  and  second  toes. 

The  external  branch,5  smaller  than  the  internal,  descends  and 
supplies  the  skin  on  the  outer  part  of  the  dorsum  of  the  foot,  giving 
branches  to  the  outer  ankle  and  side  of  the  foot,  communicating  with 
filaments  of  the  short  saphenous  nerve.  It  terminates  in  a  pair  of 
dorsal  digital  branches  which  supply  the  collateral  digitals  to  the  ad- 
joining sides  of  the  outer  three  toes. 

The  two  terminal  divisions  of  the  musculo-cutaneous  nerve  are 
variable  and  proportioned  to  each  other  and  in  a  measure  to  those  with 
which  they  communicate.  They  commonly  supply  dorsal  digital  nerves 
to  the  toes,  except  the  outer  side  of  the  last  toe,  which  is  supplied 
by  a  corresponding  branch  from  the  short  saphenous  nerve,  and  the 


1  Eecurrent  articular  nerve. 

2  N.  communicans  peronei  or  fibularis ;  n.  cutaneus  cruris  posterior ;  n.  saphenus 
peroneus. 

8  N.  cutaneus  peroneus ;  n.  peroneus  superficialis. 

4  N.  dorsi  pedis  cutaneus  anterior  or  internus. 

?  N.  dorsi  pedis  cutaneus  medius ;  n.  peroneus  externus. 


THE   NERVOUS   SYSTEM.  833 

contiguous  sides  of  the  great  and  second  toes  which  are  supplied  by 
the  anterior  tibial  nerve. 

The  anterior  tibial  nerve,1  starting  between  the  fibula  and  long 
peroneal  muscle,  descends  obliquely  forward  beneath  the  long  digital 
extensor  to  the  front  of  the  interosseous  membrane,  where  joining  the 
anterior  tibial  vessels  it  accompanies  them  to  the  ankle  and  divides 
into  internal  and  external  branches.  The  nerve  joins  the  vessels  at  the 
upper  fourth  of  the  leg  and-  descends  in  front  of  them  to  the  ankle, 
where  it  lies  at  their  inner  side. 

In  its  course  the  anterior  tibial  nerve  supplies  the  anterior  tibialis, 
long  digital  and  hallucal  flexors,  and  third  peroneal  muscle.  It  also 
gives  off  articular  filaments  to  the  ankle-joint. 

The  internal  branch z  follows  the  anterior  tibial  and  dorsal  pedal 
vessels  to  the  first  interosseous  space,  where  it  is  joined  by  a  branch 
from  the  musculo-cutaneous  nerve  and  ends  in  digital  branches  to  the 
adjoining  sides  of  the  great  and  second  toes.  It  gives  filaments  to  the 
contiguous  metatarso-phalangeal  articulations  and  interosseous  muscles. 
The  external  branch 3  turns  outward  across  the  tarsus  beneath  the 
short  digital  extensor  and  is  distributed  to  it  and  to  the  articulations 
of  the  tarsus. 

The  popliteal  nerve,4  the  larger  division  of  the  great  sciatic,  pur- 
sues the  course  of  the  trunk  and  descends  through  the  popliteal  space, 
in  company  with  the  popliteal  vessels,  to  the  lower  border  of  the  pop- 
liteal muscle,  after  which  it  continues  as  the  posterior  tibial  nerve. 
At  first  the  nerve  is  a  short  distance  behind  and  outward  from  the 
popliteal  vessels,  but  gradually  approaches  them,  behind  the  knee  lies 
in  contact  with  the  vein,  and  crosses  to  the  inner  side  of  the  vessels. 

From  the  upper  part  of  the  popliteal  nerve  two  or  three  articular 
filaments  descend  and  accompany  the  internal  and  middle  articular 
arteries  to  the  knee-joint.  Muscular  branches  also  descend  from  it 
in  the  popliteal  space,  a  pair  separately  or  together,  to  the  heads  of  the 
gastrocnemius,  a  small  one  to  the  plantaris,  a  considerable  branch  to 
the  soleus,  and  one  lower  down  for  the  popliteal  muscle. 

A  cutaneous  branch  of  the  popliteal,  the  short  saphenous  nerve,5 
descends  at  the  back  of  the  calf  in  the  furrow  between  the  heads  of 
the  gastrocnemius  to  near  the  middle  of  the  leg,  where  it  perforates 
the  fascia  and  shortly  after  is  usually  joined  by  the  peroneal  com- 
municating branch.  It  then  descends  in  company  with  the  short 
saphenous  vein  and  runs  forward  behind  the  external  ankle  to  end  in 
the  skin  on  the  outer  side  of  the  foot,  communicating  with  the  mus- 

1  N.  tibialis  anticus ;  n.  peroneus  profundus. 

2  Kamus  internus  profundus  dorsi  pedis. 

3  K.  ext.  prof,  dorsi  pedis. 

4  N.  popliteus  ;  internal  popliteal  nerve;  n.  tibialis  or  t.  posticus. 

5  N.  saphenus  externus  or  inferior;  n.  communicans  tibialis  or  surae;  n.  cutaneus 
brevis  cruris  et  pedis. 

53 


834  THE   NERVOUS   SYSTEM. 

culo-cutaneous  nerve,  and  furnishing  the  dorsal  digital  branch  to  the 
outer  side  of  the  little  toe. 

The  posterior  tibial  nerve,1  the  continuation  of  the  popliteal, 
descends  the  leg  in  company  with  and  behind  the  corresponding  blood- 
vessels, lying  at  first  for  a  short  distance  to  their  inner  side,  but  crossing 
them  and  the  greater  part  of  their  course  lying  on  the  outer  side.  With 
the  accompanying  vessels  it  lies  on  the  deep  muscles,  covered  above 
by  those  of  the  calf  and  below  by  the  fascia  and  skin.  Beachmg  the 
interval  between  the  inner  ankle  and  the  heel,  to  the  outer  side  of  the 
vessels,  it  divides  into  two  terminal  branches,  the  internal  and  external 
plantar  nerves. 

In  the  upper  part  of  its  course  the  posterior  tibial  nerve  gives 
muscular  branches  to  the  posterior  tibialis,  the  long  digital  and 
hallucal  flexors,  and  the  soleus. 

A  cutaneous  branch2  from  the  lower  part  of  the  nerve  pierces 
the  internal  annular  ligament  of  the  ankle  and  is  distributed  to  the 
skin  of  the  heel  and  inner  back  part  of  the  sole  of  the  foot.  One  or 
two  articular  filaments  in  the  vicinity  supply  the  ankle-joint. 

The  external  plantar  nerve,3  the  smaller  terminal  branch  of  the 
posterior  tibial,  runs  obliquely  across  the  sole  of  the  foot  in  company 
with  the  corresponding  vessels,  between  the  short  digital  and  accessory 
flexors,  to  the  interval  between  the  former  and  the  minimal  abductor, 
where  it  divides  into  superficial  and  deep  branches.  It  gives  muscu- 
lar branches  to  the  accessory  flexor  and  minimal  abductor  muscles. 
The  superficial  branch  divides  into  two  digitals,  of  which  one  gives 
twigs  to  the  minimal  flexor  and  runs  along  the  outer  side  of  the  little 
toe ;  while  the  other,  after  giving  a  communicating  branch  to  the 
internal  plantar,  ends  in  collateral  digital  nerves  to  the  contiguous 
sides  of  the  fourth  and  fifth  toes.  The  deep  branch  accompanies  the 
external  plantar  vessels  above  the  flexor  tendons  and  is  distributed 
to  the  interosseous,  the  outer  two  lumbrical,  and  the  hallucal  adductor 
and  transverse  muscles. 

The  internal  plantar  nerve,4  larger,  appearing  as  the  continua- 
tion of  the  posterior  tibial,  runs  forward  in  the  sole  of  the  foot  in 
company  with  the  corresponding  vessels.  It  passes  above  the  hallucal 
abductor,  then  between  it  and  the  short  digital  flexor,  gives  off  the 
internal  digital  nerve  of  the  great  toe  and  divides  into  three  common 
digital  branches.5  These  pass  from  under  cover  of  the  plantar  fascia 
and  near  the  cleft  of  the  toes  divide  into  the  collateral  digital  nerves 
of  the  adjacent  sides  of  the  inner  four  toes.  Before  dividing,  the  inter- 
nal plantar  nerve  gives  muscular  branches  to  the  hallucal  abductor 


1  N.  tibialis  posticus. 

2  N".  cutaneus  calcis  ;  n.  cut.  interims  ;  n.  cut.  plantaris  proprius. 

3  N.  plantaris  externus  or  lateralis. 

4  N.  plantaris  internus  or  medialis.  5  Nervi  digitales  communes. 


THE   NERVOUS  SYSTEM.  835 

and  short  digital  flexor  and  several  cutaneous  branches  to  the  skin 
of  the  sole  of  the  foot.  The  first  digital  nerve  gives  twigs  to  the  short 
hallucal  flexor ;  the  second  and  third  digitals,  twigs  to  the  contiguous 
pair  of  lumbrical  muscles.  The  fourth  digital  receives  a  communi- 
cating branch  from  the  external  plantar  nerve. 

The  distribution  of  the  plantar  nerves  is  similar  to  that  of  the 
median  and  ulnar  nerves  in  the  palm  of  the  hand. 

COCCYQEAL    PLEXUS. 

The  coccygeal  plexus 1  is  formed  by  the  fifth  anterior  sacral  nerve, 
with  a  division  of  the  fourth  sacral  and  the  anterior  coccygeal  nerve. 

The  fifth  sacral  nerve,  the  smallest  of  the  series,  emerges  through 
the  intervertebral  foramen  below  the  sacrum  and  perforates  the  coccy- 
geus  muscle,  in  front  of  which  it  is  joined  by  the  descending  branch 
of  the  fourth  nerve  and  receives  from  below  the  anterior  coccygeal 
nerve.  This,  the  smallest  of  the  anterior  spinal  nerves,  descends  from 
the  end  of  the  spinal  canal,  turns  forward  through  the  last  inter- 
vertebral  foramen,  between  the  first  two  coccygeal  vertebrae  and  the 
sacro-sciatic  ligaments,  and  joins  the  coccygeal  plexus,  the  filaments2 
of  which  are  distributed  to  the  coccygeus  muscle  and  skin  about  the 
end  of  the  coccyx. 

SYMPATHETIC   NEKVES. 

The  nerves  of  the  sympathetic  system  supply  the  internal  viscera 
and  the  walls  of  the  blood-vessels  and  lymphatics,  though  some  of  the 
organs,  as  the  heart,  the  lungs,  the  upper  part  and  lower  extremity  of 
the  alimentary  canal,  also  receive  nerves  from  the  cerebro-spinal  system. 

Each  sympathetic  nerve3  consists  of  a  main  gangliated  cord, 
with  three  great  prevertebral  plexuses  associated  with  ganglia^  and 
numerous  small  plexuses  distributed  with  the  blood-vessels. 

The  gangliated  cord  of  the  sympathetic  nerve  consists  of  a  series 
of  ganglia  in  the  course  of  a  cord  placed  at  the  side  of  the  vertebral 
column,  extending  from  the  base  of  the  cranium  to  the  coccyx.  The 
upper  extremity  of  the  cord  is  continued  by  a  plexus  through  the 
carotid -canal  into  the  cranial  cavity,  the  lower  extremity  joins  that  of 
the  opposite  side  in  a  loop4  or  in  a  median  ganglion5  in  front  of  the 
coccyx.  The  cord  is  conveniently  divided  according  to  the  regions 
it  occupies  into  the  cervical,  thoracic,  lumbar,  and  sacral  portions, 
and  on  them  the  ganglia  nearly  agree  in  number  with  the  vertebrae 
of  the  regions,  except  the  cervical  portion,  on  which  there  are  only 
three  ganglia. 

1  P.  coccygeus.  2  Nervi  ano-coccygei. 

3  N.  sympatheticus ;  n.  symp.  magnus ;  n.  intercostalis  magnus ;  n.  trisplanch- 
nicus ;  n.  gangliosus. 

4  Ansa  sacralis ;  arcus  nervosus  sacralis.  8  G.  impar ;  g.  Walteri. 


836  THE   NERVOUS   SYSTEM. 

The  ganglia  are  joined  with  the  commencement  of  the  nearest 
anterior  spinal  nerves  by  communicating  branches,  each  of  which 
consists  of  a  white  and  a  gray  portion,  the  former  consisting  of  fibres 
derived  from  the  spinal  nerves,  the  latter  being  a  contribution  to  them. 
The  intervening  portions  of  the  main  cord  connecting  the  ganglia  are 
likewise  composed  of  white  and  gray  portions,  of  which  the  former  is 
continuous  with  the  fibres  of  the  spinal  nerves  communicating  with  the 
ganglia. 

The  great  prevertebral  plexuses  consist  of  three  single  median 
interlacements  of  nerves  associated  with  ganglia,  common  to  the  two 
sympathetic  nerves,  situated  in  front  of  the  spine  in  succession  in  the 
cavity  of  the  thorax,  abdomen,  and  pelvis,  named  the  cardiac,  solar, 
and  hypogastric  plexuses.  These  also  receive  branches  from  the 
neighboring  cerebro-spinal  nerves,  while  from  them  proceed  divisions 
or  small  plexuses  following  the  course  of  the  blood-vessels. 

CEEVICAL   POKTION   OF   THE  SYMPATHETIC   NEKVE.1 

In  the  neck  the  gangliated  cord  is  placed  on  the  prevertebral  mus- 
cles behind  the  great  cervical  vessels  enclosed  in  their  sheath,  and  has 
upon  it  three  ganglia  distinguished  by  number  or  relative  position. 

FIRST   CERVICAL    GANGLION. 

The  first,  or  superior  cervical  ganglion,2  the  largest  of  the 
cord,  is  a  variable  reddish-gray  body,  usually  fusiform,  about  an  inch 
in  length,  resting  on  the  greater  prerectus  muscle,  behind  the  internal 
carotid  artery,  the  vagus  and  hypoglossal  nerves.  Its  upper  tapering 
end  is  the  upper  extremity  of  the  gangliated  cord  and  in  company 
with  the  internal  carotid  artery  enters  the  carotid  canal,  where  it 
forms  the  carotid  plexus ;  its  lower  end  is  continuous  with  the  cord 
descending  the  neck. 

Outwardly  the  ganglion  is  joined  by  communicating  branches3 
with  the  upper  three  or  four  cervical  nerves.  It  is  also  connected  by 
others  with  the  jugular  ganglion  and  gangliform  plexus  of  the  vagus, 
with  the  jugular  and  petrous  ganglia  of  the  glosso-pharyngeal  and 
with  the  hypoglossal  nerve. 

The  branches  from  the  ganglion  are  the  vascular  and  pharyngeal 
and  the  superior  cardiac  nerve. 

The  vascular  branches,4  a  variable  number  of  delicate  filaments, 
twine  round  the  external  carotid  artery,  on  which  they  form  the  ex- 
ternal carotid  plexus,5  whence  divisions  proceed  along  the  branches 
of  the  vessel.  From  the  plexus  on  the  facial  artery  is  given  the  fila- 

1  Pars  cervicalis  nervi  sympathetici. 

2  G.  cervicale  superior  or  magnum  ;  g.  fusiforme  ;  g.  olivare. 

3  Kami  communicantes  ;  r.  externi.  *  Nervi  molles. 
5  P.  earoticus  externus. 


THE   NERVOUS   SYSTEM. 


837 


ment  to  the  submaxillary  gland,  and  from  that  on  the  great  meningeal 
artery  a  filament  to  the  otic  ganglion  and  another1  to  the  facial  nerve. 

FIG.  418. 

FIG.  418.— THE  SYMPA- 
THETIC, VAGUS,  AND  OTHER 
ASSOCIATED  NERVES.  1,  va- 

gus  nerve ;  2,  glosso-pha- 
ryngeal  nerve ;  3,  accessory 
nerve ;  4,  hypoglossal  nerve; 
5,  gangliated  cord  of  the 
sympathetic  nerve;  6,  first 
cervical  ganglion ;  7,  upper 
end  of  the  cord  dividing 
and  forming  the  carotid 
plexus ;  8,  tympanic  branch 
of  the  glosso-pharyngeal 
nerve  on  the  promontory 
of  the  tympanum ;  9,  genic- 
ulate  ganglion  of  the  facial 
nerve  joined  by  the  super- 
ficial petrosal  nerve;  10, 
abducent  nerve  joined  by 
filaments  of  the  caver- 
nous plexus ;  11,'  ophthal- 
mic ganglion ;  12,  spheno- 
palatine  ganglion  ;  13,  otic 
ganglion ;  14,  lingual  nerve ; 
15,  submaxillary  gangli- 
on; 16,  superior  laryngeal 
nerve ;  17,  internal  laryn- 
geal nerve ;  18,  external 
laryngeal  nerve ;  19,  20,  in- 
ferior laryngeal  nerve;  21, 
termination  of  the  right 
vagus  nerve  back  of  the 
stomach  ;  22,  23,  left  vagus 
nerve ;  24,  cord  of  the  sym- 
pathetic nerve  descending 
from  the  first  to  the  second 
cervical  ganglion,  25;  26, 
superior  cardiac  nerve ;  27, 
middle  cardiac  nerve ;  28, 
29,  third  cervical  and  first 
thoracic  ganglia  fused  to- 
gether ;  30,  inferior  cardiac 
nerve ;  31,  cardiac  branches 
from  the  vagus  and  first 
thoracic  ganglion  to  the 
cardiac  plexus,  32 ;  33,  cor- 
onary plexus;  34,  35,  tho- 
racic ganglia  from  the  sec- 
ond to  the  last;  36,  great 
splanchnic  nerve;  37,  its 
termination  in  the  semi- 
lunar  ganglion;  38,  small 
splanchnic  nerve ;  39,  solar 
plexus ;  40,  phrenic  plexus ; 
41,  renal  ganglion ;  42,  loop 
formed  between  the  first  and  second  cervical  nerves ;  43,  third  anterior  cervical  nerve ;  44,  fourth 
anterior  cervical  nerve ;  45-47,  four  lower  cervical  and  first  thoracic  nerves  forming  the  brachial 
plexus;  48,  anterior  thoracic  or  intercostal  nerves ;  49,  aorta  drawn  forward  ;  50,  right  auricle ;  51, 
right  ventricle ;  52,  right  pulmonary  artery;  53,  right  bronchus;  54,  cut  edge  of  the  diaphragm; 
55,  stomach  dragged  aside  to  exhibit  the  solar  plexus. 


1  N.  petrosus  superficialis. 


838  THE   NERVOUS   SYSTEM. 

In  the  course  of  the  vascular  branches  are  some  microscopic  but 
inconstant  ganglia.  Besides  these  there  is  commonly  one,  the  tempo- 
ral ganglion,1  about  a  line  long,  situated  on  the  external  carotid  at 
the  origin  of  the  posterior  auricular  artery.  It  is  connected  by  a  fila- 
ment with  the  facial  nerve,  and  is  apparently  related  to  the  parotid 
gland  as  the  submaxillary  ganglion  is  to  the  submaxillary  gland. 

The  pharyngeal  branches,2  two  to  four,  proceed  from  the  inner 
part  of  the  ganglion  and  join  with  the  pharyngeal  branches  of  the 
glosso-pharyngeal  and  vagus  nerves  in  the  formation  of  the  pharyn- 
geal plexus.3  This  lies  on  the  middle  constrictor  and  supplies  the 
muscles  and  mucous  membrane  of  the  pharynx.  One  of  the  branches 
communicates  with  the  superior  laryngeal  nerve  and  with  its  external 
laryngeal  branch. 

The  superior  cardiac  nerve,*  a  long  slender  branch,  springs  from 
the  lower  end  of  the  ganglion  by  one  or  two  roots,  sometimes  joined 
by  another  from  the  cord  below,  or  sometimes  arising  from  it  alone. 
Descending  the  neck  on  the  long  cervical  muscle  behind  the  sheath 
of  the  cervical  vessels,  it  enters  the  thorax.  The  right  nerve  passes 
either  in  front  or  behind  the  subclavian  artery,  runs  along  the  in- 
nominate artery  to  the  back  of  the  aorta,  thence  to  end  in  the  deep 
cardiac  plexus.  The  left  nerve  follows  the  left  carotid  artery  and 
usually  crosses  in  front  of  the  arch  of  the  aorta  to  end  in  the  superficial 
cardiac  plexus,  but  sometimes  descends  behind  the  aorta  to  the  deep 
plexus. 

In  its  course  the  superior  cardiac  nerve  is  usually  joined  by  the 
cardiac  branch  of  the  superior  laryngeal  nerve  of  the  vagus,  and  in 
the  chest  by  one  or  more  of  the  cardiac  branches  of  the  inferior  laryn- 
geal nerve. 

The  superior  cardiac  nerve  is  very  variable,  even  on  the  two  sides 
of  the  body.  It  sometimes  joins  the  cardiac  nerve  derived  from  one 
or  the  other  cervical  ganglia,  and  occasionally  has  been  found  to  be 
absent  on  one  side. 

CAEOTID  PLEXUS. 

The  upper  end  of  the  first  cervical  ganglion  of  the  sympathetic 
nerve  tapers  in  a  reddish-gray,  flattened  cord,5  which  ascends  and  enters 
the  carotid  canal  beneath  the  internal  carotid  artery  and  divides  into 
two  branches.  These  in  their  further  course  by  repeated  division  and 
anastomosis  form,  around  the  artery,  the  carotid  plexus,6  which  is 
continuous  on  the  vessel  through  the  cavernous  sinus,  where  it  is  dis- 
tinguished as  the  cavernous  plexus.7 

Occasionally  a  minute  stellate   ganglion8  is  found  on  the  carotid 

1  G.  temporale.  2  Kami  pharyngei ;  r.  pharyngeo-laryngei. 

3  P.  pharyngeus.  4  IS",  cardiacus  superior,  superficialis,  or  longus. 

5  Nervus  caroticus.  6  P.  caroticus  interims. 

7  P.  cavernosus.  8  G.  caroticum  or  cavernosum. 


THE  NERVOUS  SYSTEM.  839 

plexus  to  the  outer  side  of  the  carotid  artery,  but  more  frequently  is 
substituted  by  a  little  narrow-meshed  plexus. 

The  carotid  plexus  is  connected  by  the  deep  petrosal  nerve,1  a 
branch  of  the  vidian  nerve,  with  the  spheno-palatine  ganglion.  (See 
page  789.)  Of  two  other  communicating  branches,  one2  passes  through 
a  minute  foramen  and  the  other3  through  a  fine  canal  into  the  tym- 
panum, where  they  join  the  tympanic  branch  *  of  the  glosso-pharyngeal 
nerve. 

From  the  cavernous  plexus  filaments  proceed  to  the  semilunar  gan- 
glion of  the  trifacial  nerve,  to  the  ophthalmic  branch,  and  to  the  oculo- 
motor nerve.  Two  filaments  also  are  given  by  the  plexus  to  the  ab- 
ducent nerve  as  it  crosses  the  internal  carotid  artery  in  the  cavernous 
sinus.  From  it  proceeds  the  sympathetic  root  of  the  ophthalmic 
ganglion,  either  directly  or  joined  by  the  nasal  branch  of  the  ophthalmic 
nerve. 

SECOND  AND  THIKD  CEKVICAL  GANGLIA. 

The  second,  or  middle  cervical  ganglion,5  of  the  sympathetic 
nerve  is  much  smaller  than  either  of  the  others  and  is  situated  at 
the  inner  side  of  the  inferior  thyroid  artery  opposite  the  sixth  cer- 
vical vertebra.  It  is  connected  by  communicating  branches  usually 
with  the  fifth  and  sixth  cervical  nerves,  and  gives  filaments  to  the 
inferior  thyroid  artery,  on  which  they  form  a  plexus  continued  to  the 
thyroid  gland. 

From  the  second  cervical  ganglion  springs  the  middle  cardiac 
nerve,6  which  on  the  right  side  runs  either  in  front  or  behind  the  sub- 
clavian  artery  and  on  the  trachea,  where  it  is  joined  by  filaments  from 
the  recurrent  laryngeal  nerve,  and  finally  ends  in  the  deep  cardiac 
plexus ;  on  the  left  side  it  runs  between  the  left  carotid  and  subclavian 
and  likewise  ends  in  the  deep  cardiac  plexus. 

Sometimes  the  second  ganglion  is  absent,  in  which  case  the  middle 
cardiac  nerve  comes  from  the  sympathetic  trunk. 

The  third,  or  inferior  cervical  ganglion,7  is  large,  irregularly 
angular,  and  flattened,  and  is  frequently  united  with  the  first  thoracic 
ganglion.  It  lies  in  the  recess  between  the  front  of  the  costo-trans- 
verse  process  of  the  last  cervical  vertebra  and  the  neck  of  the  first 
rib  behind  the  vertebral  artery.  It  is  connected  by  communicating 
branches  with  the  lower  two  cervical  and  first  thoracic  nerves,  and 
by  another  with  the  first  thoracic  ganglion,  forming  a  loop 8  around  the 
subclavian  artery.  It  gives  vascular  filaments  to  the  artery  and 
its  branches ;  some  of  these  filaments  with  others  from  the  second 

1  N.  petrosus  profundus  major.  2  N.  carotico-tympanicus  inferior. 

3  N.  car.-tym.  superior;  n.  petrosus  profundus  minor. 

*  N.  Jacobsonii.  5  G.  cervicale  medius. 

6  N.  cardiacus  medius,  magnus,  or  profundus. 

7  G.  cervicale  inferius.  8  Ansa  Vieussenii. 


840  THE   NERVOUS   SYSTEM. 

thoracic  ganglion  on  the  vertebral  artery  form  the  vertebral  plexus,1 
which  is  reinforced  in  its  course  by  filaments  from  the  lower  four  to 
six  cervical  nerves. 

From  the  third  cervical  ganglion  is  derived  the  inferior  cardiac 
nerve,2  which  runs  inward  behind  the  subclavian  artery  and  in  front 
of  the  trachea  to  end  in  the  deep  cardiac  plexus.  It  is  often  joined  by 
the  middle  cardiac  nerve,  especially  on  the  left  side,  when  the  common 
trunk 3  pursues  the  usual  course  to  the  deep  cardiac  plexus.  Sometimes 
it  has  its  origin  from  the  first  thoracic  ganglion. 

CAKDIAC   PLEXUS. 

The  cardiac  plexus,4  contained  within  the  chest,  is  formed  by  the 
convergence,  division,  and  anastomosis  of  the  three  cardiac  nerves  from 
the  cervical  ganglia  of  both  sympathetics,  together  with  the  cardiac 
branches  from  the  first  thoracic  ganglia  and  from  both  vagus  nerves. 
It  extends  from  the  top  of  the  aortic  arch  to  the  base  of  the  heart 
and  embraces  the  ascending  portion  of  the  aorta  and  the  trunk  of 
the  pulmonary  artery.  •  The  smaller  portion  is  distinguished  as  the 
superficial  cardiac  plexus,5  situated  between  the  arch  of  the  aorta 
and  the  front  of  the  right  pulmonary  artery.  The  larger  and  more 
intricate  portion  is  the  deep  cardiac  plexus,6  situated  behind  the 
arch  of  the  aorta  next  the  bifurcation  of  the  trachea  and  above  that  of 
the  pulmonary  artery. 

The  superficial  cardiac  plexus  receives  the  superior  cardiac  nerve 
of  the  left  sympathetic  and  the  lower  cervical  cardiac  branch  of  the 
left  vagus  nerve ;  while  the  deep  plexus  receives  all  the  other  cardiac 
nerves  of  both  sympathetics  and  the  cardiac  branches  of  both  vagus 
nerves. 

In  the  superficial  cardiac  plexus  above  the  bifurcation  of  the  pul- 
monary artery  there  is  usually  a  cardiac  ganglion,7  occasionally  a 
smaller  pair,  but  sometimes  none.  The  plexus  gives  filaments  along 
the  pulmonary  artery  to  the  anterior  pulmonary  plexus  of  the  left  side, 
but  mainly  ends  in  the  right  coronary  plexus. 

The  deep  cardiac  plexus  gives  filaments  directly  to  the  auricles,  a 
few  to  the  superficial  cardiac  plexus,  and  others  to  both  anterior  pul- 
monary plexuses,  while  the  greater  number  end  in  the  left  coronary 
plexus. 

The  cardiac  plexus  gives  filaments  to  all  the  great  vessels  spring- 
ing from  the  base  of  the  heart  and  to  the  pericardium.  Its  extension 


1  P.  vertebralis  ;  p.  vertebro-basilaris. 

2  N.  cardiacus  inferior,  parvus,  or  tertius. 

3  N.  cardiacus  crassus.  *  P.  cardiacus. 

5  P.  card,  superficialis  ;  p.  aorticus  anterior. 

6  P.  card,  profundus  or  magnus. 

7  G.  cardiacum  magnum ;  g.  card.  Wrisbergii. 


THE   NERVOUS   SYSTEM.  841 

reinforced  by  filaments  from  the  upper  thoracic  ganglia  of  both  gym- 
pathetics  forms  the  aortic  plexus  accompanying  the  aorta  through  the 
thorax.  Other  filaments  from  the  plexus  are  directly  distributed  to 
the  walls  of  the  heart  independent  of  the  course  of  the  coronary  blood- 
vessels. The  CEsophageal  and  pulmonary  plexuses  derived  from  the 
vagus  nerves  receive  few  filaments  from  the  cardiac  and  aortic  plexuses 
and  the  thoracic  ganglia. 

The  right  coronary  plexus,1  derived  from  the  superficial  cardiac 
plexus  and  the  right  side  of  the  deep  cardiac  plexus,  accompanies  the 
right  coronary  artery  in  its  distribution  to  the  heart. 

The  left  coronary  plexus,2  larger  than  the  right  and  derived 
from  the  left  of  the  deep  cardiac  plexus,  accompanies  the  left  coronary 
artery  and  its  branches  in  their  distribution  to  the  heart. 

The  nerves  of  the  cardiac  plexus  and  its  divisions,  the  coronary 
plexuses  distributed  to  the  muscular  walls  of  the  heart,  contain 
numerous  microscopic  ganglia  in  their  course.  These  minute  ganglia, 
readily  observed  without  preparation  in  the  transparent  wall  of  the 
auricles  of  the  heart  in  frogs  and  salamanders,  are  regarded  as  motor 
centres,  and  seem  to  explain  why  this  organ  may  continue  to  pulsate 
after  it  has  been  removed  from  the  animal. 

THOKACIO   PORTION  OP  THE   SYMPATHETIC   NERVE.* 

In  the  thorax  the  gangliated  cord  lies  in  front  of  the  heads  of  the 
ribs,  crossing  the  intercostal  blood-vessels  and  covered  by  the  pleura 
through  which  it  is  visible.  It  is  provided  commonly  with  twelve 
ganglia,  each  lying  on  the  head  of  the  corresponding  rib,  but  occa- 
sionally a  contiguous  pair  of  ganglia  coalesce,  when  the  number  is 
accordingly  reduced.  The  first  ganglion  is  the  largest  and  is  often 
more  or  less  blended  with  the  last  cervical  ganglion ;  the  others  are 
small  and  usually  oval,  though  variable  in  shape.  Each  ganglion  is 
connected  usually  by  a  pair  of  communicating  branches  with  the 
commencement  of  the  nearest  spinal  nerve. 

Besides  a  cardiac  branch  from  the  first  thoracic  ganglion  to  join 
the  inferior  cardiac  nerve  of  the  last  cervical  ganglion  or  directly  to 
the  deep  cardiac  plexus,  branches  from  the  upper  five  or  six  thoracic 
ganglia  proceed  to  reinforce  the  contiguous  plexuses,  mainly  the  aortic 
plexus,  but  also  the  cesophageal  and  pulmonary  plexuses. 

The  branches  of  the  lower  thoracic  ganglia  commonly  unite  in  the 
formation  of  the  great  and  small  splanchnic  nerves,  which  descend 
into  the  abdomen  and  terminate  in  the  solar  plexus.  The  splanchnic 
nerves 4  are  white,  due  to  the  predominance  of  medullated  fibres  which 


1  P.  coronarius  dexter  or  anterior. 

2  P.  coronarius  sinister  or  posterior. 

3  Pars  thoracica  nervi  sympathici.  *  N.  splanchnici. 


842 


THE   NERVOUS   SYSTEM. 


are  derived  through  the  communicating  branches  of  the  sympathetic 
from  the  spinal  nerves. 


FIG.  419. 


THE  SYMPATHETIC  NERVE  ;  lumbar  and  sacral  portions.  1,  diaphragm ;  2,  cardia ;  3,  stomach ; 
4,  small  intestine ;  5,  sigmoid  flexure  of  the  colon ;  6,  rectum ;  7,  bladder ;  8,  prostate ;  9,  left  vagus 
nerve ;  10,  right  vagus  nerve ;  11,  great  splanchnic  nerve  terminating  in  the  semilunar  ganglion, 
12 ;  small  splanchnic  nerve  ending  in  the  solar  plexus ;  13, 14,  superior  mesenteric  plexus ;  15,  15, 
lower  two  thoracic  ganglia ;  16,  16,  four  lumbar  ganglia  in  succession ;  17,  17,  communicating 
branches  with  the  adjacent  lumbar  nerves  ;  18,  branches  to  the'aortic  plexus,  19;  20,  inferior  mes- 
enteric plexus ;  21,  hypogastric  plexus ;  22,  branches  to  hypogastric  plexus  from  the  lower  lum- 
bar ganglion ;  23,  23,  series  of  four  sacral  ganglia ;  24,  24,  pelvic  plexuses ;  25,  25,  hemorrhoidal 
plexus ;  26,  26,  branches  to  hemorrhoidal  plexus  from  the  sacral  ganglia ;  27,  28,  29,  lower  three 
thoracic  nerves ;  30,  first  lumbar  nerve  dividing  into  the  ilio-hypogastric  and  ilio-inguinal 
branches ;  31-33,  second,  third,  and  fourth  nerves  forming  the  lumbar  plexus ;  34,  genito-crural 
nerve ;  35,  lumbo-sacral  cord  descending  to  the  sacral  plexus,  36 ;  37,  37,  branches  from  the  third 
and  fourth  sacral  nerves  to  the  hemorrhoidal  plexus ;  38,  fifth  sacral  nerve ;  39,  coccygeal  nerve. 


THE   NERVOUS   SYSTEM.  843 

The  great  splanchnic  nerve1  springs  by  roots  usually  from  the 
sixth  to  the  ninth  thoracic  ganglion  and  often  from  one  or  two  above. 
The  roots  successively  unite  on  the  sides  of  the  vertebral  centra,  and 
the  trunk  formed  by  their  union  passes  through  the  crus  of  the  dia- 
phragm or  rarely  through  the  aortic  orifice  and  ends  in  the  semilunar 
ganglion  of  the  solar  plexus. 

The  small  splanchnic  nerve 2  springs  from  the  tenth  and  eleventh 
thoracic  ganglia  and  descends  in  company  with  the  great  splanchnic, 
or  through  a  separate  opening  in  the  crus  of  the  diaphragm,  to  end  in 
the  cceliac  plexus,  in  its  course  usually  giving  off  a  considerable  branch, 
the  superior  renal  nerve,3  to  the  renal  plexus.  The  latter  branch 
sometimes  comes  from  the  trunk  of  the  gangliated  cord  or  from  the 
last  thoracic  ganglion  and  is  distinguished  as  the  smallest  splanchnic 
nerve.4 

Barely  a  fourth  splanchnic  nerve5  has  been  observed  arising  from 
the  upper  thoracic  ganglia  and  cardiac  plexus  and  descending  to  the 
oesophageal  plexus  of  the  vagus,  to  the  great  splanchnic  nerve,  or  the 
semilunar  ganglion. 

The  thoracic  aortic  plexus,6  the  continuation  of  the  cardiac 
plexus,  entwines  the  descending  thoracic  aorta  reinforced  by  filaments 
from  the  upper  thoracic  ganglia.  It  is  a  net- work  of  delicate  threads 
and  is  continuous  below  with  the  solar  plexus. 

SOLAK  PLEXUS. 

The  solar  plexus,7  the  largest  and  most  intricate  of  the  plexuses 
common  to  both  sympathetic  nerves,  is  situated  in  the  upper  part  of 
the  abdomen,  behind  the  stomach  on  the  front  of  the  aorta,  arOund  the 
commencement  of  the  cceliac  axis  and  superior  mesenteric  artery.  It 
consists  of  a  net-work  of  nerves,  associated  with  ganglia,  and  receives 
the  splanchnic  nerves  of  both  sides,  together  with  filaments  from  the 
thoracic  aortic  plexus  and  from  the  right  vagus  nerves. 

Among  the  ganglia  of  the  solar  plexus,  variable  in  number,  shape, 
and  size,  are  usually  two  conspicuous  ones,  the  semilunar  ganglia.8 
These  are  likewise  variable,  commonly  irregular  lunate  or  reniform, 
sometimes  horse-shoe-shaped  or  even  annular,  and  occasionally  they 
are  more  or  less  fused  into  one.  They  are  situated  one  on  each  side 
of  the  cceliac  artery  with  the  extremities  turned  up,  and  usually  receive 
by  their  outer  extremity  the  great  splanchnic  nerve. 

From  the  solar  plexus  proceed  divisions  or  'secondary  plexuses  on 

1  1ST.  splanchnicus  major.  2  N.  splanch.  minor. 

3  N.  renalis  sup.  or  posterior. 

4  N.  splanchnicus  imus,  inferior,  or  tertius. 

5  N.  splanch.  supremus.  6  P.  aorticus  thoracicus. 

7  P.  Solaris  ;  epigastric  or  cceliac  plexus  ;  p.  cceliacus  or  epigastricus. 

8  G.  semilunare,  splanchnicum,  cceliacum,  abdominale,  or  solare. 


844  THE   NERVOUS   SYSTEM. 

all  the  adjacent  arteries,  twining  and  interlacing  around  and  accom- 
panying them  in  their  ramifications  and  distribution  to  the  viscera. 

The  plexuses  derived  from  the  solar  plexus  are  as  follows  : 

The  cceliac  plexus.1  Derived  from  the  fore  part  of  the  solar 
plexus,  it  surrounds  the  cceliac  artery,  receives  a  few  filaments  from 
the  right  vagus,  and  divides  into  the  gastric,2  hepatic,3  and  splenic4 
plexuses,  which  accompany  the  corresponding  arteries  and  are  dis- 
tributed with  them. 

The  superior  mesenteric  plexus.  This  forms  a  copious  inter- 
texture  of  white  filaments  proceeding  from  the  solar  plexus  and  rein- 
forced by  filaments  from  the  abdominal  aortic  plexus,  accompanying 
the  superior  mesenteric  artery  in  its  distribution.  At  its  commence- 
ment, to  the  right  of  the  base  of  the  superior  mesenteric  artery,  it  is 
usually  furnished  with  a  superior  mesenteric  ganglion. 

The  phrenic  plexus.5  This  proceeds  from  the  upper  part  of  the 
plexus  and  accompanies  the  phrenic  arteries  to  the  diaphragm.  It 
gives  filaments  on  each  side  to  the  suprarenal  body,  and  on  its  right  it 
commonly  contains  the  small  phrenic  ganglion,6  which  gives  filaments 
to  the  contiguous  suprarenal  body,  the  inferior  cava,  and  the  hepatic 
plexus. 

The  suprarenal  plexus.  On  each  side  this  accompanies  the  cor- 
responding artery  to  the  suprarenal  body. 

The  renal  plexus.7  This  is  continued  on  each  side  from  the  solar 
j)lexus,  and  receives  the  renal  branch  of  the  small  splanchnic  nerve, 
at  the  termination  of  which  on  the  right  side  there  is  usually  a  renal 
ganglion.8  The  renal  plexus  is  reinforced  by  filaments  from  the  supe- 
rior mesenteric  and  aortic  plexuses  and  accompanies  the  renal  artery 
in  its  distribution. 

The  spermatic  plexus.9  This  proceeds  from  the  superior  mesen- 
teric and  renal  plexuses  and  accompanies  the  spermatic  artery  to  the 
testicle,  or  in  the  female  the  ovarian  artery  to  the  ovary  and  uterus.  In 
its  course  it  is  reinforced  by  filaments  from  the  aortic  and  hypogastric 
plexuses. 

LUMBAE  PORTION   OF   THE   SYMPATHETIC   NERVE.™ 

The  lumbar  portion  of  the  gangliated  cord,  in  the  abdomen,  lies  on 
the  side  of  the  vertebral  centra  along  the  inner  border  of  the  psoas 
muscle,  that  of  the  right  cord  behind  the  inferior  cava,  that  of  the  left 
cord  behind  the  aorta.  The  lumbar  ganglia,11  of  which  there  are 
commonly  four,  are  small  and  oval,  but  occasionally  they  are  fewer 


1  P.  coeliacus.  2  P.  coronarius  ventriculi. 

3  P.   hepaticus.  *  P.  lienalis. 

5  P.  diaphragmaticus.  6  G.  diaphragmaticum. 

1  P.  renalis.  8  G.  renali-aorticum.  9  P.  spermaticus. 

10  Pars  lumbalis  nervi  sympathici.  u  G.  lumbalia. 


THE   NERVOUS   SYSTEM.  845 

and  proportionately  larger.  Each  is  connected  with  the  commence- 
ment of  the  nearest  spinal  nerve,  somewhat  variably  with  one  or  the 
other,  usually  by  two  communicating  branches.  These  accompany 
the  lumbar  arteries  across  the  vertebrae,  and  are  longer  than  elsewhere 
in  consequence  of  the  greater  distance  of  the  gangliated  cord  from  the 
intervertebral  foramina. 

The  branches  from  the  lumbar  ganglia  are  variable,  and  partly 
proceed  to  the  abdominal  aortic  plexus,  while  others  descend  to  the 
hypogastric  plexus. 

The  abdominal  aortic  plexus *  is  continued  from  the  solar  and 
renal  plexuses  and  descends  on  the  abdominal  aorta  to  its  fork,  where 
it  runs  into  the  hypogastric  plexus  included  between  the  iliac  arteries. 
It  commonly  exhibits  on  each  side  of  the  aorta  a  variably  distinct  and 
thicker  string,  which  receives  the  obliquely  descending  branches  of  the 
lumbar  ganglia  and  is  united  with  its  fellow  in  front  of  the  aorta  by  a 
wide-meshed  net  of  fibres. 

From  the  aortic  plexus  proceeds  the  inferior  mesenteric  plexus,2 
at  its  commencement  including  the  inferior  mesenteric  ganglion,3 
and  accompanying  the  corresponding  artery  in  its  distribution  to  the 
intestines. 

SACKAL   PORTION   OF   THE   SYMPATHETIC   NERVE.* 

The  gangliated  cord  in  the  pelvis,  much  diminished  in  size,  descends 
in  front  of  the  sacrum  convergent  along  the  inner  side  of  the  sacral 
foramina.  The  lower  end  usually  unites  with  that  of  the  opposite 
side  in  a  loop,  on  which  sometimes  there  is  a  little,  median  coccygeal 
ganglion,5  situated  in  front  of  the  coccyx. 

The  sacral  ganglia6  are  usually  four,  often  only  three,  and  are 
small  fusiform  bodies.  Each  is  variably  connected,  usually  by  two 
communicating  branches,  with  the  contiguous  sacral  nerve.  The 
branches  distributed  by  the  sacral  ganglia  are  small  and  proceed  to 
the  hypogastric  and  coccygeal  plexuses. 

HYPOGASTRIC   PLEXUS. 

The  hypogastric  plexus,7  an  intricate  net-work  of  nerve-threads, 
without  distinct  associated  ganglia,  enveloped  in  a  copious  layer  of 
areolar  tissue,  lies  in  front  of  the  last  lumbar  vertebra  in  the  interval  of 
the  common  iliac  arteries,  covered  by  the  peritoneum.  It  is  continued 
from  the  abdominal  aortic  plexus  reinforced  by  branches  from  the 


1  P.  aorticus  abdominalis ;  p.  intermesentericus. 

2  P.  mesentericus  inferior.  3  G.  mesent.  inferius. 
•*  Pars  sacralis  nervi  sympathici. 

5  G.  coccygeum  impar ;  g.  Waltheri. 

6  G.  sacralia.  T  P.  hypogastricus. 


846  THE   NEEVOUS   SYSTEM. 

lumbar  ganglia,  and  below  divides  into  two  portions,  the  inferior  hypo- 
gastric  plexuses. 

The  inferior  hypogastric,  or  pelvic  plexus,1  reinforced  by  the 
branches  of  the  sacral  ganglia  and  additional  filaments  from  the  lower 
two  or  three  sacral  nerves,  extends  forward  at  the  side  of  the  rectum, 
and  also  the  vagina  in  the  female.  Associated  with  the  plexus  are  many 
minute  ganglia,  and  from  it  proceed  the  following  secondary  plexuses : 

The  hemorrhoidal  plexus,2  consisting  of  fine  filaments,  partly 
from  the  pelvic  plexus  and  partly  from  the  vesical  plexus,  proceeding 
upward  and  forward  to  the  rectum,  in  which  they  communicate  with 
filaments  of  the  inferior  mesenteric  plexus. 

The  vesical  plexus,3  formed  by  many  filaments  derived  from  the 
pelvic  plexus  and  distributed  to  the  lower  part  and  side  of  the  bladder, 
the  prostate,  and  the  seminal  vesicle.  In  the  female  its  filaments  are 
distributed  to  the  vagina  as  well  as  to  the  bladder,  whence  its  name  of 
the  vesico-vaginal  plexus.* 

The  cavernous  plexus,5  continued  from  the  vesical  plexus.  It 
follows  the  pudic  artery  and  its  branches  to  the  root  of  the  penis, 
where  filaments 6  penetrate  the  cavernous  body  to  be  distributed  to  the 
erectile  tissue,  while  a  larger  filament 7  runs  along  the  dorsum  of  the 
penis  anastomosing  with  the  dorsal  branch  of  the  pudic  nerve  and 
distributed  to  the  cavernous  body.  Filaments  also  supply  the  spongy 
body  and  other  parts  of  the  penis. 

The  uterine  plexus,8  derived  from  the  pelvic  plexus,  passing 
through  the  broad  ligament  in  company  with  the  uterine  artery  and 
its  branches,  to  be  distributed  to  the  uterus.  On  its  filaments  in  the 
walls  of  the  uterus  are  numerous  microscopic  ganglia. 

1  P.  hypog.  inferior  or  lateralis.  2  P.  haemorrhoidalis. 

3  P.  vesicalis.  4  P.  vesico-vaginalis. 

5  P.  cavernosus.  6  Small  cavernous  nerves. 

7  Large  cavernous  nerve.  8  P.  uterinus. 


OHAPTEE   XVI. 

ORGANS   OP    SPECIAL   SENSE. 

The  organs  of  special  sense  comprise  the  nose,  the  eyes,  the 
ears,  the  tongue,  and  the  skin. 

THE   NOSE. 

The  nose l  includes  the  prominent  feature  of  the  face,  together  with 
the  nasal  cavities.  Besides  being  the  special  organ  of  the  sense  of 
smell,  it  serves  as  the  chief  avenue  of  respiration. 

FIG.  420. 


OUTER  WALL  OF  THE  LEFT  NASAL  CAVITY.  1,  superior  turbinal ;  2,  superior  meatus ;  3,  middle 
turbinal ;  4,  middle  meatus ;  5,  portion  of  the  turbinals  of  the  ethmoid  bone,  removed  to  exhibit 
the  orifice  of  communication,  6,  with  the  anterior  ethmoidal  sinuses ;  7,  communication  with  the 
frontal  sinus;  8,  left  frontal  sinus;  9,  portion  of  the  unsymmetrical  partition  which  separates  the 
frontal  sinuses ;  10,  inferior  turbinal ;  11,  inferior  meatus ;  12,  nasal  duct  exposed  by  removing  a 
portion  of  the  bones;  13,  its  termination;  14,  edge  of  the  upper  lateral  cartilage;  15,  16,  outer 
portion  of  the  left  lower  lateral  cartilage ;  17,  cut  edge  of  the  septal  cartilage ;  18,  inner  portion 
of  the  left  lower  lateral  cartilage ;  19,  sphenoidal  sinus ;  20,  its  orifice ;  21,  pharynx;  22,  orifice  of 
the  eustachian  tube. 

The  nasal  cavities2  are  two  capacious  air-chambers  occupying 
the  middle  part  of  the  skull  between  the  orbits,  communicating  with 


1  Nasus ;  organon  olfactorium. 


Cavi  or  caverna  narium  ;  fossae  nasales. 

847 


848  OEGANS   OF   SPECIAL   SENSE. 

the  exterior  in  front  through  the  nostrils  or  anterior  nares,  and  behind 
with  the  pharynx  through  the  posterior  nares.  They  are  completely 
separated  by  the  nasal  partition,  which  forms  the  inner  wall  of  each 
cavity.  Their  outer  wall  presents  the  three  prominent  turbinals,  sepa- 
rated from  one  another  and  the  floor  by  the  three  meatuses.  Their 
roof  separates  them  from  the  cranial  cavity  and  their  floor  from  that 
of  the  mouth.  With  each  nasal  cavity  communicate  the  corresponding 
frontal,  ethmoidal,  sphenoidal,  and  maxillary  sinuses,  and  into  the  infe- 
rior meatus  of  each  opens  the  nasal  duct  from  the  lachrymal  sac.  The 

FIG.  421. 


PARTITION  OF  THE  NOSE.  1,  cartilage  of  the  partition ;  2,  its  junction  with  the  nasal  plate  of 
the  ethmoid  bone ;  3,  its  junction  with  the  nasal  bones :  4,  margin  of  continuation  with  the  lateral 
triangular  cartilage ;  5,  fibrous  membrane  connecting  the  cartilage  of  the  partition  with  the  oval 
cartilage  ;  6,  inner  portion  of  the  left  oval  cartilage ;  7,  anterior  border  of  the  vomer ;  8,  acces- 
sory cartilage;  9,  prolongation  of  the  cartilage  of  the  partition,.in  a  groove  between  the  vomer 
and  nasal  plate  of  the  ethmoid  bone ;  10,  naso-palatine  canal  of  the  right  side  opening  into  the 
anterior  palatine  foramen,  11. 

construction  of  the  nasal  cavities  as  formed  by  the  surrounding  bones 
is  described  in  the  account  of  the  skull.  (See  page  146.) 

The  nasal  cavities  are  completed  in  front  by  the  nasal  cartilages, 
and  they  are  lined  throughout  by  mucous  membrane. 

The  olfactory  region,1  or  that  which  is  especially  the  seat  of  the 
sense  of  smell,  accords  with  the  nasal  surface  of  the  ethmoid  jDone, 
comprising  the  nasal  plate  of  the  inner  wall  and  the  opposed  surface 
of  the  turbinals  of  the  outer  wall.  From  the  conformation  of  the  nasal 

1  Kegio  olfactoria. 


ORGANS   OF  SPECIAL   SENSE. 


849 


cavities  the  currents  of  air  ascending  through  the  nostrils  pass  in 
a  curve  upwaro,  backward,  and  downward,  traversing  the  olfactory 
regions  into  the  pharynx. 

The  nose 1  is  formed  by  its  bony  bridge  and  the  nasal  cartilages 
covered  by  the  skin  and  nasal  muscles.  The  sides  conjoin  in  the 
median  ridge  or  back,2  which  slopes  from  beneath  the  forehead  to 
the  point.  Below  they  bulge  outward  in  the  wings  of  the  nose.3 
Beneath  are  the  nostrils,  or  anterior  nares,4  communicating  above 
with  the  nasal  fossa3  and  separated  by  the  column  of  the  nose,5 
which  is  formed  by  the  lower  part  of  the  nasal  partition  enclosed  by 
the  skin. 

The  nostrils  are  horizontal,  fore  and  aft  elliptical  apertures,  situ- 
ated below  the  level  of  the  entrance  of  the  nasal  aperture  of  the  skull. 
The  column  is  fixed  behind  to  the  nasal  spine. 

Within  the  border  of  the  nostrils  the  skin  is  continuous  with  the 
nasal  mucous  membrane 

and  is  here  furnished  with  FIG.  422. 

a   number  of  short   stiff 
hairs. 

The  nasal  cartilages 
complete  the  fore  part  of 
the  partition  and  serve 
to  support  the  lower  fore 
part  of  the  nose.  They 
consist  of  the  septal  and 
lateral  triangular  and  oval 
cartilages. 

The  septal  cartilage 6 
is  a  quadrilateral  plate 
placed  at  the  fore  part  of 
the  nasal  partition,  which 
it  completes  in  front.  Its 
posterior  borders  are  re- 
ceived in  the  angular 
notch  between  the  nasal 
ethmoid  plate  and  the  vo- 
mer.  Its  upper  anterior 
border  is  fixed  to  the 
conjunction  of  the  nasal 
bones;  below  them  it  is 
continuous  laterally  with 
the  triangular  cartilages. 


CARTILAGES  OF  THE  NOSE.  1,  upper  lateral  cartilage ;  2,  its 
anterior  border :  3,  anterior  margin  of  the  septal  cartilage 
appearing  between  the  lateral  cartilages ;  4,  small  acces- 
sory cartilage ;  5,  lower  lateral  cartilage,  back  of  which  is 
the  wing  of  the  nose ;  6.  accessory  cartilages ;  7,  point  of  the 
nose  where  the  lower  lateral  cartilages  are  bent  inwardly 
along  the  column. 

Its   lower  anterior  and   shortest   border 


1  Nasus  ;  rhin  ;  promontorium  faciei ;  snout. 
3  Alas  nasi ;  pinnae. 
5  Columna  nasi. 

54 


2  Dorsum. 

4  Aperturae  nasi  externse. 

6  Septum  cartilagineum. 


850  ORGANS   OF   SPECIAL   SENSE. 

contributes  to  form  the  column  of  the  nose,  extending  from  the  nasal 
spine  to  the  point  of  the  nose. 

In  early  life  a  prolongation  of  the  septal  cartilage  occupies  a  narrow 
channel  along  the  sutural  conjunction  of  the  ethmoid  nasal  plate  and 
vomer  to  the  sphenoidal  rostrum. 

The  septal  cartilage  is  the  thickest  of  those  of  the  nose  and  is  thin- 
nest at  the  middle.  It  often  exhibits  a  want  of  symmetry  and  with  the 
bones  of  the  nasal  partition  may  be  more  or  less  bent  to  one  or  the 
other  side. 

The  upper  lateral,  or  triangular  cartilage,1  is  a  thin  plate  con- 
tinuous with  the  anterior  border  of  the  septal  cartilage,  reflected  from 
it  outwardly  on  each  side  and  attached  by  connective  tissue  with  the 
lower  margin  of  the  nasal  bone  and  the  nasal  notch  of  the  maxilla. 
Its  lower  border  is  connected  by  fibrous  membrane  with  the  corre- 
sponding oval  cartilage. 

The  lower  lateral,  or  oval  cartilage,2  situated  on  each  side  of 
the  nose  below  the  former,  borders  the  nostril.  It  consists  of  an  outer 
oval  plate,  nearly  flat  or  slightly  convex  externally,  and  an  inner  band. 
The  oval  plate  occupies  the  side  of  the  point  of  the  nose  attached  above 
to  the  triangular  cartilage,  while  the  band  bends  inward  from  its  fore 
part  and  extends  along  the  nasal  column  attached  to  the  septal  carti- 
lage. The  oval  cartilages  are  connected  together  at  the  tip  of  the  nose 
by  loose  fibrous  tissue,  the  line  of  union  being  usually  indicated  by  a 
slight  groove  of  the  skin.  In  the  negro  the  oval  cartilages  make  a  less 
abrupt  bend,  so  that  the  nose  is  more  obtusely  rounded  and  devoid  of 
the  groove. 

From  the  posterior  extremity  of  the  oval  cartilage  a  band  of  fibrous 
tissue  extends  over  the  wing  of  the  nose  to  be  attached  to  the  nasal 
notch  of  the  maxilla.  The  band  commonly  contains  from  one  to  three 
little  accessory  cartilages.3 

The  wing  of  the  nose  *  borders  the  nostril  outwardly  behind  the 
point  and  below  the  position  of  the  oval  cartilage.  It  is  a  fold  of  the 
skin  enclosing  a  thick  layer  of  fibro-connective  with  adipose  tissue  and 
muscular  bundles  which  are  part  of  the  contiguous  nasal  muscles. 

The  skin  of  the  nose,  except  on  the  wings,  is,  together  with  the 
subjacent  nasal  muscles,  loosely  and  movably  attached  to  the  parts  be- 
neath. It  is  remarkable  for  the  number  and  size  of  its  sebaceous  glands. 

The  muscles  of  the  nose.     See  page  250. 

The  nasal  cavities,  completely  separated  from  each  other  by  the 
nasal  partition  and  communicating  behind  with,  the  pharynx,  are 
throughout  lined  by  mucous  membrane  continuous  with  that  of  the 
latter  cavity. 

1  Cartilage  triangularis  or  lateralis  superior. 

2  Cartilago  ovalis;  c.  lateralis  inferior;  c.  alse  nasi ;  c.  pinnalis. 

3  Cartilagines  sesamoidese ;  c.  accessorii.  4  Ala  nasi. 


ORGANS   OF   SPECIAL   SENSE.  851 

The  nasal  mucous  membrane,1  highly  vascular,  bright  red  and 
sensitive,  is  closely  connected  with  the  subjacent  periosteum  and  peri- 
chondrium.  It  varies  in  thickness  in  different  positions  and  contributes 
to  diminish  the  passages  of  the  nose.  It  is  thickest  on  the  turbinals, 
especially  the  inferior  one,  and  is  prolonged  on  their  free  border  so  as 
to  make  them  appear  considerably  larger  than  the  corresponding  tur- 
binals in  the  macerated  skull.  It  is  also  thick  on  the  nasal  partition 
and  is  thinner  along  the  floor  and  meatuses.  It  lines  the  sinuses  com- 
municating with  the  nose,  and  in  them  is  thinnest  and  least  vascular. 
It  reduces  the  orifices  of  communication  to  round  apertures.  Of  these 
there  is  usually  one  which  is  common  to  the  frontal  and  anterior  eth- 
moidal  sinuses  of  each  side  opening  into  the  fore  part  of  the  middle 
meatus.  Another  aperture  behind  the  former  opens  from  the  maxil- 
lary antrum  into  the  latter.  A  third  opens  from  the  posterior  ethmoidal 
sinuses  into  the  superior  meatus,  and  a  fourth  from  the  corresponding 
sphenoidal  sinus  opens  into  the  upper  back  part  of  the  nasal  cavity. 

The  nasal  mucous  membrane  closes  the  foramina  of  the  ethmoidal 
cribriform  plate,  likewise  the  spheno-palatine,  pterygo-palatine,  ptery- 
goid,  and  naso-palatine  foramina. 

Opening  into  the  fore  part  of  the  inferior  nasal  meatus  is  the  nasal 
duct  from  the  lachrymal  sac,  the  orifice  guarded  by  one  or  two  slight 
folds  of  the  mucous  membrane. 

The  nasal  mucous  membrane,  except  in  the  olfactory  region  and 
on  the  nasal  cartilages,  is  provided  with  a  ciliated  columnar  epithelium. 
On  the  cartilages  the  epithelium  is  squamous  and  stratified  and  is 
continuous  with  the  epidermis  of  the  skin  at  the  nostrils. 

In  the  olfactory  region 2  the  mucous  membrane  is  thick,  soft,  pulpy, 
and  most  vascular.  It  exhibits  a  yellowish-red  hue  and  is  furnished 
with  a  non-ciliated  columnar  epithelium,  with  peculiar  elements,  the 
olfactory  cells.  The  columnar  cells  are  prolonged  beneath  into 
branching  processes  which  contribute  to  sustain  several  strata  of  the 
olfactory  cells.  These  are  upright,  spindle-shaped,  and  have  an  oval 
nucleus  enveloped  in  a  small  mass  of  granular  protoplasm.  The  upper 
extremity  of  the  cells  extends  as  a  rod-like  prolongation  between  the 
sustaining  cells  to  the  free  surface  of  the  mucous  membrane. 

In  birds,  reptiles,  and  amphibians  the  rod-like  prolongation  of  the 
olfactory  cells  is  furnished  with  long  hair-like  processes,  but  in  man  and 
his  class  they  are  absent. 

From  the  lower  end  of  the  olfactory  cells  descends  a  filament, 
which  sometimes  presents  a  varicose  appearance.  It  is  supposed  to 
be  connected  with  a  terminal  fibril  of  the  olfactory  nerves,  but  the 
continuity  has  not  been  satisfactorily  determined. 

1  Schneiderian    membrane ;    pituitary   membrane ;    membrana    pituitaria ;    m. 
Schneideriana. 

2  Kegio  olfactoria. 


852 


ORGANS   OF   SPECIAL   SENSE. 


Mingled  Avith  the  columnar  and  olfactory  cells  are  transitional 
forms  between  the  two.  All  are  regarded  as  being  probably  connected 
with  olfactory  nerve-fibrils. 

The  nasal  mucous  membrane  is  abundantly  supplied  with  glands, 
which  are  most  numerous  about  the  middle  and  back  parts  of  the 

nasal  cavities,  and  are  largest  on 
the  back  of  the  partition.  In  the 
olfactory  region  the  glands  are 
mostly  tubular  and  simple,  and 
somewhat  enlarged  and  convoluted 
in  their  deeper  part.1  Elsewhere 
the  nasal  glands  are  racemose.2 

The  olfactory  nerves,  from 
the  corresponding  olfactory  lobe, 
pass  through  the  numerous  fora- 
mina of  the  ethmoidal  cribriform 
plate  in  an  inner  and  an  outer 
series,  and  these  descend  in  canals, 
partly  bony  and  partly  membra- 
nous, in  the  inner  and  outer  walls 
of  the  nasal  cavity.  Diverging 
fore  and  aft  they  enter  the  mu- 
cous membrane  of  the  olfactory 
region,  the  outer  series  being  the 
larger.  In  their  distribution  they 
branch  into  flattened  tufts,  which 
anastomose  in  close  plexuses  with 
narrow,  elongated  meshes.  The 
fibres  of  the  olfactory  nerves  are 
non-medullated  and  consist  of  axis-fibres  with  a  nucleated  neurilemma, 
in  which  the  nuclei  are  fewer  than  in  the  similar  fibres  of  the  sympa- 
thetic system. 

The  nasal  mucous  membrane  is  further  supplied  with  sensory  nerves 
by  the  trifacial,  as  already  described. 

The  arteries  of  the  nasal  cavity  are  the  spheno-palatine  and  descend- 
ing palatine  branches  of  the  internal  maxillary,  the  posterior  and  an- 
terior ethmoidal  branches  of  the  ophthalmic,  and  branches  from  the 
superior  labial  of  the  facial  artery. 

The  veins  of  the  nasal  cavity  form  a  close  plexus  in  the  mucous 
membrane,  best  produced  on  the  inferior  turbinal  and  lower  back  part 
of  the  partition.  The  trunks  return  in  the  course  of  the  arteries,  the 
spheno-palatine  vein  entering  the  pterygoid  plexus,  the  ethmoidal  veins 
ending  in  the  ophthalmic  vein.  Other  and  smaller  veins  join  the  supe- 
rior labial  and  facial  veins. 


VERTICAL  SECTIONS  FROM  THE  NASAL  MUCOUS 
MEMBRANE  ;  magnified  150  diameters.  1,  from 
the  olfactory  region ;  a,  non-ciliated  columnar 
epithelium;  6,  olfactory  nerve-fibres;  c,  nasal 
tubular  gland ;  d,  its  outlet.  2,  ciliated  epithe- 
lium in  other  positions  of  the  mucous  mem- 
brane. 


Glands  of  Bowman. 


Glandulae  muciparae  aggregate. 


OEGANS   OF   SPECIAL   SENSE. 


853 


The  lymphatics  of  the  nose  are  numerous  and  large.     They  form 
a  close  plexus  of  vessels  in  the  mucous  membrane,  communicating  with 


FIG.  424. 


NERVES  OF  THE  PARTITION  OF  THE  NOSE.  I,  olfactory  bulb ;  1,  its  nerves  descending  to  the 
nasal  mucous  membrane ;  2,  internal  nasal  branch  of  the  nasal  nerve  of  the  ophthalmic ;  3, 
nasal  branches  from  the  spheno-palatine  ganglion.  II,  optic  nerve;  III,  oculo-motor ;  IV,  troch- 
lear;  V,  trifacial;  VI,  abducent;  VII,  facial;  VIII,  auditory ;  IX,  glosso-pharyngeal ;  X,  vagus; 
XI,  accessory;  XII,  hypoglossal.  4,  cavernous  plexus  of  the  sympathetic;  5,  filaments  of  com- 
munication with  the  semilunar  ganglion  of  the  trifacial ;  6,  filaments  of  communication  with  the 
oculo-motor  nerve ;  7,  branches  of  the  sympathetic  following  the  internal  carotid  artery ;  8, 
branch  connected  with  the  superior  cervical  ganglion ;  9, 10,  filaments  forming  a  plexus  upon 
the  internal  carotid  artery ;  11,  petrous  ganglion  of  the  glosso-pharyngeal ;  12,  jugular  ganglion 
of  the  vagus  nerve;  13, 14, 15,  anastomotic  filaments  between  the  sympathetic,  the  glosso-pharyn- 
geal, vagus,  accessory,  and  hypoglossal  nerves. 

lymphatic  spaces  around  the  olfactory  nerves  and  among  the  nasal 
glands. 

FIG.  425. 


3   9 


NEEVES  OF  THE  OUTER  WALL  OF  THE  LEFT  NASAL  CAVITY.  1,  olfactory  nerves ;  2,  nasal  branch 
of  the  ophthalmic  nerve ;  3,  spheno-palatine  ganglion  ;  4,  5,  6,  palatine  nerves ;  7,  branch  to  the 
nose;  8,  nasal  nerve  to  the  outer  wall  of  the  nose;  9,  nasal  nerve  to  the  inner  wall;  10,  vidian 
nerve;  11,  facial  nerve;  12,  deep  petrosal  nerve  joining  the  carotid  plexus;  13,  the  other  branch 
of  the  vidian  is  the  superficial  petrosal  nerve,  which  joins  the  facial. 


854  OKGANS   OF   SPECIAL   SENSE. 


THE  EYES  AND  THEIE  APPENDAGES. 

The  eye,  or  eyeball,  is  the  special  organ  of  sight,  but  as  all  the 
parts  within  the  orbit  and  surrounding  its  entrance  are  concerned  in 
its  functions,  they  are  included  in  the  description  as  the  appendages 
of  the  eye.  The  contents  of  the  orbit  form  a  pyramidal  mass,  from 
the  front  of  which  the  eyeball  projects  and  is  covered  by  the  eyelids 
protected  above  by  the  eyebrow.  The  mass  surrounding  the  eyeball 
consists  of  its  muscles,  the  lachrymal  gland,  and  their  vessels  and 
nerves,  with  the  intervals  filled  with  areolar  tissue  and  fat. 

THE   EYEBKOW   AND   EYELIDS. 

The  eyebrow1  is  the  arch  of  skin  and  hairs,  supported  on  the 
superciliary  ridge  and  supraorbital  margin  of  the  frontal  bone,  to 
which  it  is  loosely  and  movably  attached.  The  hairs  project  from 
within  upward  and  outward  and  in  general  are  directed  in  the  course 
of  the  brow.  The  skin  is  thick  and  dense,  resembling  that  of  the 
scalp,  and  is  closely  adherent  to  the  subjacent  muscles,  which  produce 
the  movements  «f  the  brow  and  consist  of  the  frontal,  palpebral, 
orbicular,  and  superciliary  muscles.  Besides  the  hair-follicles  embedded 
in  the  subcutaneous  connective  tissue  and  fat,  it  contains  numerous 
sebaceous  and  sweat  glands. 

The  eyelids2  are  horizontal,  movable  covers  across  the  front  of 
the  eyeball,  fringed  at  their  borders  by  the  cilia,  or  eyelashes.  They 
are  separated  by  the  palpebral  fissure,3  the  extremities  of  which  are 
angles  of  the  eye.4  When  the  lids  are  open  the  fissure  becomes 
more  or  less  widely  elliptical,  with  the  outer  angle  acute  and  the  inner 
angle  prolonged  into  the  lachrymal  lake.5  The  free  borders  of  the 
lids  are  for  the  most  part  flat,  with  the  back  edge  angular  and  the 
front  edge  rounded  and  fringed  by  the  cilia  ;  but  in  the  lake  the  borders 
are  less  pronounced,  rounded,  and  devoid  of  cilia.  At  the  entrance  of 
the  lake  each  lid  forms  a  slight  eminence,  the  lachrymal  papilla,  on 
the  summit  of  which  is  a  minute  orifice,  the  lachrymal  punctum. 
This  is  the  commencement  of  the  lachrymal  canal,  by  which  the  tears 
are  conveyed  to  the  lachrymal  sac.  The  lake  is  occupied  by  a  convex 
red  body,  the  lachrymal  caruncle. 

The  eyelids  are  opened  chiefly  by  the  raising  of  the  upper  one 
through  the  action  of  the  palpebral  elevator  muscle.  The  upper  lid  is 
much  larger,  more  prominently  convex,  and  when  open  overhangs  the 
lower  one.  Its  free  border  is  directed  downward  and  backward,  while 
that  of  the  lower  lid  is  directed  upward  and  forward. 

The  upper  eyelid  is  continuous  with  the  eyebrow,  from  which  it  is 

1  Supercilium.  2  Palpebrse.  3  Fissura  palpebrarum. 

4  Canthus  oculi  interims  et  externus  ;  corners.  5  Lacus  lachrymalis. 


ORGANS   OF   SPECIAL   SENSE.  855 

defined  by  a  deep  arching  furrow,1  which  corresponds  with  the  reflec- 
tion of  the  conjunctiva  from  the  eyelid  to  the  eyeball.  Above,  the 
furrow  is  bounded  by  a  fold,  prominent  and  convex  outwardly  and 
overhanging  the  eyelid.  In  the  advance  of  age  the  fold  commonly 
becomes  more  prominent,  due  to  the  accumulation  of  fat  in  the  are- 
olar  tissue  between  the  palpebral  elevator  tendon  and  the  palpebral 
ligament.  The  lower  lid  is  continuous  with  the  cheek,  from  which 
it  is  defined  by  a  slight  depression2  of  the  surface  in  front  of  the 
orbit.  Laterally  the  lids  unite  in  the  palpebral  commissures,3 
of  which  the  inner  forms  a  concave  hollow  at  the  side  of  the  nose, 
while  the  outer  is  slightly  depressed. 

Structure  of  the  eyelids.  The  eyelids  are  composed  of  four 
successive  layers,  the  skin,  the  palpebral  orbicular  muscle,  the  palpe- 
bral scutes  with  their  ligaments,  and  the  conjunctiva. 

The  skin  of  the  eyelids  has  the  same  structure  as  elsewhere,  but  is 
very  thin  and  is  darker  than  in  most  other  positions.  It  is  furnished 
with  papillae,  fine  hairs  and  proportionately  small  sebaceous  and  sweat 
glands.  It  adheres  closely  to  the  subjacent  muscle  by  thin  connective 
tissue  destitute  of  fat.  In  the  inner  commissure  it  exhibits  a  con- 
spicuous whitish  spot,  due  to  the  internal  palpebral  ligament  shining 
through.  The  skin  is  thrown  into  wrinkles  by  the  action  of  the  sub- 
jacent muscle. 

The  cilia,  or  eyelashes,4  are  short,  stiff  hairs  arranged  in  rows 
along  the  front  rounded  edge  of  the  margins  of  the  eyelids.  The 
upper  cilia  are  more  numerous  and  longer  than  the  lower  and  curve 
upward,  while  those  below  curve  in  the  opposite  direction.  The  roots 
of  the  cilia  with  their  follicles  are  inserted  into  the  subcutaneous 
connective  tissue  among  the  muscular  bundles  at  the  border  of  the 
palpebral  orbicular  muscle.  They  are  accompanied  by  numerous  seba- 
ceous glands,  together  with  others  resembling  in  structure  the  sweat- 
glands. 

The  second  layer  of  the  eyelids  is  formed  by  the  concentric  fibres 
of  the  palpebral  orbicular  muscle  closely  attached  to  the  skin  externally 
and  more  loosely  to  the  subjacent  layer. 

The  palpebral  scutes 5  of  the  third  layer  serve  to  give  shape  and 
firmness  to  the  lids,  and  are  dense  plates  of  felted  connective-tissue 
bundles.  The  upper  scute  is  the  larger  and  thicker,  is  half  oval,  and 
at  its  middle  more  than  twice  the  height  of  the  lower  one,  which  is 
a  narrow  band  of  nearly  uniform  depth.  Their  free  border  is  straight 
and  thickest ;  their  attached  border  is  connected  with  a  thin  fibrous 
membrane  extending  from  the  periosteum  of  the  orbital  margin.  The 
upper  and  lower  portions  of  the  membrane  are  distinguished  as  the 

1  Superior  orbito-palpebral  furrow.  2  Inferior  orbito-palpebral  furrow. 

3  Commissura  palpebrarum.  *  Gils  ;  blepharides. 

5  Palpebral  cartilages  or  plates  ;  tarsi ;  tarsal  cartilages. 


856  ORGANS   OF   SPECIAL   SENSE. 

superior  and  inferior  palpebral  ligaments,1  and  their  slightly 
thicker  conjunction  outwardly  is  the  external  palpebral  ligament,2 
which  connects  the  scutes  with  the  adjacent  border  of  the  malar  bone. 
The  internal  palpebral  ligament 3  is  a  well-marked,  strong,  fibrous 
band,  which  connects  the  inner  ends  of  the  scutes  with  the  nasal  process 
of  the  maxilla  in  front  of  the  lachrymal  fossa.  The  superior  palpebral 
ligament  is  joined  behind  by  the  expanded  tendon  of  the  palpebral 
elevator  muscle  as  it  descends  to  be  inserted  into  the  border  of  the 
upper  palpebral  scute.  The  superior  and  inferior  palpebral  ligaments 

FIG.  426. 


THE  LEFT  EYELID  AND  LACHRYMAL  GLAND,  TURNED  FORWARD  AND  INWARD  SO  AS  TO  SHOW  THEIR 

INNER  SURFACE.  1,  upper  and  lower  part  of  the  orbit;  2,  portion  of  the  palpebral  orbicular  mus- 
cle ;  3,  attachment  of  this  muscle  to  the  inner  margin  of  the  orbit ;  4,  perforation  for  the  passage 
of  the  nasal  branch  of  the  ophthalmic  artery  ;  5,  palpebral  tensor  muscle  ;  6,  palpebral  glands ; 
7,  orbital  and  8,  palpebral  portions  of  the  lachrymal  gland  ;  9,  10,  ducts;  11,  orifices  opening  on 
the  inner  surface  of  the  upper  eyelid ;  12, 13,  lachrymal  puncta  on  the  lachrymal  papillae. 

are  associated  with  some  unstriped  muscle-fibres,  most  numerous  in  the 
upper  lid.4 

Embedded  in  the  back  part  of  the  scutes  are  the  palpebral  glands,5 
distinctly  seen  through  the  lining  conjunctiva.  They  appear  as  yel- 
low, granular-looking  bodies,  arranged  vertically  in  a  row,  extending 
nearly  the  depth  of  the  scutes.  There  are  thirty  or  more  in  the  upper 
lid  and  about  twenty  in  the  lower  one,  and  their  ducts  open  in  a  regu- 
lar series  along  the  posterior  edge  of  the  margin  of  the  lids.  In 
structure  they  resemble  the  sebaceous  glands,  and  each  is  composed  of 
a  central  straight  duct  extending  the  length  of  the  gland,  surrounded 

1  Superior  and  inferior  tarsal  ligaments. 

2  External  tarsal  ligament ;  ligamentum  angulare  externum. 

3  Internal  tarsal  ligament ;  1.  angulare  internum ;   tendo  palpebrarum. 
*  Musculus  orbito-palpebralis. 

5  Glandulse  palpebrarum  or  Meibomianae  ;   Meibomian  glands  ;   folliculi  ciliares. 


ORGANS   OF   SPECIAL   SENSE.  857 

by  numerous  alveoli,1  which  are  variably  long,  simple,  or  branched  and 
flask-shaped.  The  glands  secrete  an  oleaginous  liquid,2  which  lubri- 
cates the  edges  of  the  lids  and  serves  to  prevent  the  overflow  of  the 
tears.  It  is  often  observed,  especially  after  sleep,  accumulated  as  a 
yellowish-white  matter  in  the  lachrymal  lake.  In  the  dried  condition 
it  is  also  sometimes  seen  adherent  to  the  eyelashes  as  a  yellow  solid. 

CONJUNCTIVA. 

The  conjunctiva3  is  a  delicate  transparent  mucous  membrane, 
which  lines  the  eyelids  and  is  thence  reflected  over  the  front  of  the 
eyeball.  Between  the  lids  as  defined  by  the  scutes,  and  the  cornea,  it 
forms,  above  and  below,  a  freely  movable  fold,  the  fornix,  which  is  of 
much  greater  depth  in  the  upper  than  in  the  lower  lid.  In  its  different 
positions  the  conjunctiva  is  distinguished  as  the  palpebral,  sclerotic, 
and  corneal  portions,  each  presenting  important  differences. 

The  palpebral  portion  of  the  conjunctiva 4  is  thicker,  more  vascu- 
lar and  sensitive  than  elsewhere,  and  is  closely  and  tightly  adherent  to 
the  posterior  surface  of  the  palpebral  scutes.  It  is  bright  red  in  color, 
due  to  its  numerous  vessels,  and  exhibits  the  palpebral  glands  beneath. 
At  the  edge  of  the  lids  it  is  continuous  with  the  skin,  and  at  the  lachry- 
mal puncta  with  the  lining  membrane  of  the  lachrymal  canals.  Though 
for  the  most  part  smooth,  near  the  fornix  under  a  lens  it  exhibits  minute 
transverse  folds. 

The  sclerotic  portion  of  the  conjunctiva5  forms  the  fornix,  and 
is  loosely  attached  to  the  subjacent  parts  by  areolar  tissue.  In  the 
upper  lid,  from  the  corresponding  scute,  it  extends  on  the  palpebral 
elevator  tendon,  thence  descends  on  the  sclerotica  to  the  cornea.  In 
the  lower  lid  it  is  reflected  from  the  scute  on  the  inferior  palpebral 
ligament  and  sclerotica  to  the  cornea.  Thin  and  transparent,  the 
sclerotica  is  seen  through  it,  and  is  commonly  named  with  the  latter 
the  "white  of  the  eye."  At  the  entrance  of  the  lachrymal  lake, 
adjoining  the  caruncle,  it  exhibits  a  red,  variable  fold,  the  semi- 
lunar  plica,6  which  is  a  rudiment  of  the  nictitating  membrane  or 
thii-d  eyelid  of  many  of  the  lower  vertebrates.  Frequently  the  scle- 
rotic portion  of  the  conjunctiva  exhibits  vessels  proceeding  from  the 
angles  of  the  eye  and  radiating  towards  the  cornea.  In  the  advance 
of  age  it  sometimes  shows  here  and  there  little  yellowish  eminences, 
which  are  due  to  accumulations  of  fat  in  the  subjacent  connective 
tissue.  About  the  commencement  of  the  fornix,  embedded  in  the 
scutes  there  is  a  narrow  zone  of  little  racemose  glands,  the  ducts  of 
which  open  on  the  surface  of  the  conjunctiva  near  the  line  of  reflection 
of  the  membrane. 

1  Acini.  2  Sebum  palpebrale  ;  leraa. 

3  Membrana  conjunctiva.  4  C.  palpebrarum. 

3  C.  scleroticae,  bulbi,  or  adnata  oculi. 
6  P.  semilunaris  ;  palpebra  tertia. 


858 


ORGANS   OF   SPECIAL,   SENSE. 


FIG.  427. 


The  corneal  portion  of  the  conjunctiva,1  thinner  than  the  rest  and 
devoid  of  blood-vessels,  merges  in  the  cornea,  with  which  it  is  closely 
united  and  forms  its  anterior  layer. 

The  epithelium  of  the  conjunctiva  varies  in  different  portions,  and 
for  the  most  part  is  thin  and  stratified.  It  is  thickest  on  the  margin 
of  the  lids  and  on  the  sclerotic  portion,  where  it  consists  of  superfi- 
cial strata  of  pavement  cells  succeeded  by  others  gradually  becoming 
thicker  and  finally  resting  on  a  single  stratum  of  columnar  cells. 
Thinnest  on  the  palpebral  conjunctiva,  it  here  consists  of  several 
strata  of  flattened  polygonal  cells  resting  on  short  columnar  cells. 
On  the  folded  portion  of  the  membrane  extending  to  the  fornix  it 
consists  of  a  few  strata  of  polygonal  cells  with  a  single  superficial 
stratum  of  short  thick  columnar  cells.  On  the  cornea  it  consists  of 
several  superficial  strata  of  flattened  cells,  succeeded  by  others  more 
uniformly  polyhedral,  resting  on  a  stratum  of  columnar  cells. 

The  lachrymal  caruncle,2  the 
reddish  eminence  occupying  the 
lachrymal  lake,  is  a  process  of 
the  conjunctiva  enclosing  a  group 
of  sebaceous  glands  and  furnished 
with  a  few  minute  scattered  hairs. 
A  few  conspicuous  vessels  are 
commonly  to  be  observed  in  the 
sclerotic  portion  of  the  conjunctiva, 
proceeding  from  the  angles  of  the 
eye  and  radiating  towards  the  cor- 
nea ;  but  in  inflammation  many 
more  become  visible.  At  the  bor- 
der of  the  cornea  the  vessels  form 
a  plexus  of  capillary  loops.  The 
conjunctival  arteries  are  derived 
from  the  palpebral  and  lachrymal 
branches  of  the  ophthalmic  artery. 
The  vessels  of  the  sclerotica  when 
congested  also  become  visible 
through  the  conjunctiva.  They 
are  finer  and  less  tortuous  than 
the  vessels  of  the  conjunctiva,  and 
are  derived  from  the  anterior  cili- 
ary branches  of  the  ophthalmic 
artery.  On  pressure  of  the  eye- 
lids the  sclerotic  vessels  remain  stationary,  while  those  of  the  conjunc- 
tiva move  with  the  shifting  of  the  membrane. 

The  conjunctiva  contains  some  lymphoid  tissue,  and  it  is  provided 


NERVE  END-BULBS,  FROM  THE  CONJUNCTIVA. 
1,  from  a  calf;  2,  from  man.  a,  end-bulb ;  6, 
axis-fibre  of  the  medullated  nerve-fibre  c ;  *, 
division  of  a  nerve-fibre  at  a  node.  Highly 
magnified. 


1  C.  corneas. 


2  Caruncula  lachrymalis. 


ORGANS  OF   SPECIAL  SENSE. 


859 


FIG.  428. 


18234 


with  an  abundant  plexus  of  lymphatics,  which  are  much  reduced  in 
size  at  the  margin  of  the  cornea,  where  they  communicate  with  its 
branching  cell-spaces.  Many  of  the  nerves  of  the  conjunctiva  derived 
from  the  branches  of  the  ophthalmic  nerve  terminate  in  end-bulbs. 
These  are  minute  spherical  bodies  connected  with  one  or  two  terminal 
nerve-fibres.  The  end-bulb  consists  of  a  connective-tissue  capsule  en- 
closing a  little  mass  of  polyhedral  cells  in  which  the  axis-fibres  of  the 
nerves  terminate.  The  nerve-fibres  approaching  the  bulb  are  often 
twisted  on  each  other  before  the  axis-fibres  enter  it. 

The  muscles  of  the  eyebrow  and  eyelids.     See  page  248. 

THE   LACHRYMAL  APPARATUS. 

The  lachrymal  apparatus  concerned  in  the  production  and  con- 
veyance of  the  tears  consists  chiefly  of  the  lachrymal  gland,  canals,  and 
sac,  and  the  nasal  duct. 

The  lachrymal  gland,1  which  secretes  the  tears,  consists  of  an 
orbital  and  a  palpebral  portion,  the  former  occupying  the  recess  of  the 
orbit  within  the  position  of  the  external  angular  process  of  the  frontal 
bone,  the  latter  extend- 
ing to  the  border  of  the 
upper  eyelid.  The  orbi- 
tal portion 2  is  flattened 
oval  and  curved,  with 
the  upper  convex  sur- 
face attached  to  the  ad- 
jacent periosteum  by 
connective  tissue ;  the 
lower  surface,  next  the 
eyeball,  resting  on  the 
palpebral  elevator,  supe- 
rior and  external  rec- 
tus  muscles.  The  palpe- 
bral portion 3  is  smaller, 
thinner,  and  irregularly 
quadrate,  and  is  in 
contact  beneath  with 
the  conjunctival  fornix. 
The  orbital  portion  of 

the  gland  is  about  three-fourths  of  an  inch  fore  and  aft,  five  lines 
wide,  and  two  lines  thick  ;  the  palpebral  portion  four  lines  long,  nearly 
as  wide,  and  a  line  thick.  The  lachrymal  gland  is  a  compound,  lobu- 
lated,  racemose  gland,  of  a  pale  red  color,  and  resembles  in  structure 
the  salivary  glands.  Its  ducts,  a  dozen  or  fifteen,  proceed  forward 


7    18234 

THE  LEFT  EYE,  WITH  A  PORTION  OF  THE  EYELIDS  REMOVED. 
TO  EXHIBIT  THE    LACHRYMAL  CANALS   AND  SAC.     1,  lachrymal 

canals ;  2,  commencement  of  these  on  the  lachrymal  papillae  ; 
3,  palpebral  scutes ;  4,  edges  of  the  eyelids ;  5,  lachrymal  sac : 
6,  internal  palpebral  ligament;  7,  its  point  of  division  in 
front  of  the  lachrymal  canals ;  8,  branches  of  the  ligament 
giving  attachment  to  the  fibres  of  the  palpebral  orbicular 
muscle. 


1  Glandula  lachrymalis.  a  G.  1.  superior  or  innominati  Galeni. 

3  G.  1.  inferior  Rosenmulleri  or  congregata  Monroi. 


860  ORGANS   OF  SPECIAL   SENSE. 

and  downward  and  open  in  a  row  along  the  upper  outer  part  of  the 
conjunctival  fornix. 

The  tears  1  bathe  the  conjunctiva  throughout,  and  are  especially 
important  in  maintaining  the  bright  moist  appearance  of  the  cornea. 
The  excess  of  tears  flowing  into  the  lachrymal  lake  is  absorbed  by 
the  lachrymal  puncta,2  the  minute  apertures  at  the  summits  of  the 
lachrymal  papillae.  From  the  puncta  the  lachrymal  canals 3  proceed 
to  the  lachrymal  sac,  into  which  they  open  separately  or  in  union. 
The  lower  canal  descends  a  short  distance,  bends  abruptly  inward  and 
upward  and  proceeds  to  the  sac ;  the  upper  canal,  slightly  longer  and 
narrower,  ascends  and  bends  inward  and  downward  in  its  course  to  the 
sac.  From  their  commencement  the  canals  expand  to  the  bend,  and 
then  become  narrowed  to  their  termination.  They  are  enclosed  by  the 
palpebral  and  tensor  muscles,  offsets  of  which  encircle  the  vertical  por- 
tion of  the  canals  as  sphincters.  They  are  lined  by  mucous  membrane, 
with  a  thick,  stratified,  squamous  epithelium. 

The  lachrymal  sac4  occupies  the  lachrymal  fossa  at  the  inner  fore 
part  of  the  orbit,  and  is  continuous  downward  in  the  corresponding 
osseous  canal  as  the  nasal  duct.  The  lachrymal  sac  is  a  cylindrical 
tube  closed  and  rounded  at  its  upper  extremity,  slightly  narrowing 
below  into  the  nasal  duct.  On  its  outer  side  in  front  it  receives  the 
lachrymal  canals,  behind  the  position  of  the  internal  palpebral  liga- 
ment and  in  front  of  the  palpebral  tensor  muscle.  The  nasal  duct,5 
about  half  an  inch  long,  descends  from  the  lachrymal  sac  and  opens 
into  the  fore  part  of  the  inferior  meatus  of  the  nose.  The  sac  and 
duct  are  composed  of  fibrous  membrane  united  with  the  subjacent 
periosteum  and  lined  by  mucous  membrane,  with  a  columnar  ciliated 
epithelium  like  that  of  the  nose. 

The  lachrymal  sac  and  nasal  duct  together  form  a  continuous  tube, 
descending  from  the  inner  angle  of  the  eye  to  the  nose,  with  a  slight 
inclination  inward  and  backward.  Its  communication  with  the  nose 
is  a  vertically  oval  aperture  guarded  by  a  semilunar  fold  of  the  mucous 
membrane. 

MUSCLES   OF    THE  EYEBALL. 

The  muscles  of  the  eyeball  consist  of  four  recti,  the  trochlear  and 
inferior  oblique  muscles. 

The  four  recti  muscles6  arise  tendinously  at  the  bottom  of  the 
orbit  from  the  sphenoid  bone  around  the  optic  foramen  and  entrance  of 
the  optic  nerve  and  ophthalmic  artery.  Thence  passing  forward  and 

1  Lachrymse.  2  Puncta  lachrymalia. 

3  Canaliculi  lachrymales  ;  cornua  limacum  ;  spiraculi. 
*  Saccus  or  utriculus  lachrymalis  ;  infundibulum. 

5  Ductus    naso-lachrymalis    or    nasalis ;     canalis    lachrymalis    membranaceus ; 
lachrymo-nasal  duct ;  nasal  canal. 

6  M.  recti  oculi ;  straight  muscles  of  the  eye. 


ORGANS   OF  SPECIAL  SENSE. 


861 


diverging  equidistant  from  one  another,  above,  below,  and  at  the  sides 

of  the  eyeball,  they  are  inserted  by  thin  tendons  into  the  fore  part  of 

the   sclerotica,  about   the 

fourth  of  an  inch  behind  FlG-  429' 

the  cornea. 

The  superior  rectus 
arises  above  the  optic  fo- 
ramen immediately  be- 
neath the  origin  of  the 
palpebral  elevator  muscle. 
The  internal  and  infe- 
rior recti  arise  by  a  com- 
mon tendon  to  the  inner 
side  and  below  the  optic 
foramen.  The  external 
rectus  arises  by  two 
heads,  one  in  common  with 
that  of  the  superior  rectus 
and  the  other  partly  with 
that  of  the  inferior  rectus 
and  partly  from  a  process 
at  the  outer  border  of  the 
sphenoidal  foramen. 

The  external  and  in- 
ferior recti  are  longer 
than  the  others,  the  internal  rectus  is  broadest,  and  the  superior  is 
narrowest.  At  their  insertion  the  internal  rectus  approaches  nearest 
the  cornea  and  the  superior  rectus  is  the  farthest  from  it. 

Between  the  two  heads  of  the  external  rectus  the  angular  interval 
gives  passage  to  the  third,  the  nasal  branch  of  the  fifth  and  sixth 
nerves,  and  the  ophthalmic  vein. 

The  trochlear,  or  superior  oblique  muscle,1  is  situated  at  the 
inner  upper  part  of  the  orbit  along  the  roof,  internal  to  the  palpebral 
elevator  muscle.  It  is  a  slender  muscle,  which  arises  tendinously  a 
short  distance  in  advance  and  to  the  inner  side  of  the  optic  foramen. 
Proceeding  forward  it  ends  in  a  cylindrical  tendon,  which  passes 
through  a  fibre-cartilaginous  ring,  the  trochlea,  or  pulley,  occupying 
a  little  fossa  just  within  the  supraorbital  margin  of  the  frontal  bone. 
From  the  trochlea  the  tendon  is  directed  downward,  backward,  and 
outward,  and  passing  beneath  the  superior  rectus  is  inserted  into  the 
sclerotica  a  little  way  to  the  outer  border  of  the  latter  muscle  and 
about  midway  between  the  cornea  and  entrance  of  the  optic  nerve  into 
the  eye.  The  tendon  as  it  passes  through  the  trochlea  is  invested  with 
a  sy  no  vial  sheath. 


MUSCLES  OF  THE  EYE.  1,  the  palpebral  elevator;  2,  the 
trochlear  muscle ;  3,  the  pulley  through  which  the  tendon 
of  insertion  plays ;  4,  superior  rectus  muscle ;  5,  inferior 
rectus  muscle ;  6,  external  rectus  muscle ;  7,  8,  its  two  points 
of  origin  ;  9,  interval  through  which  pass  the  oculo-motor 
and  abducent  nerves;  10,  inferior  oblique  muscle;  11, 
optic  nerve;  12,  cut  surface  of  the  malar  process  of  the 
superior  maxillary  bone ;  13,  the  nasal  notch.  A,  the  eye- 
ball. 


'  M.  trochlearis ;  m.  obliquus  superior. 


862  ORGANS  OF   SPECIAL  SENSE. 

The  inferior  oblique  muscle,1  situated  at  the  bottom  of  the  orbit, 
arises  from  a  slight  depression  of  the  orbital  plate  of  the  maxilla  near 
the  entrance  of  the  nasal  duct  and  the  orbital  margin.  Directed  out- 
ward, backward,  and  upward,  passing  beneath  the  inferior  rectus,  it  is 
inserted  by  a  thin  tendon  into  the  sclerotica  at  the  outer  part  of  the 
eye,  within  the  position  of  the  external  rectus  and  nearer  the  optic 
nerve  than  the  cornea. 

The  external  rectus  is  supplied  by  the  abducent  nerve,  the  other 
recti  and  the  inferior  oblique  muscle  by  the  oculo-motor  nerve,  and  the 
trochlear  muscle  by  the  trochlear  nerve. 

The  recti  muscles  move  the  eye  in  the  four  directions  according  to 
their  position.  Together  they  tend  to  retract  the  eye,  which  action 
in  a  measure  is  antagonized  by  the  trochlear  and  inferior  oblique  mus- 
cles. The  latter  antagonize  each  other  in  any  disposition  of  either  to 
rotate  the  ball  on  its  axis  in  opposite  directions. 

THE   EYEBALL. 

The  eye,  or  eyeball,2  occupies  the  fore  part  of  the  orbit,  partially 
embedded  in  a  mass  formed  by  its  muscles,  vessels,  and  nerves,  together 
with  a  quantity  of  connective  tissue  and  fat,  from  which  its  fore  part 
projects  and  is  covered  by  the  eyelids,  while  its  back  part  receives  the 
optic  nerve.  Both  eyes  have  their  visual  axis  directed  forward  and 
parallel,  while  the  optic  nerves  are  widely  divergent  at  their  entrance 
into  the  orbit,  but  bend  so  as  to  join  the  balls  to  the  inner  side  of  their 
axes. 

The  eyeball  is  nearly  spherical,  but  is  composed  of  parts  of  two 
different-sized  spheres,  of  which  the  posterior  and  larger,  formed  by 
the  sclerotica,  constitutes  five-sixths  of  the  ball,  while  the  smaller 
projects  from  the  front  of  the  former  as  the  transparent  cornea,  com- 
monly called  the  "  sight  of  the  eye." 

The  eyeball  is  about  an  inch  in  diameter,  slightly  varying  in 
different  directions  and  usually  greatest  fore  and  aft. 

The  posterior  part  of  the  ball,  formed  by  the  sclerotica,  is  invested 
with  a  thin,  loose,  and  viscid  fibrous  capsule,  the  vaginal  tunic,3  which 
is  attached  to  the  eye  by  delicate  connective  tissue  and  permits  free 
movement  of  the  ball  on  the  adjacent  parts.  The  tunic  is  perforated 
by  the  tendons  of  insertion  of  the  muscles  of  the  ball  and  is  intimately 
connected  with  the  sclerotica  behind  where  it  is  perforated  by  the 
ciliary  vessels  and  nerves. 

The  attachment  of  the  eyeball  to  the  vaginal  tunic  is  so  slight  that 
in  a  surgical  operation  it  is  readily  removed  with  little  injury  to  the 
adjacent  parts. 

The  eyeball  is  composed  of  three  concentric  coats  enclosing  as  many 

1  M.  obliquus  inferior.  2  Globe  or  apple  of  the  eye. 

3  Capsule  of  Tenon ;  tunica  vaginalis  ;  membrana  albuginea. 


ORGANS   OF   SPECIAL  SENSE.  863 

different  transparent  media.     The  coats  successively  from  without  in- 
ward are,  1,  the  sclerotica  and  cornea ;  2,  the  choroidea  and  iris ;  3,  the 

FIG.  430. 


VERTICAL  SECTION  ANTEEO-POSTEEIOKLY  OF  THE  EYEBALL.  1,  optic  nerve;  2,  sclerotica ;  3,  its 
posterior  thicker  portion ;  4,  sheath  of  the  optic  nerve  continuous  with  the  sclerotica ;  5,  the  nerve 
within  the  sheath  ;  6,  insertion  of  the  recti  muscles  into  the  sclerotica :  7,  8,  superior  and  inferior 
recti  muscles ;  9,  cornea ;  10,  its  conjunctival  surface ;  11,  entocornea ;  12, 13,  bevelled  edge  of  the 
cornea  fitting  into  the  sclerotica ;  14,  circular  sinus  of  the  iris ;  15,  choroidea ;  16,  the  anterior  por- 
tion, constituting  the  ciliary  body;  17,  the  ciliary  muscle ;  18,  the  ciliary  processes;  19,  retina;  20, 
its  origin ;  21,  the  ora ;  22,  central  retinal  artery ;  23,  vitreous  humor ;  24,  25,  26,  hyaloid  tunic ;  27, 
suspensory  ligament  of  the  crystalline  lens,  28 ;  29,  iris ;  30,  pupil ;  31,  posterior  chamber,  and  32, 
anterior  chamber  occupied  by  the  aqueous  humor. 

retina.     The  humors  from  without  inward  are  the  aqueous,  crystalline, 
and  vitreous  humors. 

THE    SCLEKOTICA. 

The  sclerotica  and  cornea  form  the  external  coat  of  the  eyeball 
and  serve  to  give  and  preserve  the  shape  of  the  organ  and  protect 
its  more  delicate  interior  structure. 

The  sclerotica l  is  an  opaque  white,  dense,  inelastic,  fibrous  mem- 
brane occupying  the  greater  extent  of  the  eyeball,  with  the  transpa- 
rent cornea  projecting  from  its  front  and  the  optic  nerve  penetrating 
its  back  part.  It  is  thickest  behind,  and  gradually  becomes  thinner 
to  within  a  short  distance  of  the  cornea,  when  it  again  thickens  to 
the  anterior  border.  Its  outer  surface,  for  the  most  part  smooth,  has 
inserted  into  its  fore  part  the  tendons  of  the  muscles  of  the  ball. 
The  inner  surface  is  brown,  due  to  pigmented  connective  tissue  by 
which  it  is  attached  to  the  choroidea.  The  optic  nerve  perforates  the 
sclerotica  about  an  eighth  of  an  inch  to  the  inner  side  of  the  axis  of 
the  ball  and  slightly  below  the  centre.  The  passage2  is  funnel-like, 
smaller  in  front,  and  the  sheath  of  the  nerve  is  continuous  with  its 
sides.  When  the  passage  is  cut  across  it  exhibits  a  sieve-like  plate,  the 


1  Sclera ;  albuginea ;  alba ;  cornea  opaca. 

2  Foramen  opticum  sclerotic*. 


864  OKGANS   OF  SPECIAL,  SENSE. 

cribrose  lamina,1  through  the  perforations  of  which  the  bundles  of 
nerve-fibres  enter  the  eye. 

Structure  of  the  sclerotica.  The  sclerotica  is  composed  of 
closely-intersecting  bundles  of  fibro-connective  tissue,  pursuing  dif- 
ferent directions;  many  of  them  fore  and  aft,  especially  at  the  ex- 
ternal surface,  and  others  transversely.  With  the  bundles  are  mingled 
fine  elastic  fibres  and  connective-tissue  corpuscles,  of  which  some  are 
pigmented.  The  internal  surface  contains  many  stellate  pigmented 
cells,  which  also  enter  into  the  composition  of  the  delicate  connective 
tissue2  attaching  the  sclerotica  to  the  choroidea.  Both  surfaces  of 
the  sclerotica  are  covered  by  an  endothelium,  lining  corresponding 
lymphatic  spaces. 

In  infancy  the  sclerotica  presents  a  more  or  less  bluish  tint,  due  to 
the  dark  inner  structure  shining  through  the  thinner  and  more  trans- 
lucent coat  of  early  life. 

Comparatively  few  blood-vessels  are  distributed  in  the  dense  struc- 
ture of  the  sclerotica.  The  capillaries  form  wide-meshed  nets  and  are 
most  numerous  around  the  cornea. 

THE   CORNEA. 

The  cornea3  is  the  transparent  part  of  the  external  coat  of  the  ball 
in  front  of  the  eye,  into  the  interior  of  which  it  admits  the  light.  The 
segment  of  a  smaller  sphere,  it  projects  beyond  the  curving  surface  of 
the  sclerotica  and  forms  about  a  sixth  of  the  circumference  of  the  ball. 
It  is  circular  or  nearly  so,  and  is  of  greater  extent  behind  than  in  front, 
due  to  the  border  being  bevelled  forward.  In  this  position  it  is  over- 
lapped by  the  contiguous  border  of  the  sclerotica,  so  as  to  resemble  the 
insertion  of  a  watch-crystal  in  its  frame.  It  differs  but  little  in  thick- 
ness from  the  sclerotica,  is  greatest  at  the  border  and  becomes  slightly 
thinner  to  the  centre.  It  is  more  convex  iri  youth  than  later  and  grad- 
ually decreases  in  this  respect  in  the  latter  part  of  life.  Sometimes 
also  it  is  more  or  less  unduly  convex  for  convenient  vision,  one  of  the 
conditions  of  near-sightedness. 

Structure  of  the  cornea.  The  cornea  consists  of  three  distinct 
layers,  which  may  be  distinguished  as  the  ectocornea,  the  mesocornea, 
and  the  entocornea. 

The  ectocornea,  already  noticed  as  the  corneal  conjunctiva,  is 
thin  and  dense  and  is  composed  of  an  epithelium  and  a  basement 
membrane.  The  epithelium  (see  Fig.  175,  page  349)  is  stratified.  The 
deepest  cell-stratum  consists  of  columnar  cells,  those  following  are 
polyhedral  and  become  successively  larger  and  relatively  broader,  and 
the  superficial  strata  consist  of  flattened  cells  or  scales.  The  deeper 
cells  are  corrugated,  and  the  ridges  of  adjacent  cells  conjoin  so  as  to 

1  L.  cribrosa.  2  Lamina  fusca.  s  C.  pellucida. 


ORGANS   OF  SPECIAL  SENSE.  865 

leave  between  them  narrow  intercellular  channels  occupied  by  liquid. 
The  basement  membrane  is  a  considerable  homogeneous  layer  inti- 
mately connected  with  the  mesocornea  and  defining  it  from  the  epi- 
thelium. 

The  mesocornea,  or  proper  substance  of  the  cornea,  is  its  thickest 
portion,  and  is  continuous  in  structure  with  the  sclerotica,  but  is  com- 
posed of  a  modified  connective  tissue,  in  which  the  elements  are  so 
nearly  alike  in  refractive  character  that  in  the  fresh  condition  it  ap- 
pears homogeneous.  It  is  composed  of  numerous  laminae  of  connective- 
tissue  bundles  embedded  in  homogeneous  cementing  substance.  Gen- 
erally the  bundles  pursue  a  nearly  straight  course  in  each  lamina,  but 
cross  one  another  at  right  angles  in  the  alternate  laminae.  The  adja- 
cent laminae  are  joined  by  intersecting  bundles,  and  the  intervals  of 
the  laminae  are  occupied  with  a  greater  proportion  of  the  cementing 
substance,  in  which  are  embedded  the  corneal  corpuscles.  These 
are  irregularly  stellate,  protoplasmic  cells,  which  are  flat  and  broad 
parallel  with  the  surface  of  the  cornea  and  narrow,  spindle-shaped 
in  the  cross-section.  The  rays  of  contiguous  corpuscles  conjoin,  not 
only  between  but  also  through  the  laminae,  so  as  to  form  an  extensive 
net-work  throughout  the  cornea.  The  corpuscles  have  an  oval  nu- 
cleus, around  which  the  protoplasm  appears  granular,  but  becomes  clear 
towards  the  periphery  of  the  cells.  The  corpuscles  occupjr  correspond- 
ing cell-spaces  of  the  cementing  ground  substance  of  the  cornea  and 
are  readily  brought  into  view  by  staining  this  with  silver  nitrate.  By 
means  of  their  rays  the  cell-spaces  communicate  with  one  another, 
thus  forming  an  anastomosing  system  of  canals  throughout  the  cornea. 
The  corpuscles  do  not  entirely  fill  the  cell-spaces,  but  leave  sufficient 
way  for  the  passage  of  lymph  with  lymph-corpuscles.  The  corneal 
corpuscles  are  endowed  with  slight  contractility,  which  is  exhibited 
under  various  stimuli,  as  mechanical  irritation,  heat,  electricity,  and 
inflammation. 

The  entocornea1  adheres  to  the  mesocornea,  from  which  it  may 
readily  be  detached,  and  is  in  contact  behind  with  the  aqueous  humor. 
It  is  composed  of  a  thin,  compact,  highly-elastic,  and  apparently  homo- 
geneous layer  lined  with  an  endothelium  like  that  of  the  serous  mem- 
branes. At  the  border  of  the  cornea  it  is  reflected  over  the  processes 
of  the  pectinate  ligament  and  becomes  continuous  with  the  ectiris. 

At  the  junction  of  the  cornea  and  sclerotica,  but  rather  within 
the  boundary  of  the  latter,  is  a  venous  channel,  the  circular  sinus, 
which  communicates  with  the  anterior  ciliary  veins. 

At  birth  the  cornea  is  of  more  uniform  thickness  and  less  trans- 
parent than  subsequently.  In  advanced  age  it  also  becomes  less 


1  Membrana  humoris  aquei ;  m.  Demoursiana,  Descemetiani,  or  Duddeliana ; 
capsula  aquea  cartilaginosa  or  prseaquosa ;  membrane  of  Descemet,  or  of  Demours, 
or  of  the  aqueous  humor ;  posterior  elastic  lamina. 

55 


866  ORGANS  OF  SPECIAL  SENSE. 

transparent,  especially  at  the  circumference,  where  commonly  a  white 
ring,  the  arcus  senilis,  makes  its  appearance,  due  to  fatty  deposit. 

Vessels  and  nerves  of  the  cornea.  In  the  normal  condition  of 
the  cornea  it  is  unprovided  with  vessels,  but  is  abundantly  supplied 
with  nerves  derived  from  the  ciliary  nerves.  The  capillary  blood- 
vessels of  the  sclerotica  and  conjunctiva  end  in  a  circle  of  loops  at  the 
border  of  the  cornea.  Lymphatics  appear  to  be  substituted  by  the 
free  communication  of  the  cell-spaces  occupied  by  the  corneal  corpus- 
cles. The  nerves  enter  the  cornea  from  the  sclerotica  as  medullated 
fibres,  which  divide  into  transparent  non-medullated  branches.  Of 
these  the  deeper  series  is  distributed  in  bundles  and  finally  in  indi- 
vidual fibrils  between  the  laminae  of  the  mesocornea,  where  they  freely 
anastomose  and  come  into  intimate  relation  with  the  corneal  corpuscles. 
The  superficial  series  proceeds  to  the  ectocornea  and  after  piercing 
the  basement'  membrane  splits  up  into  numerous  fibrils,  which  form 
together  a  subepithelial  plexus.  From  this  the  ultimate  fibrils  are 
distributed  among  the  epithelial  cells,  freely  anastomosing  to  form  an 
intra-epithelial  plexus.  The  ultimate  fibrils  of  the  corneal  nerves 
are  minutely  beaded  or  varicose.  The  abundance  of  nerves  accords 
with  the  sensitiveness  of  the  cornea. 

THE   CHOKOIDEA. 

The  choroidea1  is  a  thin,  chocolate-brown,  highly-vascular  mem- 
brane, adhering  to  the  inside  of  the  sclerotica,  and  like  it  is  perforated 
by  the  optic  nerve.  In  front  it  is  continuous  with  the  iris  by  the 
ciliary  body,  and  exterior  to  this  is  connected  with  the  junction  of  the 
sclerotica  and  cornea  by  the  ciliary  muscle.  Externally  it  is  attached 
to  the  sclerotica,  as  previously  described.  Internally  it  is  smooth  and 
adheres  to  the  pigmental  layer  of  the  retina,  which  in  ordinary  prepa- 
rations of  the  choroidea  is  detached  with  it  and  until  recently  was 
regarded  as  an  integral  part  of  this  membrane. 

Structure  of  the  choroidea.  The  choroidea  may  be  regarded  as 
consisting  of  three  principal  layers,  the  ecto-,  meso-,  and  entochoroidea. 

The  ectochoroidea2  is  composed  of  laminated  fibro-connective  tis- 
sue, fine  elastic  fibres,  and  flat,  branching,  pigmented  and  colorless  cells 
embedded  in  a  homogeneous  ground  substance.  Between  the  laminae 
are  lymph-spaces  lined  by  endothelial  cells. 

The  mesochoroidea3  resembles  the  former,  with  which  it  is  con- 
tinuous, but  contains  numerous  blood-vessels,  both  arteries  and  veins. 
The  arteries  are  derived  from  the  short  ciliaries  which  pierce  the  scle- 
rotica around  the  optic  nerve  and  enter  the  choroidea.  Proceeding  for- 
ward they  expand  in  the  membrane  in  numerous  inosculating  branches, 

1  Tunica  choroidea,  vasculosa,  uvea,  or  ragoides ;  choroid  coat. 
8  T.  suprachoroidea,  cellulosa,  arachnoidea,  or  villoso-glandulosa. 
3  T.  vasculosa  or  choroidea  propria. 


ORGANS   OF  SPECIAL   SENSE. 


867 


the  longest  of  which  reach  the  ciliary  muscle  and  there  anastomose 
with  the  long  and  anterior  ciliary  arteries.     The  veins  are  situated 


FIG.  431. 


Fig.  431.— THE  CHOROIDEA  AND  IRIS.  1,  ciliary  arteries  situated  at  the  sides  of  the  optic  nerve ; 
2,  the  long  ciliary  arteries ;  3,  the  same  after  having  pierced  the  sclerotica ;  4,  5,  the  main  divisions 
of  the  same  vessels ;  6,  the  ciliary  muscle ;  7,  the  anterior  ciliary  arteries ;  8,  the  short  ciliary 
arteries  to  the  choroidea ;  9,  the  iris  supplied  by  the  long  and  anterior  ciliary  arteries  ;  10,  the 
pupil. 

Pig.  432.— VEINS  OF  THE  CHOROIDEA  AND  IRIS.  1,  sclerotica;  2,  choroidea;  3,  ciliary  muscle, 
of  which  a  portion  has  been  removed  to  exhibit  the  ciliary  processes,  4 ;  5,  the  iris ;  6,  pupil ;  7,  8, 
trunks  of  the  choroid  veins;  9, 10,  vorticose  vessels;  11,  their  conjunction  with  the  veins  of  the 
ciliary  processes ;  12,  anastomosis  between  the  groups  of  vorticose  vessels. 

exterior  to  the  arteries,  than  which  they  are  considerably  larger.    They 
are  remarkable  for  their  whorled  arrangement,  from  which  they  have 


FIG.  433 


FIG.  434. 


VIEW  FROM   BEHIND   OF  THE  ANTERIOR  HALF 

OF  THE  EYEBALL.  1,  sclerotica ;  2,  choroidea ; 
3,  retina ;  4,  the  ora;  5,  ciliary  processes ;  6,  the 
crystalline  lens  behind  the  iris  and  pupil. 


THE  SAME  VIEW,  WITH  THE  CRYSTALLINE  LENS 

AND  RETINA  REMOVED.  1,  sclerotica;  2,  cho- 
roidea ;  3,  ciliary  body ;  4,  the  ora ;  5,  ciliary 
processes ;  6,  iris ;  7,  cornea  seen  through  the 
pupil. 


received  the  name  of  the  vorticose  veins.1      From  the  four  quarters 
of  the  choroidea  the  branches  pursue  a  nearly  parallel  curved  course 


Vasa  vorticosae. 


868 


ORGANS   OF   SPECIAL   SENSE. 


and  converge  to  four  central  trunks,  which  pierce  the  sides  of  the  scle- 
rotica, at  equidistant  points,  to  end  in  the  ophthalmic  vein.  Sometimes 
a  pair  of  these  trunks  unite  before  passing  from  the  sclerotica. 

Internally  the  mesochoroidea  is  defined  by  a  thin  layer  of  reticular 
elastic  fibres  and  endothelial  cells  and  is  traversed  by  the  smallest 
arteries  and  veins  of  the  choroidea  connected  with  the  capillaries  of 
the  following  layer. 

The  entochoroidea l  is  chiefly  composed  of  capillary  vessels  and 
is  internally  defined  by  a  thin,  apparently  homogeneous  membrane. 
The  capillaries  form  a  close  net,  with  intervals  narrower  than  the  ves- 
sels which  compose  it.  The  net  receives  the  arteries  of  the  meso- 
choroidea, and  its  veins  converge  in  vortices  which  terminate  in  the 
larger  vorticose  veins  of  the  latter. 

The  ciliary  body."    This  is  a  light-colored  zone  about  the  fourth 

of  an  inch  wide  at  the  fore  part  of 
the  choroidea,  connected  with  the 
conjunction  of  the  sclerotica  and 
cornea.  It  is  continuous  with  the 
choroidea,  but  is  defined  from  it 
inwardly  by  a  serrate  border,  the 
ora.8  It  is  also  continuous  with 
the  iris.  Outwardly  it  is  formed 
by  the  ciliary  muscle  and  at  its 
anterior  third  inwardly  is  pro- 
duced into  the  ciliary  processes. 

The  posterior  portion  *  of  the 
ciliary  body  appears  as  a  continu- 
ation of  the  choroidea.  has  about 
the  same  thickness  and  nearly  the 
same  constitution,  but  is  finely  and 
uniformly  striate  longitudinally 
and  is  outwardly  lighter  in  color. 
Its  vessels  from  the  choroidea  run 
in  the  same  direction  as  the  stria- 
tion,  but  it  is  devoid  of  the  capil- 
lary layer  of  the  choroidea,  which 
ceases  at  the  ora. 

The    ciliary    processes,5  of 
which  there  are  about  six  dozen, 
form    a    circle    of    half-elliptical 
ridges  projecting  inward,  side  by 
side,  from  the  fore  part  of  the  ciliary  body.      They  consist  of  a  larger 


SEGMENT  OF  THE  CHOROIDEA  AND  IRIS,  SEEN 
ON  ITS  INNER  SURFACE,  magnified  four  diam- 
eters. 1,  ciliary  processes;  2,  their  free  ex- 
tremities behind  the  iris;  3,  4,  commencement 
of  the  processes :  5.  intervals  of  the  processes ; 
6,  veins  of  the  ciliary  processes ;  7,  posterior 
margin  of  the  ciliary  body ;  8,  choroidea  with 
its  veins;  9,  iris;  10,  its  outer  border;  11,  the 
pupillary  border ;  12,  radiating  fibres  of  the  iris ; 
13,  circular  fibres. 


1  Membrana  chorio-capillaris ;  m.  Ruyschiana  or  Hovii. 

2  Corpus  ciliare  ;  corona  ciliaris.  3  Ora  serrata.  4  Orbiculus  ciliaris. 
5  Processus  ciliaris  ;  ligamenta  ciliaria  ;  plicae  corporis  ciliaris. 


OEGANS  OF  SPECIAL  SENSE.  869 

series,  about  one-eighth  of  an  inch  long,  alternating  irregularly  with  a 
smaller  series.  They  are  deepest  and  thickest  at  their  fore  part  and 
gradually  taper  away  behind.  Their  anterior  extremities  are  rounded, 
free,  and  suspended  in  the  aqueous  humor,  in  a  circle  behind  the  outer 
border  of  the  iris.  Their  posterior  extremities,  about  two-thirds  of 
their  length,  are  received  in  corresponding  grooves  of  the  vitreous 
humor,  to  which  they  give  the  appearance  of  a  striated  band,  the 
ciliary  zone,1  which  surrounds  the  crystalline  lens. 

The  ciliary  processes  are  each  composed  of  a  tortuous  plexus  of 
capillary  vessels,  supplied  by  branches  from  the  short  ciliary  arteries 
and  others  from  the  choroidea.  The  veins  run  backward  to  join  the 
vorticose  veins  of  the  choroidea.  The  largest  artery  runs  along  the 
free  border  of  each  process ;  in  like  manner  the  longest  vein  runs  along 
its  attached  border. 

Internally  the  ciliary  body  is  defined  by  a  thin  homogeneous  mem- 
brane2 and  is  covered  by  a  brown-black  pigmented  layer,3  consisting 
of  several  strata  of  polyhedral  cells,  continuous  with  the  corresponding 
pigmented  layers  of  the  retina  and  iris.  On  the  free  ends  of  the  ciliary 
processes  the  cells  are  devoid  of  pigment ;  they  therefore  appear  uncol- 
ored,  or  red  only  from  their  vascularity. 

The  ciliary  muscle4  is  a  thick  white  ring  of  the  exterior  of  the 


\  „ 

a  \   * 

SECTION  THROUGH  THE  CILIARY  REGION  OF  THE  EYE.  1,  sclerotica;  2,  cornea,  a,  radiating 
fibres  of  the  ciliary  muscle ;  b,  c,  deeper  radiating  bundles  enclosing  annular  bundles ;  d,  annular 
bundles  at  the  border  of  the  iris ;  e,  tendinous  origin  of  the  ciliary  muscle  at  the  conjunction  of 
the  sclerotica  and  cornea ;  /,  iris ;  g,  ciliary  process ;  h,  pectinate  ligament. 

ciliary  body,  at  its  conjunction  with  the  sclerotica  and  cornea  and  with 
the  iris.  Its  outer  portion  consists  of  short,  radiant  bundles  of  muscular 
fibres,  which  arise  tendinously  from  the  sclerotica  at  its  conjunction 
with  the  cornea  and  are  directed  backward  and  inward  to  terminate  in 
the  ciliary  body.  The  inner  portion 6  of  the  muscle  consists  of  bundles 
of  fibres,  which  pursue  a  circular  course,  within  the  position  of  the 

1  Zonula  ciliaris.  2  Lamina  vitrea.  3  TJvea. 

4  Musculus  ciliaris ;  ligamentum  ciliare,  iridis,  or  sclerotico-choroidale. 

5  Circular  ciliary  muscle. 


870  ORGANS   OF  SPECIAL  SENSE. 

outer  portion,  at  the  conjunction  of  the  ciliary  body  and  iris.  It  is 
composed  of  unstriped  muscle-fibres.  In  birds  it  is  composed  of  striped 
fibres. 

The  ciliary  muscle  is  more  than  usually  developed  in  hypermetropia, 
but  is  less  produced  in  myopia. 

THE  IRIS. 

The  iris,1  seen  during  life  through  the  transparent  cornea,  is  a 
colored  membranous  disk,  with  a  central  black  spot,  which  is  a  circu- 
lar hole,  the  pupil.2  It  is  placed  vertically  in  advance  of  the  choroidea 
and  ciliary  body,  with  which  it  is  a  continuous  structure.  It  is  also 
connected  with  the  adjacent  border  of  the  sclerotica  and  cornea  by  the 
ciliary  muscle  and  pectinate  ligament.  Situated  in  the  interval  between 
the  cornea  and  lens,  it  divides  the  space  occupied  by  the  aqueous  humor 
into  two  compartments,  the  anterior  and  posterior  chambers,  which 
communicate  through  the  pupil. 

Like  the  diaphragm  of  optical  instruments,  the  iris  serves  to  mod- 
erate and  otherwise  regulate  the  light  admitted  into  the  eye.  Ex- 
ceedingly sensitive  to  light,  under  its  influence  the  iris  is  excited  to 
movement:  thus,  with  an  increase  of  light  it  expands  and  the  pupil 
diminishes;  with  a  decrease  it  contracts  and  the  pupil  proportionately 
enlarges. 

The  iris  is  about  half  an  inch  in  breadth  and  is  nearly  flat  or  very 
slightly  convex  forward.  The  pupil,  slightly  nearer  the  inner  border 
of  the  iris,  moderately  dilated  is  from  one-eighth  to  one-sixth  of  an 
inch  wide,  but  may  expand  to  one-third  of  an  inch  and  contract  to 
one-sixteenth  of  an  inch.  The  iris  is  less  sensitive  in  old  age  and  the 
pupil  appears  habitually  smaller  than  in  youth. 

The  front  surface  of  the  iris,  as  ordinarily  observed  in  the  different 
races,  nations,  and  individuals  of  the  same  people,  varies  greatly  in 
color,  ranging  from  gray  to  deep  blue  or  yellowish  green,  and  from 
bright  yellow-brown  to  deep  brown-black.  In  fair-skinned,  light-haired 
people  it  is  usually  gray  or  blue ;  in  dark-skinned,  black-haired  people, 
more  or  less  brown.  In  the  negro  the  dark-brown  hue  is  so  deep 
that  at  a  little  distance  the  pupil  is  scarcely  distinguishable  from  the 
surrounding  iris.  The  iris  also  often  appears  variably  spotted  with 
brown. 

The  front  of  the  iris  exhibits  an  outer  zone3  and  a  smaller  one* 
immediately  surrounding  the  pupil.  The  outer  zone  is  commonly 
darkest  at  the  corneal  border,  especially  in  light  eyes,  while  the  inner 
border  is  slightly  prominent  and  fringed.  It  is  radially  striated,  the 
strife  being  wavy  in  the  contracted  state  of  the  iris  and  straight  in  its 

1  Tunica  coerulea.  2Pupilla;  pupula. 

3  Annulus  major  iridis ;  a.  externus  or  ciliaris. 

4  A.  minor  iridis  ;  a.  internus  or  pupillaris. 


ORGANS   OF   SPECIAL   SENSE.  871 

most  expanded  condition.  The  inner  zone,  about  a  third  the  width  of 
the  outer,  is  usually  darker,  often  differently  colored,  and  more  evenly 
and  finely  striated. 

The  posterior  surface  of  the  iris  is  radially  striated  and  of  a  deep 
brown-black  color. 

Of  less  thickness  than  the  ciliary  body,  with  which  it  is  continuous, 
the  iris  gradually  increases  to  about  the  position  of  the  small  zone,  and 
then  diminishes  to  the  pupil. 

Structure  of  the  iris.  The  iris,  like  the  choroidea,  may  be  re- 
garded as  consisting  of  three  layers,  distinguished  as  the  ectiris,  mes- 
iris,  and  entiris. 

The  ectiris l  is  continuous  with  the  entocornea  and  is  an  extension 
of  that  membrane.  The  cells  of  its  endothelium  are  smaller  and  less 
clear  than  those  of  the  cornea,  and  in  dark-colored  eyes  contain  some 
brown  pigment-granules. 

The  mesiris,2  the  principal  layer,  is  directly  continuous  with  the 
ciliary  body.  It  consists  of  a  matrix  of  fibro-connective  tissue  with 
the  muscles,  blood-vessels,  and  nerves  of  the  iris.  The  connective- 
tissue  bundles  generally  have  a  radial  disposition,  and  mingled  with 
them  are  numerous  flat,  branching  corpuscles,  which  in  dark  eyes 
contain  variable  proportions  of  brown  pigment-granules. 

The  muscles  which  occupy  the  inner  or  deeper  part  of  the  mes- 
iris are  the  dilator  and  sphincter  of  the  iris,  and  are  composed  of  un- 
striped  fibres.  The  dilator 3  is  a  thin  stratum  of  fibres  which  radiate 
from  the  pupil  to  the  ciliary  border  of  the  iris,  where  they  are  associ- 
ated with  some  circular  fibres.  The  sphincter 4  is  a  narrow  zone  of 
circular  fibres  around  the  pupil. 

The  entiris,  or   uvea,5  consists  of  several  strata  of  polyhedral 
pigmented  cells,  which  all  together  appear  intensely  black.     They  are 
filled   with    dark-brown  pigment- 
granules  and  contain  a  spheroidal  FIG.  437. 
nucleus.     The  cells  lie  on  a  thin, 
homogeneous  basement  membrane. 

In  blue  eyes,  the  cells  of  the 
entiris  alone  contain  pigment- 
granules,  there  being  no  pigment 
in  the  other  layers.  In  albinos 
the  pigment  is  altogether  absent 

in  the  iris.      The   blue  Color  of  the      on  the  side ;  c,  pigment-granules. 

iris   seems  due   to   the  uvea  seen 

through  the  white  connective  tissue  of  the  mesiris ;  the  gray  color,  to 

the  greater  proportion  and  compactness  of  the  same  tissue. 

1  Membrane  of  Descemet  or  of  Zinn  ;  lamella  iridis  anterior. 

2  Fibrous  layer  of  Kolliker.  a  M.  dilatator  pupillae. 
4  S.  iridis.  5  Pigmentary  layer. 


872 


ORGANS   OF   SPECIAL,   SENSE. 


The  pectinate  ligament1  appears  around  the  adjacent  borders 
of  the  iris  and  cornea  as  minute  bands  extended  between  them.  It 
consists  of  bands  and  laminae  of  elastic  tissue  forming  a  bond  of  union 
between  the  contiguous  borders  of  the  cornea,  sclerotica,  iris,  and  ciliary 
body.  It  is  continuous  with  the  connective-tissue  bundles  of  the  scle- 
rotica around  the  circular  sinus,  with  the  tendinous  origin  of  the  ciliary 
muscle,  and  with  the  stroma  of  the  iris.  Next  the  cornea  some  of  its 
fibres  pursue  a  circular  course.2  It  is  closely  invested  by  the  entocornea 
which  dips  into  its  recesses  and  thence  becomes  continuous  with  the 
ectiris. 

Vessels  of  the  ciliary  muscle  and  iris.  Two  branches  of  the 
ophthalmic  artery,  the  long  ciliary  arteries,  enter  the  eyeball,  by 
piercing  the  sclerotica,  on  each  side  of  the  entrance  of  the  optic  nerve. 
Proceeding  forward  between  the  sclerotica  and  choroidea,  on  each  side 
of  the  eye,  near  the  ciliary  muscle  they  divide  into  two  branches,  which 
diverge  above  and  below  and  enter  the  muscle.  Half  a  dozen  smaller 


ARTERIES  OF  THE  IRIS.    1,  long  ciliary  arteries;  2,  3,  their  principal  divisions;  4,  small  branches 
to  the  ciliary  muscle ;  5,  6,  anterior  ciliary  arteries ;  7,  the  pupil. 

vessels,  the  anterior  ciliary  arteries,  derived  from  the  muscular  and 
lachrymal  branches  of  the  ophthalmic  artery,  after  giving  off  minute 
branches  to  the  conjunctiva,  pierce  the  sclerotica  near  the  cornea  and 
anastomose  with  the  branches  of  the  long  ciliary  arteries,  forming  with 
them  the  arterial  circle  of  the  iris.  This  occupies  the  anterior 
border  of  the  ciliary  muscle  and  gives  off  numerous  branches  to  the 
iris,  freely  inosculating  and  converging  to  the  pupil,  where  they  termi- 
nate in  a  circular  plexus  of  minute  vessels.  From  the  ciliary  arteries 

1  Ligamentum  pectinatum  iridis  ;  processus  peripherici. 

2  Limiting  ring  of  Schwalbe. 


ORGANS   OF   SPECIAL   SENSE. 


873 


FIG.  439. 


and  the  circle  formed  by  their  union  small  branches  are  distributed 
to  the  ciliary  muscle  and  processes.  From  the  capillary  nets  of  the 
mesiris  the  veins  run  to  the  venous  plexuses  of  the  ciliary  processes 
and  finally  to  the  vorticose  veins  of  the  choroidea.  Other  veins  from 
the  iris  and  ciliary  muscles  accompany  the  anterior  ciliary  arteries,  in 
their  course  communicating  with  the  circular  sinus,  at  the  conjunction 
of  the  cornea  and  sclerotica. 

The  lymphatics  of  the  iris  consist  of  lymph-spaces  around  the 
blood-vessels,  chiefly  the  arteries,  and  among  the  connective-tissue 
bundles  of  the  stroma.  They  communi- 
cate with  the  recesses  of  the  pectinate 
ligament  around  the  iris. 

Nerves  of  the  choroidea  and  iris. 
Fifteen  or  more  ciliary  nerves,  derived 
from  the  ophthalmic  ganglion  and  nasal 
branch  of  the  ophthalmic  nerve,  pierce 
the  sclerotica  around  the  entrance  of  the 
optic  nerve.  They  proceed  forward  in 
shallow  grooves  of  the  sclerotica  lying  in 
contact  with  the  choroidea,  to  which  they 
give  branches,  then  after  dividing  they 
enter  the  ciliary  muscle.  Within  this  they 
continue  to  branch,  and  together  form 
the  ciliary  plexus,  encircling  the  iris. 
From  the  plexus  proceed  the  nerves  of 
the  cornea,  of  the  ciliary  muscle,  and  of 
the  iris. 

The  nerves  of  the  cornea  pierce  the 
contiguous  portion  of  the  sclerotica  and 
proceed  to  the  cornea. 

The  nerves  of  the  ciliary  muscle  end 
in  a  gangliated  plexus  of  nerve-axis  fibres. 

The  nerves  of  the  iris  enter  it  and  divide 
into  branches  which  anastomose  and  form 
together  an  irregularly-looped  plexus  in 
the  ciliary  border.  From  this  plexus  pro- 
ceed many  branches,  which  in  a  similar  manner  form  a  succession  of 
several  plexuses,  the  last  and  smallest  surrounding  the  pupil.  Branches 
from  the  larger  plexuses  of  the  iris  end  in  plexuses  of  nerve-axis  fibres 
of  the  dilator  and  sphincter  muscles  and  of  the  front  superficial  part 
of  the  iris. 

THE   KETINA. 

The  retina 1  is  the  interior,  delicate,  soft  membrane  of  the  eye,  in 
which  the  optic  nerve  terminates,  and  is  the  immediate  seat  of  visual 


VESSELS  OF  THE  CILIARY  BODY  AND 
IRIS  :  magnified  ten  diameters.  From 
a  child :  viewed  from  within,  a,  cap- 
illary plexus  of  the  anterior  part  of 
the  choroidea ;  6,  the  ora ;  c,  arteries 
of  the  ciliary  body  passing  into  the 
ciliary  processes  d,  and  partly  into 
the  iris  at  e;  f,  capillary  plexus 
around  the  pupil. 


1  Tunica  nervea  oculi. 


874 


ORGANS    OF   SPECIAL    SENSE. 


impressions.  It  is  intimately  connected  with  the  inner  surface  of  the 
choroidea,  gradually  thinning  away  to  the  ora,  where  it  for  the  most 
part  abruptly  terminates,  but  is  continued  through  one  of  its  constituent 
laminae,  distinguished  as  the  preretina. 

The  retina  is  thickest  at  the  entrance  of  the  optic  nerve  into  the 
eye,  where  it  is  about  one-fiftieth  of  an  inch,  thence  it  is  gradually  re- 
duced to  the  ora,  where  it  is  about  one-fourth  that  measurement.  The 
internal  surface  is  smooth,  and  lies  in  contact  with  the  vitreous  body. 


FIG.  440. 


FIG.  441. 


EYEBALL,  WITH  THE  SCLEROTICA,   CORNEA, 

CHOROIDEA,  AND  IRIS  REMOVED.    1,  Optic  tierVC  ; 

2, 3,  retina ;  4,  central  retinal  artery  distributed 
to  the  retina;  5,  6,  ciliary  zone;  7,  space  at 
the  circumference  of  the  crystalline  lens  8, 
artificially  inflated  and  assuming  the  form  of 
a  beaded  canal. 


4    687 

RETINA,  SEEN  ON  ITS  POSTERIOR  INNER  SUR- 
FACE. 1,  sclerotica;  2,  choroidea;  3,  retina;  4, 
the  optic  papilla ;  5,  central  retinal  artery ;  6, 
a  slight  fold  of  the  retina ;  7,  the  yellow  spot ; 
8,  its  central  fovea. 


The  exterior  layer  of  the  retina,  or  the  ectoretina,  is  deep  brown- 
black.  It  was  formerly  regarded  as  part  of  the  choroidea.  The  inte- 
rior layer,  composing  the  chief  thickness  of  the  membrane,  during  life 
is  clear,  transparent,  and  of  a  pale-pink  tint,  but  shortly  after  death, 
when  not  exposed  to  light,  it  assumes  a  purplish-red  hue.  It  quickly 
undergoes  change  and  under  the  influence  of  light  loses  its  trans- 
parency and  becomes  white,  ordinarily  presenting  the  appearance  of 
ground  glass. 

In  the  fresh  condition,  at  the  bottom  of  the  eye,  directly  in  the  axis 
of  vision,  the  inner  transparent  layer  of  the  retina  exhibits  a  circular 
or  transverse  oval  yellow  spot,1  with  a  conical  pit  or  central  fovea.2 
The  spot  is  about  a  line  in  diameter,  and  the  portion  of  the  retina 
which  forms  it  increases  in  thickness  to  the  border  of  the  central  fovea, 
when  it  rapidly  thins  away  to  the  bottom.  Here  it  is  so  much  re- 
duced that  the  dark  ectoretina  is  visible  through  and  appears  like  an 
aperture.3 

About  one-tenth  of  an  inch  to  the  inner  side  of  the  yellow  spot, 
a  circular  white  one4  indicates  the  position  of  entrance  of  the  optic 
nerve  into  the  eye.  The  retina  is  here  thickest  and  forms  a  little  ele- 
vation, the  optic  papilla,5  from  the  centre  of  which  the  retinal  blood- 


1  Macula  flava  or  lutea ;  limbus  luteus. 

3  Foramen  centrale. 

5  Papilla  optica ;  colliculus  opticus. 


2  Fovea  centralis. 
4  Porus  opticus. 


ORGANS   OF   SPECIAL,   SENSE. 


875 


vessels  diverge  above  and  below.  After  death,  as  a  result  of  evapo- 
ration, commonly  a  transverse  fold 1  makes  its  appearance  in  the  retina 
directed  outward  from  the  optic  papilla. 

Structure  of  the  retina.  The  retina  is  exceedingly  complex,  and 
has  its  chief  elements  arranged  in  strata,  which  may  be  regarded  as 
pertaining  to  three  divisions  of  the  membrane,  distinguished  as  the 

FIG.  442. 


VERTICAL  SECTIONS  OF  THE  RETINA:  highly  magnified.  A,  section  about  the  middle  of  the 
retina ;  B,  section  near  the  entrance  of  the  optic  nerve.  1,  rod  and  cone  layer  of  the  mesoretina ; 
2.  nuclear  layer  of  the  mesoretina ;  3-10,  entoretina ;  3,  outer  granular  layer ;  4,  nuclear  layer ; 
5,  inner  granular  layer ;  6,  ganglionic  layer ;  7,  layer  of  nerve-fibres ;  8,  sustentacular  fibres ;  9, 
thin  expanded  base ;  10,  inner  limiting  membrane. 

ectoretina.  mesoretina,  and  entoretina.     A  further  extension  of  one  of 
the  strata  is  the  preretina. 

The  ectoretina,2  or  pigmentary  layer  of  the  retina,  until  recently 
was  regarded  as  a  constituent  layer  of  the  choroidea.  In  ordinary 
preparations  of  the  eye  it  readily  separates  from  the  mesoretina  and 
remains  closely  adherent  to  the  choroidea.  On  the  other  hand,  in  ver- 
tical sections  through  the  tunics  of  the  eye  prepared  for  the  micro- 
scope the  pigmentary  layer  is  observed  to  hold  a  more  intimate  relation 
with  the  other  layers  of  the  retina  than  with  the  choroidea.  It  is 
composed  of  a  stratum  of  thick,  hexagonal  pigment-cells  united  by  a 
colorless  cement.  The  outer  ends  of  the  cells  are  nearly  flat  and 


1  Plica  centralis  ;  p.  transversa  retinae. 

2  Pigment-layer  of  the  choroidea ;  stratum  pigmenti ;  uvca. 


876 


ORGANS   OF  SPECIAL  SENSE. 


adhere  to  the  inner  surface  of  the  choroidea ;  while  the  inner  part  of 
the  cells  is  broken  up  into  a  brush  of  tapering  filaments  which  dip  into 
the  intervals  of  the  rods  of  the  mesoretina.  The  superficial  portion 
of  the  cell  contents,  or  that  next  the  choroidea,  is  clear,  finely  gran- 
ular, and  contains  a  central  nucleus,  while  the  deeper  portion  consists 
largely  of  dark-brown  pigment-granules  which  extend  into  the  tapering 
filaments  and  give  to  the  ectoretina  its  characteristic  deep  brown-black 
color. 

The  mesoretina1  consists  of  the  rod  and  cone  and  the  nuclear 
layers,  defined  by  offsets  of  the  retinal  stroma  forming  a  lamina  which 
is  distinguished  as  the  outer  limiting  membrane. 

The  rod  and  cone  layer2  consists  of  elements  which  are  arranged 
vertically  and  parallel  with  one  another  in  a  continuous  stratum.  The 
rods  greatly  predominate,  and  surround  the  cones,  which  are  isolated 


FIG.  443. 


FIG.  444. 


ROD  AND  CONE  LAYER  OF  THE  RETINA,  viewed 

from  the  outer  surface:  highly  magnified.  1, 
at  the  middle  of  the  retina,  four  cones  sur- 
rounded by  numerous  rods;  2,  from  the  border 
of  the  yellow  spot,  each  cone  with  a  single 
circle  of  rods ;  3,  cones  of  the  centra]  fovea. 

and  scattered  among  the  rods, 
except  within  the  yellow  spot, 
where  they  alone  exist.  From 
the  vicinity  of  the  yellow  spot, 
where  they  are  most  numerous, 
they  gradually  diminish  in  number 
approaching  the  ora. 

The  rods  are  club-shaped ;  the 
cones  are  shorter,  broader,  and 
in  shape  resemble  ninepins.  Both 

are  divided  into  an  inner  thicker  segment  or  body  and  an  outer  seg- 
ment or  process,  besides  which  they  have  attenuated  extensions  which 
run  inward  through  the  nuclear  layer.  The  body  is  elliptical,  homoge- 
neous, or  faintly  granular  and  longitudinally  striated.  In  the  cones 
it  is  shorter  and  thicker  than  in  the  rods. 


ROD    AND    CONE    FROM    THE    RETINA:    highly 

magnified.  1,  outer  segment,  or  process;  2, 
inner  segment,  or  body ;  3,  nucleus ;  4,  line  of 
the  outer  limiting  membrane. 


1  Mosaic  layer  of  Henle. 

1  Stratum  bacillosum  ;  s.  cylindrorum  ;  tunica  Jacobi ;  membrana  Jacobiana. 


ORGANS   OF   SPECIAL   SENSE.  877 

The  process  of  the  rods  is  about  as  long  as  the  body,  cylindrical, 
with  a  rounded  end,  and  striated  longitudinally  and  transversely.  The 
process  of  the  cones  is  shorter  than  the  body,  much  shorter  than  that 
of  the  rods,  tapers  to  a  blunt  point,  and  is  striated  transversely. 

The  body  of  the  cones  and  rods  is  optically  singly  refractive,  while 
the  process  is  doubly  refractive  and  exhibits  a  disposition  to  break  up 
into  transverse  disks,  especially  in  the  rods.  The  purple-red  color  ob- 
served in  the  retina  after  death  appears  to  have  its  seat  in  the  processes 
of  the  rods. 

The  processes  of  the  pigment-cells  of  the  ectoretina  extend  be- 
tween the  rods  of  the  mesoretina,  but  elsewhere  the  intervals  of  the 
rods  and  cones  are  occupied  by  a  colorless  semi-liquid  material. 

The  inner  extremity  of  the  cones  contracts,  passes  through  the 
outer  limiting  membrane,  and  encloses  a  clear  oval  nucleus,  from  the 
opposite  pole  of  which  a  cylindrical  fibre  proceeds  through  the  nu- 
clear layer  to  join  the  entoretina  by  an  expansion.  In  like  manner  the 
rods  contract  into  fine  fibres,  which  are  minutely  varicose  and  likewise 
proceed  to  join  the  entoretina  by  an  expanded  end.  In  their  course 
the  rod-fibres,  at  variable  distances,  enclose  a  nucleus,  which  differs 
from  that  of  the  cones  in  being  transversely  banded. 

The  nuclei  of  the  rods  and  cones,  proportioned  in  number  to  them, 
are  arranged  in  strata  forming  the  nuclear  layer l  of  the  mesoretina ; 
the  nuclei  of  the  cones  occupying  the  outer  stratum.  Where  the  ex- 
panded ends  of  the  rod-  and  cone-fibres  join  the  entoretina  they  send 
into  its  outer  granular  layer  diverging  filaments,  which  are  supposed 
to  join  similar  filaments  from  the  cells  of  the  nuclear  layer  of  the 
entoretina. 

The  entoretina 2  consists  of  five  layers,  distinguished  as  the  outer 
granular,  nuclear,  inner  granular,  ganglionic,  and  nerve-fibre  layers, 
defined  by  the  inner  limiting  membrane. 

The  outer  granular  layer3  of  the  entoretina  is  comparatively 
thin,  and  consists  of  a  homogeneous,  finely-granular  matrix,  with  a 
dense  interlacement  of  fine  varicose  filaments  and  of  flattened  branch- 
ing corpuscles  with  a  clear  nucleus.  It  receives  the  filaments  of  the 
rod-  and  cone-fibres  of  the  nuclear  layer  of  the  mesoretina  and  those 
of  the  cell-fibres  of  the  succeeding  layer. 

The  nuclear  layer*  of  the  entoretina,  of  less  thickness  than  that 
of  the  mesoretina,  consists  of  fewer  strata  of  generally  larger  nuclei, 
which  are  vertically  oval  and  contained  in  bipolar  spindle-shaped  cells 
prolonged  into  fibres.  The  outer  fibres  are  thicker  and  enter  the  outer 
granular  layer,  where  they  branch  into  filaments  mingled  with  those  of 

1  Outer  nuclear  layer ;  k5rner  and  ausser  faser  Schichte  of  Henle. 

2  Nervous  layer  of  Henle  ;  lamina  vasculosa  retinae. 

3  Outer  molecular  or  intergranular  layer. 

4  Inner  nuclear  layer ;  outer  ganglionic  layer  of  Henle. 


878  ORGANS   OF  SPECIAL   SENSE. 

the  latter.  The  inner  fibres  are  varicose  and  enter  the  inner  granular 
layer,  through  which  they  run  without  dividing.  Nuclei  of  more  elon- 
gated form,  mingled  with  the  others,  pertain  to  the  fibres  of  the  retinal 
stroma.  The  nuclear  layer  is  defined  inwardly  by  a  stratum  of  flat 
nucleated  cells. 

The  inner  granular  layer1  of  the  entoretina,  very  much  thicker 
than  the  outer  granular  layer,  has  a  similar  structure.  It  receives  the 
inner  fibres  of  the  bipolar  cells  of  the  adjacent  nuclear  layer  and  the 
branching  processes  of  the  nerve-cells  beneath. 

The  ganglionic  layer 2  of  the  entoretina  mainly  consists  of  large 
nerve-cells,  mostly  spheroidal  or  pyriform,  of  beautiful  clear  aspect, 
containing  a  central,  spherical  nucleus.  Each  cell  is  connected  beneath 
with  a  nerve-fibre  proceeding  from  the  adjoining  layer,  arid  the  outer 
part  gives  off  one  or  more  processes,  which  extend  into  the  inner 
granular  layer  and  branch  into  fibres,  which  are  lost  among  the  inter- 
lacing filaments  of  the  layer.  Over  the  greater  part  of  the  retina  the 
nerve-cells  form  a  single  stratum,  which  becomes  less  continuous  near 
the  ora.  In  the  vicinity  of  the  yellow  spot  the  nerve-cells  increase  to 
several  strata  and  within  it  augment  to  half  a  dozen  strata. 

The  nerve-fibre  layer3  of  the  entoretina,  the  innermost  of  the 
retinal  layers,  is  thickest  at  the  optic  papilla,  thence  gradually  thins 
away  to  the  ora.  It  is  composed  of  bundles  of  nerve  axis-fibres,  which 
enter  the  retina  from  the  optic  papilla  and  spread  out  on  the  inner 
surface  of  the  membrane.  The  bundles  of  fibres  in  their  divergence 
interchange  so  as  to  form  a  continuous  net  with  narrow  meshes.  In 
the  yellow  spot  the  layer  is  interrupted  by  the  many  strata  of  nerve- 
cells.  The  intervals  of  the  nerve-bundles  enclose  lymph-spaces  lined 
with  endothelial  cells. 

The  stroma,4  which  pervades  the  greater  part  of  the  retina  and 
connects  and  supports  its  more  essential  elements  of  structure,  is  a 
peculiar  kind  of  connective  tissue,  arranged  in  columns,  called  the 
sustentacular  fibres.5  These  commence  internally  in  a  pyramidal 
expansion,  narrowing  outwardly  in  a  column,  which  proceeds  through 
the  layers  of  the  ento-  and  mesoretina,  conforming  to  the  intervals  of 
the  nerve-elements  and  giving  off  laminar  and  filamentous  processes 
which  unite  and  enclose  the  nerve-elements.  In  passing  through  the 
nuclear  layer  of  the  entoretina,  each  fibre  encloses  an  oval  nucleus 
and  another  occupies  the  pyramidal  expansion  at  its  commencement. 
The  broad  bases  of  the  pyramidal  expansions  unite  by  their  adjoining 
edges  and  thus  form  a  thin  lamina,  which  defines  the  retina  within 
and  is  hence  called  its  inner  limiting  membrane.6  Viewed  on 

1  Inner  molecular  or  granular  layer.  2  Inner  ganglionic  layer  of  Henle. 

3  Layer  of  nerve-fibres  ;  inner  nerve-fibre  layer  of  Henle. 
*  Sustentacular  tissue.  5  Miillerian  fibres  ;  radial  fibres. 

6  Membrana  limitans  interna. 


ORGANS   OF   SPECIAL  SENSE. 


879 


FIG.  445. 


the  surface,  from  the  polygonal  outlines  of  the  bases  of  the  susten- 
tacular fibres,  the  membrane 
resembles  in  appearance  an 
endothelium.  At  the  outer 
part  of  the  nuclear  layer  of 
the  mesoretina  lateral  offsets 
from  the  sustentacular  fibres 
unite  in  a  thin  outer  limiting 
membrane,1  which  separates 
the  two  layers  of  the  meso- 
retina and  sends  processes  out- 
ward between  the  rods  and 
cones.  The  substance  of  the 
sustentacular  fibres  is  longitu- 
dinally striated,  but,  unlike  or- 
dinary connective  tissue,  is  not 
dissolved  by  boiling  in  water. 

The  yellow  spot2  of  the 
retina  owes  its  color  to  pig- 
ment diffused  among  its  struc- 
tural elements,  and,  as  the  pig- 
ment is  readily  soluble  in 
water,  the  yellow  color  quickly 
disappears  after  death.  From 
its  periphery  the  spot  thickens 
inwardly  to  the  border  of  the 
central  fovea3  and  then  rap- 
idly thins  away  to  its  bottom. 

In  the  position  of  the  yel- 
low spot  the  ectoretina  con- 
tinues unchanged. 

The  mesoretina  thickens  to 
the  border  of  the  fovea  and 
thins  away  towards  the  bot- 
tom. Beyond  the  periphery 
of  the  yellow  spot  the  rods 
disappear,  and  the  remainder 
of  the  stratum  consists  en- 
tirely of  cones,  which  be- 
come narrower  and  consider- 
ably longer  approaching  the 
bottom  of  the  central  fovea.  The  nuclear  layer  thickens  to  the  fovea 
and  thins  away  to  its  bottom.  The  nuclei  are  collected  in  a  dense  outer 


f\ 


DIAGRAM  OF  THE  ARRANGEMENT  OF  THE  STRUC- 
TURAL ELEMENTS  OF  THE  RETINA.  A,  the  retinal 
stroma  or  sustaining  element:  a,  outer  limiting 
membrane ;  6,  inner  limiting  membrane ;  c,  c,  sus- 
tentacular fibres;  d,  nuclei  of  sustentacular  fibres ; 
e,  outer  granular  layer ;  /,  inner  granular  layer.  B, 
the  nerve-elements :  a,  rods ;  b,  cone ;  c,  its  expanded 
base ;  cf,  nucleus  of  the  cone-fibre ;  d,  nucleus  of  the 
rod-fibres ;  e,  division  of  the  cone-fibre  in  the  outer 
granular  layer ;  /,  nuclei  of  the  inner  nuclear  layer ; 
g,  maze  of  fibrils  of  the  inner  granular  layer;  h, 
nerve-cells ;  h',  optic  nerve-fibre  joining  a  cell ;  i, 
layer  of  nerve-fibres. 


1  M.  limitans  externa. 
5  Fovea  centralis. 


1  Macula  flava  or  lutea. 


880 


ORGANS   OF   SPECIAL   SENSE. 


stratum ;  the  nuclear  fibres  form  a  much  thicker  inner  stratum,  with 
the  long  fibres  sweeping  in  curves  from  the  nuclei  to  the  entoretina. 

In  the  entoretina  of  the  yellow  spot  the  granular  layers  continue 
with  little  change  to  the  central  fovea,  when  they  converge  and  unite 
in  a  single  stratum  at  the  bottom.  The  nuclear  layer  also  continues 
with  little  change,  but  tapers  at  the  side  of  the  fovea  and  disappears 

FIG.  446. 


VERTICAL  SECTION  THROUGH  ONE  SIDE  OF  THE  YELLOW  SPOT  AND  CENTRAL  FOVEA  :  diagram 
highly  magnified.  1,  inner  layer  of  nerve-fibres;  2,  layer  of  nerve-cells ;  3,  inner  granular  layer; 
4,  inner  nuclear  layer ;  5,  outer  granular  layer ;  6,  outer  nuclear  layer ;  7,  layer  of  rods  and  cones ; 
8,  rods;  9,  9,  cones;  10,  bottom  of  the  central  fovea. 

at  the  bottom.  The  ganglionic  layer  especially  enlarges,  becomes  from 
one  to  six  or  eight  cells  deep,  but  narrows  at  the  sides  of  the  fovea 
and  disappears  at  the  bottom.  The  cells  are  bipolar  and  obliquely 
arranged.  The  layer  of  nerve-fibres  gradually  thins  away  to  the  border 
of  the  fovea,  the  fibres  turning  inward  to  join  the  adjacent  nerve-cells. 

Excepting  the  pigmentary  layer,  the  retina  thins  away  as  it  pro- 
ceeds forward,  and  finally  ceases  at  the  ora,  except  a  delicate  layer, 
which  is  continued  on  the  ciliary  body  and  is  distinguished  as  the 
preretina.1  This  consists  of  a  single  stratum  of  clear,  columnar,  nu- 
cleated cells,  which  appear  to  correspond  with  the  fibres  of  the  retinal 
stroma. 

Vessels  of  the  retina.  The  retina  is  supplied  by  the  central 
artery,  a  branch  of  the  ophthalmic  artery,  which  pierces  the  optic 
nerve  about  the  fourth  of  an  inch  behind  the  eyeball  and  enters  it 
in  the  axis  of  the  nerve.  Accompanied  by  the  corresponding  vein,  it 
enters  the  retina  in  the  centre  of  the  optic  papilla  and  divides  usually 
into  two  branches,  which  diverge,  the  one  above,  the  other  below. 

1  Pars  ciliaris  retinae ;  corpus  ciliare  retinae  ;  margo  flocculosus  retinae. 


ORGANS   OF  SPECIAL  SENSE.  881 

Advancing,  they  ramify  in  the  inner  part  of  the  nerve-layer  and  end  in 
capillary  nets,  which  pervade  the  different  layers  of  the  entoretina,  but 
do  not  enter  the  mesoretina  or  ectoretina.  Minute  branches  enter  the 
yellow  spot  and  terminate  in  capillary  loops  around  the  central  fovea. 
The  veins  pursue  the  same  general  course  as  the  arteries,  and  resemble 
capillaries  in  structure,  their  wall  composed  only  of  endothelial  cells. 

The  lymphatics  of  the  retina  commence  generally  as  lymph-spaces 
invaginating  the  blood-vessels,  especially  the  capillaries  and  veins;  they 
communicate  with  the  lymphatics  of  the  optic  nerve. 

THE  VITKEUM. 

The  vitreum,  or  vitreous  body,1  is  the  transparent,  colorless,  jelly- 
like  mass  which  occupies  the  space  included  by  the  retina,  with  which 
it  is  in  close  contact.  In  its  front  is  a  concave  depression 2  accommo- 
dating the  lens.  Around  this  it  is  impressed  by  the  ciliary  body, 
producing  the  ciliary  zone,3  which  in  the  detached  vitreum  appears 
conspicuously  marked  by  radial  grooves  and  adherent  portions  of  the 
black  uvea.  The  axis  of  the  vitreum  is  traversed  by  a  narrow  canal,4 
which  in  foetal  life  accommodates  a  branch  of  the  retinal  artery  des- 
tined to  the  capsule  of  the  lens.  The  mature  vitreum  contains  neither 
vessels  nor  nerves.  It  consists  chiefly  of  a  clear,  slightly  viscid,  albu- 
minoid liquid5  occupying  the  interstices  of  a  delicate,  homogeneous, 
membranous  structure,  the  hyaloidea,6  which  is  disposed  in  concen- 
tric laminae,  especially  towards  the  periphery.  On  the  surface  the 
hyaloidea  is  continuous  and  separates  the  vitreum  from  the  retina.  It 
is  strongest  in  advance,  and  is  thickest  in  the  ciliary  zone,  where  it 
forms  the  suspensory  ligament  of  the  lens.7  This  is  reinforced  by 
fine  elastic  fibres  extending  radially  between  the  ora  and  the  margin  of 
the  lens.  Approaching  the  lens  the  ligament  divides  into  two  laminae, 
attached  in  front  and  behind  to  the  contiguous  parts  of  the  capsule. 
The  space8  between  the  laminae,  when  inflated  artificially,  appears  as 
a  beaded  canal  encircling  the  lens,  the  constrictions  being  due  to  the 
alternating  narrower  intervals  of  attachment  of  the  fibres  of  the  liga- 
ment. The  vitreum  contains  many  scattered  corpuscles,  especially  be- 
neath the  hyaloidea  at  the  surface.  They  are  endowed  with  amoeboid 
power  of  movement  and  appear  to  be  colorless  blood-corpuscles. 

1  Corpus  vitreum ;  c.  hyaloideum ;  vitreous  humor. 

2  Fossa  hyaloidea,  patellaris,  or  lenticularis. 

3  Zonula  ciliaris  or  Zinni ;  orbiculus  capsulo-ciliaris  ;  lamina  ciliaris. 

4  Canalis  hyaloideus ;  area  Martegiani ;  canal  of  Stilling. 

5  Vitreous  humor  ;  vitrina  ocularis. 

6  Tunica  hyaloidea  or  arachnoidea ;  hyaloidea  interna ;  pars  cellularis. 

7  Ligamentum  suspensorium  lentis. 

8  Canal  of  Petit ;  circulus  Petiti ;  camera  tertia  aquosa. 

56 


882  ORGANS   OF   SPECIAL   SENSE. 

THE    LENS. 

The  lens,  or  crystalline  lens,1  is  a  transparent,  colorless  body, 

the  shape  of  which  is  indicated 

FIG.  447.  by  the    name.     Doubly  convex, 

i  234  5  with   rounded   border,    its    pos- 

terior surface  occupies  the  con- 
cave depression  in   front  of  the 
vitreum,  while  its  anterior  sur- 
THE  CRYSTALLINE  LENS,  i,  lens  of  a  foetus  of     face  comes  into  contact  with  the 

seven  months;  2,  lens  of  a  foetus  of  nine  months;      Dack  of  the  iris  and  is  bathed   in 
3,  lens  of  a  child  of  ten  years  ;  4,  lens  of  an  adult        . 

viewed  in  profile;    5,  the  same  seen  on  its  an-     the  aqueous  humor.      It  IS  about 
terior  surface.  one-third  of  an  inch  broad,  and 

about  one-sixth  of  an  inch  fore 
and  aft ;  the  posterior  surface  is  more  convex  than  the  anterior. 

The  lens  consists  of  a  membranous  capsule  enclosing  a  semi-solid 
albuminoid  mass.  The  capsule2  is  elastic  and  homogeneous,  with  the 
anterior  half  much  thicker  than  the  posterior  half,  which  is  contin- 
uous with  the  hyaloidea  of  the  vitreous  body.  In  the  mature  state  it 
is  entirely  devoid  of  vessels  and  nerves.  Its  fore  part  is  lined  with 
an  epithelium  consisting  of  a  single  stratum  of  hexagonal  cells,  with 
transparent  granular  contents  and  a  clear  spheroidal  nucleus.  The 
back  part  of  the  capsule  is  in  contact  with  the  lens-substance ;  com- 
monly after  death  it  is  found  to  be  separated  from  it  by  some  infiltrated 
liquid.3 

The  lens-substance*  is  soft  on  the  exterior  and  gradually  in- 
creases in  consistence  to  the  centre,  where  it  is  comparatively  hard. 
It  is  not  a  continuous  homogeneous  structure,  but  consists  of  segments 

FIG.  448.  FIG.  449. 


CRYSTALLINE  LENS,  BREAKING  UP  INTO  SEG-        SEGMENT  OP  THE  CRYSTALLINE  LENS,  exhibit- 
MENTS.  ing  the  concentric  arrangement  of  the  laminae. 

composed  of  concentric  laminae.  In  the  foetus  three  rays 5  appear  on 
each  surface  of  the  lens,  directed  from  the  poles  to  the  circumfer- 
ence, alternating  in  the  position  of  the  rays.  Thus,  in  front  one  ray  is 
directed  downward  and  the  others  laterally  upward,  while  behind  one 
is  directed  upward  and  the  others  laterally  downward.  In  the  adult 

1  Lens  crystallina ;  corpus  crystallinum. 

2  Capsula  lentis  ;  tunica  crystalloidea  or  arachnoidea. 

3  Liquor  Morgagni.  *  Humor  crystallinus. 
5  Septa  radiata ;  s.  lateralia. 


ORGANS   OF   SPECIAL   SENSE. 


883 


several  additional  rays l  diverge  from  the  former  and  divide  the  lens 
into  a  proportionate  number  of  segments.  The  laminae  are  single 
strata  of  six-sided  bands,  the  lens-fibres,2  with  the  width  in  the  same 
plane,  and  mutually  co-adapted  by  minutely  serrated  borders.  The  ser- 


FIG.  450. 


FIG.  451. 


A  B 

CRYSTALLINE  LENS  OF  THE  ADULT,  EXHIBITING  THE  ARRANGEMENT  OF  THE  FIBRES:  magnified. 
A,  viewed  in  front ;  B,  viewed  behind. 

rations  are  due  to  transverse  ridges,  which  are  more  strongly  marked 
on  the  lateral  narrow  sides  of  the  fibres  than  on  the  broad  sides.  The 
fibres  follow  the  curvature  of  the  laminae  from  one  surface  of  the  lens 
to  the  other,  pursuing 
a  sigmoid  course ;  those 
starting  from  the  rays 
near  the  pole  on  one  sur- 
face proceeding  to  the  rays 
near  the  margin  of  the 
lens  on  the  opposite  sur- 
face, and  the  intervening 
fibres  proceeding  to  corre- 
sponding points  between 
the  former.  The  ends  of 
the  lens-fibres  of  contigu- 
ous segments  of  the  lens 
come  into  contact  in  the 
rays  and  are  there  joined 
by  a  homogeneous  cement. 
The  lens-fibres  of  the  pe- 
ripheral laminae  are  broad- 
er, thicker,  and  softer  than 
those  of  the  interior  lami- 
nae, and  possess  a  distinct,  clear,  oval  nucleus,  which  is  indistinct  or 
absent  in  the  latter.  The  nuclei  are  nearer  the  anterior  extremity 


FIBRES  OF  THE  CRYSTALLINE  LENS:  highly  magnified. 
1,  nucleated  fibre  from  the  peripheral  layer  of  the  lens;  2, 
deeper  fibres  most  strongly  serrated  at  the  lateral  borders ; 
3,  transverse  section  of  the  fibres,  exhibiting  their  com- 
pressed hexagonal  columnar  form ;  4,  outline  of  the  epithe- 
lial cells  of  the  fore  part  of  the  lens. 


1  S.  1.  accessoria. 


2  Fibrillffi  lentis. 


884  ORGANS   OF  SPECIAL  SENSE. 

of  the  fibres  and  together  occupy  a  zone *  in  front  of  the  lens  near  its 
margin.  The  superficial  lens-fibres  have  their  posterior  ends  slightly 
enlarged  and  come  into  contact  with  the  lens-capsule,  while  the  ante- 
rior ends  touch  the  contiguous  epithelium.  At  the  margin  of  the  lens 
the  cells  of  the  epithelium  merge  into  the  adjacent  lens-fibres,  which 
gradually  elongate  and  curve  from  before  backward. 

The  lens-substance  is  rendered  hard  and  opaque-white  by  boiling 
water  and  other  agents  which  ordinarily  coagulate  albumen,  but  the 
lens-capsule  retains  its  transparency.  In  strong  alcohol  the  lens  be- 
comes hard  and  opaque-white  on  the  exterior,  but  retains  its  trans- 
parency on  the  interior  and  becomes  still  harder  and  amber-colored. 
In  the  hardened  condition  the  lens-substance  is  readily  broken  into 
its  constituent  laminae  and  fibres. 

In  the  foetus  the  capsule  of  the  lens  is  provided  with  a  capillary 
net  of  blood-vessels/  supplied  by  a  branch  of  the  retinal  artery,  pro- 
ceeding through  the  central  canal  of  the  vitreum  to  the  back  of  the 
lens-capsule,  on  which  it  radiates  in  branches.  At  the  fore  part  of  the 
capsule  the  capillary  net  communicates  with  the  vessels  of  the  iris  at 
the  margin  of  the  pupil,  which  is  then  closed  by  a  pupillary  mem- 
brane. 

The  lens  varies  in  size,  proportions,  and  other  respects,  with  age, 
myopia,  presbyopia,  and  other  conditions.  In  the  foetus  it  is  nearly 
spherical,  of  a  pinkish  hue,  and  less  transparent  than  subsequently. 
At  maturity  it  is  distinctly  less  convex  in  front  than  behind ;  in  old 
age  it  becomes  more  flat,  yellowish,  and  less  transparent.  The  lens  of 
animals  varies  greatly  in  convexity  with  the  character  of  the  medium 
in  which  they  live,  being  spherical  in  fishes  and  of  least  sphericity  in 
birds. 

THE  AQUEOUS   HUMOK. 

The  aqueous  humor,3  the  least  consistent  of  the  transparent 
media  of  the  eye,  is  a  colorless,  slightly-viscid,  serous  liquid,  which 
fills  the  space  between  the  lens  and  cornea,  and  includes  the  iris.  This 
divides  the  space  into  two  portions,  the  anterior  and  posterior  cham- 
bers,4 which  communicate  through  the  pupil.  The  anterior  chamber 
comprises  the  greater  part  of  the  space  bounded  in  front  by  the 
cornea  and  behind  by  the  anterior  surface  of  the  iris  bordered  by 
the  pectinate  ligament.  As  the  iris  in  great  part  lies  close  to  if  not 
in  actual  contact  with  the  lens,  the  posterior  chamber  is  a  mere  fis- 
sure widened  at  the  border,  where  it  receives  the  ends  of  the  ciliary 
processes,  which  dip  into  the  humor. 

The  aqueous  humor  probably  has  its  source  in  the  vascular  plexuses 
of  the  iris  and  ciliary  processes. 


1  Nuclear  zone  of  Mayer.  2  Vasa  capsularia  lenti?. 

3  H.  aqueus.  *  Camera  oculi  anterior  et  posterior. 


ORGANS   OF  SPECIAL   SENSE. 


885 


11 


FIG.    452. —  DIAGRAM     OF   THE  FIG.  452. 

BLOOD-VESSELS  OF  THE  EYE.  a, 
large  anterior,  and  6,  small  poste- 
rior branches  of  a  short  ciliary  ar- 
tery perforating  the  sclerotica;  c, 
a  long  ciliary  artery;  d,  choroid 
capillary  plexus;  e,  branches  of 
the  short  ciliary  artery  to  the  optic 
nerve;/,  anterior  ciliary  artery,  g, 
arterial  circle  of  the  iris  formed 
mainly  by  the  long  ciliary  arteries ; 
ft,  artery  from  the  circle  to  the  iris ; 
i,  arterial  circle  of  the  pupil;  *, 
capillary  zone  of  the  sphincter  of 
the  pupil;  I,  artery  to  the  ciliary 
process ;  m,  artery  to  the  ciliary 
muscle;  n,  branch  from  a  short  cili- 
ary artery  to  the  circle  of  the  iris ; 
o,  conjunctival  artery ;  p,  branch  to 
the  arterial  zone,  q,  at  the  border 
of  the  cornea ;  r,  central  artery  of 
the  retina:  s,  branch  to  the  inner 
sheath  of  the  optic  nerve  ;  t,  branch 
to  the  outer  sheath ;  u,  branch  from 
a  short  ciliary  artery  to  the  sclerot- 
ica ;  v,  branch  to  the  same  from  an 
anterior  ciliary  artery ;  x,  a  choroid 
vein  from  a  vortex  of  the  cho- 
roidea;  y,  posterior  ciliary  vein; 
z,  central  vein  of  the  retina.  1, 
vein  of  the  inner  sheath  of  the 
optic  nerve;  2,  vein  of  the  outer 
sheath ;  3,  vein  and  artery  of  the 
retina ;  4,  sclerotic  vein  joining  the 
choroid  vein ;  5,  anterior  ciliary 
vein ;  6,  junction  of  sclerotic  vein 
with  the  latter;  7,  vein  from  the 
capillary  zone  at  the  border  of  the 
sclerotica  and  cornea;  8,  anterior 
conjunctival  vein ;  9,  posterior 
conjunctival  vein  ;  10,  venous  cir- 
cular ciliary  plexus  (canal  of 
Schlemm);  11,  connection  of  the 
latter  with  an  anterior  ciliary  vein  ; 
12,  vein  from  the  ciliary  muscle 
ending  in  the  circular  ciliary 
plexus ;  13,  vein  of  a  ciliary  pro- 
cess ;  14,  vein  of  the  iris ;  15,  vein 
of  a  ciliary  process  and  muscle 
joining  the  vorticose  veins  of  the 
choroidea. 

THE  BAES. 

The  ear,1  or  organ  of  hearing,2  is  divisible  into  the  external,  the 
middle,  and  the  internal  ear. 

THE   EXTEKNAL   EAR. 

This  includes  the  pinna,  the  portion  of  the  ear  which  projects  from 
the  side  of  the  head,  and  the  auditory  meatus,  which  leads  to  the  middle 
ear  and  is  closed  at  bottom  by  the  tympanic  membrane. 


Auris. 


Organon  auditus. 


886 


ORGANS   OF   SPECIAL   SENSE. 


The  pinna,  or  auricle,1  the  only  outer  or  visible  portion  of  the  ear, 
is  adapted  to  the  reception  and  convergence  of  sounds  to  the  meatus.  It 

is  chiefly  composed  of  a  plate  of 

FIG.  453.  elastic  fibro-cartilage  invested  by 

the  skin,  and  is  movably  appended 
to  the  entrance  of  the  osseous 
meatus.  Mainly  projecting  behind 
the  meatus,  the  surface  directed 
inwardly  is  called  the  back  of  the 
ear.  The  largest  and  deepest  con- 
cave recess  of  its  outer  surface, 
the  concha,  directly  communi- 
cates with  the  meatus,  the  en- 
trance of  which  is  vertically  oval 
and  narrows  inwardly.  About 
two-thirds  of  the  circumference  of 
the  pinna  is  formed  by  the  helix,2 
an  incurved  ridge  which  springs 
from  near  the  centre  of  the  concha, 
thence  passes  up  in  front  and 

around  backward  and  downward. 
> 

Within  the  position  of  the  helix, 
behind  the  concha  is  another  ridge, 
the  antihelix,  which  forks  above 
and  encloses  a  fossa3  bounded  in 
front  by  the  helix.  Between  the  latter  and  the  antihelix  is  a  groove, 
the  fossa  of  the  helix.* 

In  front  of  the  concha  is  a  conical  eminence,  the  tragus,5  bent 
backward  and  usually  covered  with  conspicuous  hairs.  Behind  this, 
separated  from  it  by  a  deep  notch,  at  the  outer  part  of  the  concha  is 
another  eminence,  the  antitragus.  Below  it  is  the  soft,  pendulous 
portion  of  the  pinna,  the  ear-lobe,6  variably  produced  in  different 
individuals. 

The  back 7  of  the  pinna  presents  eminences  and  depressions  the  re- 
verse of  those  on  the  outer  part :  thus  there  are  three  successive  promi- 
nences which  accord  with  the  fossae  of  the  helix,  antihelix,  and  concha. 

The  cartilage  of  the  pinna,8  of  nearly  uniform  thickness,  and 
invested  with  perichondrium.  conforms  to  the  outward  appearance  of 
the  pinna,  of  which  it  forms  the  basis,  but  does  not  enter  into  the 
composition  of  the  ear-lobe,  which  is  a  pouch  of  skin  filled  with  areolar 
tissue  and  fat. 


THE  PINNA.  1,  helix;  2,  fossa  of  the  helix; 
3,  antihelix ;  4,  fossa  of  the  antihelix;  5,  concha 
subdivided  by  the  commencement  of  the  helix ; 
6,  tragus ;  7,  antitragus ;  8,  entrance  of  the  audi- 
tory meatus ;  9,  the  lobe.  The  large  dots  in  the 
concha  and  fossa  of  the  antihelix  are  the  orifices 
of  sebaceous  glands. 


1  Auricula ;  pavilion. 

8  Fossa  triangularis,  innominata,  or  ovalis. 
*  F.  scaphoidea  or  navicularis  ;  scapha. 
6  Lobulus.  i  Dorsum  auriculae. 


2  Capreolus. 

5  Hircus. 

8  Cartilage  auris. 


ORGANS   OF   SPECIAL   SENSE.  887 

From  the  fore  part  of  the  helix  a  conical  process 1  of  the  cartilage 
projects  forward  and  gives  attachment  to  the  preauricular  muscle. 
The  lower  end  of  the  cartilage  of  the  helix  is  separated  by  a -deep 
cleft  from  that  of  the  antihelix  and  tapers  away  into  the  ear-lobe.  The 
portion  of  the  cartilage  contributing  to  form  the  meatus  and  producing 
the  tragus  is  also  separated  by  a  deep  cleft  inwardly  and  behind  from 
that  of  the  concha.  The  contiguous  edges  of  the  clefts  are  united  by 
connective  tissue. 

The  skin  of  the  pinna  adheres  closely  to  the  subjacent  perichon- 
drium,  loosely  behind  the  ear  and  on  the  helix,  but  tightly  on  the 
outer  part,  especially  within  the  fossae.  It  has  the  common  structure, 
but  the  sebaceous  glands  are  more  abundant  than  usual  within  the 
concha  and  the  fossa  of  the  antihelix. 

Of  the  ligaments  of  the  pinna,  there  are  two  which  serve  to  connect 
it  with  the  side  of  the  head.  The  anterior  auricular  ligament  is  a 
strong  fibrous  band  which  extends  from  the  process  at  the  fore  part  of 
the  cartilage  of  the  helix  to  the  root  of  the  zygoma.  The  posterior 
auricular  ligament  is  a  fibrous  band  which  extends  from  the  back 
of  the  concha  to  the  outer  surface  of  the  mastoid  process. 

Besides  the  auricular  muscles  already  described,  page  248,  the 
pinna  is  provided  with  others,  of  which  four  are  situated  on  the  outer 
part  and  another  at  the  back  of  the  ear.  Two  of  the  outer  muscles 
occupy  the  fore  part  of  the  helix,  two  the  outer  part  of  the  tragus  and 
antitragus. 

The  smaller  muscle  of  the  helix 2  is  a  fleshy  slip  lying  on  and 
attached  to  the  cartilage  of  the  helix  where  it  springs  from  the  bottom 
of  the  concha. 

The  larger  muscle  of  the  helix 3  is  a  longer  slip  lying  on  and 
attached  to  the  front  border  of  the  cartilage  of  the  helix. 

•  The  muscle  of  the  tragus  *  is  a  nearly  vertical  slip  lying  on  and 
attached  to  the  outer  surface  of  the  tragus. 

The  muscle  of  the  antitragus 5  extends  obliquely  from  the  outer 
surface  of  the  antitragus  to  the  lower  extremity  of  the  cartilage  of  the 
helix. 

The  transversalis  muscle,6  larger  than  the  others  and  situated 
on  the  back  of  the  ear,  extends  from  the  concha  to  the  ridge  of  the 
helix  across  the  intervening  groove. 

The  muscles  of  the  pinna  are  composed  of  striped  fibres,  but  their 
office  is  obscure.  They  are  probably  rudiments  of  more  important 
ancestral  organs. 

The  auditory  meatus T  extends  from  the  concha  to  the  tympanum, 


1  Spina  helicis ;  procpssus  acutus  helicis. 

2  Musculus  helicis  minor.  s  M.  helicis  major. 
*  M.  tragicus.  8  M.  antitragicus. 

8  M.  transversalis  auriculae.  T  M.  auditorius  externus. 


888 


ORGANS   OF   SPECIAL   SENSE. 


to  which  it  conveys  sounds  from  the  exterior.  With  an  inclination 
from  without  inward  and  forward,  conforming  to  that  of  the  petrosal, 
it  curves  upward  and  then  downward  and  pursues  a  somewhat  sinuous 
course.  From  an  inch  to  an  inch  and  a  quarter  long,  it  is  narrowest 
about  the  middle,  is  oval  in  cross-section,  widest  vertically  at  the  outer 
part  and  widest  fore  and  aft  at  the  inner  extremity.  The  bottom  is 
closed  by  the  tympanic  membrane,  which  is  obliquely  inclined  from 
above  downward  and  inward,  at  an  angle  of  about  fifty  degrees  to 
the  axis  of  the  meatus  and  at  about  one-half  that  angle  to  the  inner 

FIG.  454. 


GENERAL  VIEW  OF  THE  EAR,  RIGHT  SIDE,  LAID  OPEN  FROM  THE  FRONT.  1,  pinna ;  2,  concha;  3, 
4,  auditory  meatus ;  5,  ceruminous  glands ;  6,  tympanic  membrane ;  7,  incus ;  8,  malleus ;  9,  its 
handle  inserted  into  the  tympanic  membrane ;  10,  tympanic  tensor  muscle ;  11,  cavity  of  the  tym- 
panum; 12,  eustachian  tube;  13, 14, 15,  the  three  semicircular  canals;  16,  cochlea  ;  17,  the  internal 
auditory  meatus ;  18,  facial  nerve ;  19,  superficial  petrosal  nerve  to  the  geniculate  ganglion ;  20, 
21,  auditory  nerve. 

extremity  of  the  floor.  The  meatus  consists  of  an  outer  portion  ex- 
tending from  the  pinna  and  an  inner  osseous  portion,  both  lined  by  a 
prolongation  of  the  skin. 

The  cartilage  of  the  meatus  is  a  wide  curved  plate  occupying  the 
outer  fore  part  of  the  passage  and  continuous  by  a  strip  with  the  rest 
of  the  pinna.  In  front,  the  plate  is  quadrate  in  outline ;  its  outer  bor- 
der forms  the  prominence  of  the  tragus.  Beneath,  it  forms  a  triangle 
with  the  apex  directed  inward  and  occupies  the  space  between  the 
mastoid  and  postglenoid  processes.  Its  inner  border  is  attached  by 
connective  tissue  to  the  auditory  process.  The  wide  interval  of  the 
plate  behind  the  meatus  is  completed  by  a  layer  of  connective  tissue, 
which  is  attached  to  the  upper  and  back  border  of  the  osseous  meatus 
and  outwardly  to  the  border  of  the  cartilage  of  the  concha.  The  plate 


ORGANS   OF  SPECIAL   SENSE. 


889 


has  two  or  three  elliptical  fissures1  which  are  closed  by  connective 
tissue. 

The  osseous  portion  of  the  meatus,  a  little  longer  and  narrower 
than  the  outer  portion,  is  formed  above  by  the  auditory  plate  of  the 
squamosal  and  below  by  the  tympanic  plate.  The  auditory  plate 
extends  inwardly  to  the  tympanum,  where  it  terminates  in  an  acute 

FIG.  465. 


SECTION  THROUGH  THE  SKIN  OF  THE  AUDITORY  MEATUS  :  magnified  twenty  diameters,  a, 
dermis;  6,  c,  rete  and  cuticle  of  the  epidermis;  d,  ceruminous  glands;  e,  their  ducts ;  /,  outlet  of 
ducts ;  g,  hair- follicles ;  h,  sebaceous  glands ;  i ,  masses  of  fat. 

margin.  The  tympanic  plate  is  involute,  so  as  to  form  the  floor  and  sides 
of  the  meatus,  at  the  inner  end  of  which  it  is  grooved  for  the  insertion 
of  the  tympanic  membrane. 

The  skin  of  the  meatus  is  continuous  with  that  of  the  pinna,  and 
in  the  outer  portion  of  the  passage,  in  most  respects,  is  like  it.  In  the 
inner  portion  of  the  meatus  it  is  very  thin,  tightly  adheres  to  the  sub- 
jacent periosteum,  and  is  extended  over  the  tympanic  membrane,  of 
which  it  forms  the  external  layer.  In  the  outer  portion  of  the  meatus 
it  closely  adheres  to  the  subjacent  structures  and  is  furnished  with 

1  Incisura  Santorini. 


890  ORGANS  OF  SPECIAL  SENSE. 

numerous  hairs  and  sebaceous  glands,  which  diminish  at  the  com- 
mencement and  altogether  disappear  in  the  inner  portion  of  the  pas- 
sage. In  the  subcutaneous  tissue  of  the  outer  portion  of  the  meatus 
are  numerous  brownish-yellow,  spheroidal  bodies,  the  ceruminous 
glands,1  which  secrete  the  cerumen,  or  ear-wax.  They  resemble  in 
structure  the  sweat-glands,  but  are  larger.  Their  ducts  open  on  the 
surface,  in  the  interval  of  the  hairs,  and  are  quite  obvious  after  the 
detachment  of  the  cuticle.  The  glands  are  absent  in  the  osseous  portion 
of  the  meatus  except  along  the  roof. 

The  cerumen,  or  ear-wax,  is  a  milky,  oleaginous  liquid,  which 
lubricates  the  auditory  meatus.  In  the  inspissated  condition  it  assumes 
the  appearance  of  a  brown  pasty  substance,  with  peculiar  smell  and 
bitter  taste.  It  consists  of  an  oil,  with  albuminoid  and  a  little  ex- 
tractive matter. 

THE   MIDDLE   EAR. 

The  middle  ear  consists  of  the  tympanum,  with  the  ear  ossicles,  the 
mastoid  cells,  and  the  eustachian  tube.  " 

THE   TYMPANUM. 

The  tympanum,2  or  ear-drum,  is  an  air-chamber  in  the  temporal 
bone  between  the  auditory  meatus  and  the  labyrinth,  communicating 
with  the  exterior  air  indirectly  through  the  eustachian  tube,  which 
opens  into  the  pharynx.  Within  the  tympanum  is  a  series  of  little  bones, 
the  ear  ossicles,  which  are  movably  articulated  with  one  another  and 
extend  between  the  tympanic  membrane  and  the  oval  window  of  the 
labyrinth. 

The  tympanum  may  be  conveniently  divided  into  three  portions, 
the  atrium,  the  attic,  and  the  antrum. 

The  atrium  of  the  tympanum  is  the  portion  visible  in  the  prepared 
temporal  bone  at  the  bottom  of  the  auditory  meatus.  In  the  ordinary 
condition  it  is  closed  outwardly  by  the  tympanic  membrane.  It  is 
a  biconcave  discoidal  cavity  of  little  greater  breadth  than  that  mem- 
brane, is  about  a  line  in  depth  centrally  from  without  inwardly,  in- 
creasing: to  about  two  lines  towards  the  borders.  Its  inner  wall  is 

O 

formed  by  the  labyrinth  ;  above,  it  is  continuous  with  the  attic  and  at 
the  fore  part  is  prolonged  into  the  eustachian  tube. 

In  the  prepared  temporal  bone  the  attic  exhibits  the  following 
important  parts.  Outwardly  is  the  tympanic  orifice,  an  obliquely 
oval  ring,  into  which  the  tympanic  membrane  is  inserted,  closing  the 
auditory  meatus  from  the  tympanum.  The  lower  part  and  sides 
of  the  orifice  are  formed  by  the  tympanic  margin  of  the  tympanic 
plate,  which  is  grooved  for  the  reception  of  the  tympanic  membrane 
and  ends  above  in  a  pair  of  slightly  projecting  points.3  The  interval 

1  Glandulse  ceruminosae.  2  Cavitas  tympani ;  c.  antrorsa  auris. 

3  Spina  tympanica  major  and  minor. 


ORGANS   OP   SPECIAL   SENSE. 


891 


FIG.  456. 


of  these  points,  the  tympanic  notch,1  is  completed  by  the  sharp  tym- 
panic margin  of  the  auditory  plate  of  the  squamosal. 

On  the  inner  wall  of  the  atrium,  opposite  the  tympanic  orifice,  is 
the  promontory/  a  conspicuous 
convex  eminence,  produced  by  the 
outward  projection  of  the  cochlea. 
Its  surface  is  marked  by  a  branch- 
ing groove,  which  ascends  from 
a  fine  canal  in  the  floor  of  the 
atrium  and  accommodates  the  tym- 
panic branch  of  the  glosso-pharyn- 
geal  nerve.  Behind  the  promon- 
tory is  a  niche  looking  outward 
and  backward,  having  within  it 
the  round  window,3  which  com- 
municates with  the  cochlea,  in  the 
recent  condition  closed  by  the  en- 
totympanic  membrane. 

Above  the  promontory  is  a  re- 
cess, in  which  is  the  oval  win- 
dow,4 a  larger  aperture  than  the 
former,  communicating  with  the 
vestibule.  The  window  looks  out- 
ward and  is  half  oval  with  the  con- 
vex border  upward.  In  the  com- 
plete condition  of  the  ear  it  is 
closed  by  the  base  of  the  stapes. 

In  advance  of  the  promontory  is  the  tympanic  tensor  recepta- 
cle,5 a  cylindrical  tube,  about  half  an  inch  long,  which  extends  from 
in  front  of  the  oval  window  obliquely  downward  and  inward  above 
the  eustachian  tube.  Its  upper,  posterior  end 6  is  narrowed,  curves  out- 
wardly, and  projects  into  the  atrium,  into  which  it  opens.  Its  lower, 
anterior  end  opens  beneath  the  end  of  the  tympanic  tegmen,  above  the 
lower  orifice  of  the  osseous  portion  of  the  eustachian  tube.  Commonly, 
in  the  prepared  bone,  the  receptacle  is  incomplete  along  its  outer  part, 
when  it  appears  as  an  open  scroll-like  shelf,7  which  in  the  recent  state 
is  completed  by  fibrous  membrane. 

The  receptacle  encloses  the  tympanic  tensor  muscle. 

The   posterior  wall  of  the  atrium  is  uneven.      It  encloses  the 

1  Notch  of  Kivini.  2  Promontorium  ;  tuber  cochleae. 

3  Fenestra  rotunda,  cochleae,  or  triquetra ;  foramen  rotundum  or  posterius  ;  porta 
labyrinthi. 

*  Fenestra  ovalis,  semi-ovalis,  or  vestibuli ;  foramen  ovale. 

5  Canalis  tensoris  tympani.  6  Kostrum  cochleare. 

7  Semi-canalis  tensoris  tympani ;  sulcus  muscularis  tympani ;  processus  cochleari- 
formis. 


SECTION  ACROSS  THE  PYRAMID  OP  THE  LEFT 
TEMPORAL  BONE,  giving  a  view  of  the  outer 
boundary  of  the  tympanic  cavity.  1,  tympanic 
orifice  of  the  atrium,  with  groove  for  the  tym- 
panic membrane;  2,  tympanic  scute  forming 
the  outer  wall  of  the  attic ;  3,  tympanic  tegmen ; 
4,  petro-squamosal  fissure ;  5,  supra-promontory, 
with  orifices  above,  of  the  inferior  semicircular 
canal  and  below  of  the  facial  canal ;  6,  pyra- 
mid ;  7,  orifice  of  entrance  of  the  tympanic 
branch  of  the  facial  nerve ;  8,  glenoid  canal, 
the  exit  of  the  same  branch ;  9,  antrum  and 
mastoid  cells. 


892 


ORGANS  OF   SPECIAL   SENSE. 


descending  portion  of  the  facial  canal  and  the  stapedial  receptacle, 
which  is  situated  in  advance  of  the  canal  and  is  about  a  third  of  an 
inch  long.  Its  upper  end  is  narrowed,  curves  forward,  and  projects 
into  the  atrium  as  a  little  conical  process,  the  pyramid,1  from  the  end 
of  which  the  receptacle  opens  into  the  atrium.  The  pyramid  is  con- 
nected with  the  adjacent  wall  of  the  atrium  by  several  diverging  ridges, 
of  which  one  commonly  appears  as  a  little  bar  extending  to  the  prom- 

FIG.  457. 


CAVITY  OF  THE  TYMPANUM  ;  exposed  by  removing  part  of  the  bone,  right  side.  The  atrium 
opposite  the  auditory  meatus,  1,  promontory ;  2,  pyramid ;  3,  bar  connecting  it  with  the  prom- 
ontory ;  4,  round  window ;  5,  oval  window ;  6,  eustachian  tube ;  7,  surface  of  attachment  of  the 
cartilage  of  the  tube ;  8,  receptacle  of  the  tympanic  tensor  muscle ;  9,  facial  canal,  laid  open ;  10, 
canal  for  the  superficial  petrosal  nerve;  11,  antrum  and  mastoid  cells;  12,  supra-prornontory  on 
the  inner  wall  of  the  attic ;  13,  entrance  of  the  tympanic  branch  of  the  facial  nerve. 

ontory.  Around  its  base  are  several  fossse.  The  stapedial  receptacle 
communicates  with  the  facial  canal  by  an  aperture  for  the  passage  of 
the  vessels  and  nerve  of  the  stapedial  muscle,  and  often  by  a  larger 
opening  which  is  closed  by  fibrous  membrane. 

Close  to  the  tympanic  orifice,  in  the  posterior  wall  of  the  atrium,  a 
fine  canal,2  ascending  from  the  lower  part  of  the  facial  canal,  opens 
into  the  atrium  and  transmits  the  tympanic  branch  of  the  facial  nerve. 

The  anterior  part  of  the  atrium  above  is  prolonged  obliquely 
downward,  forward,  and  inward  as  the  upper  division  or  osseous  por- 
tion of  the  eustachian  tube.  Above  the  communication  of  the  tube, 
just  within  the  anterior  margin  of  the  tympanic  orifice,  is  the  glenoid 


1  Pyramis  ;  eminentia  pyramidalis  or  papillaris. 


2  Canalis  chordae. 


ORGANS   OP   SPECIAL   SENSE.  893 

canal,1  a  short  passage  which  descends  through  the  glenoid  fissure.  It 
receives  the  long  process  of  the  malleus  and  gives  exit  to  the  tympanic 
branch  of  the  facial  nerve. 

The  floor  of  the  atrium  is  a  wide  semicircular  groove,  extending 
between  the  posterior  wall  and  fore  part  of  the  atrium,  uneven  and 
cellular. 

The  attic  *  of  the  tympanum  is  a  pyramidal  cavity  above  the  atrium, 
with  which  it  communicates  by  a  horizontal,  fore  and  aft  oval  aperture. 
It  opens  upward,  backward,  and  outward  into  the  antrum.  In  front 
it  is  bounded  by  the  tympanic  tegmen,  which  forms  for  it  and  the 
antrum  a  continuous  sloping  roof.  Outwardly  it  is  bounded  by  the 
tympanic  scute,  a  broad  crescentic  plate  ascending  from  the  auditory 
plate  of  the  squamosal,  separating  the  attic  from  the  outer  mastoid  cells. 
The  lower  concave  edge  of  the  scute  corresponds  with  the  tympanic 
margin  of  the  auditory  plate  and  forms  the  tympanic  notch  at  the  top 
of  the  tympanic  orifice.  Inwardly  the  attic  is  bounded  by  the  supra- 
promontory,3  which  overhangs  the  promontory  of  the  atrium  and  is 
a  conspicuous  convex  eminence  produced  by  the  course  of  the  facial 
canal  over  the  oval  window  and  the  inferior  semicircular  canal  above. 

The  antrum,4  the  highest  portion  of  the  tympanum,  is  a  variable- 
sized,  pouch-like  cavity  prolonged  from  the  attic  upward,  backward, 
and  outward  in  the  commencement  of  the  mastoid  cells,  by  which 
it  is  surrounded.  It  is  more  or  less  irregularly  extended  downward 
among  the  cells  of  the  mastoid  process.  Frequently  a  smaller  pas- 
sage  is  directed  outward  and  upward  among  the  cells  of  the  squamosal 
over  the  position  of  the  auditory  meatus. 

While  the  atrium  varies  little  in  size  in  different  individuals,  the 
attic  and  antrum  vary  greatly  in  capacity,  ranging  from  one  to  six 
times. 

The  mastoid  cells5  mainly  occupy  the  interior  of  the  mastoid 
portion  of  the  temporal  bone,  especially  the  mastoid  process,  but  also 
extend  into  the  contiguous  portion  of  the  squamosal  above  the  auditory 
meatus  and  on  the  under  side  of  the  tympanic  tegmen.  In  the  pre- 
pared bone  they  resemble  the  ordinary  spongy  substance,  but  are  of 
relatively  greater  capacity  and  are  differentiated,  from  that  substance 
in  other  parts  of  the  temporal  bone,  as  air-cavities,  communicating 
with  one  another  and  with  the  antrum.  "With  the  advance  of  asre  the 

O 

number  of  cells  appears  to  diminish  through  coalescence,  and  thus 
they  acquire  increased  capacity.  Ordinarily  the  largest  cells  occupy 
the  mastoid  process.  In  old  age  some  of  them  occasionally  even  exceed 
in  size  the  antrum  into  which  they  open. 

1  Canal  of  Huguier.  2  Recessus  epitympanicus. 

8  Suprapromontorium  ;  canal  petro-mastoidien,  of  Sappey. 

4  Antrum  mastoideum  ;  aditus  ad  cellulus. 

5  Cellulae  mastoideae ;  mastoid  sinuses. 


894  ORGANS   OF   SPECIAL  SENSE. 

THE   TYMPANIC   MEMBRANE. 

The  tympanic  membrane  *  closes  the  cavity  of  the  tympanum  at 
the  bottom  of  the  auditory  meatus.  It  is  variably  oval  to  nearly  cir- 
cular and  is  about  five  Hues  in  diameter.  It  is  inserted  obliquely,  at  an 
angle  of  about  fifty  degrees,  into  the  tympanic  orifice  of  the  meatus, 
into  which  its  external  face  is  directed  with  a  downward  inclination. 
Externally  it  is  centrally  depressed  in  a  shallow  funnel-like  manner,  and 
is  conformably  prominent  internally. 

The  handle  of  the  malleus  is  inserted  into  the  tympanic  membrane, 
descending  between  its  middle  and  internal  layers  to  the  centre.  The 
short  process  of  the  malleus  directed  outward  produces  a  corresponding 
prominence  of  the  membrane,  a  little  below  its  upper  border. 

The  tympanic  membrane  is  thin^translucent  grayish,  and  composed 
of  three  layers,  of  which  the  middle  layer  especially  pertains  to  it, 
while  the  external  layer 2  is  an  extension  of  the  skin  of  the  auditory 
meatus,  and  the  internal  layer3  a  continuation  of  the  lining  mucous 
membrane  of  the  tympanum. 

The  middle  layer4  of  the  tympanic  membrane  is  for  the  most  part 
composed  of  two  strata  of  fibro-connective-tissue  bundles.  In  the  outer, 
thicker  stratum  the  bundles  radiate  from  the  insertion  of  the  handle  of 
the  malleus  to  the  circumference  of  the  membrane.  The  inner  stratum 
consists  of  circular  fibres  which  are  most  abundant  at  the  circumference, 
where  they  form  an  annular  ligament,5  occupying  the  groove  in  the  tym- 
panic margin  of  the  tympanic  plate  and  continuous  with  the  adjacent 
periosteum.  In  the  tympanic  notch,  a  triangular  segment  of  the  middle 
layer  of  the  tympanic  membrane,  between  the  short  process  of  the  mal- 
leus and  the  tympanic  margin  of  the  auditory  plate,  is  formed  by  a 
looser  texture  of  connective  tissue.6 

The  entotympanic  membrane T  closes  the  round  window  of  the 
labyrinth  and  separates  the  tympanic  passage  of  the  cochlea  from 
the  cavity  of  the  tympanum.  Like  the  tympanic  membrane,  it  is  com- 
posed of  a  middle  fibro-connective-tissue  layer  in  conjunction  with  the 
lining  membranes  of  the  adjacent  cavities. 

THE   EUSTACHIAN   TUBE. 

The  eustachian  tube 8  is  a  passage  through  which  the  tympanum 
communicates  with  the  pharynx.  It  commences  in  the  tympanum  im- 

1  Membrana  tympani ;  septum  membranaceum  auris  ;  ear-drum. 

2  Stratum  cutaneum  or  externum  ;  cuticula  membranse  tympani ;  dermoid  layer. 

3  Stratum  tympanicum  or  internum  ;  lamina  nmcosa. 

4  Lamina  fibrosa  or  propria.  5  Annulus  cartilagineus. 

6  Membrana  flaccida  ;  Rivinian  segment. 

7  Secondary  membrane  of  the  tympanum ;  membrana  tympani  secundaria. 

8  Tuba  Eustachii  or  acustica ;  salpinx  ;  canalis  gutturalis  or  palatinus  tympani ; 
ear-trumpet. 


ORGANS   OF   SPECIAL  SENSE.  895 

mediately  in  advance  of  the  tympanic  membrane  and  descends  obliquely 
forward,  inward,  and  downward  to  open  at  the  side  of  the  pharynx, 
about  half  an  inch  behind  the  lower  turbinal  of  the  nose.  It  is 
trumpet-shaped,  about  an  inch  and  a  quarter  or  more  in  length,  and  is 
widest  at  the  inner  extremity.  It  consists  of  an  upper  or  outer  osseous 
portion  and  a  lower  or  inner  cartilaginous  and  partly  fibrous  portion, 
and  is  lined  throughout  by  mucous  membrane  continuous  with  that  of 
the  tympanum  and  pharynx. 

The  osseous  portion,  about  one-third  of  the  tube,  more  open  than 
the  rest,  is  trilateral  cylindi'oid,  widest  at  the  commencement,  narrow- 
ing rapidly  at  first,  then  more  gradually  to  the  inner  end  at  the  notch 
between  the  pyramid  and  squamosal  of  the  temporal  bone. 

The  inner  portion  of  the  tube  is  laterally  compressed  conical  and 
gradually  widens  from  the  osseous  portion  to  the  pharyngeal  orifice, 
which  is  obliquely  oval.  In  cross-section  its  passage  appears  as  a 
vertical  and  narrow  elliptical  fissure,  widened  at  the  upper  extremity l 
and  expanding  at  the  pharyngeal  orifice.  The  cartilage  is  a  thick, 
elongated,  triangular  plate,  bent  scroll-like,  situated  along  the  upper 
and  inner  part  of  the  tube.  Its  anterior  thinner  border  is  bent  out- 
ward and  backward  on  itself;  the  posterior  border  at  the  lower  ex- 
tremity is  in  a  less  degree  bent  outward  and  forward.  The  interval 
of  the  two  borders  of  the  cartilage,  below  and  outward,  is  occupied  by 
a  connective-tissue  layer,  which  completes  the  tube  in  this  position. 
The  border  of  the  cartilage  at  the  pharyngeal  orifice  is  thick  and  ob- 
tusely rounded  and  forms  a  prominent  arch  above  the  opening.  The 
cartilage  is  attached  above  to  the  dense  connective  tissue  occupying 
the  groove  between  the  temporal  pyramid  and  the  sphenoidal  angular 
process ;  at  its  inner  extremity  it  is  attached  to  the  inner  side  of  the 
root  of  the  internal  pterygoid  process.  In  contact  with  it  outward 
and  behind  and  partially  giving  origin  to  it  is  the  palatal  elevator 
muscle,  and  in  advance  of  this  is  the  palatal  tensor,  an  offset  of  which 
is  connected  with  the  anterior  border  of  the  cartilage. 

THE   EAK  OSSICLES. 

Three  little  bones,  the  ear  ossicles,2  are  contained  within  the  tym- 
panum, articulated  in  a  chain  between  the  tympanic  membrane  and 
the  oval  window  of  the  labyrinth,  so  as  to  transmit  the  vibrations  of 
sound  from  the  membrane  to  the  labyrinth.  In  the  order  of  their  suc- 
cession from  without  inward  they  are  the  malleus,  incus,  and  stapes. 

The  malleus,3  the  anterior  and  largest  of  the  ossicles,  is  a  bent 
club-shaped  bone,  placed  vertically  with  the  head  uppermost  and  with 
a  process,  as  long  or  longer  than  the  handle,  directed  at  a  right  angle 

1  Safety-tube  of  Ktidinger. 

2  Ossicula  auditus  or  auriura.  8  Hammer;  mallet. 


896 


ORGANS   OF  SPECIAL   SENSE. 


forward  from  the  middle.     The  head,1  nearly  half  the  length  of  the 
bone,  is  irregularly  ovoid,  thickest  and  rounded  at  the  upper  extremity. 

Crossing  it  obliquely  behind  from 

FIG.  458.  above  downward   and    inward    is 

an  elliptical,  slightly  prominent 
articular  plate,  bent  and  slightly 
narrowed  at  the  middle,  convex 
in  the  long  and  concave  in  the 
short  diameter.  In  the  fresh  state 
the  plate  is  covered  by  cartilage 
and  articulates  with  the  incus. 

Below  the  head  is  the  short 
neck,2  compressed  from  without 
inward,  and  giving  off  from  its 
fore  part  the  long  process.3  This 
is  a  slender  spicule,  which  extends 
forward  wUh  an  outward  curve 
and  is  received  within  the  glenoid 
canal.  It  is  flattened,  often  ex- 
panded towards  the  end,  where  it 
tapers  to  a  point.  Well  produced 
at  birth,  commonly  with  the  ad- 
vance of  life  it  undergoes  retro- 
grade metamorphosis  and  becomes 

fibrous  and  continuous  with  the  anterior  ligament  of  the  malleus.     It 
is  the  upper  remaining  extremity  of  the  cartilage  of  Meckel. 

The  handle  *  of  the  malleus  makes  a  sigmoid  twist  with  the  neck 
and  in  its  descent  is  bent  inward.  It  is  flattened  triangular,  viewed 
in  front  or  behind,  is  rounded  and  tapering  below,  and  terminates  in 
a  rounded  end.  Its  base  projects  outward  in  a  little  cone,  the  short 
process5  of  the  malleus,  which  produces  a  corresponding  prominence 
of  the  tympanic  membrane. 

The  incus,6  broader  but  shorter  than  the  malleus,  is  situated  behind 
and  internal  to  it.  It  is  a  flattened  quadrate  bone  extending .  behind 
in  two  tapering  and  somewhat  divergent  processes,  and  with  its  broad 
surfaces  directed  outward  and  inward.  It  is  thickest  in  front,  where 
it  presents  an  articular  plate  conformable  to  that  of  the  malleus ;  ob- 
liquely elliptical,  narrowed  at  the  middle,  concave  in  the  long  and  con- 
vex in  the  short  diameter.  The  superior  process,7  directed  backward 
and  downward  from  the  body,  is  flattened  triangular  viewed  from  with- 


EAK  OSSICLES.  1.  Malleus  seen  on  its  inoer 
surface,  a,  head ;  b,  articular  surface  for  tSe 
incus ;  c,  handle ;  d,  the  long  process.  2.  Malleus 
seen  on  its  outer  surface,  o,  head;  b,  articular 
surface;  c,  handle;  d,  long  process;  e,  short 
process.  3,  Malleus  seen  from  behind,  a,  head 
and  articular  facet ;  b,  short  process ;  c,  long 
process.  4.  Incus  seen  on  its  inner  surface,  a, 
body ;  b,  articular  facet  for  the  malleus ;  c,  supe- 
rior process ;  d,  inferior  process ;  e,  lenticular 
process.  5.  Incus  seen  on  its  outer  surface,  a, 
body ;  6,  articular  facet ;  c,  d,  superior  and  in- 
ferior processes.  6.  Lenticular  process,  at  birth 
a  distinct  bone.  7.  Stapes,  a,  head ;  b,  c,  crura ; 
d,  base.  8.  Base  of  the  stapes,  which  is  applied 
to  the  oval  window.  9,  Stapes  cut  so  as  to  ex- 
hibit the  groove  on  the  inner  side  of  its  crura,  a. 


1  Capitulum.  z  Cervix  ;  collum. 

8  Processus  longus,  gracilis,  tenuis,  anterior,  or  tertius. 

*  Manubrium  ;  processus  inferior  or  primus  ;  pedunculus  ;  cauda. 

6  Processus  brevis,  externus,  conoideus,  or  secundus  ;  tuberculum  mallei. 

6  Anvil.         7  Short  process  ;  processus  brevis,  superior,  posterior,  or  transversus. 


OEGANS   OF  SPECIAL   SENSE.  897 

out  or  within.  The  inferior  process,1  slightly  longer  than  the  superior, 
diverges  from  it,  descending  into  the  atrium.  It  is  more  abruptly  taper- 
ing into  an  elongated  cone,  slightly  bent  inward  at  the  point,  to  which 
is  attached  the  lenticular  process.*  This  is  a  minute  button-like  disk 
connected  by  a  narrow  pedicle  with  the  incus,  tipped  with  cartilage  in 
the  recent  state  and  articulating  with  the  stapes.  In  infancy  the  process 
is  a  separate  ossicle,3  but  it  quickly  ankyloses  with  the  incus. 

The  stapes,4  the  smallest  and  innermost  of  the  ossicles,  resembles 
in  shape  a  stirrup.  The  head 5  is  a  short,  flattened  cylindrical  process 
ending  in  a  transverse  oval  discoid  surface  which  articulates  with  the 
lenticular  process  of  the  incus.  From  the  head  extend  the  arching 
crura  to  join  the  base  of  the  bone.  They  are  inwardly  grooved,  and 
with  the  base  include  an  arch-like  aperture,  which  is  closed  in  the  fresh 
condition  by  a  drum-like  membrane 6  invested  with  the  mucous  mem- 
brane enveloping  the  bone.  The  anterior  crus7  is  slightly  shorter 
and  less  curved  than  the  posterior  crus.8  The  base9  of  the  stapes  is 
a  half-oval  or  slightly-reniform  plate  which  conforms  to  the  oval  window 
it  occupies. 

ARTICULATION  AND   CONNECTION   OF   THE   EAR   OSSICLES. 

The  ear  ossicles  are  movably  articulated  with  one  another  by 
synovial-lined  joints,  and  are  connected  with  the  adjacent  parts  of  the 
tympanum  by  ligaments  and  folds  of  the  lining  mucous  membrane. 

The  head  of  the  malleus  and  the  greater  part  of  the  incus  occupy 
the  outer  side  of  the  attic,  the  former  in  front  and  articulated  behind 
with  the  latter.  The  handle  of  the  malleus  and  the  inferior  process  of 
the  incus  descend  into  the  atrium  nearly  parallel  with  each  other,  the 
former  a  little  in  advance  and  external  to  the  latter.  The  stapes  is 
situated  in  the  atrium  at  its  inner  part  just  above  and  behind  the  centre, 
directed  from  the  end  of  the  inferior  process  of  the  incus  horizontally 
inward  to  the  oval  window,  which  it  closes. 

The  handle  of  the  malleus  is  inserted  into  the  tympanic  membrane, 
descending  between  the  internal  and  middle  layers  to  about  the  centre ; 
its  short  process  is  directed  outwardly  and  produces  a  slight  projection 
of  the  membrane  a  little  below  the  upper  border. 

The  base  of  the  stapes,  on  its  inner  or  vestibular  surface,  is  invested 
with  cartilage,  as  is  likewise  the  case  with  the  border  of  the  oval 


1  Long  process ;  p.  longum,  inferior,  or  anterior. 

2  Processus  lenticularis  ;  lenticulus  ;  epiphysis  incudis. 

3  Os  lenticulare,  orbiculare,  or  subrotundum ;"  ossiculum  ovale,  semilunare,  or- 
.biculare,  or  Sylvii. 

4  Stapha ;  deltoidea  ;  stirrup.  5  Capitulum. 

6  Membrana  obturatoria  stapedis  ;  ligamentum  obturatorium  stapedis. 

7  Crus  anterius  or  rectilineum. 

8  C.  posterius  or  curvilineum.  9  Basis. 

57 


898  ORGANS   OF   SPECIAL  SENSE. 

window  of  the  vestibule,  into  which  the  base  of  the  stapes  is  fitted  and 
united  by  a  fibro-elastic  annular  ligament. 

The  articulation  between  the  head  of  the  malleus  and  the  body  of 
the  incus  is  hinge-like.  The  opposed  surfaces  are  covered  with  cartilage, 
and  the  joint  is  enclosed  by  a  capsular  ligament  lined  with  synovia! 
membrane. 

The  articulation  between  the  head  of  the  stapes  and  the  lenticular 
process  of  the  incus  is  provided  with  a  capsular  ligament  usually  lined 
by  a  synovial  membrane,  though  sometimes  the  cavity  is  absent. 

The  malleus  is  attached  to  the  adjacent  parts  of  the  tympanic  wall 
by  three  ligaments.  The  anterior  ligament1  is  a  comparatively 
strong  fasciculus  extending  from  the  root  of  the  long  process  of  the 
malleus  and  attaching  it  to  the  fore  part  of  the  tympanum  and  the 
sides  of  the  glenoid  canal.  The  anterior  ligament  has  been  regarded 
as  a  muscle.2  The  external  ligament 3  is  a  thin  band  extending  from 
the  short  process  to  the  contiguous  portion  of  the  tympanic  scute. 
The  suspensory  ligament  *  is  a  slender  cord  attaching  the  head  of 
the  malleus  to  the  roof  of  the  attic. 

The  ligaments  of  the  incus 5  usually  consist  of  a  pair  of  little 
fibrous  bundles  which  diverge  from  the  end  of  the  posterior  process  to 
the  adjacent  back  part  of  the  attic  just  below  the  entrance  of  the 
antrum.6 

MUSCLES  OP   THE   TYMPANUM. 

The  tympanic  tensor7  is  a  fusiform  muscle  which  occupies  the 
corresponding  receptacle,  arising  from  its  lower  part,  from  the  contigu- 
ous portion  of  the  cartilage  of  the  eustachian  tube  and  the  sphenoid 
bone.  It  terminates  in  a  rounded  tendon  which  curves  outward  from 
the  upper  projecting  end  of  the  receptacle  and  is  inserted  to  the  inner 
side  of  the  root  of  the  handle  of  the  malleus  opposite  its  short  process. 

The  stapedial  muscle,8  like  the  former,  lodged  within  its  osseous 
receptacle,  arises  from  its  bottom  part.  It  ends  in  a  rounded  tendon 
which  turns  forward,  issues  from  the  pyramid,  and  is  inserted  into  the 
back  part  of  the  head  of  the  stapes. 

Both  muscles  within  their  osseous  receptacles  are  invested  with  a 
fibrous  sheath,  within  which  they  freely  move. 

The  tympanic  tensor  draws  the  malleus  inward,  and  thus  renders. 

1  Ligamentum  mallei  anterius. 

2  Musculus  laxator  tympani  major.  3  Lig.  mallei  externus. 
*  L.  m.  superius  ;  1.  suspensorium  mallei. 

5  Lig.  incudis  posterius ;  ligamenta  processus  brevis  incudis. 

6  Henle  describes  this  connection  as  a  synovial-lined  articulation  and  represents 
it  with  a  single  fibrous  ligament,  Fig.  570,  p.  743.     Quain's  Anatomy  represents  the 
ligament  as  consisting  of  three  divergent  bundles,  Fig.  381,  p.  442,  9th  ed.,  1882. 

7  Musculus  tensor  tympani ;  m.  mallei  internus  ;  rotator  mallei. 

8  M.  stapedius  ;  m.  pyramido-stapedius  ;  m.  auris  membranarum  laxator. 


ORGANS   OF  SPECIAL   SENSE.  899 

the  tympanic  membrane  more  tense.  From  the  connection  of  the 
malleus  with  the  other  ossicles  pressure  would  be  comntunicated  to 
the  oval  window.  The  stapedial  muscle  from  the  direction  of  its 
action  would  in  a  measure  antagonize  the  former  muscle. 

THE   LINING  MUCOUS   MEMBRANE   OF  THE   TYMPANUM. 

The  tympanum  is  lined  throughout  by  a  thin,  pale-red  mucous 
membrane,  which  also  invests  the  ear  ossicles  and  is  continuous  with 
that  of  the  eustachian  tube  and  mastoid  cells.  In  several  positions  it 
forms  more  or  less  conspicuous  folds. 

The  suspensory  fold  proceeds  from  the  suspensory  ligament  of 
the  malleus  forward  between  its  head  and  the  tympanic  tegmen  and  is 
continuous  with  the  falcate  and  circular  folds. 

The  falcate  fold  extends  from  the  suspensory  backward  between 
the  malleus  and  incus  inwardly  and  the  lower  border  of  the  tympanic 
scute  outwardly.  It  forms  a  nearly  horizontal  septum  and  cuts  off  the 
communication  between  the  attic  and  atrium  in  the  interval  of  the 
ossicles  and  the  tympanic  scute ;  but  is  sometimes  perforated. 

The  circular  fold  is  stretched  between  the  head  of  the  malleus,  its 
long  process,  the  receptacle  and  tendon  of  the  tympanic  tensor.  It 
also  closes  the  fore  part  of  the  attic  from  the  atrium,  but  is  sometimes 
perforated,  when  it  appears  as  an  annular  fold. 

In  the  complete  state  of  the  tympanum  the  attic  communicates 
with  the  atrium  by  a  horizontal  fore  and  aft  reniform  aperture,  about 
two  and  a  half  lines  long  and  scarcely  a  line  wide,  between  the  ossicles 
and  the  suprapromontory. 

The  stapedial  fold  encloses  the  stapes  stretched  across  its  aper- 
ture, but  is  occasionally  perforated.  It  is  sometimes  extended  from  the 
stapes  to  the  pyramid,  and  sometimes  an  offset  ascends  from  it  between 
the  inferior  process  of  the  incus  and  the  inner  wall  of  the  atrium. 

The  cordal  fold  encloses  the  tympanic  branch  of  the  facial  nerve, 
attaching  it  to  the  tympanic  scute  as  it  passes  across  the  tympanum 
between  the  incus  and  malleus.  It  gives  offsets  to  the  inferior  process 
of  the  incus  and  to  the  handle  of  the  malleus,  and  sometimes  to  the 
pyramid. 

Other  folds,  variable  and  inconstant,  proceed  between  adjacent  parts 
of  the  tympanum,  usually  enclosing  blood-vessels. 

The  mucous  membrane  adheres  closely  to  the  subjacent  periosteum, 
and  in  positions  in  which  the  osseous  surface  is  uneven  it  reduces  the 
irregularities.  On  the  tympanic  membranes,  on  the  promontory,  on 
the  ossicles,  and  in  the  attic  and  antrum,  it  is  provided  with  an  epi- 
thelium consisting  of  a  single  layer  of  polygonal  pavement-cells.  In 
other  positions  it  is  covered  with  a  columnar  ciliated  epithelium. 

The  mastoid  cells  are  lined  by  a  thin,  pale-red  mucous  membrane 
provided  with  a  simple,  polygonal  pavement  epithelium. 

In  the  osseous  portion  of  the  eustachian  tube  the  mucous  membrane 


900  ORGANS   OF  SPECIAL   SENSE. 

is  like  that  of  the  tympanum.  In  the  inner  cartilaginous  and  mem- 
branous portion  it  is  thicker,  and  like  that  of  the  pharynx  has  numer- 
ous mucous  glands.  Throughout,  it  is  furnished  with  ciliated  columnar 
epithelium. 

VESSELS  AND   NEKVES   OF  THE   TYMPANUM. 

The  lining  membrane  and  other  parts  of  the  tympanum  are  sup- 
plied with  arteries  from  a  number  of  sources.  The  tympanic  branch 
of  the  internal  maxillary  artery  enters  the  tympanum  through  the 
glenoid  canal.  The  tympanic  branch  of  the  stylo-mastoid  artery 
enters  the  cavity  in  company  with  the  tympanic  branch  of  the  facial 
nerve,  accompanies  it  to  the  malleus,  and  descends  upon  the  handle, 
whence  it  is  distributed  in  radiating  twigs  to  the  tympanic  membrane. 
By  anastomosis  with  the  former  branch  it  produces  an  arterial  circle 
around  the  border  of  the  membrane.  A  branch  from  the  internal 
carotid  artery  enters  the  tympanum  from  the  carotid  canal ;  several 
small  ones  in  the  cranium  from  the  great  meningeal  artery  enter 
through  the  petro-squamosal  suture  and  the  hiatus  of  the  facial  canal, 
and  a  branch  from  the  ascending  pharyngeal  artery  enters  through  the 
eustachian  tube. 

The  mastoid  cells  are  supplied  with  branches  from  the  stylo-mastoid, 
posterior  auricular,  and  occipital  arteries. 

The  eustachian  tube  is  supplied  by  the  vidian,  pterygo-palatine, 
ascending  pharyngeal,  and  deecending  palatine  arteries. 

The  veins  of  the  tympanum,  for  the  most  part,  pursue  the  course 
of  the  corresponding  arteries.  Some  terminate  in  the  temporo-max- 
illary  and  posterior  auricular  veins,  others  communicate  with  the  in- 
ternal jugular,  and  others  pass  through  the  petro-squamosal  suture  to 
the  great  meningeal  veins. 

The  veins  of  the  mastoid  cells  join  the  posterior  auricular  vein ; 
those  of  the  eustachian  tube  the  accompanying  veins  of  the  arteries. 

The  nerves  of  the  tympanum  are  mainly  those  of  the  tympanic 
plexus  derived  from  the  tympanic  branch  of  the  glosso-pharyngeal 
nerve,  joined  by  a  branch  from  the  carotid  plexus  of  the  sympathetic, 
a  filament  from  the  great  superficial  petrosal  nerve,  and  the  small 
superficial  petrosal  nerve. 

The  tympanic  tensor  muscle  is  supplied  by  a  branch  from  the  otic 
ganglion ;  the  stapedial  muscle  by  a  branch  from  the  facial  nerve. 

The  tympanic  branch  of  the  facial  nerve  traverses  the  tympanum, 
but  does  not  supply  it. 

Lymphatics  are  numerous  in  the  mucous  membrane  of  the  tym- 
panum and  its  accessory  parts.  They  commence  in  the  usual  manner, 
and  the  chief  vessels  accompany  the  temporo-maxillary  and  posterior 
auricular  blood-vessels. 


OEGANS   OF  SPECIAL  SENSE.  901 

THE   INTERNAL  EAK. 

The  internal  ear  includes  the  labyrinth,  with  the  internal  auditory 
meatus  and  the  auditory  nerve. 

The  internal  auditory  meatus,1  situated  within  the  cranial  cavity, 
is  a  short,  wide,  cylindrical  pas- 
sage, directed  outward  from  near  Fl°-  459t 
the  centre  of  the  temporal  pyra- 
mid.     Its    bottom   is   formed   by 
a  perforated  plate,  the  cribriform 
lamina.      It    is    occupied    by   the 
auditory   and   facial    nerves    and 
the  auditory  vessels. 

The   cribriform   lamina  2  sep-         CRIBRIFORM  PLATE  OF  THE  LEFT  INTERNAL 

arates   the  labyrinth  from  the  in-      AUDITORY  MEATUS  :  magnified  three  times     1, 

J  m  f  entrance  of  the  facial  canal ;  2,  superior  cribn- 

ternal   auditory   meatUS,    in   which      form  spot ;  3,  middle  cribriform  spot ;  4,  canal 

it    18    concave    and    divided    by    a      leading  to  the  inferior  cribriform  spot;  5,  spiral 

J  tract. 

transverse  ridge  or  crest3  into  two 

fossae.  In  the  upper  fossa  inwardly  is  an  oval  or  reniform  foramen,  the 
entrance  of  the  facial  canal,4  for  the  transmission  of  the  facial  nerve. 
To  the  outer  side  of  the  entrance  of  the  canal  is  a  circular  recess  with 
a  group  of  minute  foramina,  which  communicate  with  the  vestibule 
of  the  labyrinth  as  its  superior  cribriform  spot.5  Several  variable 
smaller  groups  of  foramina  occupy  the  outer  part  of  the  crest  dividing 
the  cribriform  lamina  and  also  communicate  with  the  superior  cribri- 
form spot. 

TL  e  lower,  larger  fossa  of  the  cribriform  lamina  is  mainly  impressed 
with  a  spiral  tract,6  which  is  situated  at  the  base  of  the  modiolus, 
or  axis  of  the  cochlea.  The  tract  is  pierced  with  a  multitude  of 
minute  foramina  collected  into  little  groups  arranged  in  two  rows. 
The  foramina  transmit  the  filaments  of  the  cochlear  division  of  the 
auditory  nerve. 

Above  the  outer  extremity  of  the  spiral  tract  is  a  slight  recess  with 
a  group  of  minute  foramina,  which  communicate  with  the  middle 
cribriform  spot7  of  the  vestibule. 

In  the  outer  wall  of  the  meatus  near  the  bottom  is  a  deep  narrow 
pit,  at  the  bottom  of  which  is  another  group  of  minute  foramina, 
which  communicate  with  the  inferior  cribriform  spot8  of  the  ampulla 
of  the  posterior  semicircular  canal  of  the  labyrinth. 

The  groups  of  foramina  communicating  with  the  cribriform  spots 
transmit  the  filaments  of  the  three  branches  of  the  vestibular  division 
of  the  auditory  nerve. 

1  M.  auditorius  internus.  2  L.  cribrosa. 

3  Crista  transversa.  *  Fallopian  canal ;  canalis  Pallopii. 

5  Macula  cribrosa  sup.  6  Tractus  spiralis  foraminulosus. 

7  Macula  cribrosa  media.  8  M.  cribrosa  inf. 


902  OEGANS   OF  SPECIAL  SENSE. 

The  auditory  and  facial  nerves  together  enter  the  internal  auditory 
meatus  and  proceed  to  the  bottom,  the  facial  lying  in  a  groove  at  the 
outer  part  of  the  auditory  nerve  and  with  the  auditory  artery  between 
them.  The  two  nerves  are  connected  by  one  or  two  small  intervening 
filaments.  Reaching  the  bottom  of  the  meatus  the  facial  nerve  leaves 
the  auditory  nerve  and  pursues  its  further  course  through  the  facial 
canal,  as  described  in  another  place.  See  page  794. 

The  auditory  nerve1  in  the  meatus  divides  into  the  vestibular  and 
cochlear  nerves,  of  which  the  former  is  the  more  external  and  posterior. 

FIG.  460.  FIG.  461. 


Fig.  460.— INTERNAL  EAR  LAID  OPEN.  1,  vestibular  branch  of  the  auditory  nerve ;  2,  branch  to 
the  saccule ;  3,  branch  to  the  utricle ;  4,  5,  6,  branches  to  the  ampullae  of  the  membranous  semi- 
circular canals ;  7,  cochlear  branch  of  the  auditory  nerve ;  8,  cochlea. 

Fig.  461.— NERVES  OF  THE  VESTIBULE  AND  SEMICIRCULAR  CANALS,  magnified  three  diameters. 
1,  vestibular  branch  of  the  auditory  nerve ;  2,  branch  to  the  saccule ;  3,  branch  to  the  utricle ;  4, 
5, 6,  branches  to  the  ampullae  of  the  semicircular  canals ;  7,  cochlear  nerve. 

The  vestibular  nerve,'2  after  a  slight  enlargement,8  divides  into 
three  branches.  Of  these  the  superior  branch  splits  up  into  filaments, 
which  pass  through  the  foramina  of  the  superior  cribriform  spot  of  the 
vestibule  and  form  three  bundles,  of  which  one  enters  and  terminates  in 
the  acoustic  spot  of  the  utricle,  while  the  others  proceed  to  terminate 
in  the  acoustic  crests  of  the  ampullae  of  the  superior  and  inferior  semi- 
circular canals.  The  middle  branch  splits  up  into  filaments,  which 
pass  through  the  foramina  of  the  middle  cribriform  spot  of  the  vesti- 
bule and  terminate  in  the  acoustic  spot  of  the  saccule.  The  inferior 
branch  enters  the  deep  pit  in  the  back  wall  of  the  meatus,  passes 
through  the  inferior  cribriform  spot  of  the  ampulla  of  the  posterior 
semicircular  canal,  and  terminates  in  its  acoustic  crest. 

In  the  acoustic  spots  and  crests  the  nerve-fibres  of  the  terminal 
branches  of  the  vestibular  nerve  appear  to  lose  their  medullary  sheath, 
while  the  ultimate  fibrils  of  the  axis-fibres  terminate  by  joining  the 
auditory  cells. 

The  cochlear  nerve 4  breaks  up  into  numerous  bundles  of  nerve- 

1  Nervus  auditorius;  n.  acusticus.  2  N.  vestibuli  or  vestibularis. 

3  Intumescentia  gangliformis.  *  N.  cochlearis  or  cochleae. 


ORGANS   OF   SPECIAL,   SENSE. 


903 


fibres,  which  enter  the  foramina  of  the  spiral  tract  in  the  base  of  the 
modiolus.  Proceeding  through  canals  of  the  modiolus,  the  largest 
bundles  centrally,  the  branches  are  successively  reflected  to  the  spiral 
ganglion,1  which  occupies  the  corresponding  canal  of  the  modiolus. 


FIG.  462. 


DISTRIBUTION  OF  THE  COCHLEAE  NERVE.  1,  trunk  of  the  cochlear  nerve ;  2,  basilar  membrane ; 
3,  terminal  filaments  of  the  cochlear  nerve  emerging  from  the  osseous  spiral  lamina  to  enter  the 
cochlear  duct ;  4,  orifice  of  communication  of  the  tympanic  and  vestibular  passages. 

The  ganglion  consists  of  an  intricate  intertexture  of  the  cochlear  nerves 
with  numerous  bipolar  nerve-cells.  From  it  the  nerve-fibres  proceed 
through  the  canals  of  the  spiral  lamina,  in  which  they  conjoin  in  an 
intricate  plexus,  and  finally  emerge  through  a  row  of  foramina  of  the 
basilar  membrane  along  the  tympanic  lip  of  the  spiral  lamina.  Here, 
losing  their  medullary  sheath,  the  nerve  axial  fibres  enter  the  acoustic 
organ,  but  their  exact  mode  of  termination  has  not  been  positively 
determined.  According  to  Waldeyer,  many  of  them  appear  to  termi- 
nate by  joining  the  auditory  cells. 

THE   LABYRINTH. 

The  labyrinth  is  an  exceedingly  intricate  portion  of  the  ear,  em- 
bedded in  the  dense  osseous  structure  of  the  temporal  pyramid,  situ- 
ated internally  to  the  tympanum,  with  which  it  communicates.  To  it 
alone  the  auditory  nerve  is  distributed,  reaching  it  through  the  internal 
auditory  meatus.  It  is  an  osseous  receptacle  with  conformable  mem- 
branous and  other  contents,  and  in  description  is  usually  considered 
in  two  parts,  as  the  osseous  and  membranous  labyrinth.  Between  the 
two  is  an  interval  occupied  by  a  serous  liquid,  the  perilymph,  and  the 
membranous  labyrinth  is  filled  with  a  similar  liquid,  the  endolymph. 

At  the  period  of  birth  the  labyrinth  already  appears,  like  the  ear 
ossicles,  of  mature  size,  embedded  in  the  temporal  bone,  with  its  posi- 
tion and  shape  partially  defined  and  visible  on  the  exterior  of  the  pyr- 

1  Ganglion  spirale  ;  g.  Cortii ;  habenula  ganglionaris. 


904 


ORGANS   OF   SPECIAL,   SENSE. 


amid.  In  this  condition  it  has  a  complete  and  dense  osseous  wall  fused 
with  the  surrounding  more  spongy  bone,  from  which  it  can  readily  be 
excavated  with  the  knife.  In  the  subsequent  growth  of  the  pyramid 
the  labyrinth  becomes  more  completely  embedded  and  concealed  from 
view,  while  the  surrounding  osseous  substance  becomes  as  dense  as  the 
wall  of  the  labyrinth  and  is  undefined  from  it. 

The  labyrinth  consists  of  the  vestibule,  the  semicircular  canals,  and 
the  cochlea.  The  vestibule  is  intermediate,  and  in  the  macerated  bone 
communicates  with  the  tympanum  through  the  oval  window.  The 
semicircular  canals,  of  which  there  are  three,  are  external  to  the  ves- 
tibule and  communicate  with  it.  The  cochlea  is  innermost,  produces 
the  promontory  of  the  tympanum,  and  communicates  with  it  through 
the  round  window.  Its  base  is  applied  to  the  internal  auditory  meatus 
and  contributes  to  form  the  cribriform  lamina. 


THE   OSSEOUS   LABYKINTH.1 


FIG.  463. 


The  vestibule 2  forms  an  ovoidal  cavity  placed  between  the  tym- 
panum and  internal  auditory  me- 
atus, with  the  semicircular  canals 
directed  outward  and  backward 
and  the  cochlea  inward  and  for- 
ward. In  its  outer  wall  is  the 
oval  window,3  communicating 
with  the  tympanum,  but  closed 
by  the  base  of  the  stapes. 

At  the  inner  fore  part  of  the 
cavity  of  the  vestibule  are  two  con- 
cave recesses,  of  which  the  lower 
is  the  hemispherical  fossa4  and 
the  upper  the  hemi-elliptical 
fossa.5  They  are  separated  by 

a  ridge,  the  vestibular  crest,6  which  ascends  from  below  and  behind 
the  hemispherical  fossa,  curves  forward  and  outward  between  the  two 
fossae,  and  near  the  upper  fore  part  of  the  oval  window  ends  in  a  little 
pyramidal  eminence.7  Behind  the  two  fossae  is  a  shallow  furrow, 
the  sulciform  fossa,8  into  which  opens  a  fine  canal,  the  vestibular 
aqueduct.9 

At  the  back  of  the  vestibule  are  five  circular  holes  which  communi- 


THE  RIGHT  LABYKINTH  ;  viewed  outwardly 
in  front :  magnified  two  and  a  half  times.  1, 
vestibule ;  2,  oval  window ;  3,  round  window ; 
4,  superior  semicircular  canal ;  5,  posterior 
semicircular  canal;  6,  inferior  semicircular 
canal ;  7,  ampullae ;  8,  cochlea. 


1  Labyrinthus  osseus  or  durus.  2  Vestibulum. 

3  Fenestra  ovalis  ;  foramen  ovale. 

4  Fossa  hemisphserica,  sphserica,  orbicularis,  rotunda,  or  subrotunda. 

5  Fossa  hemi-elliptica,  semi-ovalis,  or  ovalis.  6  Crista  vestibularis. 

7  Eminentia  pyramidalis  ;  pyramis  vestibuli. 

8  Sinus  sulciformis  ;  sulcus  ad  aquaeductum  vestibuli ;  recessus  labyrinth!. 

9  Aquseductus  vestibuli. 


ORGANS   OF  SPECIAL  SENSE.  905 

cate  with  the  semicircular  canals.  At  its  lower  part,  below  the  oval 
window,  is  a  large  elliptical  pit,  the  cochlear  recess,1  which  forms 
part  of  the  cochlea,  and  in  the  macerated  bone  freely  communicates 
with  it  and  with  the  tympanum  through  the  round  window. 

The  semicircular  canals  are  three  horseshoe-like  tubes,  situated 
outwardly,  behind  and  above  the  position  of  the  vestibule,  into  which 
they  open  by  five  holes.  They  are  of  unequal  length,  cylindrical  and 
slightly  compressed  laterally ;  each  at  one  end  is  enlarged  in  a  pyriform 
expansion,  the  ampulla.2  The  three  canals  are  related  in  position 
with  one  another  like  three  contiguous  sides  of  a  cube,  inward,  below, 
and  behind. 

The  superior  semicircular  canal3  is  nearly  vertical,  directed  fore 
and  aft,  internal  to  the  others,  and  ascends  highest.- 

The  posterior  semicircular  canal  *  is  the  longest,  and  is  directed 
from  within  outward  and  backward,  behind  the  others. 

The  inferior  semicircular  canal 5  is  shortest,  is  directed  horizon- 
tally outward,  and  is  external  to  the  superior  and  in  advance  of  the  pos- 
terior canal. 

The  ampullae  of  the  superior  and  inferior  canals  occupy  their  fore 
ends,  are  contiguous,  and  open  near  together  into  the  vestibule  above 
the  oval  window.  The  ampulla  of  the  posterior  canal  occupies  its 
lower  end  and  opens  into  the  lower  back  part  of  the  vestibule.  The 
back  end  of  the  superior  canal  and  the  upper  end  of  the  posterior  canal 
unite  in  a  common  canal  which  opens  into  the  upper  back  part  of  the 
vestibule,  while  the  back  end  of  the  inferior  canal  opens  into  it  at  its 
middle  back  part. 

In  the  temporal  bone  at  birth  the  internal  semicircular  canal  pro- 
duces an  arching  ridge  across  the  middle  of  the  upper  border  of  the 
pyramid,  usually  with  a  deep  recess  beneath  as  large  as  the  adjacent 
internal  auditory  meatus.  In  the  mature  bone  the  canal  produces  a 
conspicuous  prominence  at  the  upper  fore  part  of  the  pyramid,  with  a 
remaining  trace  of  the  recess  beneath.  The  summit  of  the  posterior 
semicircular  canal  produces  a  less-marked  ridge  on  the  posterior  sur- 
face of  the  pyramid,  which  also  is  visible  at  maturity.  The  inferior 
semicircular  canal,  with  the  facial  canal,  forms  the  suprapromontory 
of  the  tympanic  attic. 

Communicating  with  the  vestibule  and  the  ampulla  of  the  posterior 
semicircular  canal  are  three  groups  of  minute  foramina  which  trans- 
mit the  filaments  of  the  three  branches  of  the  vestibular  division  of 
the  auditory  nerve  from  the  internal  auditory  meatus.  The  groups 
are  circular,  have  a  chalky  appearance,  and  are  distinguished  as  the 
cribriform  spots.6 

1  Recessus  cochlearis.  2  Sinus  or  recessus  ampullaceus. 

3  Frontal.  *  Sagittal,  internal,  or  inferior. 

5  Horizontal,  external,  or  middle.  6  Maculae  cribrosae. 


906 


ORGANS   OF   SPECIAL   SENSE. 


FIG.  464. 


The  superior  cribriform  spot,  the  largest,  occupies  the  pyrami- 
dal eminence  of  the  vestibular  crest  and  the  contiguous  outer  extrem- 
ity of  the  hemi-elliptical  fossa.  The 
middle  cribriform  spot  occupies 
the  bottom  of  the  hemispherical 
fossa.  The  inferior  cribriform 
spot  occupies  the  ampulla  of  the 
posterior  semicircular  canal. 

The  cochlea,1  named  from  its 
resemblance  to  a  snail-shell,  forms 
the  innermost  of  the  three  por- 
tions of  the  labyrinth.  Situated 
to  the  inner  side  and  in  advance 
of  the  position  of  the  vestibule,  it 
communicates  with  its  lower  fore 
part.  It  is  a  cone  wider  than  long, 

12  9  and  is  directed  fore  and  aft,  with 

its  base  applied  to  the  internal 
auditory  meatus  and  its  apex  con- 
tiguous to  the  bend  of  the  carotid 
canal,  close  to  the  eustachian  tube. 
It  is  completely  concealed  within 
the  temporal  pyramid,  except  that 
its  commencement  produces  the 
promontory  of  the  tympanum. 
Inwardly  its  compact  osseous  wall 
is  separated  from  the  axis  of  the  pyramid  by  spongy  substance  with 
marrow. 

The  cochlea  is  a  cylindrical  tube,  the  cochlear  canal,2  compressed 
fore  and  aft  and  somewhat  tapering,  wound  spirally  round  a  central 
axis,  the  modiolus.  The  canal  makes  about  two  and  a  half  turns 
concentrically,  the  turns  successively  projecting  forward  and  ending 
in  a  rounded  summit,  the  cupola.8  From  its  commencement  in  the 
promontory  below  the  oval  window,  in  each  ear,  it  turns  downward 
and  inward,  then  upward  and  outward,  and  so  on  to  the  cupola. 

The  modiolus*  is  a  spirally-grooved,  conical  column,  in  the  first 
turn  of  the  cochlea  about  as  thick  as  it  is  long,  but  rapidly  decreasing 
in  the  successive  turns  of  the  canal.  Its  bottom  forms  part  of  the 
cribriform  lamina  of  the  internal  auditory  meatus  and  is  impressed  by 
the  spiral  tract,  the  numerous  foramina  of  which  communicate  with 
canals  of  the  modiolus  for  the  transmission  of  the  cochlear  nerves  and 
blood-vessels. 

From  the  modiolus,  along  the  middle  of  the  cochlear  canal,  projects 


A 5 


INTERIOR  OF  THE  VESTIBULE,  SUPERIOR  AND 
POSTERIOR  SEMICIRCULAR  CANALS;  right  side, 
looking  from  behind :  magnified  three  diam- 
eters. 1,  superior  semicircular  canal ;  2,  its 
ampulla ;  3,  posterior  semicircular  canal ;  4, 
union  of  the  two  canals :  5,  section  of  the  facial 
canal ;  6,  sulciform  fossa :  7,  hemi-elliptical 
fossa ;  8,  hemispherical  fossa ;  9,  vestibular 
crest;  10,  superior,  11,  middle,  and  12,  inferior 
cribriform  spots ;  13,  promontory ;  14,  vestibu- 
lar passage;  15,  round  window,  communi- 
cating with  the  tympanic  passage. 


1  Cavitas  cochleata. 
3  Cupula. 


2  Canalis  cochlearis  ;  c.  spiralis  cochleae. 
*  Columella  ;  pyramis. 


ORGANS   OP  SPECIAL  SENSE. 


907 


a  thin  osseous  shelf,  the  spiral  lamina,1  which  extends  about  half-way 
across  the  canal.  Widest  at  its  commencement,  it  gradually  narrows  in 
its  course  and  in  the  cupola  ends  in  a  little  hook,'2  which  projects  from 
the  summit  of  the  modiolus. 

The  spiral  lamina  divides  the  cochlear  canal  into  two  passages, 
which  in  the  entire  condition  of  the  labyrinth  are  completely  separated 
by  the  membranous  cochlea.  One  of  the  passages,  opening  directly  into 
the  vestibule,  is  distinguished  as  the  vestibular  passage,3  and  the  other, 


Fio.  460. 


THE  COCHLEA,  LAID  OPEN,  ITS  SUMMIT  TURNED 

urwABD :  magnified  three  diameters.  1, 2, 3,  the 
tympanic  passage;  4,  5,  6,  the  vestibular  pas- 
sage; 7,  8,  osseous  spiral  lamina;  9,  membra- 
nous spiral  lamina;  10,  orifice  of  communica- 
tion of  the  two  passages  at  the  summit  of  the 
cochlea;  11,  12,  termination  of  the  osseous 
and  membranous  spiral  laminae. 


fi  1 


THE  COCHLEA,  LAID  OPEN.  AND  VIEWED  FROM 

ITS  SUMMIT:  magnified  three  diameters.  1,  cut 
edges  of  the  osseous  wall  of  the  cochlea ;  2, 
osseous  spiral  lamina,  seen  within  the  vestibu- 
lar passage ;  3,  end  of  the  lamina ;  4,  5,  its 
outer  border ;  6,  basilar  membrane ;  7,  its  end ; 
8,  foramen  of  communication  with  the  tym- 
panic passage. 


communicating  with  the  round  window  of  the  tympanum,  is  the  tym- 
panic passage.4  The  two  passages  communicate  by  a  common  orifice 5 
within  the  cupola. 

The  numerous  canals  proceeding  through  the  modiolus  for  the  pas- 
sage of  the  cochlear  nerves  and  vessels  are  successively  reflected  out- 
ward towards  the  spiral  lamina  and  communicate  with  a  spiral  canal,6 
which  traverses  the  modiolus  along  the  course  of  the  spiral  lamina 
and  is  occupied  by  the  spiral  ganglion  of  the  cochlear  nerve  and  by  a 
spiral  vein.  Among  the  longitudinal  canals  of  the  modiolus  a  larger 
central  canal 7  transmits  the  central  artery. 

The  spiral  lamina  consists  of  two  layers  with  an  intervening  more 
spongy  layer  traversed  by  numerous  anastomosing  canals,  which  com- 
municate with  the  spiral  canal  of  the  modiolus  and  with  a  series  of 
apertures  along  the  free  border  of  the  lamina. 


1  L.  spiralis  ossea  ;  zonula  ossea ;  septum  osseum  cochleae. 

J  Hamulus  ;  rostrum.  8  Scala  vestibuli. 

4  Scala  tympani.  5  Helicotrema. 

6  Canalis  spiralis  modioli.  T  Canalis  centralis  modioli. 


908  ORGANS  OF  SPECIAL  SENSE. 

The  surfaces  of  the  modiolus  and  spiral  lamina  are  more  or  less 
porous  in  different  positions,  for  the  transmission  of  blood-vessels  to  the 
interior  membranous  structures.  In  the  vestibular  passage,  at  the  con- 
junction of  the  spiral  lamina  and  modiolus,  is  a  row  of  comparatively 
large  foramina,  which  extend  in  grooves  on  the  latter  and  give  to  it  a 
somewhat  fluted  appearance.  Elsewhere  the  surface  of  the  cochlear 
canal  is  less  porous.  Opposite  the  spiral  lamina  it  exhibits  a  slight 
linear  ridge,1  which  indicates  the  course  of  attachment  of  the  spiral 
ligament. 

Near  the  commencement  of  the  tympanic  passage  is  the  opening 
of  a  fine  canal,  the  cochlear  aqueduct,2  which  descends  to  the  jugular 
fossa  and  transmits  a  vein. 

The  cochlear  canal,  including  the  spiral  lamina,  is  lined  throughout 
with  a  periosteum  of  fibre-connective  tissue  with  elastic  tissue. 

THE   MEMBKANOUS   LABYKINTH. 

The  interior  of  the  osseous  labyrinth  is  lined  with  a  thin  perios- 
teum,3 which  resembles  in  structure  the  ectochoroidea  of  the  eye.  It 
consists  of  an  intertexture  of  fibro-elastie  tissue  with  cell-elements, 
including  scattered  stellate  pigment-cells,  and  is  well  supplied  with 
blood-vessels. 

The  membranous   labyrinth*  consists  of  corresponding  parts, 

which  nearly  accord  in  form  with 

FIG.  467.  those    of  the    osseous    labyrinth. 

Narrow  membranous  semicircular 
canals   are   contained   within  the 
osseous  canals  attached  along  their 
convex  border;   the  membranous 
vestibule  occupies  the  osseous  cav- 
ity attached  at  the  points  of  en- 
THE  MEMBRANOUS  LABYRINTH:  magnified  two      trance    Qf   the    nerveg     the   mem. 
and  a  half  times.     1,  utricle;  2,  saccule;  3,  7 

semicircular  canals;  4,  ampullae  of  semicircular  branOUS  Cochlea  as  the  Cochlear 
canals;  5,  vestibular  aqueduct;  6,  cochlear  duct  jg  fixed  to  the  irftl  larnjna 
duct ;  7,  canal  connecting  the  latter  with  the 

saccule.  and  the  opposite  wall  of  the  coch- 

lear canal.  The  intervals  of  the 

membranous  and  osseous  labyrinths  are  filled  with  the  perilymph,  and 
the  interior  of  the  membranous  labyrinth  with  the  endolj'mph. 

The  membranous  vestibule5  occupies  about  two-thirds  of  the 
cavity  of  the  osseous  vestibule,  and  consists  of  two  pouches  separated 
by  a  constriction  but  not  directly  communicating. 

The  smaller  pouch,  or  saccule,6  occupies  the  lower  fore  part  of  the 

1  Lamina  spiralis  externa  or  secondaria.  2  Aquaeductus  cochleae. 

3  External  membranous  labyrinth.  *  Labyrinthus  membranosus. 

5  Vestibulum  membranosum. 

6  Sacculus  rotundus,  sphsericus,  or  proprius  ;  small  vestibular  vesicle.  • 


OEGANS   OF   SPECIAL   SENSE. 


909 


FIG.  468. 


osseous  vestibule,  including  the  hemispherical  fossa.  It  is  fore  and  aft 
compressed  flask-shaped,  with  the  neck  narrowing  to  a  short  canal,1 
which  opens  into  the  cochlear  duct. 

The  larger  pouch,  or  utricle,2  occupies  the  upper  and  back  part 
of  the  osseous  vestibule,  including  the  hemi-elliptical  fossa,  and  at  its 
outer,  upper,  and  back  part  is  joined  by  the  three  membranous  semi- 
circular canals. 

The  saccule  is  attached  to  the  wall  of  the  osseous  vestibule  at  the 
bottom  of  the  hemispherical  fossa,  and  the  saccule  to  the  outer  part 
of  the  vestibular  wall  and  hemi-elliptical  fossa.  Elsewhere  the  pouches 
are  separated  from  the  wall,  especially  outwardly  and  next  the  oval 
window. . 

Though  not  directly  opening  into  each  other,  the  saccule  and  utricle 
communicate  through  a  narrow  Y-shaped  canal,  the  vestibular  aque- 
duct,3 the  common  branch  of  which  occupies  the  corresponding  osseous 
aqueduct,  in  which  it 
ends  in  a  blind  pouch. 

The  membranous 
semicircular  canals4 
nearly  conform  to  the 
osseous  canals  which 
contain  them.  They  are 
compressed  cylindrical, 
and  about  one-third  of 
the  diameter  of  the  os- 
seous canals,  along  the 
outer  side  of  which  they 
lie  attached  to  the  peri- 
osteum. The  ampullae 
are  proportionately  so 
much  larger  that  they 
nearly  fill  the  corre- 
sponding osseous  am- 
pullae. The  three  canals 
communicate  with  the 
utricle  of  the  vestibule 
by  five  openings. 

Structure  of  the  membranous  vestibule  and  semicircular 
canals.  The  walls  of  the  saccule,  the  utricle,  and  the  semicircular 
canals  are  delicate  and  transparent.  They  are  not  of  uniform  thick- 
ness, and  are  composed  of  three  principal  layers. 

1  Canalis  reuniens. 

2  Utriculus  ;  sacculus  communis,  hemi-ellipticus,  oblongus,  or  semi-ovalis ;  alveus 
utriculosus ;  sinus  medianus. 

3  Aquaeductus  vestibuli. 

4  Canales  semicircu lares  membranacei ;  tubuli  or  ductus  semicirculares. 


DIAGRAM  OF  A  CROSS-SECTION  OF  A  SEMICIRCULAR  CANAL,  mag- 
nified. 1,  osseous  canal ;  2,  section  of  the  membranous  canal ; 
3,  papillary  layer  with  endothelium ;  4,  membrana  propria ; 
5,  periosteum  of  the  osseous  canal;  6,  band  of  the  same; 
7,  blood-vessel ;  8,  8,  spaces  occupied  by  the  perilymph. 


910 


ORGANS   OP   SPECIAL   SENSE. 


The  external  layer  is  like  the  adjacent  periosteum,  with  which  it 
is  continuous.  Where  the  parts  are  not  immediately  in  contact  with 
the  periosteum,  they  are  connected  with  the  opposite  osseous  walls 
by  delicate  cords  of  the  same  structure,  which  also  serve  to  support 
accompanying  blood-vessels.  The  middle  layer,  or  membrana  pro- 
pria,  is  a  denser  and  apparently  homogeneous  stratum  of  variable  thick- 
ness and  is  thinnest  at  the  attachment  of  the  parts  to  the  subjacent 
osseous  wall.  Within  the  semicircular  canals  it  is  variably  produced 
into  broad  conical  papillae,  which  are  absent  where  the  wall  is  thinnest, 
next  the  attachment  of  the  membranous  to  the  osseous  canal.  The 
papillae  are  undeveloped  at  birth,  and  sometimes  are  not  evident  even 
at  maturity.  The  internal  layer  is  a  pavement  endothelium. 

Where  the  utricle  and  saccule  adhere  to  the  wall  of  the  osseous 
vestibule,  over  the  position  of  the  corresponding  cribriform  spot,  the 
membrane  exhibits  a  circular  thickening,  distinguished  as  the  acoustic 
spot.1  It  receives  the  terminal  fibrils  of  the  branches  of  the  vestibular 
nerve,  and  is  invested  with  a  peculiar  epithelium,  of  which  the  chief 
structural  elements  are  the  acoustic  hair-cells.  These  are  columnar 
and  have  their  attached  extremity  tapering  and  apparently  connected 
with  an  axial  fibre  of  the  vestibular  nerve.  The  free  extremity  is  pro- 
vided with  a  long,  rigid,  conical,  hair-like  process,  which  when  treated 


FIG.  469. 


FIG.  470. 


OTOLITES,  highly  magnified. 

with  reagents  breaks  up  into  a 
bundle  of  cilia-like  filaments.  With 
the  hair-cells  are  mingled  numer- 
ous supporting  cells  of  narrower 
form,  devoid  of  the  hair-like  pro- 
cess and  not  connected  with  a 
nerve-fibril. 

The  acoustic  hairs  are  not  di- 
rectly bathed  in  the  surrounding 
endolymph,  but  seem  enveloped 
in  a  more  viscid  mass,  which  is  es- 
pecially remarkable  from  its  being 

mingled  with  a  multitude  of  minute  crystals,  the  otolites."  These 
are  of  various  sizes,  composed  of  calcium  carbonate,  and  generally 
in  the  form  of  .six-sided  prisms  with  short  pyramidal  terminations. 


DIAGRAM  OF  ACOUSTIC  EPITHELIUM:  highly 
magnified.  1,  acoustic  hair-cell;  2,  supporting 
cell ;  3,  immature  cell. 


1  Macula  acustica. 


2Otoconia;  otolithes ;  ear-sand. 


ORGANS   OF  SPECIAL   SENSE. 


911 


FIG.  471. 


Similar  bodies  are  found  in  the  vestibule  of  the  ear  of  all  vertebrate 
animals. 

In  the  membranous  ampullae  of  the  semicircular  canals  a  more  con- 
spicuous thickening  forms  the  acoustic  crest.1  This  appears  as  a 
transverse  reniform  ridge  projecting  from  the  inner  side  of  the  corre- 
sponding ampulla.  Like  the  acous- 
tic spot,  it  receives  the  terminal 
fibrils  of  branches  of  the  vestib- 
ular  nerve  and  has  the  same  kind 
of  peculiar  epithelium.  The  audi- 
tory hairs  are  enveloped  in  a  dome- 
like mass,  or  cupola,2  of  viscid, 
semi-liquid  matter  distinct  from 
the  surrounding  endolymph. 

The  membranous  cochlea,3 
or  cochlear  duct,4  is  a  trilateral, 
prismatic  tube,  which  commences 
in  a  rounded  pouch  within  the 
promontory  of  the  tympanum,  be- 
low the  oval  window  of  the  ves- 
tibule, thence  winds  along  the 
middle  of  the  cochlear  canal  and 
ends  in  a  closed  extremity  in  the 
cupola.  It  occupies  a  position  in 
advance  of  the  spiral  lamina,  be- 
tween it  and  the  opposite  wall  of 
the  cochlear  canal,  separating  the 

vestibular  and  tympanic  passages,  than  which  it  is  much  smaller. 
The  cochlear  duct  with  the  latter  forms  three  distinct  passages  in  the 
cochlea. 

In  a  cross-section  of  the  cochlea  the  vestibular  and  tympanic  pas- 
sages in  general  appear  transverse  oval ;  that  of  the  cochlear  duct  tri- 
angular and  less  than  half  the  capacity  of  the  others. 

The  vestibular  passage  commences  above  the  tympanic  passage,  but 
subsequently  runs  outward  and  in  advance  of  it  and  the  cochlear  duct 
to  the  cupola.  The  tympanic  passage  is  at  first  considerably  larger 
than  the  vestibular  passage,  but  after  the  first  turn  the  difference  dis- 
appears ;  approaching  the  third  turn  the  vestibular  becomes  the  larger. 
The  cochlear  duct,  though  slightly  decreasing,  is  more  uniform  in  size 
throughout  its  course. 

The  cochlear  duct,  a  little  in  advance  of  its  commencement,  is  joined 
by  the  short  descending  neck  or  canal5  of  the  saccule  of  the  mem- 


DlAGEAM  OF  A  CROSS-SECTION  OF  THE  ACOUSTIC 

CREST  OF  AN  AMPULLA:  highly  magnified.  1, 
acoustic  cupola;  2,  acoustic  hair-cells;  3,  acous- 
tic hairs ;  4,  epithelium ;  5,  blood-vessel ;  6, 
medullated  nerve-fibres  of  the  vestibular 
nerve. 


1  Crista  acustica  ;  septum  nerveum  or  transversum  ;  papilla  semilunaris. 

2  Cupula  acustica.  3  Canalis  membranaeeus  cochleae  ;  canalis  cochleae. 
*  Ductus  cochlearis  ;  scala  media.  5  Canalis  reuniens. 


912 


ORGANS   OF   SPECIAL   SENSE. 


branous  vestibule,  but  elsewhere  is  closed  throughout.  Its  exterior 
surface  is  bathed  with  the  perilymph  of  the  vestibular  and  tympanic 
passages ;  its  interior  is  filled  with  endolymph. 

The  outer  wall  of  the  cochlear  duct,  or  that  opposite  the  spiral 
lamina,  is  formed  by  the  contiguous  periosteum  of  the  cochlear  canal, 


DIAGRAM  OF  A  CROSS-SECTION  OF  ONE  OF  THE  TURNS  OF  THE  COCHLEA  :  much  magnified.  1, 
vestibular  passage ;  2,  tympanic  passage ;  3,  cochlear  duct ;  4,  osseous  wall  of  the  cochlea ;  5, 
modiolus ;  6,  two  layers  of  the  osseous  spiral  lamina ;  7,  8,  periosteum ;  9,  vestibular  membrane ; 
10,  basilar  membrane;  11,  spiral  ligament;  12,  spiral  crest;  13,  spiral  groove;  14,  lining  epithe- 
lium of  the  cochlear  duct;  15,  acoustic  organ,  the  number  placed  within  the  spiral  tunnel;  16, 
tectorial  membrane;  17,  cochlear  nerve;  18,  spiral  ganglion;  19,  nerve  passing  through  the 
spiral  lamina ;  20,  emergence  of  the  nerve  into  the  cochlear  duct. 

thicker  than  elsewhere,  and  lined  by  a  simple  epithelium  of  short 
columnar  cells,  defined  from  the  periosteum  by  a  thin,  clear  basement 
membrane. 

The  anterior  wall  of  the  cochlear  duct,  or  the  vestibular  mem- 
brane,1 is  a  thin  partition  which  separates  the  passage  of  the  duct 
from  the  vestibular  passage.  It  is  extended  obliquely  from  the  outer 
fore  part  of  the  spiral  lamina  to  the  outer  fore  part  of  the  cochlear 
canal.  It  consists  of  a  delicate  connective-tissue  layer  continuous  with 
the  periosteum  of  the  canal,  lined  in  the  cochlear  duct  with  a  simple 
pavement  epithelium,  and  in  the  tympanic  passage  with  an  endothelium 
of  larger  cells. 

1  Membrana  vestibularis ;  membrane  of  Keisner. 


ORGANS  OF  SPECIAL   SENSE.  913 

The  posterior  wall  of  the  cochlear  duct,  the  basilar  mem- 
brane,1 is  continued  in  the  same  plane  from  the  spiral  lamina  to  the 
spiral  ligament  and  separates  the  passage  of  the  duct  from  the  tym- 
panic passage.  It  is  narrowest  in  the  commencement  of  the  cochlea 
and  widens  with  the  decrease  of  the  spiral  lamina  in  its  course  to  the 
cupola.  The  membrane  consists  of  a  somewhat  rigid,  clear,  homoge- 
neous layer,  with  a  stratum  of  transverse  fibres  next  the  passage  of 
the  cochlear  duct,  and  a  thin  stratum  of  connective  tissue  with  spindle- 
shaped  cells  next  the  tympanic  passage.  In  the  cochlear  duct  an 
inner  zone2  of  the  membrane  supports  the  acoustic  organ,  continuous 
with  the  epithelial  covering  of  the  outer  zone.3  Externally  the  basilar 
membrane  is  continuous  with  the  spiral  ligament.  Blood-vessels  pene- 
trate the  inner  portion  of  the  connective-tissue  stratum,  and  along  the 
middle  of  the  membrane  runs  a  spiral  vein.4 

The  spiral  ligament5  is  a  prismatic  thickening  of  the  periosteum 
and  outer  wall  of  the  cochlear  duct,  composed  of  fibro-connective  tissue 
with  numerous  stellate  corpuscles  and  wrell  supplied  with  vessels.  In 
advance  of  it  is  a  less  prominent  ridge,8  and  parallel  with  this  a  more 
vascular  belt7  of  the  wall  of  the  duct. 

The  free  border  of  the  osseous  spiral  lamina  forms  the  inner  corner 
of  the  cochlear  duct.  The  periosteum  of  the  front  surface  of  the  spiral 
lamina  ends  in  a  prominent  convex  ridge,  the  spiral  crest,8  which  is 
outwardly  excavated  in  a  wide  spiral  groove.9  The  front  or  top  of 
the  crest  is  broken  up  into  irregular  rows  of  tubercles,10  with  flat  sum- 
mits and  separated  by  deep  furrows  which  widen  at  the  bottom.  The 
last  tubercles  are  largest  and  longest  and  form  a  uniform  row,  distin- 
guished as  the  auditory  teeth.  They  have  wide,  flat  summits,  which 
overhang  the  spiral  groove  and  define  it  by  a  sharp  border,  called  its 
vestibular  lip.11  The  thickened  ends  of  the  tubercles  resemble  carti- 
lage and  are  homogeneous  in  structure.  Their  flat  summits  are  naked, 
smooth,  and  shining,  but  the  intervals  of  the  tubercles  are  occupied  by 
cells  of  the  epithelium  of  the  cochlear  duct. 

The  tympanic  lip 12  of  the  spiral  duct  is  formed  by  the  periosteum 
from  behind  the  ossepus  spiral  lamina  extended  beyond  it  into  the  basilar 
membrane.  Along  the  lip  a  row  of  foramina13  open  from  the  canals 

1  Membrana  basilaris  ;  zona  membranacea. 

2  Zona  interna  or  Isevis  ;  habenula  tecta  or  arcuata. 

3  Zona  externa  or  peclinata  ;  portio  or  habenula  pectinata.         4  Vas  spirale. 

5  Ligamentum  spirale  membranae  basilaris ;  cochlear  ligament  and  muscle. 

6  Vas  prominens.  7  Stria  vascularis. 

8  Crista  spiralis  ;  limbus  laminae  spiralis ;  zona  cartilaginea,  choriacea,  mediana, 
or  nervea. 

9  Sulcus  spiralis ;  s.  s.  internus  ;  s.  semicanalis  spiralis. 

10  Lamina  or  zona  denticulata  ;  crista  or  habenula  sulcata. 

11  Labium  vestibulare  ;  crista  spiralis  acustica. 

12  Labium  tympanicum.  13  Habenula  perforata. 

58 


914  ORGANS   OF   SPECIAL   SENSE. 

of  the  spiral  lamina  into  the  cochlear  duct  and  transmit  the  terminal 
branches  of  the  cochlear  nerve  to  the  acoustic  organ. 

The  spiral  groove  is  lined  with  a  short  columnar  epithelium,  con- 
tinuous inwardly  with  that  occupying  the  intervals  of  the  auditory 
teeth  and  outwardly  with  the  acoustic  organ. 

The  acoustic  organ  of  the  cochlea,  or  organ  of  Corti,1  is  at- 
tached to  the  inner  zone  of  the  basilar  membrane  within  the  cochlear 
duct,  and  consists  in  a  peculiar  modification  of  its  lining  epithelium. 
It  produces  a  convex  spiral  ridge 2  external  to  the  position  and  course 
of  the  spiral  groove,  continuous  with  its  epithelium  and  that  investing 
the  outer  zone  of  the  basilar  membrane.  Its  chief  structural  elements 
are  distinguished  as  the  acoustic  rods  and  hair-cells. 

The  acoustic  rods 3  are  long  narrow  columnar  cells  with  expanded 
extremities,  arranged  in  an  inner  and  an  outer  row.  They  are  com- 
paratively rigid,  bent  in  a  sigmoid  manner,  and  are  attached  by  a  broad 
conical  base  to  the  inner  zone  of  the  basilar  membrane.  The  inner 
rods  rest  on  it  immediately  external  to  the  foramina  of  the  cochlear 
nerves,  while  the  outer  rods  rest  on  the  membrane  some  distance  from 
the  others  externally.  From  their  base  the  two  rows  of  rods  incline 
towards  each  other  and  interlock  by  their  opposite  extremity  or  head. 
They  thus  enclose  a  spiral  canal 4  in  the  course  of  the  cochlear  duct, 
filled  with  endolymph.  The  inner  rods  are  more  numerous  and  more 
closely  applied  together  than  the  outer  rods,  which  are  longer  and  come 
near  together  laterally  only  at  the  extremities.  The  head  of  the  inner 
rods  is  externally  excavated,  and  embraces  that  of  the  outer  rods,  from 
which  a  paddle-like  process,  or  phalanx,  is  directed  outward. 

The  acoustic  rods  are  longitudinally  striated  and  within  the  head 
contain  a  nucleus.  In  the  angle  at  their  base,  on  each  side  of  the  spiral 
canal,  lies  a  wedge-shaped  cell  with  granular  contents  and  a  nucleus. 

Adjoining  the  inner  acoustic  rods  internally  is  a  row  of  acoustic 
hair- cells;  externally  to  the  outer  rods  are  four  successive  rows,  in 
which  the  hair-cells  alternate  in  position.  The  acoustic  hair-cells  are 
long  columns  in  general  fixed  by  an  abrupt  tapering  process  to  the 

basilar  membrane.     They  conform  to  the  inclination  of  the  acoustic 

• 
rods  and  end  in  a  rounded  extremity  which  is  furnished  with  a  curved 

row  of  short,  stiff,  hair-like  filaments. 

The  acoustic  hair-cells  have  a  granular  protoplasm  with  a  central 
nucleus.  They  are  regarded  as  being  directly  connected  with  the  ulti- 
mate axial  fibrils  of  the  cochlear  nerves. 

The  intervals  of  the  rods  and  hair-cells  extending  to  the  basilar 
membrane  are  occupied  by  long,  narrow,  columnar  supporting  cells,5 
which  conform  to  the  spaces  and  are  for  the  most  part  fusiform. 

1  Terminal  acoustic  apparatus.  2  Papilla  spiralis. 

3  Hods,  pillars,  or  fibres  of  Corti ;  bacilli  acustici. 

4  Arch  of  Corti.  5  Prop-cells  ;  cells  of  Deiters. 


OEGANS   OF   SPECIAL   SENSE.  915 

The  sloping  sides  of  the  acoustic  ridge  are  formed  of  columnar 
cells  successively  decreasing  in  length,  finally  merging  into  the  lining 
epithelium  of  the  spiral  groove  and  of  the  outer  part  of  the  basilar 
membrane. 

Covering  the  area  of  the  outer  hair-cells  is  a  reticular  membrane,1 
which  is  composed  of  elongate,  fiddle-shaped  plates,  or  phalanges. 
These  are  connected  with  one  another  and  with  those  of  the  outer  rods, 
and  leave  between  them  apertures,  through  which  protrude  the  ends 
of  the  acoustic  hair-cells  with  their  hairs.  The  ends  of  the  inner 
hair-cells  are  also  enclosed  by  a  cuticular  ring  connected  with  a  slight 
projection  from  the  head  of  the  inner  rods,  which  appears  to  accord 
with  the  reticular  membrane  of  the  outer  hair-cells. 

Covering  the  acoustic  organ  is  the  tectorial  membrane,2  which 
springs  from  the  spiral  crest,  is  thence  extended  over  the  spiral  groove 
and  rests  on  the  spiral  ridge  in  contact  with  the  acoustic  rods  and 
hair-cells.  At  its  commencement  it  is  thin,  but  thickens  into  a  cushion, 
which  partially  fills  the  spiral  groove  and  then  thins  away  as  it  lies  on 
the  spiral  ridge  over  the  area  of  the  acoustic  rods  and  hair-cells.  It 
is  finely  striated,  appears  filamentous  in  structure,  and  seems  to  be  a 
cuticular  production  from  the  adjacent  epithelium.  In  relation  to  the 
acoustic  hair-cells,  it  holds  the  same  position  as  the  otolites  and  cupolas 
do  to  the  hair-cells  of  the  acoustic  spots  and  crests  of  the  vestibule  and 
semicircular  canals. 

The  labyrinth  is  supplied  by  the  auditory  artery,  a  branch  of  the 
basilar  artery.  It  accompanies  the  auditory  and  facial  nerves,  and  in 
the  auditory  meatus  divides  into  vestibular  and  cochlear  branches, 
which  accompany  the  corresponding  nerves.  The  veins  generally 
pursue  the  same  course,  to  end  in  the  auditory  vein,  which  emerges 
from  the  internal  auditory  meatus  and  joins  the  inferior  petrosal  vein. 
Small  veins  from  the  cochlea  and  vestibule  also  pass  through  the  cor- 
responding aqueducts,  to  end  in  the  internal  jugular  vein  and  inferior 
petrosal  sinus. 

THE  SKIN. 

The  skin,  or  integument,3  forms  a  complete  covering  to  the  body, 
and  serves  as  a  protection  as  well  as  other  important  functions.  It 
is  highly  sensitive,  and  constitutes  the  special  sense  organ  of  touch. 
While  it  prevents  undue  evaporation,  it  is  the  seat  of  the  perspiratory 
function.  The  hairs  and  nails  are  appendages  of  the  skin,  and  embedded 
in  it  besides  the  perspiratory  glands  are  numerous  sebaceous  glands. 

The  skin  is  not  of  uniform  thickness,  but  varies  considerably  on 
different  parts  of  the  body.  Generally  it  is  thickest  on  those  parts 
which  are  least  protected,  as  on  the  back  of  the  trunk,  on  the  upper 

1  Membrana  or  lamina  reticularis. 

2  Membrana  or  lamina  tectoria  ;  membrane  of  Corti. 

3  Integumentum ;  cutis. 


910 


ORGANS   OF   SPECIAL  SENSE. 


FIG.  473. 


10 


and  back  parts  of  the  skull,  and  on  the  outer  back  part  of  the  limbs ; 
also  on  those  parts  habitually  exposed  to  friction,  as  on  the  palms  of  the 
hands  and  soles  of  the  feet.  It  is  thinnest  on  the  eyelids  and  lips,  on  the 
prepuce,  at  the  entrance  of  the  vulva,  and  at  the  margin  of  the  anus. 

The  skin  is  flexible,  very  tenacious,  moderately  extensible,  and  elas- 
tic. Smooth  in  infancy,  it  subsequently  becomes  more  or  less  furrowed 
and  wrinkled,  especially  at  points  of  habitual  flexion  and  extension 
and  at  other  more  movable  parts.  From  emaciation,  especially  in  the 
advance  of  age,  it  becomes  more  wrinkled,  but  under  active  nutrition 
and  in  obesity  it  remains  comparatively  smooth. 

The  skin  beneath  is  connected  with  the  superficial  fascia,  in  most 
positions  more  or  less  loosely  and  movably,  but  in  others  very  closely, 

as  in  the  scalp,  the  palms,  and  the 
soles.  The  connection  is  between 
the  deeper  looser  structure  of  the 
skin  and  the  superficial  layer  of 
the  superficial  fascia,  the  two  more 
or  less  merging  and  forming  the 
usual  seat  of  the  accumulation  of 
subcutaneous  fat. 

Where  the  skin  is  thinnest  it 
is  about  one-twenty-fifth  of  an 
inch ;  where  thickest  it  reaches 
one-eighth  of  an  inch  or  more.  It 
consists  of  two  chief  layers,  the 
dermis  and  the  epidermis. 

The  dermis l  forms  the  deeper 
layer  of  the  skin,  and  it  is  for  the 
most  part  proportioned  in  thick- 
ness to  the  skin.  It  is  chiefly 
composed  of  a  close  intertexture 
of  bundles  of  fibro-connective  tis- 
sue, interwoven  in  different  direc- 
tions and  mingled  with  more  or 
less  elastic  tissue  varying  in  differ- 
ent-parts. Its  structure  is  more 
compact  next  the  outer  surface, 
while  its  deeper  part  is  looser  and 
of  more  open  texture.  Beneath 
it  gradually  blends  with  the  super- 
ficial fascia,  and  its  meshes  are  filled  with  adipose  tissue  often  enclosing 
sweat-glands,  and  in  some  parts  the  roots  of  the  hairs. 

Unstriped  muscular  tissue  also  enters  into  the  structure  of  the 
dermis.  Mostly  it  occurs  in  little  bundles  of  fibres  connected  with  the 


DIAGRAM  OF  A  VERTICAL  SECTION  OF  THE  SKIN 
OF  THE  FOREFINGER  ACROSS  TWO  OF  THE  RIDGES 
OF  THE  SURFACE:  highly  magnified.  1,  dermis 
composed  of  an  intertexture  of  bundles  of 
fibro-connective  tissue ;  2,  epidermis ;  3,  its 
cuticle ;  4,  its  rete ;  5,  subcutaneous  connective 
and  adipose  tissue ;  6,  tactile  papillse ;  7,  sweat- 
glands;  8,  duct;  9,  spiral  passage  from  duct 
through  the  epidermis ;  10,  termination  of  the 
passage  on  the  summit  of  the  ridge. 


1  Derm  ;  derma  ;  cutis  vera ;  corium  ;  true  skin. 


ORGANS   OF  SPECIAL  SENSE. 


917 


FIG.  474 


hair-follicles  embedded  in  the  dermis.  In  other  parts  it  is  an  abun- 
dant constituent  of  the  skin,  as  in  that  of  the  scrotum,  the  perineum, 
the  penis,  and  the  nipple. 

The  various  markings  seen  on  the  surface  of  the  skin,  the  minute 
pits,  the  reticular  lines  and  furrows,  extend  into  the  superficial  portion 
of  the  dermis. 

The  dermis  is  furnished  with  little  eminences,  the  tactile  papillae, 
or  papillae  of  touch,1  which  are  most  abundant  and  largest  where 
the  sense  of  touch  is  most  acute, 
as  on  the  palms  and  soles,  and 
especially  on  the  digits.  They 
are  conical  processes  of  the  der- 
mis, with  a  rounded  summit.  The 
larger  ones  are  commonly  divided 
into  two  or  three,  thus  forming 
compound  papillae. 

On  the  palms  and  soles  the 
tactile  papillae  are  arranged  closely 
in  double  rows,  which  form  the 
conspicuous  linear  ridges  observed 
in  these  positions  running  parallel 
with  one  another  in  curving  lines 
and  separated  by  narrow  furrows. 
In  other  parts  of  the  skin  the 
papillae  are  fewer,  smaller,  and 
irregularly  scattered,  and  in  some 
parts  almost  disappear  or  seem  to  be  substituted  by  the  slightest  ridges. 

The  larger  tactile  papillae  range  from  ^^  to  y^-  of  an  inch  in 
height;  on  the  face  they  are  much  reduced  and  range  from  -g^  to 
-^y  of  an  inch. 

The  dermis  is  highly  vascular  and  also  well  supplied  with  nerves. 
The  arteries,  which  enter  beneath  from  the  superficial  fascia  and  freely 
ramify  and  anastomose  throughout  the  dermal  structure,  supply  in 
their  course  the  numerous  perspiratory  and  sebaceous  glands  and  the 
hair-follicles.  They  end  in  a  rich  capillary  net  at  the  surface,  whence 
loops  extend  into  most  of  the  tactile  papillae.  Veins  closely  accompany 
the  arteries,  to  end  in  the  subcutaneous  venous  plexuses.  Lymphatics 
are  exceedingly  abundant,  commencing  in  lymph-spaces  in  the  inter- 
stices of  the  connective-tissue  structure  of  the  dermis.  They  form 
a  capillary  plexus  at  the  external  surface  beneath  that  of  the  blood- 
Vessels,  and  the  capillary  lymphatics  are  larger  than  those  of  the  blood- 
vessels. A  coarser  plexus  in  the  deeper  part  of  the  dermis  commu- 
nicates with  the  superficial  plexus  and  with  lymphatic  trunks,  which 
mostly  pursue  the  course  of  the  subcutaneous  blood-vessels. 


Two  TACTILE  PAPILLAE:  highly  magnified; 
from  the  skin  of  the  finger.  The  tactile  cor- 
puscle seen  in  the  interior,  and  medullated 
nerve-fibres  connected  with  them. 


Papillae  tactus. 


918 


ORGANS   OF   SPECIAL   SENSE. 


FIG.  475. 


The  nerves  of  the  dermis  are  numerous,  and  are  everywhere  con- 
spicuous in  the  subcutaneous  fascia  as  the  cutaneous  branches  of  the 
cerebro-spinal  nerves.  They  ascend  obliquely  into  the  dermis  and 
form  a  plexus  which  becomes  closer  and  finer  approaching  the  external 
surface.  From  the  plexus  medullated  nerve-fibres  enter  the  tactile 
papillae ;  from  many  the  axial  fibres  proceed  to  be  distributed  in  the 
epidermis.  The  cutaneous  nerves  also  supply  the  hair-follicles  and 
their  muscles,  and  the  sweat  and  sebaceous  glands. 

In  the  skin  of  the  hands  and  feet,  especially  in  the  palm  and  sole, 
many  of  the  tactile  papillae  contain  a  peculiar  body,  named  the  tactile 
corpuscle.1  It  occupies  the  greater  part  of  the  papillae  and  appears 
to  exclude  the  usual  looped  capillary  vessel.  It  is  elliptical  in  shape, 
is  provided  with  a  connective-tissue  capsule  with  incomplete  partitions, 
and  is  continuous  with  the  surrounding  tissue  of  the  papilla  and  that 
of  the  nerve-sheath  connected  with  it.  Usually  one  or  two  medullated 
nerve-fibres  enter  a  corpuscle,  directly  or  after  winding  several  times 

around  it.  Within  the  corpuscle 
the  nerve-fibres  lose  their  medul- 
lary sheath,  the  axis-fibres  branch, 
and  the  divisions,  often  more  or 
less  varicose,  become  convoluted 
and  terminate  in  a  bulbous  enlarge- 
ment at  the  surface  of  the  enclosing 
capsule. 

Pacinian  corpuscles.  Along 
the  course  of  the  cutaneous  nerves 
of  the  hand  and  foot  attached  to 
the  branches  are  many  little,  oval, 
pearly-white,  glistening  bodies  em- 
bedded in  the  areolar  tissue  and 
fat,  named  the  pacinian  corpus- 
cles.2 A  few  are  found  on  other 
cutaneous  nerves,  as  in  those  of 
the  neck  and  arm.  They  also 
occur  on  the  branches  of  the  pudic 
nerves  in  the  penis  and  clitoris, 
also  on  the  intercostal  nerves,  on 
those  of  the  mammae,  and  else- 
where. They  have  been  likewise 
found  on  the  nerves  of  the  solar 
plexus  of  the  sympathetic  nerve. 

In  the  mesentery  of  the  cat  they  are  remarkable  for  their  distinctness. 

On   the   digital  nerves  they  are   commonly  from  half  a   line  to 

a  line  in  length  or  more,  and  are  readily  distinguishable  from  the 


PACINIAN  CORPUSCLES,  from  the  digital  nerve 
of  the  finger  of  a  new-born  child.  1,  much 
magnified  corpuscle,  which  was  reniform; 
2,  the  pedicle;  3,  portion  of  the  digital  nerve; 
4,  several  nerve-fibres ;  5,  the  fibrous  sheath ; 

6,  medullated  nerve-fibre   to   the   corpuscle; 

7,  axis-fibre  of  the  nerve-fibre ;  8,  portion  of 
a  digital  nerve  with  pacinian  corpuscles  at- 
tached, of  the  natural  size. 


Corpusculum  tactus. 


Corpuscles  of  Vater. 


ORGANS   OF   SPECIAL   SENSE. 


919 


surrounding  yellowish  fat  and  con-  .  FIG.  476. 

nective  tissue. 

Each  corpuscle  is  attached  by 
a  short  stalk  or  pedicle  of  connec- 
tive tissue,  traversed  by  a  single 
medullated  nerve-fibre,  with  a 
small  accompanying  artery  and 
vein. 

The  corpuscle  is  composed  of 
numerous  concentric  tunics,  which 
in  the  larger  ones  are  from  thirty 
to  double  the  number.  The  central 
capsule,  which  is  long  and  narrow, 
is  filled  with  a  clear  core  traversed 
by  a  nerve-fibre.  The  tunics  are 
continuous  with  the  neurilemma  of 
the  nerve-fibre  of  the  pedicle,  and 
are  composed  of  fibro-connective 
with  elastic  tissue,  invested  on 
their  surfaces  with  an  endothe- 
lium.  The  nerve-fibre  of  the  pedi- 
cle passes  directly  through  to  the 
inner  capsule,  where  it  loses  its 
medullary  sheath,  thence  runs 
through  the  central  core  to  the 
opposite  extremity  and  ends  in  a 
little  knob,  or  sometimes  divides 
into  twTo  or  three  short  branches, 
which  end  in  the  same  manner. 

No  satisfactory  function  has 
been  ascertained  for  the  pacinian 
corpuscles. 

The  epidermis,1  forming  the 
free  or  exterior  surface  of  the  skin, 
is  in  general  much  thinner  than 
the  subjacent  dermis,  and  is  of 
more  uniform  thickness,  though 
for  the  most  part  proportioned  to 
it.  It  is  thickest  in  the  palm  of 
the  hand  and  sole  of  the  foot, 
where  the  skin  is  habitually  sub- 
jected to  pressure  and  friction, 
and,  though  the  condition  is  in  a  measure  independent  of  these  cir- 
cumstances, they  nevertheless  greatly  promote  it,  as  exemplified  by  the 


DIAGRAM  OF  THE  EPIDERMIS  WITH  A  TACTILE 
PAPILLA,  in  perpendicular  section :  highly  mag- 
nified. 1,  dermis  with  a  tactile  papilla  con- 
taining a  looped  capillary  vessel;  2-6,  epi- 
dermis ;  2,  deep  stratum  of  columnar  cells  of 
the  epidermal  rete ;  3,  strata  of  polyhedral  cor- 
rugated cells  of  the  epidermal  rete ;  4,  the  lucid 
layer ;  5,  cell-strata  of  the  cuticle ;  6,  superficial 
dry  scales  of  the  cuticle. 


Epiderma;   cuticula. 


920  ORGANS   OP   SPECIAL   SENSE. 

hard  hands  of  the  laborer.  Its  increase  in  thickness  from  the  same 
causes  is  also  illustrated  in  the  production  of  corns,  which  consist  of 
thickenings  of  the  epidermis. 

The  epidermis  is  a  stratified,  cellular,  or  epithelial  structure,  re- 
markable for  the  great  comparative  number  of  its  cell-strata.  It  ad- 
heres most  intimately  to  the  dermis,  though  this  is  not  defined  in  the 
manner  usual  to  similar  membranous  structures  by  an  even  basement 
membrane,  but  conforms  to  the  adjacent  cells,  which  seem  to  fit  into 
corresponding  depressions  or  pits  of  the  surface. 

The  epidermis  is  separable  into  two  principal  layers,  of  which  the 
exterior,  distinguished  as  the  cuticle,1  is  the  thicker,  drier,  and  harder, 
and  is  horn-like  in  character  where  it  is  thickest.  The  deeper  layer,  or 
epidermal  rete,2  is  soft,  adheres  to  the  dermis  beneath,  and  merges 
into  the  cuticle  above.  From  its  soft  condition  and  reticular  appear- 
ance, due  to  its  being  impressed  by  the  papillary  surface  of  the  dermis, 
it  acquired  the  name  of  the  rete  mucosum.  Ordinarily  after  death  it 
quickly  softens  from  decomposition  and  thus  permits  the  cuticle  to  be 
easily  detached.  Through  burns  and  blisters  it  is  readily  broken  up 
and  the  cuticle  is  separated  by  the  effusion  of  liquid  from  the  dermis. 

The  cell-strata  of  the  epidermis  are  proportioned  in  number  to  its 
thickness ;  the  cells  composing  them  vary  greatly  in  shape,  size,  and 
physical  and  chemical  constitution. 

The  superficial  strata  of  the  cuticle  are  incessantly  shed,  con- 
stituting scurf  and  dandruff,  while  the  deep  strata  of  the  epidermal 
rete  are  as  incessantly  produced  and  the  successive  cell-strata  of  the 
epidermis  are  constantly  undergoing  transformation ;  the  deeper  into 
the  condition  of  the  more  superficial. 

The  epidermal  rete,3  the  soft,  deep  layer  of  the  epidermis,  is 
thinner  and  more  uniform  than  the  cuticle. 
FlG-  477-  It  consists  of  many  cell-strata,  of  which  the 

deepest,  or  that  adherent  to  the  dermis,  ia 
composed  of  columnar  cells,  while  the  others 
consist   of  polyhedral   cells,   in    the   deeper 
layers  of  nearly  uniform  diameter,  but  suc- 
cessively becoming  larger,  and  in  the  higher 
CORRUGATED  OR  FURROWED     layers  proportionately  of  greater  horizontal 
CELLS   FROM   THE   EPIDERMAL     breadth.    The  cells  *  are  corrugated  or  ridged ; 

RETE  :  highly  magnified.  ,          .,  „  .  ,,  ... 

the  ridges  01  contiguous  cells  conjoining  so 

as  to  leave  intercellular  channels  permeable  to  nutritive  liquid  from 
the  dermis. 

Where  the  epidermal  rete  is  about  to  merge  into  the  cuticle,  sev- 
eral strata,  in  which  the  cells  are  flatter  or  of  greater  breadth  and  lesa 

1  Cuticula. 

2  Stratum  or  rete  Malpighi ;  corpus  reticulare,  cvibrosum,  or  mucosum. 

3  Kete  mucosum  ;  r.  Malpighi.  *  Spinous,  furrowed,  or  ridged  cells. 


ORGANS   OF   SPECIAL   SENSE. 


921 


depth  and  less  distinctly  outlined,  form  a  layer  which  has  been  distin- 
guished as  the  lucid  stratum.1 

The  cuticle2  consists  of  many  strata  of  polyhedral  cells  larger 
than  those  of  the  epidermal  rete,  mainly  in  the  breadth,  as  in  the  lucid 


FIG.  478. 


FIG.  479. 


SCURF  FROM  THE  LEG:  magnified.  1,  a  frag- 
ment of  scurf,  consisting  of  dried,  flattened, 
non-nucleated  cells  or  scales;  2,  a  few  cells 
with  a  nucleus;  3,  a  cell  more  highly  magni- 
fied, to  exhibit  its  polyhedral  form. 


FRAGMENT  OF  DANDRUFF  FROM  THE  HEAD  : 
magnified.  1,  portion  of  dandruff,  consisting 
of  non-nucleated  cells ;  2,  several  fragments, 
consisting  of  nucleated  cells :  3,  isolated  cells, 
some  with  and  others  without  nuclei ;  4,  a  cell 
more  highly  magnified,  from  the  deep  part  of 
the  cuticle. 


stratum  regarded  as  pertaining  to  the  rete.  The  cells  are  also  more 
translucent  and  homogeneous  and  generally  without  a  nucleus  or  with 
only  indistinct  traces.  At  the  exterior  surface  the  cell-strata  form  a 
comparatively  dry  layer  of  flat,  homogeneous  scales.  The  more  super- 
ficial cell-strata  are  readily  detached  in  fragments  or  flakes  by  friction, 
and  these  are  constantly  removed  in  ablution. 

The  soft  cells  of  the  epidermal  rete  are  readily  dissolved  by  certain 
reagents,  as  acetic  acid,  which 

has  no  effect  on  the  cells  of  the  FlG-  48°- 

cuticle.  The  dry  scales  of  this 
layer,  when  acted  on  by  a  solution 
of  potash,  swell  up  and  assume 
the  appearance  of  vesicular  cells. 

The  cells  of  the  epidermis 
contain  some  coloring  matter. 
In  the  negro  and  other  dark- 
skinned  races  the  pigment,  as 
minute  black  granules,  is  in  great 
measure  contained  in  the  cells  of  the  epidermal  rete.  It  disappears 
in  the  transformation  of  the  cells  into  those  of  the  cuticle ;  hence  the 
thick  cuticle  of  the  hand  of  the  blackest  man  differs  but  little  in  color 
from  that  of  the  white  man. 

The  epidermis,  like  all  other  epithelial  structures,  is  entirely  devoid 
of  blood-vessels  and  lymphatics.  The  cuticle  is  utterly  insensible, 
though  nerves,  as  fine  varicose  nerve-fibrils,  have  been  traced  proceeding 
from  the  dermis  and  ramifying  among  the  cells  of  the  epidermal  rete.  • 


CELLS  FROM  THE  EPIDERMAL  RETE.  1,  from  the 
face  of  a  white  man;  2,  from  a  negro:  highly 
magnified. 


Stratum  lucidum. 


Cuticula ;  stratum  corneum. 


922 


ORGANS   OF  SPECIAL   SENSE. 


Certain  cells,  distinguished  as  tactile  cells,1  have  been  indicated 
as  occurring  in  the  epidermal  rete  and  the  superficial  layer  of  the 
dermis.  They  are  described  as  pyriform  cells,  which  terminate  nerve- 
fibrils. 

THE  NAILS. 

The  nails2  are  plates  of  horn,  and  are  homologous  with  the  claws 
and  hoofs  of  other  animals.  They  are  continuous  with  the  epidermis, 
of  which  they  are  modified  appendages,  and  like  it  are  products  of  the 
subjacent  dermis. 

The  nail  rests  on  the  nail-bed s  of  the  dermis,  the  middle  portion 


FIG.  481. 


FIG.  482 


FIG.  483. 


Kg.  481.— BED  OF  THE  NAIL.  1,  fold  of  the  skin  which  covers  the  root  of  the  nail ;  2,  the  fold 
partially  turned  up  to  show  the  depth  of  the  groove  beneath ;  3,  4,  posterior  and  anterior  portions 
of  the  nail-bed,  the  former  the  less  vascular,  and  giving  rise  to  the  appearance  called  the 
lunula.  The  longitudinal  lines  indicate  the  ridges  bordered  with  papillae. 

Fig.  482. — UNDER  SURFACE  OF  THE  NAIL.  1,  root;  2,  part  corresponding  with  the  lunula; 
3,  grooved  surface  adapted  to  the  ridges  of  the  nail-bed ;  4,  free  border. 

fig.  483. — VERTICAL  SECTION  OF  THE  END  OF  A  FINGER.— 1,  epidermis  on  the  back  of  the  finger ; 
2,  point  at  which  it  is  reflected  to  become  continuous  with  the  nail ;  3,  the  nail ;  4,  epidermis  at 
the  end  of  the  finger ;  5,  6,  7,  8,  epidermal  rete ;  9, 10, 11, 12,  dermis ;  13,  last  phalanx ;  14,  flexor 
tendon. 

being  distinguished  as  its  body.  The  back  portion,  or  root,  a  fourth 
or  more  of  the  length  of  the  whole  nail,  occupies  a  deep  crescentic 
cleft  of  the  nail-bed,  while  the  lateral  margins  occupy  shallower  grooves 
and  the  free  edge  projects  beyond  the  end  of  the  digit. 

The  nails  are  whitish  or  nearly  colorless,  and  translucent,  and  on 
the  bed  appear  pink  from  its  vascularity.  Next  the  root  there  often 
appears  the  segment  of  a  circle,  the  lunule,  of  whiter  hue,  due  to 
less  vascularity  in  the  corresponding  portion  of  the  bed.  Not  unfre- 
quently  irregular  white  spots  occur  in  the  nails. 

The  nails  are  longitudinally  striate,  and  their  under  surface  is  finely 
and  deeply  furrowed  in  accordance  with  the  striae.  The  body  of  the 
nail  is  of  uniform  thickness,  but  the  root  is  thinner  and  tapers  to  a 
sharp  edge. 

Beneath  the  free  edge  and  at  the  lateral  borders  the  nail  is  con- 
tinuous with  the  epidermis,  and  is  also  continuous  with  it  in  advance 
of  the  root  above,  where  it  forms  a  narrow  band  adherent  to  the  nail. 


Cells  of  Merkel. 


Ungues. 


Matrix. 


ORGANS  OF  SPECIAL  SENSE. 


923 


In  the  nail-bed  the  dermis  presents  numerous  fine  longitudinal 
ridges  divided  at  their  summits  into  rows  of  vascular  papillae  and 
received  in  furrows  of  the  nail. 

The  nails  are  composed  of  numerous  strata  of  cells,  of  which  the 


FIG.  484. 


CELLS  OF  THE  NAIL,  after  boiling  in  solution 
of  soda.  A,  cells  viewed  laterally  ;  B,  from  the 
upper  surface,  a,  cell-membrane ;  b,  nuclei  seen 
on  the  broad  surface ;  c,  nuclei  seen  on  the  side. 


TRANSVERSE  SECTION  THROUGH  THE  NAIL  AND 
ITS  BED  :  magnified  250  diameters.  A,  dermis : 
B,  deep  layer  of  the  nail ;  C,  horny  layer,  a, 
ridges  of  the  bed ;  b,  deep  cell-strata ;  c,  ridges 
of  the  under  surface  of  the  nail ;  d,  deep  stratum 
of  columnar  cells ;  e,  upper  strata  of  polyhe- 
dral cells ;  /,  cell-strata  of  the  horny  layer. 


deeper  correspond  with  the  epider- 
mal rete,  are  continuous  with  it, 
and  accord  with  it  in  structure. 
The  thicker,  hard  portion  of  the 
nail,  corresponding  with  the  cuticle 

of  the  epidermis,  consists  of  many  strata  of  broad,  flattened  cells  inti- 
mately coherent  and  indistinctly  defined.  Treated  with  caustic  soda, 
the  constituent  cells  of  the  nail  assume  a  vesicular  form  and  exhibit  a 
nucleus. 

The  nails  grow  like  the  epidermis,  by  an  incessant  production  of 
cells  in  the  nail-bed ;  the  growth  in  length  being  due  to  the  production 
at  the  bottom  of  the  cleft  enclosing  the  root  of  the  nail,  and  the  increase 
in  thickness  to  the  production  over  the  general  surface  of  the  nail- 
bed. 

THE   HAIK. 

Hairs1  are  appendages  of  the  epidermis.  They  grow  and  pro- 
ject from  pockets  of  the  dermis,  named  the  hair-follicles.  In  the 
smaller  hairs  the  follicles  are  embedded  in  the  thickness  of  the  dermis, 
but  in  the  larger  hairs  the  follicles  extend  from  the  dermis  beneath,  into 
the  subjacent  areolar  tissue  and  fat. 

Hair  is  found  nearly  everywhere  over  the  body  except  on  the  palms 


1  Pili ;  pile  ;  crinis  ;  tbrix. 


924 


ORGANS   OF  SPECIAL   SENSE. 


of  the  hands  and  soles  of  the  feet,  the  knuckles,  the  back  of  the  last 
joints  of  the  digits,  the  lips,  nipples  and  areolse,  the  glans,  prepuce, 
and  verge  of  the  anus.  Hairs  are  generally  implanted  in  the  skin  in 
a  slanting  manner,  and  only  in  the  eyelashes  do  they  project  at  right 
angles  to  it.  They  vary  in  extent  of  development  and  other  characters 
in  different  parts  of  the  body,  and  in  different  races,  sexes,  and  indi- 
viduals. They  are  in  general  most  conspicuously  produced  as  the  hair 


FIG.  486. 


HAIR-FOLLICLE:  magnified,  a,  shaft  of  the 
hair ;  6,  root ;  c,  bulb ;  d,  cuticle  of  the  hair ;  e, 
inner  hair-sheath ;/,  outer  hair-sheath  ;  g,  base- 
ment membrane  defining  the  fibrous  layer,  h.  of 
the  follicle;  i,  hair-papilla;  k,  termination  of 
ducts  of  two  sebaceous  glands ;  I,  dermis ;  m,  n, 
rete  and  cuticle  of  the  epidermis. 


FIG.  487. 


14 


SECTION  OF  THE  SKIN  OF  THE  SCALP  WITH  A 
HAIR-FOLLICLE.  1,  cuticle;  2,  epidermal  rete: 
3,  tactile  papilla:  4,  dermis;  5,  hair-papilla;  6, 
vessel ;  7,  hair-bulb ;  8,  hair ;  9,  inner  root- 
sheath  ;  10,  outer  root-sheath ;  11,  wall  of  the 
hair-follicle;  12,  erector  muscle;  13,  sebaceous 
follicles;  14,  subcutaneous  areolar  tissue  and 
fat.  Highly  magnified. 


of  the  head,  on  the  eyebrows,  as  the  eyelashes,  on  the  pubes,  in  the 
axillae,  and  as  the  beard  in  the  male.  The  hair  of  the  head  is  longest, 
especially  in  the  female,  and  is  the  finest  of  the  larger  hairs,  while  that 
of  the  beard  is  the  coarsest.  Elsewhere  the  hair  is  variably  produced, 
often  to  the  greatest  extent  in  the  male  on  the  breast  and  outer  part 
of  the  limbs,  but  in  general,  except  in  the  parts  mentioned,  it  is  rudi- 
mentary compared  with  its  condition  in  other  animals  of  man's  class. 


ORGANS   OF   SPECIAL   SENSE. 


925 


PIG.  488. 


The  usually  short  and  often  downy  hairs 1  spread  over  most  parts  of 
the  body  are  less  developed  in  the  female  than  in  the  male,  and  com- 
monly less  in  the  negro  than  in  the  white  man. 

The  hair  of  the  head 2  in  the  white  race  is  long,  fine  and  straight 
or  moderately  curling,  and  variously  colored.  In  the  American  Indian 
and  Mongolian  it  is  long,  coarse,  straight,  and  black.  In  the  negro  it 
is  short,  fine,  crisp,  closely  curled,  and  commonly  black. 

The  hairs  of  the  beard,  the  pubes,  and  the  axillae  are  generally  more 
alike,  coarse,  crisp,  and  curling. 

In  general  straight  hairs  are  cylindrical ;  in  those  which  are  curling 
or  woolly  they  are  more  or  less  flattened  cylindrical. 

The  hairs  are  lustrous  and  smooth  in  appearance,  though  they  are 
minutely  and  sufficiently  scabrous  to  possess 
the  felting  quality  which  is  common  in  the 
hair  of  animals. 

The  long  hairs  usually  grow  indefinitely, 
and  if  not  habitually  reduced  by  cutting 
become  worn  and  broken  or  split  at  the 
ends.  Many  short  hairs,  like  those  of  the 
eyebrows  and  eyelashes,  grow  to  a  certain 
length,  are  tapering  at  the  free  end.  and 
from  time  to  time  are  shed,  to  be  succeeded 
by  others. 

The  main  part  of  a  hair  is  its  body, 
shaft,  or  stem,3  and  the  portion  implanted 
in  the  skin  is  distinguished  as  the  root.4 

Light-colored  hairs  viewed  with  the 
microscope  appear  translucent,  longitudi- 
nally finely  striate,  and  marked  on  the 
surface  by  crossing  wave-like  lines.  Dark 
or  black  hairs  possess  the  same  characters 
more  or  less  obscured  by  the  color. 

The  hair  is  mainly  composed  of  longi- 
tudinal tapering  fibres,5  which  are  flattened, 
fusiform  fibre-cells  with  a  central,  linear 
nucleus.  The  color  of  the  hair  is  in  great 
measure  due  to  diffused  pigment  in  the 
fibrous  structure  and  to  more  defined  spots 

and  streaks  of  granules  of  pigment.  In  silvery-white  hairs  of  aged 
people  minute  lacuna?  in  the  fibrous  substance  contain  air,  which  may 
be  expelled  by  the  application  of  hot  oil  of  turpentine,  when  the  hairs 
are  rendered  more  transparent.  In  the  whitening  of  hair  with  the 
advance  of  age  the  pigment  matter  ceases  to  be  produced. 

In  many  hairs,  especially  the  coarser  ones,  as  those  of  the  beard, 


PORTION  OF  A  HAIR  FROM  THE 
OUTER  PART  OF  THE  THIGH  :  mag- 
nified. 1,  shaft  of  the  hair  covered 
with  transverse  markings  indicat- 
ing the  projecting  edges  of  the  cu- 
ticular  scales;  2,  fibrous  substance 
at  the  end  of  the  hair  broken  up 
into  coarse  fibres  as  the  result  of 
friction  of  the  clothing. 


1  Down ;  lanugo. 


Capilli. 


3  Scapus. 


Kadix  pili.        6  Cortex. 


926  ORGANS   OF   SPECIAL   SENSE. 

the  axis  is  occupied  by  a  pith  or  medulla.  This  appears  by  trans- 
mitted light  more  opaque  than  the  surrounding  fibrous  substance,  and 
by  reflected  light  is  white.  It  is  sometimes  more  or  less  interrupted, 
and  in  pointed  hairs,  like  those  of  the  eyebrow,  ceases  near  the  end. 
It  is  composed  of  rounded,  polyhedral,  granular  cells,  often  with  minute 
air-bubbles.  Mostly  in  the  hair  of  the  scalp  and  the  fine  downy  hair  of 
the  body  the  medulla  is  absent. 

The  hairs  are  covered  with  a  delicate  cuticle,  which  consists  of  a 
single  stratum  of  imbricating  scales  overlapping  from  below,  with  the 
upper  edges  sufficiently  projecting  to  render  the  surface  uneven. 

FIG.  489. 


A.  PORTION  OF  THE  SHAFT  OF  A  LIGHT  HAIR  :  magnified.  The  longitudinal  lines  are  pro- 
duced by  the  fibrous  substance ;  the  transverse,  undulating  lines,  by  the  cuticle.  B.  Isolated 
scales  of  the  cuticle. 

The  root  of  the  hair  at  its  lower  part  gradually  enlarges,  is  softer 
and  lighter  in  color,  and  ends  in  a  still  softer  swelling,  the  hair-bulb.1 
This  is  continuous  with  the  bottom  of  the  hair-follicle  and  encloses  a 
papilla  projecting  from  it.  The  hair-papilla  is  conical,  usually  a  little 
enlarged  at  the  extremity  so  as  to  appear  fungiform.  The  hair-bulb  is 
composed  of  polyhedral  nucleated  cells,  which  gradually  merge  above 
into  the  structure  of  the  hair-shaft. 

The  hair-follicle2  conforms  in  shape  to  the  root  of  the  hair,  is 
variably  deep,  and  mostly  proportioned  to  the  size  of  the  hair.  Near  its 
mouth  in  the  dermis  it  receives  the  ducts  of  several  sebaceous  glands, 
and  above  this  point  is  funnel-shaped  and  formed  by  the  epidermis. 

The  wall  of  the  hair-follicle  consists  of  an  outer  dermic  layer  and 
an  inner  epithelium  continuous  with  that  of  the  sebaceous  glands 
opening  into  the  follicle,  and  with  the  epidermis. 

The  dermic  layer  is  thin  and  compact,  outwardly  composed  of 
connective  tissue,  and  inwardly  of  transverse  unstriped  muscle-fibres, 
defined  from  the  epithelium  by  a  clear  basement  membrane.  At  the 
bottom  of  the  follicle  it  is  continuous  with  the  hair-papilla,  which 
is  composed  of  connective  tissue  in  a  hyaline  matrix,  and  is  supplied 
with  capillary  vessels  and  nerve-fibres. 

The  epithelium  of  the  hair-follicle,  from  its  directly  enclosing  the 
root  of  the  hair,  is  named  the  root-sheath.  It  is  thick  and  stratified, 
and  is  divisible  into  two  principal  layers,  distinguished  as  the  inner 
and  the  outer  root-sheath. 

1  Bulbus  or  pulpa  pili ;  capitulum;  hair-button.  2  Folliculus  pili. 


ORGANS   OF   SPECIAL  SENSE. 


927 


The  outer  root- sheath  is  continuous  with  the  deep  layer  of  the 
epidermis  and  accords  with  it  in  composition.  Around  the  hair-bulb 
it  becomes  thinner  and  at  its  base  is  continuous  with  it. 

The  inner  root-sheath  corresponds  with  the  cuticle  of  the  epi- 


FIG.  491. 


DIAGRAM  OF  THE  STRUCTURE  OF  THE 
ROOT  OF  A  HAIR  AND  ITS  FOLLICLE.  1,  hair- 
papilla  ;  2,  capillary  vessel ;  3,  nerve-fibres ; 
4,  fibrous  wall  of  the  hair-follicle ;  5,  base- 
ment membrane ;  6,  outer  root-sheath  ;  7, 
inner  root-sheath;  8,  cuticle  of  the  hair;  9, 
fibrous  structure;  10,  medulla;  11,  cellular 
structure  of  the  hair-bulb ;  12,  transition 
cells.  Highly  magnified. 


DIAGRAM  OF  THE  STRUCTURE  OF  A  TRANSVERSE  SEC- 
TION OF  A  HAIR  WITH  ITS  FOLLICLE  :  highly  magnified. 
1,  fibrous  and  muscular  layer  of  the  follicle ;  2,  base- 
ment membrane ;  3-6,  epidermic  layer  of  the  folli- 
cle or  root-sheath  of  the  hair ;  3,  strata  of  polyhedral 
cells;  4,  deep  stratum  of  columnar  cells;  5,  6,  cutic- 
ular  layer  or  inner  root-sheath ;  7,  hair ;  8,  its  cuti- 
cle. 


dermis,  and  is  composed  of  several  cell- 
strata,  of  which  the  outer  ones1  consist 
of  small  polyhedral  cells.  These  are 
succeeded  by  a  stratum2  of  clear,  ob- 
long cells  with  frequent  gaps  between 
them,  so  as  to  appear  like  a  perforated  membrane.  Internal  to  this 
is  a  stratum  of  overlapping  scales,  the  projecting  edges  of  which  are 
directed  downward  and  conform  to  those  of  the  cuticular  layer  of  the 
hair,  the  projecting  edges  of  which  are  directed  upward.  In  conse- 
quence of  this  relation  of  the  inner  root-sheath  with  the  hair-root, 
when  the  hair  is  extracted  the  sheath  is  detached  with  it. 

The  hairs  grow  through  the  incessant  reproduction  of  cells  in  the 
hair-bulb  in  contact  with  the  hair-papilla.  Successive  series  of  cells 
advance  and  are  transformed  into  the  structural  elements  of  the  shaft 
of  the  hair,  mostly  into  the  fibre-cells,  but  the  outer  stratum  into  the 
cuticle  of  the  hair  and  the  central  ones  into  the  medulla,  when  this 
occurs.  Most  of  the  larger  hairs  grow  indefinitely,  while  others  are 
shed  at  variable  periods,  to  be  succeeded  by  others. 

The  rate  of  growth  of  the  hair  of  the  scalp  is  about  half  an  inch 
monthly.  When  hairs  are  shed  ordinarily,  the  papillae  are  atrophied,  to 


1  Henle's  layer. 


Huxley's  layer. 


928 


ORGANS   OF   SPECIAL,   SENSE. 


be  followed  by  the  production  of  others.     When  hairs  are  pulled  out, 
the  new  ones  commonly  grow  from  the  same  papillae. 

Connected  with  the  hair-follicles,  embedded  in  the  dermis,  are  little 
erector  muscles,1  commonly  one  for  each  follicle,  situated  beneath 
the  slant  of  the  hair.  They  spring  from  the  superficial  part  of  the 
dermis  and  descend  obliquely  to  the  wall  of  the  follicle  near  its  bottom. 
They  are  composed  of  unstriped  muscle-fibres.  The  erection  of  the 
hairs  through  these  muscles  is  exemplified  in  the  production  of  "  goose- 
flesh." 

THE  SEBACEOUS   GLANDS. 

The  sebaceous  glands 2  of  the  skin  are  numerous,  and  are  gener- 


FIG.  492. 


FIG.  493. 


SEBACEOUS  GLANDS  OPENING  INTO  THE  MOUTH 
OF  A  HAIK- FOLLICLE  :  much  magnified. 

ally  associated  with  the  hairs,  into 
the  follicles  of  which  their  ducts 
open.  They  secrete  a  greasy  sub- 
stance, the  sebaceous  matter,  which 
is  of  service  from  its  imbuing  the 
hair  and  epidermis.  The  glands 
are  embedded  in  the  dermis  at  the 
sides  of  the  hair-follicles,  usually 
two  or  more  to  each  follicle.  Com- 
monly proportioned  in  size  to  the 
hairs,  in  some  instances  the  con- 
dition is  reversed  and  the  largest 
glands  accompany  the  smallest 
hairs,  as  exemplified  by  those  in  the  region  of  the  nose. 


A  LARGE    SEBACEOUS    GLAND  FROM  THE  NOSE, 

viewed  by  transmitted  light,  and  highly  mag- 
nified, a,  epithelium  of  the  gland  ;  6,  the  same 
continuous  with  the  epidermis ;  c,  the  sebaceous 
matter ;  d,  subdivisions  of  the  gland ;  e,  a  hair- 
follicle  ;  /,  a  hair. 


In   the 


skin  of  the  scrotum  and  penis  they  are  visible  in  conspicuous  whitish 
groups  at  the  roots  of  the  hairs.  Similar  groups  are  seen  on  the  areola? 
of  the  mammae  unaccompanied  by  hairs.  On  the  sides  of  the  nose 
the  glands  and  their  ducts  are  often  so  large  in  comparison  with  the 


1  Arrectores  pili. 


2  Glandulae  sebacese. 


ORGANS   OF  SPECIAL,  SENSE. 


929 


accompanying  hairs  that  the  hair-follicles  appear,  contrary  to  the  usual 
condition,  to  open  into  them.  In  these  and  other  parts  of  the  face 
the  ducts  of  the  sebaceous  glands  frequently  become  more  or  less  dis- 
tended with  the  secretion,  and  adherent  dirt,  at  the  mouths  of  the 
ducts,  appears  as  black  spots.  When  the  secretion  is  squeezed  out, 
from  the  worm-like  appearance  it  assumes  it  has  been  regarded  as  an 
actual  worm.  The  sebaceous  glands  of  the  face  are  nevertheless  re- 
markable from  the  fact  that  the  secretion  does  very  commonly  harbor  a 
peculiar  parasitic  animal,  the  pimple  mite,  Demodex  folliculorum.1 
The  sebaceous  glands  are  pyriform  racemose  glands,  according  to 
the  size  composed  of  from  two  or  three  to  twenty  follicles.  These 
have  a  connective-tissue  wall  with  a  net  of  capillary  blood-vessels  and 


FIG.  494. 


FIG.  495. 


Fig.  494.— SEBACEOUS  MATTER,  FROM  ONE  OF  THE  SEBACEOUS  GLANDS  OF  THE  NOSE  :  magnified. 
1,  cells  filled  with  granular  matter ;  2,  one  of  the  cells,  more  highly  magnified;  3,  oil-drops 
mingled  with  the  cells. 

Fig.  495. — STRUCTURE  OF  THE  SEBACEOUS  GLANDS.  A,  a  simple  sebaceous  gland,  or  one  of  the 
divisions  of  a  compound  gland,  highly  magnified,  a,  epithelial  cells ;  6,  sebaceous  matter.  B, 
sebaceous  cells,  much  more  highly  magnified,  a,  small  cells  from  the  epithelial  layer ;  6,  larger 
cells  abounding  in  fat;  c,  cell  in  which  the  fat  has  accumulated  in  large  drops;  d,  cell  distended 
with  fat ;  e,  f,  cells  from  which  the  fat  has  partially  escaped. 

are  lined  with  a  stratified  epithelium  of  polyhedral  cells,  the  contents 
of  which  are  granular  and  mingled  with  numerous  fat-globules.  The 
epithelium  extends  into  the  ducts  and  is  continuous  with  that  of  the 
hair-follicles.  The  lumen  of  the  follicles  and  ducts  is  occupied  with 
the  cast-off  epithelial  cells  with  abundance  of  free  fat. 

THE   SWEAT-GLANDS. 

The  sweat-glands,  or  perspiratory  glands,2  are  mostly  tiny, 
spheroidal,  reddish  bodies,  existing  in  great  numbers  and  situated  at 
somewhat  variable  depths,  embedded  in  the  subcutaneous  connective 
and  adipose  tissue  of  the  skin.  They  exist  nearly  everywhere  over  the 
surface  of  the  body,  in  variable  proportions.  They  are  most  abundant 
in  the  palms  and  soles,  where  they  are  estimated  to  be  several  thousands 
to  the  square  inch  ;  are  about  half  the  number  on  the  back  of  the  hands 

1  Acarus  folliculorum. 

2  Sudoriferous  glands  ;  glandulse  sudoriparae  ;  g.  glomiformes. 

59 


930  ORGANS   OF   SPECIAL.  SENSE. 

and  feet  and  on  the  forehead,  a  less  number  in  front  of  the  trunk,  and 
the  least  number  on  the  back.  They  are  commonly  about  one-seventieth 
of  an  inch  in  diameter,  but  in  some  parts  are  much  larger,  as,  for 
example,  in  the  groin,  and  especially  in  the  axilla. 

In  the  palm  and  sole,  the  orifices  of  the  sweat-ducts  are  visible  with 
a  pocket-lens  and  appear  as  little  pits  in  a  row  along  the  lines  of  the 
tactile  papillae. 

Ordinarily  each  sweat-gland  consists  of  a  fine  cylindrical  tube  coiled 
up  into  a  ball,  from  which  the  tube,  somewhat  reduced  in  diameter,  pro- 
ceeds as  the  sweat-duct.  This  ascends  tortuously  through  the  dermis 
to  its  surface,  whence  a  passage  continues  through  the  epidermis  and 
opens  in  a  funnel-shaped  orifice.  Excepting  where  the  epidermis  is 
thin,  the  passage  from  the  sweat-duct  forms  a  tolerably  close  spiral, 
with  the  number  of  turns  proportioned  to  the  thickness  of  the  epider- 
mis. At  its  lower  part,  and  throughout  where  the  epidermis  is  thin, 
the  passage  is  nearly  straight.  In  the  larger  sweat-glands,  from  the 
duct  the  tube  forks,  which  condition  is  repeated  more  and  more  in  the 
largest  glands.  Even  some  of  the  smaller  glands  consist  of  a  pair  of 
tubes  which  unite  to  form  the  duct. 

The  gland-tube  is  provided  with  a  wall  of  connective  tissue  defined 
internally  by  a  thin  basement  membrane  and  provided  with  a  stratum 
of  longitudinal,  unstriped  muscle-fibres.  The  wall  encloses  a  net  of 
capillary  blood-vessels.  The  coils  of  the  tube  are  held  together  and 
enveloped  with  a  looser  texture  of  connective  tissue,  which  supports 
the  vessels.  The  epithelial  lining  of  the  tube  consists  of  a  stratum 
of  short,  stout  columnar  cells  with  granular  protoplasm  and  a  nucleus. 
The  duct  of  the  sweat-gland  has  its  connective-tissue  wall  continuous 
with  the  dermis  through  which  it  passes,  and  is  devoid  of  muscle- 
fibres.  The  epithelium  of  the  duct  consists  of  several  strata  of  cells, 
together  with  a  fine  cuticular  layer,  and  is  continuous  with  the  epi- 
dermis. The  passage  from  the  sweat-duct  through  the  epidermis  is 
formed  alone  by  its  cells,  which  in  general  conform  in  direction  to  the 
course  of  the  passage. 

When  the  epidermis,  after  maceration  of  the  skin,  is  raised  from 
the  dermis,  the  extracted  epithelium  of  the  sweat-ducts  appears  as 
delicate  threads  proceeding  from  the  dermis  to  the  epidermis  in  the 
angle  of  separation  of  the  two  layers  of  the  skin. 

In  the  axilla,  the  sweat-glands  appear  beneath  the  skin,  in  a 
brownish  patch  from  an  inch  and  a  half  to  two  inches  in  breadth, 
thickest  centrally  and  thinning  out  towards  the  circumference.  They 
lie  close  together  embedded  in  the  subcutaneous  connective  and  adipose 
tissue,  and  are  irregularly  rounded  and  polyhedral.  In  this  position 
they  range  from  one-thirty-sixth  to  one-twelfth  of  an  inch,  the  largest 
being  situated  centrally.  In  the  negro  they  are  ordinarily  more  con- 
siderably developed,  and  sometimes  the  larger  glands  reach  one-eighth 
of  an  inch  or  more  in  diameter. 


CHAPTEE  XVII. 

ANATOMY   OP   THE   GROIN   IN   RELATION   TO   HERNIA. 

ONE  of  the  common  accidents  to  which  the  body  is  liable  is  hernia, 
or  protrusion  of  a  portion  of  the  bowels  through  the  abdominal  wall, 
occurring  most  frequently  in  the  region  of  the  groin.  In  this  position 
the  inguinal  and  femoral  canals  are  especially  weak  points,  which  with 
undue  pressure  gradually  or  more  or  less  abruptly  yield  and  permit  the 
escape  of  a  portion  of  the  intestines  or  omentum.  The  hernia  is  ac- 
companied by  a  corresponding  protrusion  of  the  peritoneum,  called  the 
hernial  sac. 

The  most  common  kind,  inguinal  hernia,  occurs  through  the  in- 
guinal canal ;  while  femoral  hernia  occurs  through  the  femoral  canal. 

INGUINAL  HEKNIA. 

The  inguinal  canal  lies  immediately  above  Poupart's  ligament,  and 
gives  passage  in  the  male  to  the  spermatic  cord  and  in  the  female  to 
the  round  ligament  of  the  uterus.  It  is  about  an  inch  and  a  half  long, 
and  extends  from  the  internal  abdominal  ring  at  the  middle  of  the 
groin  to  the  external  abdominal  ring  above  and  to  the  outer  side  of 
the  pubic  spine.  It  is  considerably  narrower  in  the  female,  who  is 
therefore  less  liable  to  inguinal  hernia. 

In  front  the  canal  is  formed  by  the  aponeurosis  of  the  external  ob- 
lique muscle,  and  below  by  the  same  aponeurosis  curving  backward  and 
forming  Poupart's  ligament.  Behind,  it  is  formed  by  the  transversalis 
fascia,  together,  at  the  lower  part,  with  the  conjoined  tendon  of  the 
internal  oblique  and  transversalis  muscles.  Above,  it  is  formed  by  the 
arching  borders  of  these  muscles. 

The  epigastric  blood-vessels,  ascending  in  the  transversalis  fascia, 
cross  the  course  of  the  canal  behind,  and  Poupart's  ligament  separates 
it  from  the  femoral  blood-vessels  and  canal. 

The  constituents  of  the  spermatic  cord  are  the  spermatic  duct,  ar- 
tery, veins,  nerves,  and  lymphatics,  united  by  connective  tissue,  often 
associated  with  more  or  less  fat.  Within  the  canal  it  is  invested  by 
the  infundibuliform  fascia  and  cremaster  muscle,  and,  after  emerging, 
in  addition  by  the  spermatic  fascia,1  the  superficial  fascia  continuous 
with  the  dartos,  and  by  the  skin. 

1  External  spermatic  or  intercolumnar  fascia. 

931 


932  INGUINAL   HERNIA. 

The  round  ligament  in  the  inguinal  canal  has  the  same  investment 
except  the  cremaster  muscle,  which  is  absent  in  the  female,  and  after 
leaving  the  canal  the  ligament  becomes  attenuated  and  diffused  in 
the  tissues  of  the  mons. 

Two  varieties  of  inguinal  hernia  are  distinguished,  the  oblique  and 
the  direct. 

In  oblique  inguinal  hernia,1  the  most  common  form,  the  pro- 
truding intestine  pursues  the  course  of  the  spermatic  cord  through 
the  inguinal  canal  into  the  scrotum.  The  hernia  in  its  descent  becomes 
successively  invested  with  the  coverings  of  the  spermatic  cord,  and 
lies  in  front  of  the  spermatic  vessels.  In  the  female,  oblique  inguinal 
hernia  takes  a  similar  course,  and  after  emerging  at  the  external  ab- 
dominal ring  it  occupies  the  labium. 

In  direct  inguinal  hernia 2  the  bowel  directly  protrudes  through 
the  lower  end  of  the  inguinal  canal  at  the  external  abdominal  ring. 
Behind  the  ring  is  a  triangular  space3  covered  by  the  conjoined  tendon 
and  defined  outwardly  by  the  epigastric  blood-vessels.  Through  this 
space  the  hernia  protrudes  into  the  external  abdominal  ring,  covered  by 
the  transversalis  fascia,  the  conjoined  tendon,  the  spermatic  and  super- 
ficial fascise,  and  the  skin.  The  hernia  may  protrude  through  a  slit 
of  the  conjoined  tendon.  Sometimes  it  protrudes  to  the  outer  side  of 
the  tendon  into  the  inguinal  canal  and  descends  as  in  ordinary  oblique 
inguinal  hernia. 

The  inner  surface  of  the  anterior  wall  of  the  abdomen,  on  each  side, 
exhibits  a  slight  fold  of  the  peritoneum  in  the  course  of  the  obliterated 
umbilical  artery*  from  the  side  of  the  pelvis  and  groin  to  the  umbili- 
cus. The  fold  divides  the  space  opposite  the  groin  into  two  shallow 
concavities,  which  are  called  the  external  and  internal  inguinal 
fossae.  These  correspond  with  the  position  respectively  of  the  ab- 
dominal rings  and  of  the  two  forms  of  inguinal  hernia. 

In  the  foetus  up  to  the  seventh  month  the  testicles  are  contained 
within  the  abdominal  cavity,  below  the  kidneys,  behind  the  perito- 
neum, which  invests  them  in  front  and  at  the  sides. 

In  the  seventh  month  the  testicle  descends  through  the  inguinal 
canal,  and  by  the  end  of  the  eighth  month  has  usually  passed  into  the 
scrotum.  The  vaginal  tunic,  as  a  pouch  prolonged  from  the  perito- 
neum, precedes  the  testicle  in  its  descent.  Shortly  before  birth  the 
narrowed  neck  of  the  pouch  generally  becomes  closed,  and  the  vaginal 
tunic  is  then  completely  shut  from  the  peritoneal  cavity.  Occasion- 
ally the  neck  of  the  pouch  remains  open  later  than  usual,  and  may 
form  the  passage  of  a  hernial  protrusion,  constituting  the  variety 
named  congenital  hernia.5 

1  External  inguinal  hernia.  2  Internal  or  ventro-inguinal  hernia. 

*  Triangle  of  Hesselbach.  *  Hypogastric  artery. 

5  Hernia  tunicse  vaginalis. 


FEMORAL   HERNIA.  933 

In  the  female  foetus  a  pouch l  of  peritoneum  accompanies  the  round 
ligament  a  short  distance  at  the  entrance  of  the  inguinal  canal.  A 
depression  or  little  pocket,  usually  to  be  seen  in  the  adult  in  the  posi- 
tion of  the  internal  abdominal  ring,  is  the  remains  of  the  pouch.  This 
at  times  becomes  the  commencement  of  a  hernial  sac. 

FEMORAL   HERNIA. 

The  space  between  Poupart's  ligament,  or  the  femoral  arch,2 
and  the  hip-bone  is  occupied  outwardly  by  the  ilio-psoas  muscle  with 
the  crural  and  external  cutaneous  nerves;  inwardly  by  the  femoral 
blood-vessels  and  lymphatics  enveloped  in  a  common  connective-tissue 
sheath,  which  is  continuous  above  with  the  lining  fasciae  of  the  abdo- 
men. The  femoral  artery  lies  to  the  outer  side,  the  vein  in  the  middle, 
and  the  lymphatics  to  the  inner  side.  The  space  occupied  by  the  latter, 
together  with  a  lymphatic  gland,  connective  tissue,  and  fat,  is  distin- 
guished as  the  femoral  canal,3  and  is  the  passage  of  femoral  hernia. 
The  femoral  canal  is  about  half  an  inch  long  and  of  the  capacity  of  the 
last  joint  of  the  little  finger.  Its  upper  extremity,  the  femoral  ring,4 
is  closed  by  the  adjacent  peritoneum  and  connective  tissue ; 5  its  lower 
extremity  is  at  the  saphenous  opening  of  the  fascia  lata,  closed  by  the 
cribriform  fascia. 

To  the  inner  side  of  the  femoral  canal  extending  outwardly  in  front 
are  Gimbernat's  ligament,  the  conjoined  tendon,  and  a  thickened  band6 
of  the  transversalis  fascia.  In  front  of  it  are  Poupart's  ligament  and 
its  union  with  the  upper  extremity  of  the  falciform  process  of  the 
fascia  lata.  To  its  outer  side  is  the  femoral  vein,  separated  by  a  parti- 
tion of  the  common  sheath.  Behind  it  is  the  pubis,  with  the  pectineus 
muscle  covered  by  the  pubic  portion  of  the  fascia  lata. 

The  epigastric  blood-vessels  lie  above  to  the  outer  side  of  the  fem- 
oral ring,  and  the  obturator  artery,  when  not  running  in  the  usual 
course,  descends  into  the  pelvis  at  the  outer  side  or  rarely  at  the  inner 
side  of  the  ring. 

A  femoral  hernia  descends  the  femoral  canal  to  the  saphenous  open- 
ing, where  finding  less  resistance  forward  it  takes  this  direction,  and  in 
a  further  increase  turns  outwardly  in  the  groin.  Its  coverings,  succeed- 
ing the  hernial  sac,  are  a  thin  connective-tissue  layer7  derived  from 
that  of  the  femoral  canal  and  the  sheath  of  the  femoral  vessels,  the 
cribriform  fascia,  and  the  skin. 

The  femoral  canal  is  commonly  larger  in  the  female ;  hence  femoral 
hernia  is  more  common  in  that  sex  than  in  the  male. 


1  Canal  of  Nuck.         3  Superficial  femoral  or  crural  arch.         J  Crural  canal. 
*  Crural  ring.  5  Septum  crurale  ;  crural  septum. 

6  Deep  femoral  or  crural  arch.  7  Fascia  propria. 


INDEX. 


A. 

Aperture,  nasal,  144. 

Artery,     cerebral,    posterior, 

Aponeurosis,  236,  243. 

499. 

Abdomen,  366. 
cavity  of,  366. 

epicranial,  246. 
Apophysis,  33. 

cervical,  ascending,  499. 
deep,  502. 

muscles  of,  270. 

Apparatus,  alimentary,  376. 

occipital,  491. 

regions  of,  367. 

lachrymal,  859. 

superficial,  500. 

viscera   of,    416,    621,  680, 

reproductive,  634,  654. 

transverse,  500. 

686. 

respiratory,  597. 

choroid,  484,  499. 

Abdominal     ring,     external, 

Appendages  of  the  eye,  854. 

ciliary,  486,  872. 

273. 

Aqueduct,  cochlear,  113,  908. 

circumflex,  anterior,  504. 

internal,  278. 

of  Sylvius,  762. 

external,  536. 

Absorbent  system,  579. 

ventricular,  762. 

iliac,  533,  535. 

Absorbents,  579. 

vestibular,  112,  904,  909. 

internal,  535. 

jffcervulus  cerebri,  763. 

Aqueous  humor,  884. 

posterior,  504. 

Acetabulum,  191. 

Arachnoid,  772,  774. 

coccygeal,  531. 

Acini,  360. 

Arantius,  corpuscles  of,  474. 

coeliac,  518. 

Acoustic  crest,  911. 

Arbor  vitse,  663,  729. 

colic,  left,  522. 

hair-cells,  910,  914. 

Arch,  carpal,  anterior,  508. 

middle,  522. 

organ,  914. 

posterior,  509,  513. 

right,  522. 

rods,  914. 

crural,  933. 

communicating,     anterior, 

spots,  910. 

femoral,  933. 

485. 

Acromion,  160. 

of  the  aorta,  478,  479. 

posterior,  484. 

Adventitia,  454,  580. 

of  the  colon,  435. 

coronary,  left,  480. 

Afferent  nerves,  694. 

palatine,  anterior,  379. 

right,  479. 

vessels,  582. 

posterior,  379. 

deferential,  527,  651. 

After-brain,  767. 

palmar,  deep,  507. 

dental,  anterior,  495. 

Agminated  glands,  430. 

superficial,  501,  509. 

inferior,  494. 

Air-cells,  605. 

plantar,  545. 

posterior,  495. 

Albuginea,  636,  645,  668. 

supraorbital,  102. 

digitals,  510,  514,  546. 

Alimentary  canal,  376. 

zygomatic,  141. 

dorsal,  509,  513,  542. 

Alveoli,  119,  359,  674. 

Arcus  senilis,  866. 

dorsal,  of  clitoris,  530. 

Amphiarthrosis,  50. 

Arm-bone,  163. 

of  intercostals,  516. 

Ampullae,  673. 

Arterial  cone,  471. 

of  lateral  sacral,  531. 

Anapophysis,  61. 

Artery,  or  arteries,  453. 

of  lumbars,  525. 

Angle,  of  eye,  854. 

adventitia  of,  454. 

pedal,  541. 

facial,  152. 

anastomotic,  507,  537. 

of  penis,  530. 

of  jaw,  131. 

angular,  of  facial,  490. 

emulgent,  523. 

of  mouth,  377. 

auditory,  498. 

epigastric,  533. 

of  pubis,  190. 

auricular,  492,  493. 

superficial,  535. 

of  ribs,  81. 

axillary,  502. 

superior,  501. 

sacro-vertebral,  63,  66. 

basilar,  498. 

ethmoidal,  486. 

of  scapula,  158,  159. 

brachial,  504. 

facial,  489. 

Ankle,  218. 

variations  of,  505. 

transverse,  492. 

bone,  211. 

bronchial,  515. 

femoral,  533. 

joint,  218. 

buccal,  495. 

profunda,  535. 

Annulus  ovalis,  469. 

bulbar,  529. 

frontal,  487. 

Antihelix,  886. 

calcanean,  545. 

gastric,  518. 

Antitragus,  886. 

carotid,  external,  487. 

short,  520. 

Antrum  Highmorianum,  118. 

internal,  483. 

gastrocnemial,  538. 

mastoid,  893. 

left  common,  480. 

gastro-duodenal,  519. 

maxillary,  118. 

right  common,  481. 

gastro-epiploic,  left,  520. 

pyloric,  417. 

carpal,  anterior,  508,  514. 

right,  519. 

tympanic,  893. 

posterior,  509,  513. 

gluteal,  deep,  532. 

Aorta,  777. 

cavernous,  529. 

superficial,  532. 

abdominal,  478,  517. 

central,  of  cochlea,  907. 

helicine,  637. 

arch  of,  478,  479. 

of  retina,  485,  880. 

hemorrhoidal,  inferior,  529. 

branches  of,  479. 

cerebellar,     inferior,     497, 

middle,  528. 

semilunar  valves  of,  473. 

498. 

superior,  523. 

thoracic,  478,  514. 

superior,  499. 

hepatic,  519,  520. 

variations   in  branches  of, 

cerebral,  anterior,  484. 

hypogastric,  526. 

478. 

middle,  485. 

iliac,  531. 

935 

INDEX. 


Artery,  iliac,  circumflex,  533. 

common,  526. 

external,  532. 

internal,  526. 
ilio-colic,  521. 
ilio-lumbar,  531. 
infraorbital,  495. 
innominate,  480. 
intercostal,  516. 

anterior,  501. 

superior,  502. 
interosseous,  anterior,  512. 

metatarsal,  542. 

posterior,  512. 

recurrent,  512. 
intestinal.  521. 
intima  of,  456. 
ischiatic,  530. 
labial,  inferior,  490. 

superior,  490. 
lachrymal,  485. 
lingual,  488. 
lumbar,  525. 
malleolar,  541,  544. 
mammary,  501. 
masseteric,  495. 
maxillary,  internal,  493. 
media  of,  455. 
median,  512. 
mediastinal,  501,  515. 
medullary,  nutritious,  507, 

512,  537,  543. 
meningeal,  491. 

great,  494. 

posterior,  497. 

small,  494. 
mesenteric,  inferior,  522. 

superior,  521. 
metacarpal,  dorsal,  509, 513. 

palmar,  511. 
metatarsal,  541. 
musculo-phrenic,  501. 
mylo-hyoid,  495. 
nasal,  486,  490,  496. 
obturator,  527. 
occipital,  491. 
cesophageal,  515,  518. 
ophthalmic,  485. 
orbital,  493. 
ovarian,  523. 
palatine,  inferior,  489. 

superior,  495. 
palpebral,  486. 
pancreatic,  520. 
pancreatioo-duodenal,  519, 

520. 

perforating,  501,  536. 
peroneal,  543. 

anterior,  544. 

posterior,  544. 

superficial,  529. 

transverse,  529. 
pharyngeal,  491. 
phrenic,  501,  525. 
plantar,  external,  545. 

internal,  544. 
popliteal,  537. 
profunda,  femoral,  535. 

inferior,  506. 

superior,  506. 
pterygoid,  495. 
pterygo-palatine,  496. 
pubic,  533. 


Artery,  pudic,  external,  535. 

internal,  528. 
radial,  507. 
ranine,  489. 
recurrent,  radial,  508. 

tibial,  anterior,  541. 
posterior,  540. 

ulnar,  512. 
renal,  523. 
retinal,  central,  485. 
sacral,  middle,  518. 

lateral,  531. 

scapular,  posterior,  500. 
sciatic,  531. 
sigmoid,  523. 
spermatic,  524,  533,  650. 
spinal,  anterior,  497. 

posterior,  497. 
splenic,  520. 
sternal,  501. 
structure  of,  454,  462. 
stylo-mastoid,  492. 
subclavian,  496. 

left,  482. 

right,  482. 

surgical  relations  of,  502. 
submaxillary,  490. 
subscapular,  504. 
supraorbital,  485. 
suprarenal,  523. 
suprascapular,  499. 
tarsal,  541. 
temporal,  492. 

anterior,  493. 

deep,  495. 

middle,  493. 

posterior,  493. 
thoracic,  acromial,  503. 

inferior,  503. 

superior,  503. 
thyroid,  inferior,  499. 

superior,  487. 
tibial,  anterior,  539. 

posterior,  542. 
tonsillar,  490. 
tunics  of,  454,  456. 
tympanic,  484,  494. 
ulnar,  511. 
umbilical,  578. 
uterine,  530,  664. 
vertebral,  496. 
vesical,  inferior,  526. 

superior,  526. 
vesico-vaginal,  530. 
vidian,  496. 
volar,  508. 

Articulation,  ankle-joint,  218. 
astragalo-calcanean,  219. 

calcaneo-scaphoid,  220. 
atlanto-axial,  77. 

occipital,  77. 
calcaneo-cuboid,  220. 
carpo-metacarpal,  185. 
costo-central,  85. 

sternal,  86. 

transverse,  82. 
crico-arytenoid,  614. 

thyroid,  614. 
of  the  ear-ossicles,  895. 
elbow-joint,  181. 
of  the  hand,  183. 
of  the  hip-joint,  200. 
immovable,  50. 


Articulation,  intercarpal,  185. 

intercostal,  87. 

of  the  jaws,  155. 

of  the  knee-joint,  206. 

of  the  lower  jaw,  155. 

metacarpo-phalangeal,  186. 

movable,  51. 

movements  of,  51. 

odonto-atlantal,  78. 
transverse,  78. 

of  the  pelvis,  195. 

phalangeal,  186. 

of  the  pubes,  196. 

radio-carpal,  184. 

radio-ulnar,  182. 

sacro-iliac,  195. 

scapulo-clavicular,  178. 

scapulo-humeral,  180. 

shoulder-joint,  179. 

sternal,  87. 

sterno-clavicular,  178. 

of  the  tarsus,  219. 

temporo-mandibular,  155. 

ternporo-maxillary,  155. 

tibio-fibular,  210. 

of  the  upper  limbs,  178. 
Arthrosis,  50. 
Astragalus,  211. 
Atlas,  57. 
Atrium,  of  the  heart,  468. 

of  the  tympanum,  890. 
Attic,  893. 
Auditory  meatus,  887. 

cartilaginous  portion  of,. 

888. 

external,  887. 
internal,  901. 
osseous  portion  of,  889. 

nerve,  902. 
Auricle  of  the  ear,  886. 

of  the  heart,  468,  470. 
Auricular  appendix,  468,  470. 

septum,  468,  469. 
Auriculo-ventricular    orifice, 

468. 
Axillary  artery,  502. 

plexus,  812. 

vein,  562. 
Axis,  58. 

cerebro-spinal,  689. 

cosliac,  518. 

thyroid,  497. 
Azygos  vein,  566. 


B. 

Backbone,  54. 
Band,  dentate,  754. 

ilio-tibial,  316. 

semicircular,  752. 
Basement  membrane,  357, 
Basilar  artery,  498. 

groove,  91. 

membrane,  912. 
Basilic  vein,  564. 
Belly,  366. 
Bicuspid  teeth,  397. 

valve,  473. 
Bile,  452. 

canaliculi,  448. 

capillaries,  362,  448. 

duct,  449. 


INDEX. 


937 


Bladder,  gall,  451. 

urinary,  626. 
Blood,  463. 
clot,  464. 
corpuscles,  463. 
liquor,  463,  466. 
plasma,  463,  466. 
vessels,  453. 
Body,  ciliary,  868. 

geniculate,  759. 

olivary,  717. 
Pacchionian,  772. 

pineal,  762. 

pituitary,  763. 

pyramidal,  716. 

quadrigeminal,  761. 

restiform,  719. 

suprarenal,  686. 

thyroid,  683. 
Bone,  alisphenoid,  99. 

astragalus,  211. 

atlas,  57. 

axis,  58. 

basi-hyal,  156. 

basi-occipital,  90,  93. 

basi-sphenoid,  99. 

calcaueum,  212. 

canaliculi  in,  40. 

cancellated  substance  of,  35. 

carpal,  171. 

cernto-hyal,  157. 

clavicle,  162. 

coccyx,  65. 

collar,  162. 

compact  substance  of,  35. 

composition  of,  34. 

cuboid,  214. 

cuneiform,  172,  214. 

development  of,  44,  48. 

ectethmoid,  106,  107. 

ecto-cuneiform,  215. 

ensiform,  84. 

ento-cuneiform,  215. 

epiotic,  116. 

episternal,  85. 

ethmoid,  106. 

exoccipital,  93. 

femur,  196. 

fibula,  204. 

forms  of,  33. 

frontal,  102. 

growth  of,  44,  48. 

haunch,  187. 

Haversian  canals  in,  38. 

hip,  187. 

humerus,  164. 

hyoid,  156. 

ilium,  187. 

incisive,  121. 

inferior  turbinated,  124. 

innominate,  187. 

intermaxillary,  121. 

ischium,  189. 

knee-cap,  knee-pan,  200. 

lachrymal,  128. 

lacunae  of,  40,  48. 

leg,  202. 

lower  jaw,  129. 
limbs,  187. 

lunar,  172. 

mandible,  129. 

magnum,  173. 

malar,  128. 


Bone,  marrow  of,  35,  48. 

mastoid,  110. 

maxillary,  118,  129. 
inferior,  129. 
superior,  118. 

medullary  cavity  of,  35. 
space  of,  48. 

mesethmoid,  106. 

meso-cuneiform,  215. 

meso-sternum,  83. 

metacarpal,  174. 

metatarsal,  215. 

nasal,  126. 

nerves  of,  43. 

occipital,  90. 

opisthotic,  116. 

orbito-sphenoid,  99. 

palate,  122. 

parietal,  101. 

patella,  200. 

of  pelvis,  188,  190. 

perforating  fibres  of,  41. 

petrosal,  110,  115,  117. 

phalanges,  177,  217. 

pisiform,  172. 

prefrontal,  106,  107. 

premaxillary,  121. 

presphenoid,  99. 

presternum,  82. 

prootic,  116. 

pterygoid,  99. 

pubic,  190. 

radius,  169. 

scaphoid,  171,  213. 

scapula,  158. 

sesamoid,  178,  217. 

sphenoid,  93. 

spheno-turbinal,     96,     9! 
100. 

spongy,  35,  107,  124. 

squamosal,  115,  117. 

sternum,  82,  83,  84. 

structure  of,  35. 

supraoccipital,  93. 

sutural,  137. 

tarsal,  211. 

temporal,  109,  11.0. 

thigh,  196. 

thyro-hyal,  157. 

trapezium,  172. 

trapezoid,  173. 

turbinated,  107, 124. 

tympanal,  112,  116,  117. 

ulnar,  167. 

unciform,  173. 

unguiform,  125. 

vascular  canals  of,  38. 

vessels  of,  43. 

vomer,  127. 

Wormian,  116. 

xiphisternum,  84. 
Bone-cartilage,  34. 

corpuscles,  40,  48. 

earth,  34. 

tissue,  34. 
Bosom,  363. 
Brachial  artery,  504. 

plexus,  812. 

veins,  563. 
Brain,  713. 

arteries  of,  484,  497. 

blood-vessels  of,  775. 

commissures  of,  749,  759. 


Brain  of  embryo,  767. 

membranes  of,  770. 

nerves  of,  778. 

ventricles  of,  719,  750,  757. 
Breasts,  363,  672. 
Brim  of  pelvis,  193. 
Broad  ligam'ents,  661,  664. 
Bronchial  glands,  591. 

tubes,  602. 

Bronchioles,  603,  605. 
Bronchus,  bronchi,  598,  602. 
Bursa  mucosa,  354. 

subcutaneous,  354. 

synovial,  354. 


C. 

Caecum,  433. 

Calamus  scriptorius,  719. 

Calcaneum,  212. 

Calcar,  753. 

Calcification,  48,  233. 

Callosum,  735,  749. 

Calvaria,  134. 

Calyces  of  the  kidney,  623. 

627. 
Canal,  33. 

alimentary,  376. 

carotid,  113. 

central,  of  modiolus,  907. 
of  spinal  cord,  706. 

cochlear,  906. 

crural,  933. 

deferent,  647,  649. 

dental,  119,  131. 

digital,  307. 

facial,  112,  901. 

Fallopian,  112,  901. 

femoral,  933. 

glenoid,  113,  116. 

Haversian,  38. 

of  Huguier,  113. 

Hunter's,  324. 

infraorbital,  119. 

inguinal,  277. 

lachrymal,  858. 

of  Nuck,  933. 

palatine,  124. 
anterior.  120. 
posterior,  142. 

portal,  449. 

pterygoid,  98. 

pterygo-palatine,  99,  123. 

semicircular,  905,  909. 

spheno-palatine,  123. 

spiral,  907,  914. 

Vidian,  98. 
Canaliculi,  bile,  448. 

bone,  40. 

lachrymal,  860. 
Canines,  396,  399. 
Capillaries,  453,  460. 

bile,  448. 

lymphatic,  581. 
Capitulum,  165. 
Capsule    of    cerebrum,    755, 
756. 

of  Glisson,  450. 

of  lens,  882. 
Cardia,  416. 

Cardiac  muscular  tissue,  243. 
Carpus,  171. 


938 


INDEX. 


Cartilage  or  cartilages,  230. 

accessory,  of  nose,  850. 

articular,  231,  233. 

arytenoid,  611. 

bronchial,  603. 

corniculate,  612. 

costal,  80,  82. 

cricoid,  612. 

cuneiform,  612. 

diarthrodial,  52. 

of  ear,  886. 

elastic,  235. 

ensiform,  84. 

epiglottic,  612. 

of  eustachian  tube,  895. 

of  larynx,  608. 

lateral,  of  nose,  850. 

of  Meckel,  133. 

of  nose,  849. 

oval,  of  nose,  850. 

palpebral,  855. 

permanent,  231. 

semilunar,  207. 

septal,  849. 

temporary,  231. 

thyroid,  608. 

tracheal,  603. 

triangular,  850. 

tympano-mandibular,  133. 

of  Wrisberg,  612. 
Caruncle,  lachrymal,  858. 
Cauda  equina,  712. 
Caudate  lobe  of  the  liver,  444. 
Cava,  inferior,  565. 

superior,  548. 

Cavernous  bodies  of  the  clit- 
oris, 656. 

of  the  penis,  636. 
Cavity,  abdominal,  366. 

ootyloid,  191. 

cranial,  137. 

glenoid,  160. 

nasal,  847. 

oral,  377. 

pelvic,  193. 

thoracic,  364. 

tympanic,  890. 

uterine,  663. 
Cells,  acoustic  hair,  910,  914. 

air,  605. 

apolar,  696. 

beaker,  348. 

bipolar,  696. 

chalice,  348. 

daughter,  31. 

ganglion,  695. 

goblet,  348,  356. 

gustatory,  386. 

hepatic,  448. 

mastoid,  893. 

migratory,  466. 

multipolar,  696. 

nerve,  695. 

olfactory,  851. 

organic,  27. 

parietal,  422. 

peptic,  422. 

secreting,  349. 

seminal,  647. 

supporting,  682. 

sustentacular,  682. 

tactile,  922. 

unipolar,  696. 


Cell-wall,  28. 
Cementum,  404. 
Central  canal  of  the  spinal 
cord,  706. 

fovea  of  the  retina,  874,  879. 
Centre,  medullary,  765. 
Centrifugal  nerves,  694. 
Centripetal  nerves,  694. 
Centrum     ovale     Vieussenii, 

749. 
Cerebellum,  728. 

arteries  of  the,  777. 

cortex  of  the,  729,  730. 

cortical  layers  of  the,  734. 

hemispheres  of  the,  729. 

peduncles  of  the,  732. 

valley  of  the,  729. 
Cerebral  crura,  747. 

nerves,  778. 
origin  of,  778. 

vesicles,  767. 
Cerebro-spinal  axis,  689,  703. 

blood-vessels  of,  775. 

gray  matter  of,  690,  703. 

membranes  of,  769. 

white  matter  of,  690,  702. 
Cerebro-spinal  fluid,  772. 
Cerebrum,  715,  734. 

arteries  of,  776. 

convolutions  of,  736. 

crura  of,  747. 

gray  matter  of,  736. 

hemispheres  of,  735. 

interior  of,  749. 

white  matter  of,  736. 
Cerumen,  890. 
Ceruminous  glands,  890. 
Chambers 'of  the  eye,  870,  884. 
Cheeks,  377. 
Chest,  87,  363. 
Chiasm,  optic,  760. 
Chorda  tympani,  792,  795. 
Chorion,  671. 

Choroid   plexuses,    722,    768, 
769. 

telse,  768,  769. 
Choroidea,  866. 
Chyle,  585,  589. 

receptacle  of  the,  585. 
Cilia,  348,  855. 
Ciliary  body,  868. 

muscle,  869. 

plexus,  873. 

processes,  868. 

zone,  881. 
Gils,  348. 
Circle,  arterial,  of  the  iris,  872. 

of  Willis,  485. 
Claustrum,  756. 
Clava,  718. 
Clavicle,  162. 
Clitoris,  655. 
Coccyx,  65. 
Cochlea,  906. 

membranous,  911. 
Cochlear  duct,  911. 
Coeliac  axis,  518. 
Collar-bone,  162. 
Colles,  fascia  of,  676. 
Colon,  432. 
Columns,  Burdach's,  711. 

carneous,  471,  472. 

Clark's,  708,  712,  775. 


Columns    of    the    oblonzata, 
711. 

of  the  spinal  cord,  705. 
Commissure,    great   cerebral, 
735,  794. 

optic,  759,  760. 
Commissures,  labial,  377. 

palpebral,  855. 

of    the    spinal    cord,    705, 
706. 

of  the  third  ventricle,  759, 
760. 

of  the  vulva,  655. 
Common  bile-duct,  451. 
Condyles,  33. 

of  femur,  198. 

of  humerus,  166. 

of  mandible,  132. 

of  occipital  bone,  92. 
Conjunctiva,  857. 
Connective  tissue,  223. 
Connivent  valves,  355,  426. 
Convolutions  of  the  cerebrum, 
716,  736. 

angular,  741. 

annectant,  741,  742. 

central,  739,  740. 

fornicate,  745. 

frontal,  739. 

hippocampal,  744. 

marginal,  741. 

occipital,  742. 

occipito-temporal,  743. 

orbital,  739,  740. 

parietal,  740,  741. 

temporal,  743. 

uncinate,  744. 
Cord,  spinal,  703. 
Cordiform  tendon,  267. 
Cords,  vocal,  614,  619. 
Corium,  345. 
Cornea,  864. 

Cornua,  of  the   lateral   ven- 
tricles, 750. 

of  the  spinal  cord,  706. 
Cornucopia,  720,  721,  732. 
Corona  radiata,  765. 
Corpus  callosum,  735,  749. 

dentatum,  718. 

Highmori,  645. 

luteum,  671. 

olivare,  717. 

pyramidale,  716. 

restiform,  719. 

striatum,  751. 
Corpuscles  of  Arantius,  474. 

blood,  464. 

bone,  40. 

cartilage,  231. 

colorless,  465. 

colostrum,  675. 

concentric,  686. 

connective  tissue,  224. 

corneal,  865. 

lymph,  584. 

lymphoid,  583. 

Pacinian,  918. 

red,  464. 

tactile,  918. 

white,  465. 
Cortex,  cerebellar,  733. 

cerebral,  736. 

renal,  623. 


INDEX. 


939 


Cortex,  suprarenal,  687. 

Duct,  milk,  673. 

Epidermis,  346,  919. 

Corti,  organ  of,  914. 

of  Muller,  672. 

Epididymis,  644. 

Cortical     labyrinth     of     the 

nasal,  860. 

Epigastric  region,  367. 

kidney,  624. 

pancreatic,  441. 

Epigastrium,  367. 

layers   of    the   cerebellum, 

parotid,  390. 

Epiglottic  cartilage,  612. 

734. 

right  lymphatic,  586. 

cushion,  618. 

Cranium,  89,  133. 

of  Rivinus,  389. 

Epiglottis,  612. 

base  of  the,  134. 

spermatic,  649. 

Epineurium,  698. 

fossae  of,  137. 

of  Steno,  389. 

Epiploic  appendages,  436. 

interior  of,  137. 

thoracic,  585. 

Epiploon,  great,  371. 

Crassamentum,  464. 

of  Wharton,  389. 

Epithelial  tissue,  345. 

Crescents  of  Giannuzzi,  392. 

of  Wirsung,  441. 

Epithelium,  345,  346. 

Crest,  33. 

Ductus  arteriosus,  578. 

ciliated,  347. 

ethmoidal,  91. 

communis  choledochus,  449. 

columnar,  346. 

iliac,  187. 

venosus,  578. 

cylinder,  346. 

occipital,  106. 

Dura  of  the  brain,  770. 

glandular,  360. 

t    pubic,  190. 

of  the  spinal  cord,  773. 

pavement,  346. 

tibial,  202. 

Dura  mater,  770. 

polyhedral,  348. 

urethral,  641. 

scaly,  346. 

vestibular,  904. 

E. 

simple,  346. 

Crista  galli,  106. 

squamous,  350. 

Crown  of  the  head,  133. 

Ear,  885. 

stratified,  346. 

Crura  of  the  cerebrum,  747. 

drum,  890. 

tessellated,  346. 

of  the  diaphragm,  268. 

external,  885. 

transitional,  350. 

of  the  fornix,  752. 

internal,  901. 

Eustachian  tube,  894. 

Crural  arch,  272. 

middle,  890. 

Excretion,  358. 

canal,  933. 

lobe,  886. 

Eye,  854. 

ring,  933. 

ossicles,  895. 

appendages  of,  854. 

Crusta,  747. 

articulations  of,  897. 

blood-vessels  of,  885. 

petrosa,  404. 

ligaments  of,  898. 

Eyeball,  854,  862. 

Crystalline  lens,  882. 

muscles  of,  898. 

muscles  of,  860. 

Cuneus,  743. 

Ectiris,  871. 

Eyebrow,  854. 

Cupola,  906,  911. 

Ectochoroidea,  860. 

Eyelashes,  854,  855. 

Cuticle,  920,  921. 

Ectocornea,  864,  865. 

Eyelids,  854. 

Cystic  duct,  451. 

Ectoretina,  874,  875. 

structure  of,  855. 

Efferent  nerves,  694. 

D. 

tubules,  647. 

F. 

vessels,  582. 

Dartos,  271,  643. 

Egg,  670. 

Face,  89,  133,  144. 

Daughter-cells,  31. 

Elements,  sarcous,  241. 

Facial  angle,  152. 

Deferent  canal,  647,  649. 

structural,  27. 

Fallopian  tube,  666. 

Deiters,  nucleus  of,  725. 

Embryology,  26. 

Falx,  cerebellar,  771. 

Demodex  folliculorum,  929-. 

Eminence,  auditory,  721. 

cerebral,  770. 

Dental  tissues,  401. 

cinereous,  721. 

Fascia,  238. 

production  of,  407. 

collateral,  755. 

of  abdomen,  271. 

Dentate  band,  744. 

cuneate,  719. 

anal,  677,  279. 

Denticulate  ligament,  774. 

frontal,  242. 

axillary,  290. 

Dentine,  402. 

ilio-pectineal,  190. 

of  the  back,  280. 

Dermis,  915. 

ilio-pubic,  190. 

cervical,  257. 

Diaphragm,  267. 

mammillary,  749. 

of  Colles,  676. 

arcuate  ligaments  of,  268. 

parietal,  101. 

costo-coracoid,  293. 

central  tendon  of,  267. 

terete,  721. 

crural,  330. 

crura  of,  268. 

Enamel,  403. 

deep,  236. 

openings  of,  269. 

organ,  408. 

of  the  forearm,  300. 

Diaphysis,  45. 

Enarthrosis,  51. 

of  the  leg,  330. 

Diapophyses,  56. 

Encephalon,  713. 

of  the  thigh,  315. 

Diarthrosis,  51. 

Endangium,  456. 

of  the  upper  limb,  290. 

Diencephalon,  767. 

Endocardium,  476. 

dorsal,  of  foot,  331 

Digestion,  organs  of,  416. 

Endomysium,  242. 

of  hand,  310. 

Digits,  177,  217. 

Endoneurium,  698. 

femoral,  315. 

Diploe,  35.  134. 

Endothelium,  346,  352,  456. 

ilio-psoas,  317. 

Diploic  sinuses,  35. 

Entiris,  871. 

infundibuliform,  271. 

Disks,  intervertebral,  71. 

Entochoroidea,  871. 

laryngeal,  615. 

Dorsum  of  foot,  217. 

Entocornea,  868. 

lata,  315. 

of  hand,  183. 

Entoretina,  877. 

lumbar,  278. 

of  tongue,  383. 

Entotympanic       membrane, 

obturator,  279. 

Duct,  bile,  449. 

894. 

palmar,  301. 

cochlear,  911. 

Epencephalon,  767. 

pelvic,  279. 

cystic,  451. 

Ependyma,  769. 

of  penis,  635. 

ejaculatory,  652. 

Epicardium,  474,  476. 

perineal,  676. 

glandular,  359. 

Epicondyles  of  femur,  199. 

plantar,  331. 

hepatic,  449. 

of  humerus,  166. 

prevertebral,  265. 

lactiferous,  673. 

Epidermal  rete,  920. 

propria,  933. 

940 


INDEX. 


Fascia,  recto-vesioal,  279. 
spermatic,  273,  643. 
superficial,  236. 
of  the  abdomen,  271. 
of  the  back,  280. 
of  the  forearm,  300. 
of  the  lower  liinb,  315. 
of  the  upper  limb,  290. 

temporal,  254. 

transversalis,  277. 

vertebral,  285. 
Fascicles,  fornicate,  766. 

gyral,  767. 

longitudinal,  767. 

uncinate,  767. 
Fat-cells,  230. 

tissue,  228. 
Fauces,  379. 
Femoral  arch,  933. 

canal,  933. 

ring,  933. 
Femur,  196. 
Fibres,  arciform,  724. 

connective-tissue,  223. 

lens,  883. 

muscle,  238. 

nerve,  691. 

osteogenic,  49. 

perforating,  41. 

of  Remak,  693. 

sustentacular,  878. 
Fibrin,  464,  466. 
Fibro-cartilages,  234. 

circumferential,  235. 

connecting,  234. 

interarticular,  234. 

intervertebral,  71. 

investing,  235. 
Fibro-connective  tissue,  223. 
Fibrous  tissue,  223. 
Fibula,  204. 
Fifth  ventricle,  751. 
Fillet,  733. 
Filum,  terminal,  773. 
Fimbria,  754. 
Fingers,  177. 
Fissures,  calcarine,  744. 

callosal,  745. 

calloso-marginal,  745. 

central,  738. 

of  the  cerebellum,  729. 

of  the  cerebrum,  736. 

collateral,  744. 

dentate,  754. 

Glaserian,  110,  112. 

glenoid,  110. 

great  horizontal,  729. 
longitudinal,  735. 

hippocampal,  744. 

interparietal,  740. 

of  the  liver,  445. 

of  the  medulla  oblongata, 
716. 

occipital,  742,  743. 

palpebral,  854. 

parieto-occipital,  738. 

of  Rolando,  738. 

of  spinal  cord,  705. 

Sylvian,  735,  737. 

temporal,  743. 

transverse,  757. 

triradiate,  740. 

of  the  vulva,  655. 


Flanks,  367. 

Flexures  of  the  colon,  435. 

Floecule,  731. 

Floor  of  the  fourth  ventricle, 

720. 
Folds,  ary-epiglottic,  617. 

recto-uterine,  375. 

recto-vesical,  375. 

of  the  rectum,  438. 

synovial,  353. 

thyro-arytenoid,    614,  615, 
619. 

of  the  tympanum,  899. 

vesico-uterine,  375. 
Follicles,   359. 

Graafian,  670. 
Follicular  lymphatic   glands, 

380. 

Fontanels,  150. 
Foot,  211,  217. 
Foramen  or  foramina,  33. 

Botali,  469,  577. 

caecum,  104,  383. 

condyloid,  92. 

coracoid,  159. 

great  sciatic,  196. 

incisive,  120,  144. 

infraorbital,  119. 

intervertebral,  55. 

jugular,  140. 

lacerate,  139. 

lacerum,  middle,  136,  139. 

of  Magendie,  722,  769. 

magnum,  92. 

mental,  130. 

of  Monro,  751,  757. 

obturator,  191. 

occipital,  92. 

omental,  371. 

optic,  98. 

oval,  of  the  heart,  462,  469, 
577. 

oval,  sphenoidal,  98. 

pre-ethmoidal,  146. 

quadratum,  267. 

rotundum,  98,  142. 

sacral,  63. 

sciatic,  great,  196. 
small,  196. 

sphenoidal,  98,  146. 

spheno-maxillary,  142. 

spheno-palatine,  142. 

spinal,  55. 

spinous,  98. 

stylo-mastoid,  113. 

supraorbital,  193. 

of  third  ventricle,  757. 

of  Winslow,  371. 
Foramina  Thebesii,  469. 
Fore-brain,  734,  767. 
Forehead,  133. 
Foreskin,  635. 
Formation,  reticular,  724. 
Fornix  of  brain,  752. 

of  conjunctiva,  857. 
Fossa,  33. 

canine,  120. 

cerebellar,  91,  140. 

coronoid,  166. 

digastric,  110. 

glenoid,  110. 

hemielliptical,  904. 

hemispherical,  904. 


Fossa,  iliac,  188. 

incisive,  120, 131. 

infraspinous,  159. 

infrasternal,  364. 

inguinal,  932. 

intercondyloid,  199. 

ischio-rectal,  279. 

jugular,  113,  363. 

lachrymal,  146. 

mesocranial,  139. 

nasal,  847. 

navioular,  655. 

olecranon,  166. 

olfactory,  138. 

oval,  of  heart,  469. 

pituitary,  93. 

postcranial,  139. 

precranial,  138. 

sigmoid,  of  the  ulna,  168. 

spheno-maxillary,  141. 

subscapular,  158. 

sulciform,  904. 

supraclavicular,  363. 

supraspinous,  159. 

temporal,  141. 

trochanteric,  198. 

zygomatic,  141. 
Fourth  ventricle,  719. 
Fovea,  central,  of  retina,  874. 
Foveae  of  oblongata,  721. 
Frasna,  glosso-epiglottic,  386. 
Fraenum,  635. 

labial,  377. 

lingual,  379,  383. 
Frenule,  733. 
Fringes,  synovial,  53. 
Funicle,  cuneate,  719. 

gracile,  718. 

of  nerves,  698. 

terete,  720. 

G. 

Gall,  452. 

bladder,  451. 

Ganglion    or    ganglia,    690, 
700. 

Anderschii,  798. 

Arnoldi,  793. 

cervical,  836,  839. 

coccygeal,  845. 

Ehrenritteri,  798. 

Gasserian,  782. 

geniculate,  795. 

jugular,  798,  800. 

lumbar,  844. 

Meckel's,  794. 

mesenteric,  inferior,  845. 
superior,  844. 

ophthalmic,  785. 

otic,  793. 

petrous,  798. 

phrenic,  844. 

renal,  844. 

sacral,  845. 

semilunar,  of  sympathetic, 

843. 
trifacial,  782. 

spinal,  903. 

submaxillary,  794. 

temporal,  838. 

thoracic,  841. 
Ganglion-cells,  695. 


INDEX. 


941 


Gastric  glands,  421. 

juice,  440. 
Gelatinosa,  707. 
Geniculate  bodies,  759. 
Germinal  spot,  671. 

vesicle,  671. 
Ginglymus,  51. 
(J  label  la,  103. 
Gladiolus,  83. 
Glands,  338. 

agminated,  430. 

alveoli  of,  359. 

arytenoid,  619. 

of  Bartholin,  658. 

of  Brunner,  429. 

cardiac,  422. 

carotid,  688. 

ceruminous,  890. 

coccygeal,  688. 

colic,  436. 

of  colon,  462. 

compound,  359. 

convoluted,  361. 

of  Cowper,  642,  658. 

ducts  of,  359. 

duodenal,  429. 

enteric,  428. 

epiglottic,  619. 

follicles  of,  359. 

follicular,  359. 
lymphatic,  380. 

gastric,  421.  • 

of  Havers,  353. 

labial,  377. 

lachrymal,  859. 

of  Lieberkiihn,  428. 

of  Littrg,  642. 

lobes  of,  360. 

lobules  of,  360. 

of  Luschka,  688. 

lymphatic,  579,  580,  581. 

matrix  of,  359. 

Meibomian,  856. 

membrana  propria  of,  359, 

360. 

of  Mery,  642. 
of  Morgagni,  642. 
nasal,  852. 
oesophageal,  415. 
oxyntic,  422. 
of  Pacchioni,  772. 
palatine,  378. 
palpebral,  856. 
parotid,  389. 
peptic,  422,  423. 
perspiratory,  929. 
of  Peyer,  430. 
pharyngeal,  411. 
prostatic,  640. 
pyloric,  422. 
racemose,  359. 
salivary,  389. 
sebaceous,  928. 
secreting  cells  of,  360. 
simple,  359. 
of  small  intestine,  428. 
solitary,  429,  436. 
sublingual,  389. 
submaxillary,  389. 
suburethral,  642. 
sweat,  929. 
thymus,  685. 
thyroid,  683. 


Glands,  tubular,  428,  436. 

Hernia  tunica:  vaginalis,  932. 

uterine,  664. 

ventro-inguinal,  932. 

Glans  of  the  clitoris,  656,  657. 

Hernial  sac,  931. 

of  the  penis,  634. 

Hesselbach,  triangle  of,  932. 

Globules,  milk,  675. 

Hiatus  aorticus,  267. 

Glomerules,  renal,  624,  626. 

Fallopii,  111. 

Glottis,  618. 

Hilus  of  kidney,  621. 

Goblet-cells,  348,  356. 

of  lung,  599. 

Graaflan  follicles,  670. 

of  lymphatic  glands,  582. 

Grinders,  397. 

of  ovary,  667. 

Groove,  auriculo-ventricular, 

of  spleen,  680. 

468. 

of  suprarenal  capsule,  687. 

basilar,  140. 

Hind-brain,  767. 

bicipital,  163. 

Hippocampus,  754. 

inter-auricular,  468. 

Histology,  26. 

inter-ventricular,  468. 

Homo,  26. 

musculo-spiral,  164. 

Horns  of  the  lateral  ventri- 

spiral, of  the  cochlea,  913. 

cles,  750,  753. 

vertebral,  167. 

Humerus,  164. 

Gubernaculum  dentis,  409. 

Humor,  aqueous,  884. 

Gullet,  414. 

crystalline,  863,  882. 

Gut,  424. 

vitreous,  863,  881. 

Gyri,  716,  736. 

Hunter's  canal,  324. 

Hyaloidea,  881. 

H. 

Hymen,  658. 

Haemapophyses,  82. 

Hypochondriac  region,  367. 
Hypochondrium,  367. 

Haematoblasts,  466. 

Hypogastrium,  367. 

Haemoglobin,  467. 

Hair,  923. 

I. 

follicle,  926. 

medulla  of  the,  926. 

Ileo-colic  valve,  434. 

papilla,  926. 

Ileum,  425. 

root  of,  926. 

Ilium,  187. 

Hallux,  217. 

Incisors,  395,  399. 

Hand,  171. 

Incus,  896. 

Harmonia,  50. 

Inferior  cava,  548. 

Havers,  canals  of,  38. 

Infraturbinal,  148. 

glands  of,  53. 

Infundibula  of  the  lungs,  605. 

Haversian  canals,  38. 

Infundibulum  of  brain,  748. 

Head,  33. 

of  frontal  sinus,  148. 

of  the  femur,  198. 

Inlet  of  the  pelvis,  193. 

of  the  fibula,  205. 

Instep,  217. 

of  the  humerus,  163. 

Integument,  915. 

of  the  radius,  170. 

Interbrain,  767. 

of  the  tibia,  203. 

Intercellular  substance,  27. 

Heart,  467. 

Interlobular   ducts   of    liver, 

auricles  of,  468. 

362. 

carneous  columns   of,   471, 

veins  of  liver,  448. 

472. 

Intermediate  portion  of   au- 

nerves of,  476. 

ditory    and   facial  nerves, 

papillary  muscles  of,   471, 

795. 

472. 

Internodes     of     nerve-fibres, 

pectinate  muscles  of,  470. 

693. 

tendinous  cords  of,  471,  472. 

Intestinal  juices,  440. 

valves  of,  472,  473. 

Intestine,  large,  432. 

ventricles  of,  470. 

small,  424.                , 

vessels  of,  476. 

Intima,  580. 

Heel-bone,  212. 

Iris,  870. 

Helix,  886. 

dilator  of,  871. 

muscles  of,  887. 

nerves  of,  873. 

Hepatic  cells,  448. 

sphincter  of,  871. 

duct,  449. 

structure  of,  871. 

lobules,  446. 

vessels  of,  872. 

substance,  442. 

Ischium,  189. 

Hernia,  931. 

Isthmus  of  the  fauces,  379. 

congenital,  932. 

Iter  dentium,  409. 

femoral,  933. 

inguinal,  931. 

T. 

direct,  932. 

J* 

external,  932. 

Jejunum,  425. 

internal,  932. 

Joints,  50. 

oblique,  932. 

ankle,  218. 

942 


INDEX. 


Joints,  diarthrodial,  51. 

elbow,  181. 

ginglymoid,  51. 

hip,  200. 

knee,  206. 

shoulder,  179. 

wrist,  184. 
Jugular  gulf,  550. 

vein,  550. 
Juice,  gastric,  440. 

pancreatic,  442. 


K. 

Karyokinesis,  30. 
Kerkring,  valve  of,  426. 
Kidneys,  621. 

pelvis  of,  622. 

structure  of,  623. 

vessels  and  nerves  of,  625, 

626. 

Knee-cap,  200. 
Knee-pan,  200. 


L. 

Labia,  655. 

majora,  655. 

minora,  657. 
Labyrinth,  cortical,  624. 

ear,  903. 

membranous,  908. 

osseous,  904. 
Lachrymal  Apparatus,  859. 

canals,  860. 

caruncle,  858. 

gland,  859. 

lake,  854. 

papilla,  854. 

punctum,  854,  860. 

sac,  860. 
Lacteals,  589. 
Lacunae  of  bone,  48. 
Lamina,  cribriform,  112,  901. 

cribrosa,  864. 

spiral,  907. 

terminal,  757.  761. 
Larynx,  597,  608. 

articulations  of,  612. 

cartilages  of,  608. 

ligaments  of,  612. 

muscles  of,  615. 

ventricles  of,  618. 

vessels  and  nerves  of,  619. 
Lateral  ventricles,  749,  750. 
Laura,  nucleus  of,  725. 
Lens,  882. 
Leucocytes,  465. 
Lieberkiihn,  crypts  of,  436. 
Ligaments,  52. 

acromio-clavicular,  179. 

of  the  ankle,  218. 

annular,  of  the  ankle,  332, 

333. 
of  the  wrist,  300,  301. 

arcuate,  268. 

articular,  of  the  spine,  75. 

astragalo-scaphoid,  220. 

atlanto-axial,  76,  77. 

atlanto-occipital,  76. 

auricular,  887. 


Ligaments  of  the  bladder,  631 . 
broad,  661,  664. 
calcaneo-cuboid,  220,  221. 
calcaneo-scaphoid,  220. 
capsular,  52,  75,  155,  180, 

186,  201,  209,  218. 
of  the  carpus,  185. 
conoid,  179. 
coraco-acromial,  180. 
coraco-clavicular,  179. 
coraco-humeral,  180. 
coronary,  370. 
costo-central,  85. 
costo-clavicular,  179. 
costo-colic,  680. 
costo-sternal,  86,  87. 
costo-transverse,  86. 
costo-vertebral,  85. 
costo-xiphoid,  87. 
cotyloid,  200. 
crico-arytenoid,  614. 
crico-ary-thyroid,  613. 
crico-thyroid,  613. 
crucial,  207. 
cruciform,  78. 
denticulate,  774. 
of  the  digits,  186. 
dorsal,  221. 

of  the  ear-ossicles,  898. 
elastic,  75. 
of  the  elbow,  181. 
funicular,  52. 
Gimbernat's,  273. 
Hay's,  317. 
hepatico-colic,  371. 
hepatico-renal,  370. 
of  the  hip,  200. 
hyo-epiglottic,  614. 
ilio-femoral,  201. 
ilio-lumbar,  196. 
intercarpal,  185. 
interclavicular,  179. 
intercostal,  87. 
interosseous,  182. 
interspinous,  76. 
intertarsal,  219. 
intertransverse,  76. 
intervertebral,  71. 
of  the  knee,  206. 
of  the  larynx,  612. 
lateral,  155,  181,  185,  208, 

219,  370. 
of  the  liver,  370. 
of  the  lower  jaw,  155,  156. 
nuchal,  75. 
odontoid,  78. 
orbicular,  181. 
ovarian,  668. 
palmar,  185. 
palpebral,  249,  856. 
patellar,  207. 
pectinate,  872. 
of  the  pelvis,  195. 
phrenico-colic.  371,  680. 
phrenico-gastric,  371. 
phrenico-splenic,  371. 
of  the  pinna,  887. 
plantar,  221. 
Poupart's,  272. 
pterygo-maxillary,  254. 
pubic,  196. 
pulmonary,  601. 
radiate,  85. 


Ligaments,  rhomboid,  179. 

of  the  ribs,  85,  86. 

round,  201,  575,  664. 

sacro-coccygeal,  73,  79. 

sacro-iliac,  195. 

sacro-sciatic,  196. 

of  the  shoulder,  180. 

spheno-maxillary,  156. 

spiral,  913. 

sterno-clavicular,  178,  179. 

of  the  sternum,  87. 

stylo-hyoid,  157. 

stylo-maxillary,  156,  258. 

supraspinous,  76. 

suspensory,    370,  375,  635, 
656,  680,  881. 

of  the  tarsus,  219. 

of  the  thorax,  85,  86. 

thyro-epiglottic,  614. 

thyro-hyoid,  613. 

transverse  atlantal,  78. 

transverse  metatarsal,  221. 

trapezoid,  179. 

triangular,  180,  273,  677. 

uterine,  664. 

vaginal,  307. 

vertebral,  73,  74. 

vesical,  280. 

of  the  wrist,  185. 
Ligamentum  nuchte,  71. 

patellae,  207. 

teres,  201,445. 
Line,  ilio-pectineal,  191. 

intertrochanteric,  198. 

popliteal,  203. 
Linea  alba,  276. 

aspera,  197. 

semilunaris,  276. 
Lineae  transversae,  275,  276. 
Lingule,  94,  730,  732. 
Lips,  662. 
Liver,  442. 

fissures  of,  445. 

notches  of,  444. 

structure  of,  446. 

vessels  of,  448. 
Lobe  of  the  ear,  886. 
Lobes     of     the     cerebellum, 
729. 

biventral,  731. 

central,  730. 

crescentic,  730. 

gracile,  731. 

inferior,  731. 

posterior,  730,  731. 

superior,  730. 
Lobes  of  the  cerebrum,  736. 

central,  744. 

frontal,  739. 

occipital,  742. 

olfactory,  745. 

parietal,  740. 

temporal,  743. 

temporo-sphenoidal,  743. 
Lobes  of  the  liver,  443. 

of  the  lungs,  599. 

of  the  prostate,  639. 

of  the  thymus,  685. 

of  the  thyroid,  683. 
Lobule,  cuneate,  743. 

quadrate,  742. 
Locus  niger,  748. 
Loins,  367. 


INDEX. 


943 


Longitudinal    fissure,    great, 

Lymphatics,  obturator,  588. 

735. 

occipital,  594. 

of  liver,  445. 

oesophageal,  592. 

Lower  jaw,  129. 

pancreatic,  590. 

Lungs,  597. 

parietal,  594. 

structure  of,  605. 

pelvis,  588. 

vessels  and  nerves  of,  607. 

penis,  587. 

Lymph,  584. 

perivascular,  581. 

Lymph-corpuscles,  584. 

pudic,  588. 

path,  583. 

pulmonary,  591. 

plasma,  584. 

rectum,  588. 

spaces,  581. 

sacral,  588. 

Lymphatic  capillaries,  581. 

scrotum,  588. 

glands,  579,  581. 

spermatic,  589. 

axillary,  593. 

splenic,  590. 

bronchial,  591. 

subareolar  plexus  of,  593. 

cardiac,  591. 

thorax,  591. 

cervical,  596. 

tongue,  595. 

coeliac,  591. 

urethral,  587. 

colic,  590. 

uterus,  588. 

femoral,  587. 

vagina,  588. 

gastric,  590. 

Lymphoid  nodules,  357. 

iliac,  588. 

tissue,  357. 

inguinal,  587. 

Lyre,  752. 

lumbar,  589. 

M. 

mastoid,  595. 

mediastinal,  592. 

Macula  lutea,  874,  879. 

mesenteric,  589. 

Magnum  of  the  carpus,  173. 

parotid,  595. 

Malar  bone,  128. 

phrenic,  590. 

Malleolus,  external,  206. 

popliteal,  587. 

internal,  204. 

splenic,  590. 

Malleus,  895. 

submaxillary,  596. 

Malpighi,  corpuscles  of,  584, 

system,  579. 

626,  683. 

trunks,  581. 

pyramids  of,  623. 

intestinal,  590,  591. 

Mamma,    mammary     gland, 

jugular,  596. 

672,  673. 

lumbar,  589. 

Mammals,  25. 

subclavian,  593. 

Mammillary  eminences,  749. 

vessels,  579. 

Mandible,  129. 

afferent,  582. 

Manubrium  of  sternum,  82. 

efferent,  582. 

Manus,  183. 

tunics  of,  580. 

Marrow,  42. 

valves  of,  580. 

red,  43. 

Lymphatics  of  the  abdomen, 

spinal,  703. 

587,  588,  589. 

yellow,  43. 

back,  593. 

Marrow-cells,  43. 

cardiac,  591. 

Masseter,  254. 

cervical,  596. 

Mastoid  cells,  893. 

chest,  593. 

Maxilla,  118. 

chief  trunks  of  the,  585. 

Meatus,  33. 

colic,  590. 

auditory,    114,     777,    887, 

cranial  cavity,  595. 

901. 

diaphragm,  592. 

external,  114. 

ear,  595. 

internal,  777,  801. 

eyeball,  595. 

nasal,  inferior,  148. 

facial,  595. 

middle,  107,  148. 

femoral,  586. 

superior,  107,  148. 

frontal,  594. 

Meckel,  cartilage  of,  133. 

gastric,  590. 

Meckel's  ganglion,  794. 

gluteal,  588. 

Media,  580. 

head,  594. 

Mediastinum,  anterior,  364. 

hepatic,  590. 

middle,  364. 

iliac,  588. 

posterior,  364. 

intercostal,  592. 

superior,  365. 

ischiatic,  588. 

testis,  645. 

limbs,  lower,  586. 

Medulla,  42. 

limbs,  upper,  592,  593. 

of  bones,  42. 

lumbar,  588. 

of  brain,  702. 

mamma,  593.                        . 

of  hairs,  426. 

mediastinal,  592. 

oblongata,  716. 

nasal  cavity,  595. 

renal,  623. 

neck,  594. 

spinalis,  703. 

Medullary    rays   of    kidney, 

623. 

Meibomian  glands,  856. 
Meisner,  plexus  of,  432. 
Membrana  propria,  356,  456. 
Membrane,  345. 

basement,  345,  357. 

basilar,  913. 

of  brain,  770. 

fenestrated,  353. 

interosseous,  182,  211. 

limiting,  879. 

mucous,  355. 

reticular,  915. 

Schneiderian,  850. 

serous,  351. 

of  spinal  cord,  773. 

synovial,  353. 

tectorial,  915. 

tympanic,  894. 

vestibular,  912. 

vocal,  613. 
Meninges,  771,  773. 
Mental  foramen,  130. 

protuberance,  130. 
Mesencephalon,  767. 
Mesentery,  368,  373. 
Mesiris,  871. 
Mesocsecum,  434. 
Mesochoroidea,  866. 
Mesocolon,  369,  374. 
Mesocornea,  865. 
Mesorectum,  375,  438. 
Mesoretina,  876,  877. 

layers  of,  877,  878. 
Mesoturbinal,  107,  148. 
Metacarpus,  174. 
Metapophysis,  61. 
Metasternum,  84. 
Metatarsus,  215. 
Metencephalon,  767. 
Midbrain,  767. 
Milk,  675. 

teeth,  399. 
Mitral  valve,  473. 
Modiolus,  906. 
Molars,  397,  399. 
Monro,  foramen  of,  751. 
Mons  veneris,  655. 
Mother-cell,  31. 
Motorial  end-plate,  246. 
Mouth,  377,  380. 

floor  of,  379. 

roof  of,  378. 

vestibule  of,  377. 
Mucosa,  345,  356. 
Mucous  membrane,  355. 
epithelium  of,  355. 
of  the  bladder,  632. 
of  the  colon,  436. 
of  the  iatestines,  428. 
of  the  mouth,  380. 
of  the  nose,  850. 
of  the  rectum,  439. 
of  the  tympanum,  899. 
of  the  uterus,  663. 
of  the  vagina,  659. 
Mucus,  358. 
Muscle  or  muscles,  237. 

abdominal,  271. 

external  oblique,  271. 
internal  oblique,  273. 
pyramidal,  275. 


944 


INDEX. 


Muscle  or  muscles : 
abdominal  rectus,  275. 

transversalis,  274. 
accessory  flexor,  347. 
anal  elevator,  677. 

sphincter,  677. 
anconeus,  299. 
of  the  arm,  296. 
arytenoid,  617. 
atlantal,  264. 
auricular,  248. 
of  the  back,  281,  285,  293. 
belly  of,  366. 
biventer,  288. 
brachial  biceps,  296. 

triceps,  298. 
of  the  breast,  291. 
buccinator,  253. 
of  the  buttock,  324. 
capito-splenius,  287. 
cervical  ascending,  287. 
cervico-splenius,  287. 
ciliary,  869. 
coccygeal,  678. 

extensor,  290. 
complexus,  288. 
constrictor,  of  pharynx, 

411,  412. 

coraco -brachial,  297. 
costal -elevator,  267. 
of  the  cranial  vault,  246. 
oremaster,  276,  644. 

inferior,  651. 
orico-arytenoid,  616. 
crico-thyroid,  616. 
crureus,  320. 
deltoid,  296. 
diaphragm,  267. 
digastric,  260. 
digital  extensor,  309. 

flexor,  deep,  305. 
long,  339. 
short,  341. 
superficial,  304. 
dorsal  extensor,  285. 
erector,  of  the  skin,  928. 
of  the  eyeball,  860. 
of  the  face,  248. 
fascial  tensor,  318. 
femoral  adductors,  323. 

biceps,  328. 

flexor,  321. 

quadrate,  327. 

rectus,  319. 
fibres  of,  237. 
fibrils  of,  241. 
of  the  foot,  341. 
of  the  forearm,  302,  307. 
frontal,  246. 
gastrocnemius,  337. 
geminus,  827.. 
genio-glossal,  386. 
genio-hyoid,  261. 
gluteal,  great,  324. 

middle,  325. 

small,  325. 
gracilis,  320. 
great  serratus,  293. 
hallucal  abductor,  342. 

adductor,  343. 

extensor,  334. 

flexor,  long,  340. 
short,  343. 


Muscle  or  muscles : 
ballucal  transverse,  343. 
of  the  hand,  312. 
of  the  head,  246. 
hyo-glossal,  387. 
iliac,  322. 
ilio-costalis,  286. 
ilio-psoas,  321. 
indical  extensor,  311. 
infralabial  depressor,  253. 

elevator,  253. 
infralingual,  387. 
infraoblique,  262. 
infraserratus,  284. 
infraspinatus,  294. 
insertion  of,  239. 
intercostal,  266. 
interosseous,  314,  344. 
interspinous,  289. 
intertransverse,  289. 
involuntary,  238. 
ischio-cavernous,  678. 
of  the  larynx,  615. 
latissimus,  282. 
of  the  leg,  333. 
lingual,  388. 
long  cervical,  265. 
longissimus,  285. 
lumbrical,  of  foot,  342. 

of  hand,  312. 
masseter,  254. 
of  mastication,  254. 
minimal  abductor,  314,  343. 

adductor,  314. 

extensor,  311. 

flexor,  314,  344. 
multifidus,  288. 
mylo-hyoid,  260. 
nasal  compressor,  250. 

depressor,  251. 

dilator,  250. 

pyramidal,  250. 
naso-labial  elevator,  251. 
of  the  neck,  256,  264. 
of  the  nose,  250. 
oblique,  of  eye,  861,  862. 
obturator,  external,  327. 

internal,  326. 
occipital,  246. 
occipito-frontal,  246. 
omo-hyoid,  262. 
oral  angle  depressor,  253. 

sphincter,  251. 
origin  of,  239. 
palatal  elevator,  382. 

tensor,  382. 
of  the  palate,  381. 
palato-glossal,  381. 
palato-pharyngeal,  381. 
palmar,  long,  303. 

short,  312. 
palpebral  elevator,  249. 

orbicular,  248. 

tensor,  249. 
papillary,  471,  472. 
pectinate,  470. 
pectineus,  322. 
pectoral,  greater,  291. 

small,  292. 
penniform,  240. 
of  perineum,  677. 
peroneal,  anterior,  334. 

long,  335. 


Muscle  or  muscles : 
peroneal,  short,  336. 
of  the  pharynx,  411. 
of  the  pinna,  887. 
plantaris,  338. 
platysma,  256. 
pollical  abductor,  313. 

adductor,  313. 

extensor,  first,  310. 
second,  311. 
third,  311. 

flexor,  long,  307. 
short,  313. 

opponent,  313. 
popliteus,  338. 
postauricular,  248. 
postrectus,  greater,  265. 

small,  265. 
preauricular,  248. 
prerectus,  greater,  264. 

lateral,  264. 

small,  264. 
pronator,  quadrate,  302. 

terete,  302. 
psoas,  322. 

small,  322. 
pterygoid,  external,  255. 

internal,  255. 
pyriform,  326. 
quadrate  lumbar,  279. 

pronator,  302. 
radio-carpal  extensor,  long- 
er, 308. 
shorter,  309. 

flexor,  304. 
rhomboid,  greater,  283. 

small,  284. 
sartorius,  318. 
scalenus,  anterior,  263. 

middle,  263. 

posterior,  263. 
scapular  elevator,  284. 
semimembranosus,  330. 
semipenniform,  240. 
semispinalis,  cervical,  288. 

thoracic,  288. 
semitendinosus,  329. 
of  the  shoulder,  291. 
smooth,  238. 
spinalis,  286. 
spinal  rotator,  289. 
splenius,  287. 
stapedial,  898. 
sterno-costal,  266. 
stern  o-hyoid,  261. 
sterno-mastoid,  258. 
sterno-thyroid,  261. 
striped,  239,  240. 
stylo-glossal,  388. 
stylo-hyoid,  260. 
stylo-pharyngeal,  413. 
subanconeus,  299. 
subclavian,  292. 
subcostal,  266. 
subscapular,  295. 
superciliary,  250. 
supinator,  307. 
supra-auricular,  248. 
supralabial  elevator,  252. 
supraoblique,  265. 
supraserratus,  284. 
supraspinatus,  294. 
sural  triceps,  336. 


INDEX. 


945 


Muscle  or  muscles : 
temporal,  254. 
teres,  greater,  295. 

lesser,  294. 
termination   of   nerves   in, 

245. 
of  the  thigh,  318,  321,  328. 

adductors,  323. 
of  the  thorax,  266. 
thyro-arytenoid,  616. 
thyro-hyoid,  261. 
tibialis  anterior,  333. 

posterior,  340. 
of  the  tongue,  386. 
trachelo-mastoid,  287. 
transversalis,  287. 

of  the  pinna,  887. 
transverse  perineal,  678. 
trapezius,  281. 
trochlear,  861. 
tympanic  tensor,  898. 
of  the  tympanum,  898. 
ulno-carpal  extensor,  309. 

flexor,  304. 
unstriped,  237,  238. 
of  the  upper  limb,  290. 
urethral  compressor,  679. 
urethro-bulbar,  678. 
vaginal  sphincter,  678. 
vastus,  external,  319. 

internal,  320. 
vesical  sphincter,  631,  640. 
vessels  and  nerves  of,  244. 
voluntary,  239. 
zygotnatic,  252. 

lesser,  252. 
Muscular  tissue,  237. 

cardiac,  243. 
system,  237. 
Muscularis  mucosa,  357. 
Myeloplaxes,  43. 
Myelencephalon,  767. 
Myolemma,  241. 
Myrtiform  caruncles,  658. 

N. 

Nail-bed,  922. 
Nails,  922. 
Nares,  849. 

posterior,  147. 
Nasal  cavities,  146. 

fossae,  146. 

septum,  147. 
Navel,  366. 
Neck,  363. 
Nerve  or  nerves,  690. 

abducent,  779,  794. 

accessory,  780,  805. 

afferent,  694. 

anastomotic,  797. 

articular  branches  of,  817, 
818,  827,  831,  832. 

auditory,  780,  798,  902. 

auricular,  796,  802. 
great,  811. 

auriculo-temporal,  791. 

axis  fibre  of,  692. 

of  brachial  plexus,  813. 

buccal,  791,  797. 

cardiac,  803. 
inferior,  840. 
middle,  839. 


Nerve  or  nerves : 

cardiac,  superior,  838. 
cells,  675. 
centrifugal,  694. 
centripetal,  694. 
cerebral,  778. 
cerebro-spinal,  689. 
cervical,  798. 

anterior,  809,  812. 

first,  807. 

posterior,  807. 

superior,  811. 
of  cervical  plexus,  809. 
cervico-facial,  797,  798. 
ciliary,  long,  784. 

short,  785. 
circumflex,  814. 
coccygeal,  anterior,  823. 

posterior,  808. 
cochlear,  902. 
communicating,  832. 
crural,  827. 

anterior,  826. 
cutaneous,  of  abdomen,  822. 

external,  825. 

internal,  815,  827. 

last  thoracic,  823. 

middle,  827. 

of  thorax,  821. 

ulnar,  817. 
dental,  anterior,  787. 

inferior,  792. 

middle,  787. 

posterior,  786. 
digitals  of  foot,  834. 

of  hand,   817,  819,  820, 

821. 
dorsal,  of  clitoris,  830. 

of  penis,  830. 
facial,  779,  794. 

branches  of,  795,  798. 

cervico-facial      division, 
798. 

temporo-facial    division, 

797. 

fibres  of,  691. 
gastric,  804. 
genito-crural,  824. 
glosso-pharyngeal,  798. 

lingual  branches  of,  800. 

pharyngeal   branches  of, 
800. 

tonsillitic    branches    of, 

800. 

gluteal,  829. 
gustatory,  792. 
hemorrhoidal,  830. 
hypoglossal,  780,  805. 

descending  .    cervical 

branch,  806. 
ilio-hypogastric,  823. 
ilio-inguinal,  824. 
infraorbital,  797. 
infratrochlear,  784. 
intercostal,  821. 
intereosto-humeral,  822. 
internodes  of,  673. 
interosseous,  819. 
Jacobson's,  793,  798. 
labial,  787. 
lachrymal,  783. 
laryngeal,  803. 
lumbar,  anterior,  823. 
60 


Nerve  or  nerves : 

lumbar,  posterior,  808. 
mandibular,  797. 
masseteric,  791. 
maxillary,  inferior,  790. 

superior,  786. 
median,  818. 
medullated,  691. 
membranous  sheath  of,  693. 
meningeal,  802. 
muscular  branches  of   the 
brachial  plexus,  813. 

great  sciatic,  831. 

median,  819. 

musculo-spiral,  820. 

sacral  plexus,  828. 

ulnar,  817. 
musculo-cutaneous,       815, 

832. 

musculo-spiral,  820. 
mylo-hyoid,  792. 
nasal,  784. 
naso-palatine,  789. 
nodes  of,  693. 
non-medullated,  693. 
obturator,  826. 
occipital,  great,  807. 

least,  811. 

small,  811. 

oculo-motor,  778,  781. 
olfactory,  778,  781,  852. 
ophthalmic,  783. 
optic,  778,  781. 
origin  of,  699. 
palatine,  788,  789. 
palmar,  817. 
palpebral,  787. 
patellar,  828. 
perforating,  829. 
perineal,  830. 
peroneal,  831,  832. 

small,  815. 
petrosal,  deep,  789. 

small,  793,  799. 

superficial,  789. 
pharyngeal,  810. 
phrenic,  802. 
plantar,  external,  834. 

internal,  834. 
pneumogastric,  780,  800. 
popliteal,  833. 
pterygoid,  791. 
pudendal,  829. 
pudic,  829. 
pulmonary,  804. 
radial,  820. 
recurrent,  832. 
sacral,  anterior,  823. 

posterior,  808. 
saphenous,  internal,  827. 

long,  827. 

short,  833. 
sciatic,  great,  830. 

small,  829. 

spheno-palatine,  786. 
spinal,  806. 

anterior,  808. 

posterior,  807. 
splanchnic,  841. 

great,  842. 

small,  842. 

smallest,  842. 
suboccipital,  807. 


946 


INDEX. 


Nerve  or  nerves : 

subscapular,  814. 

structure  of,  698. 

supraclavicular,  811. 

supraorbital,  784. 

suprarenal,  842. 

suprascapular,  814. 

suprati  ochlear,  784. 

sympathetic,  835. 

temporal,  791. 

temporo-facial,  797. 

temporo-frontal,  797. 

teniporo-malar,  786. 

thoracic  anterior,  814,  821. 
last,  823. 
posterior,  807,  814. 

tibial,  anterior,  833. 
posterior,  834. 

trifacial,  779,  782. 

trochlear,  779,  782. 

tympanic,  795,  798. 

ulnar,  816. 

vagus,  800. 

vestibular,  902. 

vidian,  789. 
Nervous  system,  689. 
Neurilemnia,  693. 
Neuroglia,  701. 
Nipple,  672. 

Nodule  of  cerebellum,  731. 
Nodules,  lymphoid,  357. 
Nose,  847,  849,  850. 

cartilages  of,  849. 

column  of,  849. 

muscles  of,  250. 

wings  of,  849,  850. 
Nostrils,  849. 
Notch,  cotyloid,  191. 

ethmoidal,  104. 

jugular,  92. 

of  kidney,  621. 

of  liver,  444. 

popliteal,  203. 

sacro-sciatic,  194. 

scapular,  160. 

sciatic,  great,  188. 
small,  190. 

tympanic,  891. 
Nuck,  canal  of,  933. 
Nuclei  of  t  halam  us,  760. 
Nucleolus,  30. 
Nucleoplasm,  30. 
Nucleus,  28,  29. 

accessory,  725. 

ambiguous,  779. 

arciform,  724. 

auditory,  725,  726. 

caudate,  752. 

cuneate,  719,  723. 

dentate,  733 

emboliform,  733. 

facial,  779. 

fastigiate,  733. 

globose,  733. 

glosso-pharyngeal,  725. 

gracile,  719,  722. 

bypoglossal,  725. 

lateral,  723. 

lenticular,  755. 

olivary,  718,  723,  728. 

tegmental,  748. 

vagus,  725. 
Nymphae,  657. 


O. 

Obex,  721. 
Oblongata,  716. 

arteries  of,  777. 

columns  of,  716,  717,  718. 

interior  of,  722. 

pyramids  of,  716. 
Occipital  bone,  90. 
Occiput,  134. 
(Esophageal  glands,  415. 
(Esophagus,  414,  415. 
Olecranon,  167. 
Olfactory  bulb,  746. 

glomeruli,  746. 

lobe,  778. 

nerve,  745,  778,  852. 

region,  848. 

tract,  746. 

tuber,  745. 
Olivary  body,  717. 
Olive,  717. 
0  mental  foramen,  371. 

sac,  371,  372. 
Omentum,  gastro-colic,  371. 

gastro-hepatic,  371. 

gastro-splenic,  680. 

great,  369,  371. 

small,  369,  371. 
Opening,  aortic,  269. 

caval,  269. 

oesophageal,  269. 

saphenous,  317. 
Operculum,  737. 
Ophthalmic  ganglion,  785. 

nerve,  783. 
Optic  chiasm,  760. 

commissure,  760. 

nerve,  760,  778,  863. 
Ora,  868. 
Orbits,  145. 
Organ  of  Corti,  914. 
Organic  cell,  27. 
Organized  bodies,  28. 
Organs,  26. 

of  digestion,  416. 

of  reproduction,  634,  654. 

of  special  sense,  847. 
Orifice,  cardiac,  416,  422. 

pyloric,  416,  422. 

tympanic,  890. 
Os  uteri,  662. 
Ossein,  34. 
Osseous  tissue,  48. 

development  of,  48. 

growth  of,  48. 
Ossicles,  ear,  895. 
Ossification,  45,  48. 

centre  of,  45. 
Ossiterra,  34. 
Osteoblast,  40,  48,  49. 
Osteoclast,  43,  50. 
Osteogenic  fibres,  49. 

tissue,  48. 
Osteoplast,  42. 
Otic  ganglion,  737. 
Otolites,  910. 
Outlet  of  the  pelvis,  193. 
Oval  window  of  the  ear,  891, 

904. 
Ovaries,  667. 

structure  of,  668. 
Oviducts,  666. 


Ovigenous  layer,  668. 
Ovisac,  670. 
Ovum,  670. 


P. 

Pacchioni,  glands  of,  772. 
Pacchionian  bodies,  138,  772. 
Pacinian  corpuscles,  918. 
Pancreas  440. 
Pancreatic  duct,  441. 

juice,  442. 
Palate,  143,  378. 

arches  of,  379. 

hard,  378. 

muscles  of,  381. 

pillars  of,  379. 

soft,  378. 
Palpebrae,  854. 
Palpebral  cartilages,  235. 
Papillae,  cireuinvallate,  383. 

conical,  384. 

filiform,  385. 

foliate,  383. 

fungiform,  384. 

renal,  623. 

tactile,  916. 

of  taste,  383. 

of  touch,  916. 
Parepididymis,  651. 
Parovarium,  672. 
Passage,  tympanic,  907. 

vestibular,  907." 
Patella,  200. 

ligament  of,  207. 
Pavilion  of  ear,  886. 

of  oviduct,  666. 
Pectiniform  septum,  637. 
Peduncles,  callosal,  750. 

of  the  cerebellum,  732. 
Pelvis,  192. 

of  the  kidney,  622. 
Penis,  634. 

cavernous  bodies  of,  636. 

glans,  638. 

spongy  body  of,  638. 

suspensory      ligament    of, 
271. 

vessels  and  nerves  of,  638, 

639. 

Perforating  bone  fibres,  41. 
Pericardium,  467. 
Perichondrium,  231. 
Perimysium,  242. 
Perineum,  675. 

fasciae  of,  676. 

muscles  of,  676. 
Perineurium,  698. 
Periosteum,  41. 

osteogenic  layer  of,  42. 
Peritoneum,  368. 
Perspiratory  glands,  929. 
Pes  hippocampi,  754. 
Peyer,    glands,    patches,    or 

plaques  of,  430. 
Phalanges    of    the    cochlea, 
914,  915. 

of  the  fingers,  177. 

of  the  toes,  217. 
Pharyngeal  glands,  411. 
Pharynx,  410. 

muscles  of  the,  411. 


IXDEX. 


947 


Pia,  771,  773. 

Pia  mater,  771. 

Pillars  of  the  fauces,  379. 

of  the  fornix,  752. 
Pimple  mite,  929. 
Pinna,  886. 

cartilage  of,  886. 

muscles  of,  887. 
Pit    of    the    stomach,    364, 

417. 

Plane  of  the  ischium,  194. 
Plate,  auditory,  114. 

cribriform,  106. 

orbital,  106,  107. 

tympanic,  112. 
Pleura,  601. 
Plexuses,  nervous,  698. 

aortic,  843,  845. 

Auerbach's,  432. 

brachial,  812. 

cardiac,  840. 

carotid,  836,  838. 

cavernous,  838,  846. 

cervical,  809,  812. 

ciliary,  873. 

coccygeal,  835. 

coaliac,  844. 

coronary,  841. 

crural,  826. 

dental,  787. 

gangliform,  800. 

gastric,  804,  844. 

hemorrhoidal,  846. 

hepatic,  844. 

hypogastric,  845,  846. 

infraorbital,  788. 

intraepithelial,  866. 

lumbar,  823. 

Meisner's,  432. 

mesenteric,  844,  845. 

ossophageal,  804. 

parotid,  795. 

pelvic,  846. 

phrenic,  844. 

prevertebral,  831. 

pulmonary.  804. 

renal,  844. 

sacral,  828. 

sacro-coccygeal,  808. 

solar,  843. 

spermatic,  844. 

splenic,  844. 

subepithelial,  866. 

suprarenal,  844. 

vertebral,  840. 

vesical,  846. 

vesico-vaginal,  846. 

uterine,  846. 
Plexuses,  vascular,  458. 

choroid,  768,  769. 

dorsi-spinal,  568. 

hemorrhoidal,  574. 

intraspinal,  568. 

pampiniform,  569. 

prostatic,  574. 

pterygoid,  555. 

pudendal,  573. 

spermatic,  569. 

uterine,  574. 

vaginal,  574. 

venous,  458. 

vesical,  574. 
Plica  semilunaris,  857. 


Pollex,  177. 
Pomum  Adami,  363. 
Pons,  715,  726. 

arteries  of,  777. 

Varolii,  726. 
Ponticulus,  721. 
Portal  canals,  449. 

vein,  574. 
Pouch  of  Douglas,  375,  659. 

recto-uterine,  369,  375. 

recto-vaginal,  375. 

recto-vesical,  369,  375. 
Prascuneus,  742. 
Premolars,  397. 
Prepuce,  635,  657. 
Preretina,  874. 
Primates,  25. 
Process  or  processes,  33. 

accessory,  61. 

acromion,  160. 

alveolar,  31,  119. 

angular,  97. 

articular,  55. 

auditory,  113. 

basilar,  90. 

ciliary,  868. 

clinoid,  94. 

coracoid,  160. 

coronoid,  131,  167. 

ensiform,  84. 

mammillary,  61. 

mastoid,  110. 

nasal,  120. 

oblique,  55. 

odontoid,  58. 

olecranon,  167. 

postarticular,  55. 

prearticular,  55. 

pterygoid,  97. 

spinous,  55. 

styloid,  113,  168,  171,  206. 

transverse,  56. 

unciform,  744. 

vocal,  611. 

xiphoid,  84. 

zygomatic,  106,  109. 
Proencephalon,  734. 
Proligerous  disk,  670. 
Promontory   of   the   sacrum, 
63. 

of  the  tympanum,  891. 
Proseneephalon,  767.  ' 
Prostate,  639. 
Protoplasm,  29. 
Protuberance,  mental,  130. 

occipital,  91. 
Pseudostoma,  352. 
Pubic  arch,  194. 
Pubis,  190. 
Pudendum,  654. 
Pulvinar,  758. 
Punctum  ossificatiouis.  45. 
Pupil,  870. 
Purkinje,  cells  of,  234. 

corpuscles  of.  40. 
Pyloric  antrum,  417. 

sphincter,  419. 

valve,  420. 
Pylorus.  416. 

Pyramid   of  the   cerebellum, 
731. 

temporal,  110. 

of  the  tympanum,  892. 


Pyramids,  decussation  of  the, 

717. 

of  Ferrein,  623. 
of  Malpighi,  623. 
of  oblongata,  716. 
renal,  623. 


R. 

Radius,  169. 

Ramus  of  ischium,  189. 

of  mandible,  131. 

of  pubis,  190. 
Ranvier,  nodes  of,  693. 
Raph6  of  oblongata,  724. 

of  penis,  635. 

of  perineum,  676. 

of  scrotum,  643. 

of  tongue,  383. 
Receptacle  of  the  chyle,  585. 

stapedial,  892. 

tympanic  tensor,  891. 
Receptaculum  chyli,  585. 
Recess,  chiasmal,  761. 

cochlear,  905. 

intercrural,  747. 
Rectum,  437. 

blood-vessels  of,  439. 

coats  of,  438. 

valves  of,  438. 

Regions  of  the  abdomen,  367. 
Reruak,  fibres  of,  693. 
Restiform  body,  719. 
Rete,  epidermal,  920. 

mucosum,  920. 
Reticular  formation,  724. 
Retina,  873. 

central  fovea  of,  874. 

structure  of,  875. 

sustentacular  fibres  of,  878. 

vessels  of,  880. 
Rhinencephalon,  745. 
Ribs,  80. 
Ridge,  33. 

bicipital,  165. 

mylo-hyoid,  130. 

superciliary,  103. 

supracondylar,  164. 
Ring,  crural,  933. 

external  abdominal,  273. 

femoral,  933. 

internal  abdominal,  278. 

tympanic,  116. 
Rivinus,  duct  of,  389. 
Rods,  acoustic,  914. 

of  the  retina,  876. 
Rolando,  fissure  of,  738. 

funicle  of,  719. 

nucleus  of,  719. 

tubercle  of,  719,  723,  779. 
Root  or  roots : 

of  auditory  nerve,  780. 

of  hair,  926. 

of  lung,  597. 

of  olfactory  lobe,  746. 

of    ophthalmic     ganglion, 
785. 

of  otic  ganglion,  793. 

of  spinal  nerves,  711. 

of  trifacial  nerve,  779,  782. 
Root-sheath  of  hair,  927. 
Rosenmiiller,  organ  of,  672. 


948 


INDEX. 


Rostrum,  750. 

Round   window   of    the   ear, 
891. 

S. 

Saccule  of  labyrinth,  909. 
Sacrum,  62. 

Santorini,  cartilages  of,  612. 
Saphenous  opening,  317. 

veins,  571. 

Sarcolemma,  238,  241. 
Sarcous  disks,  242. 

elements,  241. 
Scapula,  158. 
Scarpa's  triangle,  319. 
Schindylesis,  50. 
Schwann,  white  substance  of, 

692. 

Sclerotica,  863. 
Sorobiculus  cordis,  417. 
Scrotum,  643. 
Scute,  palpebral,  855. 

tympanic,  893. 
Sebaceous  glands,  928. 
Secreting  cells,  360. 
Secretion,  358. 
Sella,  sphenoidal,  93. 

turcica,  93. 
Semen,  653. 

Semibulbs  of  clitoris,  659. 
Semicircular  canals,  905,  909. 
Semilunar  valves,  473. 
Seminal  vesicles,  651. 
Seminiferous  tubules,  647. 
Sense,  organs  of  special,  847. 
Sensory  nerves,  694. 
Septum,  auricular,  468. 

intermuscular,  290,  316. 

ventricular,  470. 
Serosa,  345,  353. 
Serous  membrane,  351. 
Serum,  351,  355,  464,  466. 
Shin-bone,  202. 
Sigmoid  flexure  of  colon,  435. 
Sinews,  243. 
Sinuses,  33. 

cavernous,  558. 

circular,  558,  865. 

confluence  of,  557. 

coronary,  547. 

diploio,  37,  134. 

of  the  dura,  556. 

ethmoidal,  107. 

frontal,  105. 

lateral,  556. 

longitudinal,  557,  558. 

occipital,  558. 

petrosal,  559. 

portal,  575. 

prostatic,  641. 

sphenoidal,  95,  559. 

straight,  558. 

tarsal,  217. 

transverse,  558. 

valvular,  478. 
Skeleton,  32. 
Skin,  915. 
Skull,  89,  133. 

base  of,  133,  143. 

brachycephalic,  152. 

cavity  of,  137. 

development  of,  149. 


Skull,  dolicho-cephalic,  152. 
eurygnathous,  152. 
growth  of,  149. 
guttural  region  of,  144. 
inferior  region  of,  143. 
mechanical  construction  of, 

153. 

occipital  region,  144. 
oral  region,  143. 
orthognathous,  152. 
palatine  region,  143. 
prognathous,  152. 
variations  of,  152. 
Small  intestine,  424. 
Sole,  217. 

Space,  perforated,  745,  747. 
subarachnoid,  772. 
subdural,  772. 
Sperm,  653. 
Spermatic  cones,  647. 

rete,  647. 

Spermatozoa,  648,  653. 
Sphincter,  anal,  677. 
of  the  iris,  871. 
oral,  251. 
pyloric,  419. 
vesical,  631. 

Spigelian  lobe  of  liver,  444. 
Spinal  column,  54. 
cord,  703. 

arteries  of,  775. 
central  canal  of,  706. 
cervical  enlargement  of, 

704. 

columns  of,  705,  711. 
commissures  of,  705. 
cornua  of,  706. 
gray    columns    of,    706, 

707. 
lumbar    enlargement  of, 

705. 

marrow,  703. 
nerves,  711,  806. 
ganglia  of,  712. 
origin  of,  711. 
roots  of,  711. 
Spine,  spinal  column,  54. 
of  ischium,  189. 
of  pubis,  190. 
of  scapula,  160. 
of  tibia,  203. 
Spines,  iliac,  188. 
Spinous  process,  33,  55. 
Spiral  ganglion,  903. 
groove,  913. 
lamina,  907. 
ligament,  913. 
Spleen,  680. 

structure  of,  681. 
Splendid     line    of     Haller, 

773. 

Splenic  pulp,  681. 
Splenium,  749. 
Spongiosa,  707. 
Spongy     body     of     clitoris, 

657. 

of  penis,  638. 
Spots,  acoustic,  910. 

cribriform,  901,  908. 
Stapes,  897. 
Steno,  duct  of,  389. 
Sternum,  82. 
Stigma  of  ovary,  670. 


Stomach,  416. 

curvatures  of,  416. 

glands  of,  419,  420. 
Stomata,  352,  462,  581. 
Straits  of  the  pelvis,  193. 
Striae,  auditory,  221. 

callosal,  750. 

pineal,  758. 
Striatum,  751. 
Structural  elements,  27. 
Subcutaneous  bursae,  354. 
Submucous  layer,  355. 
Subserous  tissue,  351. 
Suburethral  glands,  658. 
Superciliary  ridge,  103. 
Supercilium,  854. 
Superior  cava,  548. 
Suprapromontory,  893. 
Suprarenal  bodies,  686. 
Supraturbinals,  107, 148. 
Suspensory  ligament  of  blad- 
der, 375. 

of  clitoris,  656. 

of  lens,  881. 

of  liver,  370. 

of  penis,  271,  635. 
Sustentacle     of     calcaneum, 

213. 
Sustentacular  fibres  of  retina, 

878. 
Sutures,  50,  134. 

basilar,  136. 

coronal,  135. 

dentate,  50,  134. 

fron  to-parietal,  135. 

interparietal,  135. 

lambdoid,  135. 

neuro-central,  70. 

occipito-mastoid,  135. 

occipito-parietal,  135. 

petro-squamosal,  115. 

sagittal,  135. 

serrate,  50. 

squamo-parietal,  135. 

squamous,  50,  135. 

transverse  facial,  136. 

palate,  136. 
Sweat-glands,  929. 
Sweetbread,  685. 
Sylvius,  aqueduct  of,  762. 

fissure  of,  737. 
Sympathetic  nerves,  835. 

cervical  portion,  836. 

communicating     branches, 
836. 

gangliated  cord,  835. 

lumbar  portion,  844. 

sacral  portion,  845. 

thoracic  portion,  841. 
Symphysis,  50. 

of  mandible,  130. 

of  pubes,  190,  196. 
Synarthrosis,  50. 
Synovia,  51,  52,  355. 
Synovial  bursae,  354. 

folds,  353. 

membrane,  353. 

sheath,  354. 
System,  absorbent,  579. 

arterial,  477. 

lymphatic,  579. 

nervous,  689. 

reproductive,  634,  654. 


INDEX. 


949 


System,  vascular,  453. 
venous,  546. 

T. 

Tactile  corpuscles,  918. 

papillae,  916. 
Tarsi,  235. 
Tarsus,  211. 
Taste-buds,  386. 

goblets,  386. 

papillae  of,  383. 
Tectorial  membrane,  915. 
Teeth,  393. 

auditory,  913. 

bicuspid,  397. 

canine,  396,  399. 

deciduous,  399. 

development  of,  405,  408. 

eruption  of,  393,  399. 

incisor,  395,  399. 

milk,  393,  399. 

molar,  397,  399. 

permanent,  393,  394. 

premolar,  397. 

structure  of,  401. 

temporary,  393,  399. 

wisdom,  397. 
Tegmentum,  748. 

subthalamic,  760. 
Tendon  of  Achilles,  338. 

central,  of  diaphragm,  267. 

conjoined,  274. 

cordiform,  267. 
Tendons,  243. 
Tentorium,  770. 
Testes,  643. 
Testicle,  643. 

structure  of,  646. 

vessels  and  nerves  of,  650. 
Thalamencephalon,  767. 
Thalamus,  757. 
Third  ventricle  of  the  brain, 

757. 
Thoracic  cavity,  364. 

duct,  585. 
Thorax,  87,  363. 
Thumb,  177. 
Thymus,  685. 
Thyroid  axis,  497. 

body,  683. 
Tibia,  202. 
Tissue,  26. 

adenoid,  357,  583. 

adipose,  228. 

areolar,  225. 

bone,  34. 

cardiac  muscular,  243. 

cartilage,  230. 

cellular,  225. 

connective,  223. 

dental,  401. 

elastic,  224,  227. 

epithelial,  345. 

erectile,  637. 

fat,  228. 

fibro-cartilage,  234. 

fibro-connective,  223. 

fibrous,  223. 

lymphoid,  357,  583. 

muscular,  237. 

nerve,   691,  695. 

osseous,  34,  48. 


Tissue,  osteogenic,  48. 

white  fibrous,  223. 

yellow  elastic,  224. 
Tongue,  383. 

muscles  of,  386. 

nerves  of,  388. 

papillae  of,  383. 

vessels  of,  388. 
Tonsilla,  731. 
Tonsils,  381. 
Torcular,  557. 
Touch,  papillae  of,  916. 
Trachea,  602. 
Tract,  cerebellar,  710. 

direct  sensory,  766. 

ganglionic,  708. 

intermedio- lateral,  707. 

mixed  lateral,  710. 

olfactory,  746. 

optic,  759. 

principal,  711. 

pyramidal,  765. 
anterior,  710. 
crossed,  710. 
direct,  711. 
lateral,  710. 

radicular,  anterior,  710. 

spiral,  901. 
Tract  of  Flechsig,  711. 

of  Goll,  711. 
Tragus,  886. 
Triangle,  Hesselbach's,  932. 

Scarpa's,  319. 

vesical,  632. 
Tricuspid  valve,  472. 
Trochanters,  198. 
Trochlea  of  the  femur,  199. 

of  the  humerus,  165. 

of  the  trochlearis   muscle, 

861. 

True  pelvis,  193. 
Tube,  eustachian,  114,  894. 

Fallopian,  666. 
Tuber  of  cerebellum,  731. 

cinereous,  748. 
Tubercles,  33. 

of  the  calcaneum,  212. 

quadrigeminal,  761. 

of  the  thalamus,  758. 

of  the  tibia,  202. 
Tuberculum  Loweri,  469. 
Tuberosities  of  the  humerus, 
163. 

of  the  tibia,  203. 
Tuberosity,  33. 

of  the  calcaneum,  212. 

of  the  ischium,  189. 

of  the  radius,  163. 
Tubules,  efferent,  647. 

seminiferous,  647. 

straight,  647. 

uriniferous,  633. 
Tunic,  vaginal,  645,  862. 

vascular,  648. 
Turbinals,  nasal,  148. 
Tiirck,  fasciculus  of,  710. 
Tympanic  membrane,  894. 

orifice,  890. 

tegmen,  111. 

tensor,  898. 
Tympanum,  890. 

lining  membrane  of,  899. 

muscles  of,  898. 


u. 

Ulna,  167. 
Umbilical  cord,  578. 
Umbilicus,  276,  366. 
Unipolar  nerve-cells,  696. 
Ureters,  627. 
Urethra,  female,  658. 

male,  640. 

membranous  portion,  641. 

prostatic  portion,  641. 

spongy  portion,  642. 
Urethral  crest,  641. 
Urinary  bladder,  626. 
coats  of,  631. 
vessels  of,  632. 

organs,  621. 
Uterus,  661. 

periodic  changes  of,  665. 

structure  of,  663. 

vessels  and  nerves  of,  664. 
Utricle  of  the  vestibule,  909. 
Utriculus,  641. 
Uvea,  871. 
Uvula  of  the  bladder,  632. 

of  the  cerebellum,  731. 

of  the  palate,  378. 

V. 

Vagina,  659. 
Vaginal  tunic,  645. 
Vagus  nerve,  800,  801. 
Valsalva,  sinuses  of,  473,  478. 
Valves,  aortic,  355. 

bicuspid,  473. 

connivent,  355,  426. 

coronary,  548. 

eustachian,  469. 

ileo-caecal,  434. 

ileo-colic,  434. 

of  lymphatics,  580. 

mitral,  473. 

pyloric,  420. 

semilunar,  473. 

tricuspid,  472. 

of  veins,  458. 

of  Vieussens,  720. 
Valvulae     conniventes,     355, 
426. 

Thebesii,  469. 
Vas  aberrans,  651. 

deferens,  649. 
Vasa  vasorum,  463. 
Vaso-motor  nerves,  463. 
Vault  of  cranium,  134. 
Veins,  454,  458. 

alveolar,  555. 

anastomotic,  560. 

angular,  553. 

auditory,  559. 

auricular,  554,  555. 

axillary,  562. 

azygos,  566. 

basilar,  559,  560. 

basilic,  564. 
median,  565. 

brachial,  563. 

bronchial,  568. 

cardiac,  547. 

central,  of  vertebrae,  568. 

cephalic,  564. 
median,  564. 

cerebellar,  561. 


950 


INDEX. 


Veins,  cerebral,  560. 

Veins,  petrosal,  551. 

Vertebrae,  centrum  of,  55. 

cervical,  deep,  549. 

pharyngeal,  552. 

cervical,  56. 

transverse,  556. 

phrenic,  569. 

coccygeal,  65. 

choroid,  561. 

popliteal,  570. 

dorsal,  59. 

ciliary,  559. 

portal,  574. 

lumbar,  60. 

circumflex,  563. 

pterygoid,  555. 

sacral,  62. 

colic,  576. 

pubic,  571. 

structure  of,  61. 

companion,  458. 

pudic,  572,  573. 

thoracic,  59. 

condylar,  562. 

pyloric,  576. 

true,  54. 

coronary,  547,  548. 

radial,  564. 

Vertebral  column,  54,  66. 

cystic,  575. 

ranine,  552. 

articulations  of,  71. 

deep,  458. 

renal,  569. 

curves  of,  66. 

dental,  555. 

retinal,  central,  559. 

development  of,  69. 

digital,  564. 

sacral,  lateral,  573. 

growth  of,  69. 

diploic,  561,  562. 

middle,  570. 

movements  of,  79. 

dorsal,  of  clitoris,  573. 

saphenous,  external,  571. 

Vertebrates,  25. 

of  penis,  573. 

internal,  571. 

Vertex  of  skull,  133. 

dorsal  lingual,  552. 

long,  571. 

Vesical  sphincter,  631. 

emissary,  562. 

short,  571. 

triangle,  632. 

epigastric,  571. 

sciatic,  573. 

uvula,  632. 

ethmoidal,  559. 

sigmoid,  576. 

Vesicles,  seminal,  651. 

facial,  552. 

spermatic,  569. 

Vesiculse  seininales,  651. 

deep,  553. 

of  the  spinal  cord,  569. 

Vessel  -arteries,  463. 

transverse,  554. 

of  the  spine,  568. 

veins,  463. 

femoral,  571. 

spiral,  913. 

Vessels,  afferent,  582. 

frontal,  553. 

splenic,  576. 

blood,  453. 

of  Galen,  560. 

striatum,  561. 

capillary,  460. 

gastric,  576. 

structure  of,  456,  462. 

efferent,  582. 

gastro-epiploic,  576. 

stylo-mastoid,  555. 

lymphatic,  579. 

gluteal,  573. 

subclavian,  562. 

Vestibular  membrane,  912. 

hemiazygos,  567. 

subcutaneous,  458. 

Vestibule  of  labyrinth,  904, 

hemorrhoidal,  576. 

submental,  553. 

908. 

hepatic,  569. 

subscapular,  563. 

of  mouth,  377. 

ileo-colic,  576. 

superficial,  458. 

of  vulva,  658. 

iliac,  circumflex,  571. 

supralabial,  553. 

Villi  of  intestine,  427. 

common,  570. 

supraorbital,  553. 

Vitellus,  671. 

external,  571. 

suprarenal,  569. 

Vitreous  body,  881. 

internal,  573. 

suprascapular,  556. 

humor,  881. 

ilio-lumbar,  570. 

temporal,  554,  555. 

layer  of  the  skull,  134. 

innominate,  548. 

thoracic,  563. 

Vitreum,  881. 

intercostal,  567. 

thyroid,  inferior,  549. 

Vocal  cords,  614,  619. 

interosseous,  564. 

superior,  552. 

membrane,  613. 

intestinal,  576. 

tibial,  anterior,  570. 

processes,  611. 

jugular,  anterior,  555. 

posterior,  570. 

Vulva,  654. 

external,  553. 

transverse,  548. 

vessels  and  nerves  of,  658. 

internal,  550. 

tunics  of,  459,  460. 

posterior,  555. 

ulnar,  564. 

W. 

lachrymal,  559. 

•  umbilical,  578. 

lingual,  552. 
longitudinal,  spinal,  568. 
of  lower  limbs,  570. 

of  upper  limbs,  562. 
valves  of,  458,  460. 
vertebral,  549. 

Wharton,  duct  of,  389. 
White  matter  of  brain,  763. 
of  cerebro-spinal  axis,  702. 

lumbar,  566. 

vorticose,  867. 

of  spinal  cord,  705. 

mammary,  internal,  550. 

Velum,  anterior,  720,  732. 

Window,  oval,  891,  904. 

masseteric,  555. 
mastoid,  562. 
maxillary,  internal,  554. 

inferior,  721. 
posterior,  720,  732. 
Vena  cava  adscendens,  565. 

round,  891. 
Windpipe,  602. 
Winslow,  foramen  of,  371. 

median,  564. 

descendens,  548. 

Wirsung,  duct  of,  441. 

mesenteric,  inferior,  576. 

inferior,  565. 

Wrisberg,  cartilages  of,  612. 

superior,  576. 

superior,  548. 

nasal,  555. 

innominata,  548. 

Y. 

oblique,  548. 

Ventricles  of  the  brain,  719, 

Yelk,  671. 

obturator,  573. 
occipital,  555,  562. 

749,  750,  751. 
of  the  heart,  470,  472. 

Yellow  spot  of  retina,  874. 

ophthalmic,  559. 

of  the  larynx,  618. 

ovarian,  569. 

Ventricular  aqueduct,  762. 

• 

palatine,  inferior,  553,  555. 

septum  of  brain,  750,  751. 

Zone,  ciliary,  881. 

pancreatic,  576. 

of  heart,  470. 

of  Zinn,  881. 

pancreatico-duodenal,  576. 

Vermiform  appendix,  433. 

Zygapophyses,  55. 

parietal,  562. 

Vertebrae,  54. 

Zygoma,  141. 

THE    END. 


r  • 


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